Delay-Tolerant Networking                                     E. Birrane
Internet-Draft                                               K. McKeever
Intended status: Standards Track                                 JHU/APL
Expires: May 3, September 13, 2017                               March 12, 2017                                    October 30, 2016

                 Bundle Protocol Security Specification
                        draft-ietf-dtn-bpsec-03
                        draft-ietf-dtn-bpsec-04

Abstract

   This document defines a security protocol providing end to end data
   integrity and confidentiality services for the Bundle Protocol.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on May 3, September 13, 2017.

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   Copyright (c) 2016 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Motivation  . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Supported Security Services . . . . . . . . . . . . . . .   3
     1.3.  Specification Scope . . . . . . . . . . . . . . . . . . .   4
     1.4.  Related Documents . . . . . . . . . . . . . . . . . . . .   5
     1.5.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   5
   2.  Key Properties  . . . . . . . . . . . . . . . . . . . . . . .   7   6
     2.1.  Block-Level Granularity . . . . . . . . . . . . . . . . .   7   6
     2.2.  Multiple Security Sources . . . . . . . . . . . . . . . .   7
     2.3.  Mixed Security Policy . . . . . . . . . . . . . . . . . .   8   7
     2.4.  User-Selected Ciphersuites Cipher Suites . . . . . . . . . . . . . . .   8
     2.5.  Deterministic Processing  . . . . . . . . . . . . . . . .   9   8
   3.  Security Blocks . . . . . . . . . . . . . . . . . . . . . . .   8
     3.1.  Block Definitions . . . . . . . . . . . . . . . . . . . .   9
     3.1.  Block
     3.2.  Uniqueness  . . . . . . . . . . . . . . . . . . . . . . .   9
     3.3.  Target Multiplicity . . . . . . . . . . . . . . . . . . .  10
     3.4.  Target Identification . . . . . . . . . . . . . . . . . .  10
     3.2.
     3.5.  Block Representation  . . . . . . . . . . . . . . . . . .  10
     3.3.  11
     3.6.  Abstract Security Block . . . . . . . . . . . . . . . . .  11
     3.7.  Block Integrity Block . . . . . . . . . . . . . . . . . .  13
     3.4.  14
     3.8.  Block Confidentiality Block . . . . . . . . . . . . . . .  14
     3.5.  15
     3.9.  Block Interactions  . . . . . . . . . . . . . . . . . . .  16
     3.6.
     3.10. Parameters and Result Fields Types . . . . . . . . . . . . . . .  17
     3.7.
     3.11. BSP Block Example . . . . . . . . . . . . . . . . . . . .  18  20
   4.  Canonical Forms . . . . . . . . . . . . . . . . . . . . . . .  20  22
     4.1.  Technical Notes . . . . . . . . . . . . . . . . . . . . .  20  22
     4.2.  Primary Block Canonicalization  . . . . . . . . . . . . .  21  23
     4.3.  Non-Primary-Block Canonicalization  . . . . . . . . . . .  22  23
   5.  Security Processing . . . . . . . . . . . . . . . . . . . . .  22  24
     5.1.  Bundles Received from Other Nodes . . . . . . . . . . . .  23  24
       5.1.1.  Receiving BCB Blocks  . . . . . . . . . . . . . . . .  23  24
       5.1.2.  Receiving BIB Blocks  . . . . . . . . . . . . . . . .  23  25
     5.2.  Bundle Fragmentation and Reassembly . . . . . . . . . . .  24  26
   6.  Key Management  . . . . . . . . . . . . . . . . . . . . . . .  25  26
   7.  Security Policy Considerations  . . . . . . . . . . . . . . . . . . . .  25  26
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  26  27
     8.1.  Attacker Capabilities and Objectives  . . . . . . . . . .  27  28
     8.2.  Attacker Behaviors and BPSec Mitigations  . . . . . . . .  28  29
       8.2.1.  Eavesdropping Attacks . . . . . . . . . . . . . . . .  28  29
       8.2.2.  Modification Attacks  . . . . . . . . . . . . . . . .  28  29
       8.2.3.  Topology Attacks  . . . . . . . . . . . . . . . . . .  29  31
       8.2.4.  Message Injection . . . . . . . . . . . . . . . . . .  30  31
   9.  Ciphersuite  Cipher Suite Authorship Considerations  . . . . . . . . . . . .  30  32
   10. Defining Other Security Blocks  . . . . . . . . . . . . . . .  31  33
   11. Conformance . . . . . . . . . . . . . . . . . . . . . . . . .  32  34
   12. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  32  34
     12.1.  Bundle Block Types . . . . . . . . . . . . . . . . . . .  32
     12.2.  Cipher Suite Flags . . . . . . . . . . . . . . . . . . .  32
     12.3.  Parameters and Results . . . . . . . . . . . . . . . . .  33  34
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  34
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  34
     13.2.  Informative References . . . . . . . . . . . . . . . . .  34  35
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .  35
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  35

1.  Introduction

   This document defines security features for the Bundle Protocol
   [BPBIS] (BP)
   [BPBIS].  This BP Security Specification (BPSec) is intended for use
   in delay-tolerant networks, in order Delay Tolerant Networks (DTNs) to provide Delay-Tolerant Networking (DTN) end-to-end security
   services.

1.1.  Motivation

   The Bundle Protocol is used specification [BPBIS] defines DTN as referring to
   "a networking architecture providing communications in DTNs that overlay multiple networks,
   some of which and/or through
   highly stressed environments" where "BP may be challenged by limitations such viewed as intermittent
   and possibly unpredictable loss sitting at
   the application layer of some number of constituent networks, forming
   a store-carry-forward overlay network".  The term "stressed"
   environment refers to multiple challenging conditions including
   intermittent connectivity, long or large and/or variable
   delay, delays, asymmetric
   data rates, and high bit error rates.  The purpose of
   the Bundle Protocol

   There is to support interoperability across such
   stressed networks.

   The stressed environment of the underlying networks over which the
   Bundle Protocol operates makes it important for the DTN to be
   protected from unauthorized use, and this stressed environment poses
   unique challenges for the mechanisms needed to secure the Bundle
   Protocol.  Furthermore, DTNs a reasonable expectation that BP may be deployed in environments where such a
   way that a portion of the network might become compromised, posing
   the usual security challenges related to confidentiality and
   integrity.  However, the stressed nature of the BP operating
   environment imposes unique requirements such that the usual security
   mechanisms to usual security challenges may not apply.  For example,
   the store-carry-forward nature of the network may require protecting
   data at rest while also preventing unauthorized consumption of
   critical resources such as storage space.  The heterogeneous nature
   of the networks comprising the BP overlay, and/or associated timing,
   might prevent the establishment of an end-to-end session to provide a
   context for a security service.  The partitionability of a DTN might
   prevent regular contact with a centralized security oracle (such as a
   certificate authority).

   An end-to-end security service is needed that operates in all of the
   environments where the BP operates.

1.2.  Supported Security Services

   This specification supports

   BPSec provides end-to-end integrity and confidentiality services associated with for
   BP bundles.

   Integrity services ensure data within a bundle are not changed.  Data
   changes may be caused by processing errors, environmental conditions,
   or intentional manipulation.  An integrity service is one that
   provides sufficient confidence to a data receiver that data has not
   changed since its value was last asserted.

   Confidentiality services ensure that the values of some only authorized receivers can
   view those data within a bundle can only identified as needing to be determined by authorized receivers of private
   amongst the data.
   When a bundle traverses data source and data receivers.  A confidentiality
   services is one that provides confidence to a DTN, many data receiver that
   private data was not viewed by other nodes in as the network other than bundle traversed
   the destination node MAY see the contents of a bundle.  A
   confidentiality service allows a destination node to generate data
   values from otherwise encrypted contents of a bundle. DTN.

   NOTE: Hop-by-hop authentication is NOT a supported security service
   in this specification, for three reasons.

   1.  The term "hop-by-hop" is ambiguous in a BP overlay, as nodes that
       are adjacent in the overlay may not be adjacent in physical
       connectivity.  This condition is difficult or impossible to
       predict in the overlay and therefore makes the concept of hop-by-
       hop authentication difficult or impossible to enforce at the
       overlay.

   2.  Networks in which BPSec may be deployed may have a mixture of
       security-aware and not-security-aware nodes.  Hop-by-hop
       authentication cannot be deployed in a network if adjacent nodes
       in the network have different security capabilities.

   3.  Hop-by-hop authentication can be viewed as a special case of data
       integrity.  As such, it is possible to develop policy that
       provides a version of authentication can be achieved
       by using the integrity mechanisms defined in this specification.

1.3.  Specification Scope

   This document describes defines the Bundle Protocol Security Specification
   (BPSec), which provides security services for blocks within a bundle. provided by the BPSec.
   This includes the data specification for individual representing these services
   as BP extension
   blocks blocks, and the processing instructions rules for those blocks. adding, removing, and
   processing these blocks at various points in the bundle's traversal
   of the DTN.

   BPSec applies, by definition, applies only to those nodes that implement it, known as
   "security-aware" nodes.  There MAY might be other nodes in the DTN that
   do not implement BPSec.  All  While all nodes in a BP overlay can interoperate with the
   exception that exchange
   bundles, BPSec security operations can only happen at BPSec
   security-aware security-
   aware nodes.

   This specification does not address individual cipher suite
   implementations.  Different networking conditions and operational
   considerations require varying strengths of security mechanism such
   that mandating a cipher suite in this specification may result in too
   much security for some networks and too little security in others.
   The definition and enumeration of cipher suites
   should is assumed to be
   undertaken in other, separate specification documents.

   This specification does not address the implementation of security
   policy and does not provide a security policy for the BPSec.
   Security  Similar
   to cipher suites, security policies are typically based on the nature and
   capabilities of individual networks and network operational concepts.  However,
   this
   This specification does recommend provide policy considerations when building a
   security policy.

   This specification does not address how to combine the BPSec security
   blocks with other protocols, other BP extension blocks, or other best
   practices to achieve security in any particular network
   implementation.

1.4.  Related Documents

   This document is best read and understood within the context of the
   following other DTN documents:

   "Delay-Tolerant Networking Architecture" [RFC4838] defines the
   architecture for delay-tolerant networks, but does not discuss DTNs and identifies certain security at any length. assumptions
   made by existing Internet protocols that are not valid in a DTN.

   The DTN Bundle Protocol [BPBIS] defines the format and processing of the blocks used to implement
   bundles that both carry the Bundle Protocol, excluding data and the
   security-specific blocks defined here. security services operating
   on those data.  This document also defines the extension block format
   used to capture BPSec security blocks.

   The Bundle Security Protocol [RFC6257] and Streamlind Streamlined Bundle
   Security Protocol [SBSP] introduce documents introduced the concepts of BP
   security blocks for security services. services in a DTN.  The BPSec is based off a
   continuation and refinement of these documents.

1.5.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119].

   This section defines those terms whose definition is important terminology either unique to the BPSec or
   otherwise necessary for understanding of the concepts within defined in this
   specification.

   o  Source  Forwarder - the bundle any node from which that transmits a bundle originates.

   o  Destination - in the bundle node to which a bundle is ultimately
      destined.

   o  Forwarder - DTN.  The Node
      ID of the bundle node Bundle Protocol Agent (BPA) that forwarded sent the bundle on its
      most recent hop.

   o  Intermediate Receiver, Waypoint, or "Next Hop" - the neighboring
      bundle any node to which that
      receives a forwarder forwards bundle from a bundle. Forwarder that is not the Destination.
      The Node ID of the BPA at any such node.

   o  Path - the ordered sequence of nodes through which a bundle passes
      on its way from source Source to destination. Destination.  The path is not
      necessarily known in advance by the bundle, bundle or any bundle-aware nodes.

   The BPAs in the DTN.

   o  Security Block - a BPSec extension block in a bundle.

   o  Security Operation - the application of these terms applied a security service to a sample network topology
   is shown
      security target, notated as OP(security service, security target).
      For example, OP(confidentiality, payload).  Every security
      operation in Figure 1.  This figure shows four bundle nodes (BN1, BN2,
   BN3, BN4) residing above some transport layer(s).  Three distinct
   transport and network protocols (T1/N1, T2/N2, and T3/N3) are also
   shown.

   +---------v-|   +->>>>>>>>>>v-+     +->>>>>>>>>>v-+   +-^---------+
   | BN1     v |   | ^   BN2   v |     | ^   BN3   v |   | ^  BN4    |
   +---------v-+   +-^---------v-+     +-^---------v-+   +-^---------+
   | T1      v |   + ^  T1/T2  v |     + ^  T2/T3  v |   | ^  T3     |
   +---------v-+   +-^---------v-+     +-^---------v +   +-^---------+
   | N1      v |   | ^  N1/N2  v |     | ^  N2/N3  v |   | ^  N3     |
   +---------v-+   +-^---------v +     +-^---------v-+   +-^---------+
   |         >>>>>>>>^         >>>>>>>>>>^         >>>>>>>>^         |
   +-----------+   +------------+      +-------------+   +-----------+
   |                     |                    |                      |
   |<--  An Internet --->|                    |<--- An Internet  --->|
   |                     |                    |                      |

         Figure 1: Bundle Nodes Sitting Above the Transport Layer.

   Consider the case where BN1 originates a bundle MUST be unique, meaning that it forwards a security
      service can only be applied to
   BN2.  BN2 forwards a security target once in a bundle.
      A security operation is implemented by a security block.

   o  Security Service - the bundle to BN3, security features supported by this
      specification: integrity and BN3 forwards the confidentiality.

   o  Security Source - a bundle node that adds a security block to
   BN4.  BN1 is the source of a
      bundle.

   o  Security Target - the block within a bundle and BN4 is that receives a
      security-service as part of a security-operation.

   o  Source - the destination node which originates a bundle.  The Node ID of the
      BPA originating the bundle.  BN1

2.  Key Properties

   The application of security services in a DTN is a complex endeavor
   that must consider physical properties of the first forwarder, network, policies at
   each node, and BN2 is the first
   intermediate receiver; BN2 then becomes the forwarder, and BN3 the
   intermediate receiver; BN3 then becomes the last forwarder, and BN4
   the last intermediate receiver, as well as the destination.

   If node BN2 originates a bundle (for example, a bundle status report
   or a custodial signal), which is then forwarded on to BN3, and then
   to BN4, then BN2 is the source of the bundle (as well as being the
   first forwarder of the bundle) various application security requirements.  This
   section identifies and BN4 is the destination of the
   bundle (as well as being defines the final intermediate receiver).

   The following security-specific terminology is also defined to
   clarify security operations in this specifiation.

   o  Security Service - key properties guiding design
   decisions for the security features supported services provided by this
      specification: integrity and confidentiality.

   o specification.

2.1.  Block-Level Granularity

   Security Source - services within this specification MUST allow different
   blocks within a bundle node that adds a to have different security block services applied to a
      bundle.

   o  Security Target - the
   them.  As such, each security block within a bundle that receives a
      security-service as part of MUST be
   associated with a security-operation.

   o  Security Block - specific security operation.

   Blocks within a BPSec extension bundle represent different types of information.  The
   primary block in contains identification and routing information.  The
   payload block carries application data.  Extension blocks carry a bundle.

   o  Security Operation -
   variety of data that may augment or annotate the application payload, or
   otherwise provide information necessary for the proper processing of
   a bundle along a path.  Therefore, applying a single level and type
   of security service across an entire bundle fails to recognize that blocks in
   a bundle may represent different types of information with different
   security target, notated as OP(security service, security target). needs.

   For example, OP(confidentiality, payload).  Every security
      operation in a bundle MUST be unique, meaning that a security
      service can only be applied to a security target once in a bundle.
      A security operation is implemented by a security block.

2.  Key Properties

   The application of security services in a DTN is a complex endeavor
   that must consider physical properties of the network, policies at
   each node, and various application security requirements.  Rather
   than enumerate all potential security implementations in all
   potential DTN topologies, this specification defines a set of key
   properties of a security system.  The security primitives outlined in
   this document MUST enable the realization of these properties in a
   DTN deploying the Bundle Protocol.

2.1.  Block-Level Granularity

   Blocks within a bundle represent different types of information.  The
   primary block contains identification and routing information.  The payload block carries application data.  Extension blocks carry a
   variety of data that may augment or annotate the payload, or
   otherwise provide information necessary for the proper processing of
   a bundle along a path.  Therefore, applying a single level and type
   of security across an entire bundle fails to recognize that blocks in
   a bundle may represent different types of information with different
   security needs.

   Security services within this specification MUST provide block level
   granularity where applicable such that different blocks within a
   bundle may have different security services applied to them.

   For example, within a bundle, a payload might be encrypted to protect its contents, whereas
   contents and an extension block containing summary information
   related to the payload might be integrity signed but
   otherwise unencrypted to
   provide certain nodes waypoints access to payload-
   related payload-related data without providing
   access to the payload.

   Each security block in a bundle will be associated with a specific
   security operation.

2.2.  Multiple Security Sources

   A bundle MAY have multiple security blocks and these blocks MAY have
   different security sources.

   The Bundle Protocol allows extension blocks to be added to a bundle
   at any time during its existence in the DTN.  When a waypoint node adds a
   new extension block to a bundle, that extension block may have
   security services applied to it by that waypoint.  Similarly, a
   waypoint node may add a security service to an existing extension block,
   consistent with its security policy.  For example, a node
   representing a boundary between a trusted part of the network and an
   untrusted part of the network may wish to apply payload encryption
   for bundles leaving the trusted portion of the network.

   In each case,

   When a node other than the bundle originator may add waypoint adds a security service to the bundle and, as such, bundle, the source for waypoint
   is the security service will be different than the source of the bundle
   itself.  Security services MUST track their orginating node so as to
   properly apply policy and key selection associated with processing
   the for that service.  The security block(s) which
   represent that service at in the bundle destination.

   Referring may need to Figure 1, if the bundle that originates at BN1 is given
   security blocks by BN1, then BN1 is the record this security
   source for those
   blocks as well as being the source of the bundle.  If the bundle that
   originates at BN1 is then given destination might need this information for
   processing.  For example, a destination node might interpret policy
   as it related to security block by BN2, then BN2 is blocks as a function of the security source
   for that block even though BN1 remains the bundle
   source. block.

2.3.  Mixed Security Policy

   Different

   The security policy enforced by nodes in a the DTN may have different security related
   capabilities. MAY differ.

   Some nodes waypoints may not be security aware and will not
   understand any be able to
   process security related extension blocks.  Other nodes may
   have security policies that require evaluation of security services
   at places other than the bundle destination (such as verifying
   integrity signatures at certain waypoint nodes).  Other nodes may
   ignore any security processing if they are not the destination of the
   bundle.  The  Therefore, security services described in this specification must
   allow each of these scenarios.

   Extension blocks representing security services MUST have their block
   processing flags set such that the block will be treated
   appropriately by non-security-aware nodes.

   Extension blocks providing integrity services within a bundle MUST
   support options to allow waypoint nodes to evaluate these signatures
   if such nodes waypoints
   Some waypoints will have the proper configuraton to do so.

2.4.  User-Selected Ciphersuites

   The security policies that require evaluating
   security services defined in this specification rely on a variety even if they are not the bundle destination or the
   final intended destination of cipher suites providing the service.  For example, a waypoint
   may choose to verify an integrity signatures, ciphertext, service even though the waypoint is
   not the bundle destination and the integrity service will be needed
   by other node along the bundle's path.

   Some waypoints will determine, through policy, that they are the
   intended recipient of the security service and terminate the security
   service in the bundle.  For example, a gateway node may determine
   that, even though it is not the destination of the bundle, it should
   verify and remove a particular integrity service or attempt to
   decrypt a confidentiality service, before forwarding the bundle along
   its path.

   Some waypoints may understand security blocks but refuse to process
   them unless they are the bundle destination.

2.4.  User-Selected Cipher Suites

   The security services defined in this specification rely on a variety
   of cipher suites providing integrity signatures, cipher-text, and
   other information necessary to populate security blocks.  Users may
   wish to MAY
   select different cipher suites to implement different security services.  For
   example, some users may wish to use might prefer a SHA-256 based hash for integrity
   whereas other users may require prefer a SHA-384 hash instead.  The security
   services defined in this specification MUST provide a mechanism for
   identifying what cipher suite has been used to populate a security
   block.

2.5.  Deterministic Processing

   In all cases, the processing order of security services within

   Whenever a
   bundle node determines that it must avoid ambiguity when evaluating process more than one
   security block in a received bundle (either because the policy at a
   waypoint states that it should process security blocks or because the
   node is the bundle
   destination. destination) the order in which security blocks
   are processed MUST be deterministic.  All nodes MUST impose this same
   deterministic processing order for all security blocks.  This
   specification MUST provide provides determinism in the application and evaluation
   of security services, even when doing so results in a loss of
   flexibility.

3.  Security Blocks
3.1.  Block Definitions

   There are

   This specification defines two types of security blocks that may be included in a
   bundle.  These are block: the Block
   Integrity Block (BIB) and the Block Confidentiality Block (BCB).

      The BIB is used to ensure the integrity of its security target(s).
      The integrity information in the BIB MAY (when possible) be verified by any node
      in between the BIB security source and the bundle destination.
      Security-aware waypoints may add or remove BIBs MAY be added to, and removed from, from bundles as a matter of in
      accordance with their security policy.

      The BCB indicates that the security target(s) has been encrypted,
      in whole or in part, at the BCB security source in order to
      protect its content while in transit.  The BCB may be decrypted by
      appropriate
      security-aware nodes in the network, up to and including the
      bundle destination, as a matter of security policy.

   A

3.2.  Uniqueness

   Security operations in a bundle MUST be unique - the same security operation
   service MUST NOT be applied to a security target more than once in a
   bundle.
   For example, the two  Since a security operation is represented as a security
   block, this limits what security blocks may be added to a bundle: if
   adding a security block to a bundle would cause some other security
   block to no longer represent a unique security operation then the new
   block MUST NOT be added.

   If multiple security blocks representing the same security operations: operation
   were allowed in a bundle at the same time, there would exist
   ambiguity regarding block processing order and the property of
   deterministic processing blocks would be lost.

   Using the notation OP(service,target), several examples illustrate
   this uniqueness requirement.

   o  Signing the payload twice: The two operations OP(integrity,
      payload) and OP(integrity, payload) are considered redundant and MUST NOT appear
   together cannot both
      be present in a bundle.  However, the same bundle at the same time.

   o  Signing different blocks: The two security operations OP(integrity,
      payload) and OP(integrity, extension_block_1) MAY are not redundant
      and both may be present in the bundle.  Also, same bundle at the same time.
      Similarly, the two security operations OP(integrity, extension_block_1) and OP(integrity, extension_block_2)
      OP(integrity,extension_block_2) are unique also not redundant and may
      both appear be present in the same bundle.

   If bundle at the same security service is to time.

   o  Different Services on same block: The two operations
      OP(integrity,payload) and OP(confidentiality, payload) are not
      inherently redundant and may both be applied present in the bundle at the
      same time, pursuant to other processing rules in this
      specification.

3.3.  Target Multiplicity

   Under special circumstances, a single security block can represent
   multiple security
   targets, and cipher suite parameters for each operations as a way of reducing the overall number
   of security service are
   identical, then blocks present in a bundle.  In these circumstances,
   reducing the number of security blocks in the bundle reduces the
   amount of redundant information in the bundle.

   A set of security operations can may be represented as by a single security
   block with multiple security targets.  In such a
   case, all if and only if the following conditions are true.

   o  The security operations represented in apply the same security service.  For
      example, they are all integrity operations or all confidentiality
      operations.

   o  The cipher suite parameters and key information for the security
      operations are identical.

   o  The security source for the security operations is the same.
      Meaning the set of operations are being added/removed by the same
      node.

   o  No security operations have the same security target, as that
      would violate the need for security operations to be unique.

   o  None of the security operations conflict with security operations
      already present in the bundle.

   When representing multiple security operations in a single security
   block, the information that is common across all operations is
   represented once in the security block, and the information which is
   different (e.g., the security targets) are represented individually.
   When the security block is processed all security operations
   represented by the security block MUST be applied/evaluated together.

3.1.  Block Identification

   This specification requires at that every
   time.

3.4.  Target Identification

   A security target is a block of in the bundle to which a security
   operation
   service applies.  This target MUST be uniquely identifiable. and unambiguously
   identifiable when processing a security block.  The definition of the
   extension block header from [BPBIS] provides such a mechanism in the "Block Number" field, which provides a unique identifier field
   for a block within
   a bundle.  Within exactly this specification, purpose.  Therefore, a security target will be
   identified by its unique Block Number.

   A security block MAY apply to multiple security targets if and only
   if all cipher suite parameters, security source, and key information
   are common for the security operation.  In such in a case, the security
   block MUST contain security results for each covered security target.
   The use be represented as the Block Number of multiple the target block.

3.5.  Block Representation

   Each security targets block uses the Canonical Bundle Block Format as defined
   in a security block provides an
   efficiency mechanism so that identical ciphersuite information does
   not need to be repeated across multiple security blocks.

3.2.  Block Representation

   Each security block uses the Canonical Bundle Block Format as defined
   in [BPBIS].  That is, each [BPBIS].  That is, each security block is comprised of the
   following elements:

   o  Block Type Code

   o  Block Number

   o  Block Processing Control Flags

   o  CRC Type and CRC Field (if present)

   o  Block Data Length

   o  Block Type Specific Data Fields

   Security-specific information for a security block is captured in the
   "Block Type Specific Data Fields".

3.6.  Abstract Security Block

   The structure of the security-specific portions of a security block
   is identical for both the BIB and BCB Block Type Specific Data fields are
   identifcal and illustrated in Figure 2.  In Types.  Therefore, this figure, field names
   prefaced with
   section defines an '*' are optional Abstract Security Block (ASB) data structure and their inclusion in
   discusses the block definition, processing, and other constraints for using
   this structure.  An ASB is
   indicated by never directly instantiated within a
   bundle, it is only a mechanism for discussing the Cipher Suite Flags field.

   +=================================================
   |    Field Name       |     Field Data Type      |
   +=================================================
   | # Security Targets  | Unsigned Integer         |
   +---------------------+--------------------------+
   | Security Targets    | Array (Unsigned Integer) |
   +---------------------+--------------------------+
   | Cipher Suite ID     | Unsigned Integer         |
   +---------------------+--------------------------+
   | Cipher Suite Flags  | Unsigned Integer         |
   +---------------------+--------------------------+
   | Security Source     | URI - OPTIONAL           |
   +---------------------+--------------------------+
   | Cipher Parameters   | Byte Array - OPTIONAL    |
   +---------------------+--------------------------+
   | Security Result     | Byte Array               |
   +---------------------+--------------------------+

                   Figure 2: common aspects of
   BIB and BCB Block Structure

   Where the block fields are identified as follows.

   o  # Security Targets - security blocks.

   The number fields of security targets for this
      security block.  This value MUST the ASB SHALL be at least 1.

   o as follows, listed in the order in
   which they MUST appear.

   Security Targets - Targets:
         This array contains field identifiers the unique identifier block or blocks that are the target
         of the blocks targetted security operation(s) represented by this security operation.
         block.  Each security target MUST represent a block present in is identified as the Block Number
         of the bundle.  A security target MUST NOT block.  This field SHALL be repeated in this array.

   o represented by a CBOR
         array of data items.  Each target within this CBOR array SHALL
         be represented by a CBOR unsigned integer.  This array MUST
         have at least 1 item.

   Cipher suite ID - Identifies Suite Id:
         This field identifies the cipher suite used to implement the
         security service represented by this block and applied to each
         security target.

   o  This field SHALL be represented by a CBOR
         unsigned integer.

   Cipher suite flags - Identifies Suite Flags:
         This field identifiers which optional security block fields are present in the
         security block.  The structure of the Cipher
      Suite Flags  This field is shown in Figure 3.  The presence of an
      optional SHALL be represented as a CBOR
         unsigned integer containing a bit field is indicated by setting the value of 5 bits indicating
         the
      corresponding flag to one.  A value presence or absence of zero indicates the
      corresponding optional field is not present.  The BPSEC Cipher
      Suite Flags are defined other security block fields, as
         follows.

         Bit 1  (the most-significant bit, 0x10): reserved.

         Bit 2  (0x08): reserved.

         Bit 3  (0x04): reserved.

         Bit 4  (0x02): Security Source Present Flag.

         Bit   Bit   Bit   Bit
                7     6 5     4     3     2     1     0
             +-----------------------------------+-----+-----+
             |    reserved                       | src |parm |
             +-----------------------------------+-----+-----+
               MSB                                       LSB

                       Figure 3:  (the least-significant bit, 0x01): Cipher Suite Flags

      Where:

      *  bits 7-2 are reserved for future use.

      *  src - bit
                Parameters Present Flag.

         In this field, a value of 1 indicates whether that the Security Source is present associated
         security block field MUST be included in the security block.

      *  parm - bit  A
         value of 0 indicates whether or not that the Cipher Suite
         Parameters associated security block field is present
         MUST NOT be in the security block.

   o  (OPTIONAL)

   Security Source (URI) - (Optional Field):
         This field identifies the node Endpoint that inserted the security service
         block in the bundle.  If the security source field is not
         present then the source MAY be inferred from other information,
         such as the bundle source, source or the previous hop, or some other node as defined by
         security policy.

   o  (OPTIONAL)  This field SHALL be represented by a CBOR
         array in accordance with [BPBIS] rules for representing
         Endpoint Identifiers (EIDs).

   Cipher Suite Parameters (Byte Array) - Compound (Optional Field):
         This field of the
      following two items.

      *  Length (Unsigned Integer) - specifies the length of the next
         field, which captures the parameters data.

      *  Data (Byte Array) - A byte array encoding one or more cipher suite parameters, with each parameters that
         should be provided to security-aware nodes when processing the
         security service described by this security block.  This field
         SHALL be represented by a CBOR array.  Each entry in this array
         is a single cipher suite parameter.  A single cipher suite
         parameter SHALL also be represented as a Type-
         Length-Value (TLV) triplet, defined CBOR array comprising
         a 2-tuple of the type and value of the parameter, as follows.

         +  Type (Byte) - The

         *  Parameter Type.  This field identifiers which cipher suite
            parameter type.

         +  Length (Unsigned Integer) - The length of is being specified.  This field SHALL be
            represented as a CBOR unsigned integer.  Potential parameter
            types are described in Section 3.10.  Other specifications
            MAY define additional parameter types for use in this field.

         *  Parameter Value.  This field captures the value associated
            with this parameter.

         +  Value (Byte Array) - The  This field SHALL be represented by the
            applicable CBOR representation of the parameter value.

         See type.  These
            specifications are given in Section 3.6 3.10 for a list of parameter types
            defined in this specification.  Other specifications that
            define other parameter types MUST include the appropriate
            CBOR encoding of the parameter value.

         Therefore, this field SHALL be
         supported by BPSEC implementations.  BPSEC cipher suite
         specifications MAY define their own parameters represented as a CBOR array of
         CBOR arrays.

   Security Results:
         This field captures the results of applying a security service
         to the security targets in this security block.  This field
         SHALL be represented as a CBOR array.  Each entry in this byte array.

   o  Security Result (Byte Array) - A security result is the output array
         represents a "target list" of
      an appropriate cipher suite specific calculation (e.g., security results for a
      signature, Message Authentication Code (MAC), or cipher-text block
      key). specific
         security target.  There MUST exist be one security result "target list" for each security
         entry in the Security Targets field and target lists in the security block.  A security result is a multi-field
      component, described
         Security Results field MUST be in the same order as follows.

      *  Total Length (Unsigned Integer) - specifies the length,
         Security Targets field (e.g., the first "target list" MUST hold
         results for the first entry in
         bytes, of the remaining security result information.

      *  Results (Byte Array) - This field captures each Security Targets field, and
         so on).

         A "target list" is also represented as a CBOR array of the
         individual security
         results, catenated together, one results for each security target
         covered by the that target.  An individual
         security block.  Each result is captured by also represented as a CBOR array comprising
         the
         four-tuple of (Target, Type, Len, Value).  The meaning 2-tuple of each
         is given below.

         +  Target (Optional) (Unsigned Integer) - If the security block
            has multiple security targets, the target result type and result value, defined as
         follows.

         *  Result Type.  This field is captures the Block
            Number type of the security target to which this
            result.  Some security result field
            applies.  If types capture the security block only has primary
            output of a single cipher suite.  Other security
            target, this results contain
            additional annotative information from the cipher suite
            processing.  This field is omitted.

         +  Type (Unsigned Integer) - The type of security SHALL be represented as a CBOR
            unsigned integer.  Potential result types are described in
            Section 3.10.  Other specifications MAY define additional
            result types for use in this field.

         +  Length (Unsigned Integer) - The length

         *  Result Value.  This field captures the value associated with
            this result for this target.  This field SHALL be
            represented by the applicable CBOR representation of the
            result field.

         +  Value (Byte Array) - The results type.  These specifications are given in Section 3.10
            for result types defined in this specification.  Other
            specifications that define other result types MUST include
            the appropriate CBOR encoding of the cipher suite
            specific calculation.

3.3. result value.

3.7.  Block Integrity Block

   A BIB is an ASB a bundle extension block with the following characteristics: characteristics.

   o  The Block Type Code value MUST be 0x02. is as specified in Section 12.1.

   o  The Block Processing Control flags value can be set to whatever
      values are required by local policy.  Cipher suite designers
      should carefully consider Type Specific Data Fields follow the effect structure of setting flags that either
      discard the block or delete the bundle in the event that this
      block cannot be processed.
      ASB.

   o  A security target for a BIB listed in the Security Targets field MUST NOT
      reference a security block defined in this specification (e.g., a
      BIB or a BCB).

   o  The cipher suite ID Cipher Suite Id MUST be documented as an end-to-end
      authentication-cipher suite or as an end-to-end error-detection-
      cipher suite.

   o  An EID-reference to the security source MAY be present.  If this
      field is not present, then the security source of the block SHOULD
      be inferred according to security policy and MAY default to the
      bundle source.  The security source may also be specified as part
      of key information described in Section 3.6.

      The security result captures the result of applying the cipher
      suite calculation (e.g., the MAC or signature) to the relevant
      parts of the security target, as specified in the cipher suite
      definition.  This field MUST be present. 3.10.

   o  The cipher suite MAY process less than the entire security target.
      If the cipher suite processes less than the complete, original
      security target, the cipher suite parameters MUST specify which
      bytes of the security target are protected.

   Notes:

   o  It is RECOMMENDED that cipher suite designers carefully consider
      the effect of setting flags that either discard the block or
      delete the bundle in the event that this block cannot be
      processed.

   o  Since OP(integrity, target) is allowed only once in a bundle per
      target, it is RECOMMENDED that users wishing to support multiple
      integrity signatures for the same target define a multi-signature
      cipher suite.

   o  For some cipher suites, (e.g., those using asymmetric keying to
      produce signatures or those using symmetric keying with a group
      key), the security information MAY be checked at any hop on the
      way to the destination that has access to the required keying
      information, in accordance with Section 3.5. 3.9.

   o  The use of a generally available key is RECOMMENDED if custodial
      transfer is employed and all nodes SHOULD verify the bundle before
      accepting custody.

3.4.

3.8.  Block Confidentiality Block

   A BCB is an ASB a bundle extension block with the following characteristics: characteristics.

      The Block Type Code value MUST be 0x03. is as specified in Section 12.1.

      The Block Processing Control flags value can be set to whatever
      values are required by local policy, except that this block MUST
      have the "replicate in every fragment" flag set if the target of
      the BCB is the Payload Block.  Having that BCB in each fragment
      indicates to a receiving node that the payload portion of each
      fragment represents cipher-text.  Cipher suite designers should
      carefully consider

      The Block Type Specific Data Fields follow the effect structure of setting flags that either discard the block or delete the bundle in the event that this block cannot
      be processed.
      ASB.

      A security target for a BCB listed in the Security Targets field MAY
      reference the payload block, a non-security extension block, or a
      BIB block.  A security target
      in a BCB MUST NOT be include another BCB. BCB as a security
      target.  A BCB MUST NOT target the primary block.

      The cipher suite ID Cipher Suite Id MUST be documented as a confidentiality cipher
      suite.

      Any additional bytes generated as a result of encryption and/or
      authentication processing of from applying the cipher suite to a
      security target SHOULD (such as additional authenticated text) MAY be
      placed in an "integrity check value" field (see Section 3.6) or other
      such appropriate area in the security result of the BCB.

      An EID-reference to the security source MAY be (e.g., an Integrity Check
      Value) in accordance with cipher suite and security policy.

      An EID-reference to the security source MAY be present.  If this
      field is not present, then the security source of the block SHOULD
      be inferred according to security policy and MAY default to the
      bundle source.  The security source may also be specified as part
      of key information described in Section 3.6.

      The security result MUST be present in the BCB.  This compound
      field normally contains fields such as an encrypted bundle
      encryption key and/or authentication tag. 3.10.

   The BCB modifies the contents of its security target. target(s).  When a BCB
   is applied, the security target body data are encrypted "in-place".
   Following encryption, the security target body data Block Type Specific Data
   Fields contains cipher-
   text, cipher-text, not plain-text.  Other security target block fields (such as
   type, processing control flags, and length)
   remain unmodified. unmodified, with the exception of the Block Data Length field,
   which may be changed if the BCB is allowed to change the length of
   the block (see below).

   Fragmentation, reassembly, and custody transfer are adversely
   affected by a change in size of the payload block due to ambiguity
   about what byte range of the block is actually in any particular
   fragment.  Therefore, when the security target of a BCB is the bundle
   payload, the BCB MUST NOT alter the size of the payload block body
   data.
   Cipher suites SHOULD place any block expansion, such as
   authentication tags (integrity check values) and any padding
   generated by a block-mode cipher, into an integrity check value item
   in the security result field (see Section 3.6) of the BCB.  This "in-
   place" "in-place" encryption allows fragmentation, reassembly,
   and custody transfer to operate without knowledge of whether or not
   encryption has occurred.

   If a BCB cannot alter the size of the security target (e.g., the
   security target is the payload block or block length modifications
   are disallowed by policy) then differences in the size of the cipher-
   text and plain-text MUST be handled in the following way.  If the
   cipher-text is shorter in length than the plain-text, padding must be
   used in accordance with the cipher suite policy.  If the cipher-text
   is larger than the plain-text, overflow bytes MUST be placed in
   overflow parameters in the Security Result field.

   Notes:

   o  It is RECOMMENDED that cipher suite designers carefully consider
      the effect of setting flags that either discard the block or
      delete the bundle in the event that this block cannot be
      processed.

   o  The cipher suite MAY process less than the entire original
      security target body data.  If the cipher suite processes less
      than the complete, original security target body data, the BCB for
      that security target MUST specify, as part of the cipher suite
      parameters, which bytes of the body data are protected.

   o  The BCB's "discard" flag may BCB block processing control flags MAY be set independently
      from its
      security target's "discard" flag.  Whether or not the BCB's
      "discard" flag is set is an implementation/policy decision for processing control flags of the
      encrypting node.  (The "discard" flag is more properly called the
      "Discard if block cannot security target(s).  The
      setting of such flags SHOULD be processed" flag.) an implementation/policy decision
      for the encrypting node.

   o  A BCB MAY include information as part of additional authenticated
      data to address parts of the target block, such as EID references, block that are not converted
      to cipher-text.

3.5.

3.9.  Block Interactions

   The security block types defined in this specification are designed
   to be as independent as possible.  However, there are some cases
   where security blocks may share a security target creating processing
   dependencies.

   If confidentiality is being applied to a target that already has
   integrity applied to it, then an undesirable condition occurs where a
   security aware intermediate node waypoint would be unable to check the integrity result
   of a block because the block contents have been encrypted after the
   integrity signature was generated.  To address this concern, the
   following processing rules MUST be followed.

   o  If confidentiality is to be applied to a target, it MUST also be
      applied to any integrity operation already defined for that
      target.  This means that if a BCB is added to encrypt a block,
      another BCB MUST also be added to encrypt a BIB also targeting
      that block.

   o  An integrity operation MUST NOT be applied to a security target if
      a BCB in the bundle shares the same security target.  This
      prevents ambiguity in the order of evaluation when receiving a BIB
      and a BCB for a given security target.

   o  An integrity value MUST NOT be evaluated if the BIB providing the
      integrity value is the security target of an existing BCB block in
      the bundle.  In such a case, the BIB data contains cipher-text as
      it has been encrypted.

   o  An integrity value MUST NOT be evaluated if the security target of
      the BIB is also the security target of a BCB in the bundle.  In
      such a case, the security target data contains cipher-text as it
      has been encrypted.

   o  As mentioned in Section 3.3, 3.7, a BIB MUST NOT have a BCB as its
      security target.  BCBs may embed integrity results as part of
      cipher suite parameters.
      security results.

   These restrictions on block interactions impose a necessary ordering
   when applying security operations within a bundle.  Specifically, for
   a given security target, BIBs MUST be added before BCBs.  This
   ordering MUST be preserved in cases where the current BPA is adding
   all of the security blocks for the bundle or whether the BPA is a
   waypoint adding new security blocks to a bundle that already contains
   security blocks.

3.6.

3.10.  Parameters and Result Fields

   Various cipher suites include several items in the cipher Types

   Cipher suite parameters and/or and security result fields.  Which items MAY appear is
   defined results may capture multiple
   types of information in a security block.  This section identifies a
   set of parameters and results that are available in any BPSec
   implementation for use by the particular any cipher suite description. suite.  Individual cipher suites
   MAY define additional parameters and results.  A cipher suite MAY support several
   include multiple instances of the same type within of parameter or result in
   a single security block.

   Each item is

   Parameters and results are represented as a type-length-value.  Type is using CBOR, and any
   identification of a single
   byte indicating the item.  Length is new parameter or result type MUST include how the count
   value of data bytes to
   follow, and is an Unsigned Integer.  Value is the data content of type will be represented using the
   item.

   Item types, name, and descriptions CBOR specification.
   Types themselves are always represented as a CBOR unsigned integer.

   Cipher suite parameter types, as defined by this specification, are
   as follows.

                       Cipher suite parameters and result fields.

   +-------+----------------+-----------------------------+------------+ Suite Parameter Types.

   +------+----------------+--------------------------+----------------+
   | Type |      Name      | Description              | Field CBOR           |
   +-------+----------------+-----------------------------+------------+
   |   0      |    Reserved                |                          | Representation |
   +-------+----------------+-----------------------------+------------+
   +------+----------------+--------------------------+----------------+
   |   1  0   | Initialization | A random value, typically          | Cipher Byte String    |
   |      |     Vector (IV)     | typically eight to sixteen bytes.     | Suite       |                |
   |      |                | Parameters |
   +-------+----------------+-----------------------------+------------+
   |   2   |    Reserved    | sixteen bytes.           |                |
   +-------+----------------+-----------------------------+------------+
   +------+----------------+--------------------------+----------------+
   |   3  1   |      Key       | Material encoded or      | Cipher Byte String    |
   |      |  Information   | protected by the key     | Suite                |
   |      |                | management system and used    | Parameters                |
   |      |                | used to transport an ephemeral     |                |
   |      |                | ephemeral key protected by a long-  |                |
   |      |                | term by a long-term key.      |                |
   +-------+----------------+-----------------------------+------------+
   +------+----------------+--------------------------+----------------+
   |   4  2   | Content Range  | Pair of Unsigned Integers         | Cipher CBOR Array     |
   |      |                | Integers (offset,length) specifying | Suite comprising a   |
   |      |                | specifying the range of payload bytes  | Parameters 2-tuple of     |
   |      |                | payload bytes to which   | CBOR unsigned  |
   |      |                | an operation applies.    | integers.      |
   |      |                | applies. The offset MUST be the   |                |
   |      |                | the offset within the        |                |
   |      |                | original bundle, even if |                |
   |      |                | the current bundle is a  |                |
   |      |                | fragment.                |                |
   +-------+----------------+-----------------------------+------------+
   |   5   |   Integrity
   +------+----------------+--------------------------+----------------+
   | Result of BIB digest or  3   | Security      Salt      | An IV-like value used by | Byte Array     |   Signatures
   | other signing operation.      | Results                |
   +-------+----------------+-----------------------------+------------+ certain confidentiality  |                |
   |      |                | suites.                  |                |
   +------+----------------+--------------------------+----------------+
   | 4-31 |    Reserved    | Reserve for future BPSec |                |
   |   6      |                | protocol expansion       |                |
   +------+----------------+--------------------------+----------------+
   |  >=  |   Unassigned   | Unassigned by this       |                |
   +-------+----------------+-----------------------------+------------+
   |   7  32  |      Salt                | An IV-like value used specification. Can be    |                |
   |      |                | assigned by cipher suite | Cipher                |
   |      |                | certain confidentiality specifications.          | Suite                |
   +------+----------------+--------------------------+----------------+

                                  Table 1

   Security result parameter types, as defined by this specification,
   are as follows.

                          Security Result Types.

   +------+----------------+--------------------------+----------------+
   | Type |      Name      | Description              | CBOR           | suites.
   | Parameters      |
   +-------+----------------+-----------------------------+------------+                |   8                          | Representation |
   +------+----------------+--------------------------+----------------+
   |  0   |   Integrity    | Result of BIB digest or  | Byte String    |
   |      |   Signatures   | other signing operation. |                |
   +------+----------------+--------------------------+----------------+
   |  1   | BCB Integrity  | Output from certain      | Security Byte String    |
   |      |  Check Value   | confidentiality cipher   | Results                |
   |      |    (ICV) /     | suite operations to be used   |                |
   |      | Authentication | used at the destination to  |                |
   |      |      Tag       | to verify that the protected       |                |
   |      |                | protected data has not   |                |
   |      |                | been modified. This      |                |
   |      |                | This value MAY contain        |                |
   |      |                | padding if required by the   |                |
   |      |                | the cipher suite.        |                |
   +-------+----------------+-----------------------------+------------+
   +------+----------------+--------------------------+----------------+
   | 9-255 2-31 |    Reserved    | Reserve for future BPSec |                |
   |      |                | protocol expansion       |                |
   +------+----------------+--------------------------+----------------+
   |  >=  |   Unassigned   | Unassigned by this       |                |
   |  32  |                | specification. Can be    |                |
   |      |                |
   +-------+----------------+-----------------------------+------------+ assigned by cipher suite |                |
   |      |                | specifications.          |                |
   +------+----------------+--------------------------+----------------+

                                  Table 1

3.7. 2

3.11.  BSP Block Example

   An example of BPSec blocks applied to a bundle is illustrated in
   Figure 4. 1.  In this figure the first column represents blocks within a
   bundle and the second column represents a unique identifier for each
   block, suitable for use as the security target of a BPSec security
   block.  Since Block Number for the mechanism and format of a security target is not
   specified in this document,
   block, using the terminology B1...Bn is used to
   identify blocks in the bundle for the purposes purpose of illustration.

            Block in Bundle            ID
   +===================================+====+
   |         Primary Block             | B1 |
   +-----------------------------------+----+
   |             BIB                   | B2 |
   |  OP(integrity, target=B1)         |    |
   +-----------------------------------+----+
   |             BCB                   | B3 |
   |  OP(confidentiality, target=B4)   |    |
   +-----------------------------------+----+
   |      Extension Block              | B4 |
   +-----------------------------------+----+
   |             BIB                   | B5 |
   |  OP(integrity, target=B6)         |    |
   +-----------------------------------+----+
   |      Extension Block              | B6 |
   +-----------------------------------+----+
   |             BCB                   | B7 |
   |  OP(confidentiality,target=B8,B9) OP(confidentiality,targets=B8,B9) |    |
   +-----------------------------------+----+
   |   BIB  (encrypted by B7)          | B8 |
   |  OP(integrity, target=B9)         |    |
   +-----------------------------------+----|
   |         Payload Block             | B9 |
   +-----------------------------------+----+

                   Figure 4: 1: Sample Use of BSP BPSec Blocks

   In this example a bundle has four non-security-related blocks: the
   primary block (B1), three two extension blocks (B4,B6), and a payload block
   (B9).  The following security applications are applied to this
   bundle.

   o  An integrity signature applied to the canonicalized primary block.
      This is accomplished by a single BIB (B2).

   o  Confidentiality for the first extension block (B4).  This is
      accomplished by a BCB block (B3).

   o  Integrity for the second extension block (B6).  This is
      accomplished by a BIB block (B5).  NOTE: If the extension block B6
      contains a representation of the serialized bundle (such as a hash
      over all blocks in the bundle at the time of its last
      transmission) then the BIB block is also providing an
      authentication service from the prior BPSEC-BPA to this BPSEC-BPA. service.

   o  An integrity signature on the payload (B10).  This is accomplished
      by a BIB block (B8).

   o  Confidentiality for the payload block and it's integrity
      signature.  This is accomplished by a BCB block, B7, encrypting B8
      and B9.

4.  Canonical Forms

   By definition, an integrity  In this case, the security source, key parameters, and
      service determines whether any aspect of are identical, so a single security block MAY be used for
      this purpose, rather than requiring two BCBs one to encrypt B8 and
      one to encrypt B9.

4.  Canonical Forms

   By definition, an integrity service determines whether any aspect of
   a block was changed from the moment the security service was applied
   at the security source until the point of current evaluation.  To
   successfully verify the integrity of a block, the data passed to the
   verifying cipher suite MUST be the same bits, in the same order, as
   those passed to the signature-generating cipher suite at the security
   source.

   However, [BPBIS] does not specify a single on-the-wire encoding of
   bundles.  In cases where a security source generates a different
   encoding than that used at a receiving node, care MUST be taken to
   ensure that the inputs to cipher suites at the receiving node is a
   bitwise match to inputs provided at the security source.

   This section provides guidance on how to create a canonical form for
   each type of block in a bundle.  This form MUST be used when
   generating inputs to cipher suites for use by BPSec blocks.

   This specification does not define any security operation over the
   entire bundle and, therefore, provides no canonical form for a
   serialized bundle.

4.1.  Technical Notes

   The following technical considerations hold for all canonicalizations
   in this section.

   o  Any numeric fields defined as variable-length MUST be expanded to
      their "unpacked" form.  For example, largest unpacked form before being used by a cipher suite.
      If a field does not specify a maximum size, a 32-bit maximum size of 32
      bits for integer value MUST and 64 bits for floating point values SHALL be unpacked to a four-byte representation.

   o  Each block encoding MUST follow the CBOR encodings provided in
      [BPBISCBOR].
      assumed.

   o  Canonical forms are not transmitted, they are used to generate
      input to a cipher suite for secuity security processing at a security-aware security-
      aware node.

   o  Reserved flags MUST NOT be included in any canonicalization as it
      is not known if those flags will chaneg change in transit.

   o  These canonicalization algorithms assume that endpoint Endpoint IDs
      themselves are immutable do not
      change from the time at which a security source adds a security
      block to a bundle and they are unsuitable for use in
      environments where the time at which a node processes that assumption might be violated.
      security block.

   o  Cipher suites MAY define their own canonicalization algorithms and
      require the use of those algorithms over the ones provided in this
      specification.  In the event of conflicting canonicalization
      algorithms, cipher suite algorithms take precedence over this
      specification.

4.2.  Primary Block Canonicalization

   The canonicalization of the primary block canonical form is the same as the CBOR encoding of
   the block, specified in [BPBIS]
   with certain modifications to account for allowed block
   changes as the bundle traverses the DTN.  The fields that compromise the primary block, and any special considerations for their
   representation in a canonical form, are as follows.

   o  The Version field is included, without modification. following exceptions.

   o  The following Bundle Processing Control Flags field is used, with modification.
      Certain bundle processing flags MAY change as a
      bundle transits the DTN without indicating an integrity error.  These flags, which
      are identified below, error and,
      therefore, MUST NOT be represented included in the canonicalized
      form canonicalization of the bundle processing flags and, instead, be represented
      by the bit 0.

      *  Reserved flags.
      primary block.

      *  Bundle is a Fragment flag.

   o  The CRC Type, Destination EID, Source Node ID, Report-To EID,
      Creation Timestamp, and Lifetime fields are included, without
      modification.

   o  The fragment ID field MAY change if fragment.  (Bit 15, 0x0001)

      *  Custody transfer requested for this bundle.  (Bit 12, 0x0008)

      *  Reserved (Bits 0-2, 0xE000)

      Regardless of the bundle is fragmented value of these flags in
      transit and, as such, this field the primary block, they
      MUST NOT be included in the
      canonicalization. set to 0 when canonicalized for security processing.

   o  The CRC field MAY change at each hop - for example, if a bundle
      becomes fragmented, each fragment will have a different CRC value
      from the original signed primary block.  As such, this field MUST
      NOT be included in the canonicalization.

4.3.  Non-Primary-Block Canonicalization

   All non-primary blocks (NPBs) in [BPBIS] share the same block structure and should be are
   canonicalized as specified in [BPBIS] with the same way.

   Canonicalization for NPBs is dependent on whether following exceptions.

   o  If the security
   operation service being performed is integrity or confidentiality.  Integrity
   operations consider every field in the block, whereas confidentiality
   operations only consider the block-type-specific data.  Since
   confidentiality is applied to hide information (replacing plaintext
   with ciphertext) it provides no benefit to include in the is a confidentiality calculation information that MUST remain readable,
   such as block fields other than service, then
      the block-type-specific data.

   The fields that comprise a NPB, Block Type Code, Block Number, Block Processing Control Flags,
      CRC Type and any special considerations for
   their representation CRC Field (if present), and Block Data Length fields
      MUST NOT be included in a canonical form, the canonicalization.  Confidentiality
      services are as follows.

   o  The used to convert the Block Type Code field is included, without modification, for
      integrity operations and omitted for confidentiality operations.

   o  The Block Number field is included, without modification, for
      integrity operations and omitted for confidentiality operations. Specific Data Fields
      from plain-text to cipher-text.

   o  The Block Processing Control Flags field Type Specific Data Field is included, without
      modification, for both integrity operations and omitted for confidentiality operations, services,
      with the exception of reserved flags
      which are treated as 0 in both cases.

   o  The CRC type and CRC fields are included, without modification,
      for integrity operations and omitted for confidentiality
      operations.

   o  The Block Type Specific Data field is included, without
      modification, for both integrity and confidentiality operations,
      with the exception that that in some cases only a portion of the
      payload data is to be processed.  In such a case, only those bytes
      are included in the canonical form and additional cipher suite
      parameters are required to specify which part of the field is
      included.

5.  Security Processing

   This section describes the security aspects of bundle processing.

5.1.  Bundles Received from Other Nodes

   Security blocks MUST be processed in a specific order when received
   by a security-aware node.  The processing order is as follows.

   o  All BCB blocks in the bundle MUST be evaluated prior to evaluating
      any BIBs in the bundle.  When BIBs and BCBs share a security
      target, BCBs MUST be evaluated first and BIBs second.

5.1.1.  Receiving BCB Blocks

   If a received bundle contains a BCB, the receiving node MUST
   determine whether it has the responsibility of decrypting the BCB
   security target and removing the BCB prior to delivering data to an
   application at the node or forwarding the bundle.

   If the receiving node is the destination of the bundle, the node MUST
   decrypt any BCBs remaining in the bundle.  If the receiving node is
   not the destination of the bundle, the node MAY decrypt the BCB if
   directed to do so as a matter of security policy.

   If the security policy of a security-aware node specifies that a
   bundle should have applied confidentiality to a specific security
   target and no such BCB is present in the bundle, then the node MUST
   process this security target in accordance with the security policy.
   This MAY involve removing the security target from the bundle.  If
   the removed security target is the payload block, the bundle MAY be
   discarded.

   If the relevant parts of an encrypted payload block cannot be
   decrypted (i.e., the decryption key cannot be deduced or decryption
   fails), then the bundle MUST be discarded and processed no further.
   If an encrypted security target other than the payload block cannot
   be decrypted then the associated security target and all security
   blocks associated with that target MUST be discarded and processed no
   further.  In both cases, requested status reports (see [BPBIS]) MAY
   be generated to reflect bundle or block deletion.

   When a BCB is decrypted, the recovered plain-text MUST replace the
   cipher-text in the security target body data Block Type Specific Data Fields.
   If the Block Data Length field was modified at the time of encryption
   it MUST be updated to reflect the decrypted block length.

   If a BCB contains multiple security targets, all security targets
   MUST be processed if when the BCB is processed by the Node.  The effect of
   this is to processed.  Errors and other
   processing steps SHALL be the same made as if each security target had been
   represented by an individual BCB with a single security target.

5.1.2.  Receiving BIB Blocks

   If a received bundle contains a BIB, the receiving node MUST
   determine whether it has the final responsibility of verifying the
   BIB security target and whether to remove the BIB removing it prior to delivering data to an
   application at the node or forwarding the bundle.  If a BIB check
   fails, the security target has failed to authenticate and the
   security target SHALL be processed according to the security policy.
   A bundle status report indicating the failure MAY be generated.
   Otherwise, if the BIB verifies, the security target is ready to be
   processed for delivery.

   A BIB MUST NOT be processed if the security target of the BIB is also
   the security target of a BCB in the bundle.  Given the order of
   operations mandated by this specification, when both a BIB and a BCB
   share a security target, it means that the security target MUST have
   been encrypted after it was integrity signed and, therefore, the BIB
   cannot be verified until the security target has been decrypted by
   processing the BCB.

   If the security policy of a security-aware node specifies that a
   bundle should have applied integrity to a specific security target
   and no such BIB is present in the bundle, then the node MUST process
   this security target in accordance with the security policy.  This
   MAY involve removing the security target from the bundle.  If the
   removed security target is the payload or primary block, the bundle
   MAY be discarded.  This action may occur at any node that has the
   ability to verify an integrity signature, not just the bundle
   destination.

   If the bundle has a BIB and the receiving node is the destination for does not have the bundle, final responsibility of
   verifying the node MUST BIB it MAY still attempt to verify the security target in accordance
   with BIB to prevent
   the cipher suite specification. needless forwarding of corrupt data.  If a BIB the check fails, the
   node SHALL process the security target has failed to authenticate and the security target
   SHALL be processed according to the security policy.  A bundle status
   report indicating the failure MAY be generated.  Otherwise, if the
   BIB verifies, the security target is ready to be processed for
   delivery.

   If the bundle has a BIB and the receiving node is not the bundle
   destination, the receiving node MAY attempt to verify the value in
   the security result field.  If the check fails, the node SHALL
   process the security target in accordance in accordance to local
   security policy.  It is RECOMMENDED that if a payload integrity check
   fails at a waypoint that it is processed in the same way as if the
   check fails at the destination.  If the check passes, the node MUST
   NOT remove the BIB prior to forwarding.

   If a BIB contains multiple security targets, all security targets
   MUST be processed if the BIB is processed by the Node.  The effect of
   this is to  Errors and
   other processing steps SHALL be the same made as if each security target had
   been represented by an individual BIB with a single security target.

5.2.  Bundle Fragmentation and Reassembly

   If it is necessary for a node to fragment a bundle payload, and
   security services have been applied to that bundle, the fragmentation
   rules described in [BPBIS] MUST be followed.  As defined there and repeated
   summarized here for completeness, only the payload block may be
   fragmented; security blocks, like all extension blocks, can never be
   fragmented.

   Due to the complexity of bundle payload block fragmentation, including the
   possibility of fragmenting bundle payload block fragments, integrity and
   confidentiality operations are not to be applied to a bundle
   representing a fragment (i.e., fragment.  Specifically, a BCB or BIB MUST NOT be
   added to a bundle whose "bundle if the "Bundle is a Fragment" flag is set in the
   Bundle Processing Control Flags field).
   Specifically, a BCB or BIB MUST NOT be added to a bundle fragment,
   even if field.

   Security processing in the security target presence of the security payload block is not the payload.
   When integrity and confidentiality must fragmentation
   MAY be applied to a fragment, we
   RECOMMEND that handled by other mechanisms outside of the BPSec protocol or
   by applying BPSec blocks in coordination with an encapsulation be used instead.
   mechanism.

6.  Key Management

   Key management

   There exist a myriad of ways to establish, communicate, and otherwise
   manage key information in delay-tolerant networks a DTN.  Certain DTN deployments might
   follow established protocols for key management whereas other DTN
   deployments might require new and novel approaches.  BPSec assumes
   that key management is recognized handled as a
   difficult topic separate part of network design
   and is one that this specification does not attempt
   to solve. neither defines nor requires a specific key
   management strategy.

7.  Security Policy Considerations

   When implementing BPSec, several policy decisions must be considered.
   This section describes key policies that affect the generation,
   forwarding, and receipt of bundles that are secured using this
   specification.  No single set of policy decisions is envisioned to
   work for all secure DTN deployments.

   o  If a bundle is received that contains more than one security
      operation, in violation of BPSec, then the BPA must determine how
      to handle this bundle.  The bundle may be discarded, the block
      affected by the security operation may be discarded, or one
      security operation may be favored over another.

   o  BPAs in the network MUST understand what security operations they
      should apply to bundles.  This decision may be based on the source
      of the bundle, the destination of the bundle, or some other
      information related to the bundle.

   o  If an intermediate receiver a waypoint has been configured to add a security operation to a
      bundle, and the received bundle already has the security operation
      applied, then the receiver MUST understand what to do.  The
      receiver may discard the bundle, discard the security target and
      associated BPSec blocks, replace the security operation, or some
      other action.

   o  It is recommended that security operations only be applied to the
      payload block, the primary block, and any block-types specifically
      identified in the security policy.
      blocks that absolutely need them.  If a BPA were to apply security
      operations such as integrity or confidentiality to every block in
      the bundle, regardless of the block type, need, there could be downstream errors
      processing blocks whose contents must be inspected or changed at
      every hop in along the network path.

   o  Adding a BIB to a security target that has already been encrypted
      by a BCB is not allowed.  Therefore, we recommend three methods to
      add an integrity signature  If this condition is likely to an encrypted security target. be
      encountered, there are (at least) three possible policies that
      could handle this situation.

      1.  At the time of encryption, an integrity signature may be
          generated and added to the BCB for the security target as
          additional information in the security result field.

      2.  The encrypted block may be replicated as a new block and
          integrity signed.

      3.  An encapsulation scheme may be applied to encapsulate the
          security target (or the entire bundle) such that the
          encapsulating structure is, itself, no longer the security
          target of a BCB and may therefore be the security target of a
          BIB.

8.  Security Considerations

   Given the nature of delay-tolerant networking DTN applications, it is expected that bundles may
   traverse a variety of environments and devices which each pose unique
   security risks and requirements on the implementation of security
   within BPSEC. BPSec.  For these reasons, it is important to introduce key
   threat models and describe the roles and responsibilities of the BPSEC
   BPSec protocol in protecting the confidentiality and integrity of the
   data against those threats
   throughout the DTN. threats.  This section provides additional
   discussion on security threats that BPSEC BPSec will face and describe in additional
   detail describes how BPSEC
   BPSec security mechanisms operate to mitigate these threats.

   It should be noted that BPSEC addresses only the security of data
   traveling over the DTN, not the underlying DTN itself.  Additionally,
   BPSEC
   BPSec addresses neither the fitness of externally-defined
   cryptographic methods nor the security of their implementation.  It
   is the responsibility of the BPSEC BPSec implementer that appropriate
   algorithms and methods are chosen.  Furthermore, the BPSEC BPSec protocol
   does not address threats which share computing resources with the DTN
   and/or BPSEC BPSec software implementations.  These threats may be
   malicious software or compromised libraries which intend to intercept
   data or recover cryptographic material.  Here, it is the
   responsibility of the BPSEC BPSec implementer to ensure that any
   cryptographic material, including shared secret or private keys, is
   protected against access within both memory and storage devices.

   The threat model described here is assumed to have a set of
   capabilities identical to those described by the Internet Threat
   Model in [RFC3552], but the BPSEC BPSec threat model is scoped to
   illustrate threats specific to BPSEC BPSec operating within DTN
   environments and therefore focuses on man-in-the-middle (MITM)
   attackers.

8.1.  Attacker Capabilities and Objectives

   BPSEC

   BPSec was designed to protect against MITM threats which may have
   access to a bundle during transit from its source, Alice, to its
   destination, Bob.  A MITM node, Mallory, is a non-cooperative node
   operating on the DTN between Alice and Bob that has the ability to
   receive bundles, examine bundles, modify bundles, forward bundles,
   and generate bundles at will in order to compromise the
   confidentiality or integrity of data within the DTN.  For the
   purposes of this section, any MITM node is assumed to effectively be
   security-aware even if it does not implement the BPSec protocol.
   There are three classes of MITM nodes which are differentiated based
   on their access to cryptographic material:

   o  Unprivileged Node: Mallory has not been provisioned within the
      secure environment and only has access to cryptographic material
      which has been publicly-shared.

   o  Legitimate Node: Mallory is within the secure environment and
      therefore has access to cryptographic material which has been
      provisioned to Mallory (i.e., K_M) as well as material which has
      been publicly-shared.

   o  Privileged Node: Mallory is a privileged node within the secure
      environment and therefore has access to cryptographic material
      which has been provisioned to Mallory, Alice and/or Bob (i.e.

      K_M, K_A, and/or K_B) as well as material which has been publicly-
      shared.

   If Mallory is operating as a privileged node, this is tantamount to
   compromise; BPSec does not provide mechanisms to detect or remove
   Mallory from the DTN or BPSec secure environment.  It is up to the
   BPSec implementer or the underlying cryptographic mechanisms to
   provide appropriate capabilities if they are needed.  It should also
   be noted that if the implementation of BPSec uses a single set of
   shared cryptographic material for all nodes, a legitimate node is
   equivalent to a privileged node because K_M == K_A == K_B.

   A special case of the legitimate node is when Mallory is either Alice
   or Bob (i.e., K_M == K_A or K_M == K_B).  In this case, Mallory is
   able to impersonate traffic as either Alice or Bob, which means that
   traffic to and from that node can be decrypted and encrypted,
   respectively.  Additionally, messages may be signed as originating
   from one of the endpoints.

8.2.  Attacker Behaviors and BPSec Mitigations

8.2.1.  Eavesdropping Attacks

   Once Mallory has received a bundle, she is able to examine the
   contents of that bundle and attempt to recover any protected data or
   cryptographic keying material from the blocks contained within.  The
   protection mechanism that BPSec provides against this action is the
   BCB, which encrypts the contents of its security target, providing
   confidentiality of the data.  Of course, it should be assumed that
   Mallory is able to attempt offline recovery of encrypted data, so the
   cryptographic mechanisms selected to protect the data should provide
   a suitable level of protection.

   When evaluating the risk of eavesdropping attacks, it is important to
   consider the lifetime of bundles on a DTN.  Depending on the network,
   bundles may persist for days or even years.  If a bundle does persist
   on the network for years and the cipher suite used for a BCB provides
   inadequate protection, Mallory may be able to recover the protected
   data before that bundle reaches its intended destination.

8.2.2.  Modification Attacks

   As a node participating in the DTN between Alice and Bob, Mallory
   will also be able to modify the received bundle, including non-BPSec
   data such as the primary block, payload blocks, or block processing
   control flags as defined in [BPBIS].  Mallory will be able to
   undertake activities which include modification of data within the
   blocks, replacement of blocks, addition of blocks, or removal of
   blocks.  Within BPSec, both the BIB and BCB provide integrity
   protection mechanisms to detect or prevent data manipulation attempts
   by Mallory.

   The BIB provides that protection to another block which is its
   security target.  The cryptographic mechansims mechanisms used to generate the
   BIB should be strong against collision attacks and Mallory should not
   have access to the cryptographic material used by the originating
   node to generate the BIB (e.g., K_A).  If both of these conditions
   are true, Mallory will be unable to modify the security target or the
   BIB and lead Bob to validate the security target as originating from
   Alice.

   Since BPSec security operations are implemented by placing blocks in
   a bundle, there is no in-band mechanism for detecting or correcting
   certain cases where Mallory removes blocks from a bundle.  If Mallory
   removes a BCB block, but keeps the security target, the security
   target remains encrypted and there is a possibility that there may no
   longer be sufficient information to decrypt the block at its
   destination.  If Mallory removes both a BCB (or BIB) and its security
   target there is no evidence left in the bundle of the security
   operation.  Similarly, if Mallory removes the BIB but not the
   security target there is no evidence left in the bundle of the
   security operation.  In each of these cases, the implementation of
   BPSec MUST be combined with policy configuration at endpoints in the
   network which describe the expected and required security operations
   that must be applied on transmission and are expected to be present
   on receipt.  This or other similar out-of-band information is
   required to correct for removal of security information in the
   bundle.

   A limitation of the BIB may exist within the implementation of BIB
   validation at the destination node.  If Mallory is a legitimate node
   within the DTN, the BIB generated by Alice with K_A can be replaced
   with a new BIB generated with K_M and forwarded to Bob.  If Bob is
   only validating that the BIB was generated by a legitimate user, Bob
   will acknowledge the message as originating from Mallory instead of
   Alice.  In order to provide verifiable integrity checks, both a BIB
   and BCB should be used.  Alice creates a BIB with the protected data
   block as the security target and then creates a BCB with both the BIB
   and protected data block as its security targets.  In this
   configuration, since Mallory is only a legitimate node and does not
   have access to Alice's key K_A, Mallory is unable to decrypt the BCB
   and replace the BIB.

8.2.3.  Topology Attacks

   If Mallory is in a MITM position within the DTN, she is able to
   influence how any bundles that come to her may pass through the
   network.  Upon receiving and processing a bundle that must be routed
   elsewhere in the network, Mallory has three options as to how to
   proceed: not forward the bundle, forward the bundle as intended, or
   forward the bundle to one or more specific nodes within the network.

   Attacks that involve re-routing the packets throughout the network
   are essentially a special case of the modification attacks described
   in this section where the attacker is modifying fields within the
   primary block of the bundle.  Given that BPSec cannot encrypt the
   contents of the primary block, alternate methods must be used to
   prevent this situation.  These methods MAY include requiring BIBs for
   primary blocks, using encapsulation, or otherwise strategically
   manipulating primary block data.  The specifics of any such
   mitigation technique are specific to the implementation of the
   deploying network and outside of the scope of this document.

   Furthermore, routing rules and policies may be useful in enforcing
   particular traffic flows to prevent topology attacks.  While these
   rules and policies may utilize some features provided by BPSec, their
   definition is beyond the scope of this specification.

8.2.4.  Message Injection

   Mallory is also able to generate new bundles and transmit them into
   the DTN at will.  These bundles may either be copies or slight
   modifications of previously-observed bundles (i.e., a replay attack)
   or entirely new bundles generated based on the Bundle Protocol,
   BPSec, or other bundle-related protocols.  With these attacks
   Mallory's objectives may vary, but may be targeting either the bundle
   protocol or application-layer protocols conveyed by the bundle
   protocol.

   BPSec relies on cipher suite capabilities to prevent replay or forged
   message attacks.  A BCB used with appropriate cryptographic
   mechanisms (e.g., a counter-based cipher mode) may provide replay
   protection under certain circumstances.  Alternatively, application
   data itself may be augmented to include mechanisms to assert data
   uniqueness and then protected with a BIB, a BCB, or both along with
   other block data.  In such a case, the receiving node would be able
   to validate the uniqueness of the data.

9.  Ciphersuite  Cipher Suite Authorship Considerations

   Cipher suite developers or implementers should consider the diverse
   performance and conditions of networks on which the Bundle Protocol
   (and therefore BPSec) will operate.  Specifically, the delay and
   capacity of delay-tolerant networks can vary substantially.  Cipher
   suite developers should consider these conditions to better describe
   the conditions when those suites will operate or exhibit
   vulnerability, and selection of these suites for implementation
   should be made with consideration to the reality.  There are key
   differences that may limit the opportunity to leverage existing
   cipher suites and technologies that have been developed for use in
   traditional, more reliable networks:

   o  Data Lifetime: Depending on the application environment, bundles
      may persist on the network for extended periods of time, perhaps
      even years.  Cryptographic algorithms should be selected to ensure
      protection of data against attacks for a length of time reasonable
      for the application.

   o  One-Way Traffic: Depending on the application environment, it is
      possible that only a one-way connection may exist between two
      endpoints, or if a two-way connection does exist, the round-trip
      time may be extremely large.  This may limit the utility of
      session key generation mechanisms, such as Diffie-Hellman, as a
      two-way handshake may not be feasible or reliable.

   o  Opportunistic Access: Depending on the application environment, a
      given endpoint may not be guaranteed to be accessible within a
      certain amount of time.  This may make asymmetric cryptographic
      architectures which rely on a key distribution center or other
      trust center impractical under certain conditions.

   When developing new cipher suites for use with BPSec, the following
   information SHOULD be considered for inclusion in these
   specifications.

   o  New Parameters.  Cipher suites MAY define new parameter types that
      may appear in security blocks and used to configure the cipher
      suite.

   o  New Results.  Cipher suites MAY define new security result types
      that may appear in security blocks and capture the outputs of the
      cipher suite.

   o  New Canonicalizations.  Cipher suites MAY define new
      canonicalization algorithms as necessary.

10.  Defining Other Security Blocks

   Other security blocks (OSBs) may be defined and used in addition to
   the security blocks identified in this specification.  Both the usage
   of BIB, BCB, and any future OSBs MAY co-exist within a bundle and MAY
   be considered in conformance with BPSec if each of the following
   requirements are met by any future identified security blocks.

   o  Other security blocks (OSBs) MUST NOT reuse any enumerations
      identified in this specification, to include the block type codes
      for BIB and BCB.

   o  An OSB definition MUST state whether it can be the target of a BIB
      or a BCB.  The definition MUST also state whether the OSB can
      target a BIB or a BCB.

   o  An OSB definition MUST provide a deterinistic deterministic processing order in
      the event that a bundle is received containing BIBs, BCBs, and
      OSBs.  This processing order MUST NOT alter the BIB and BCB
      processing orders identified in this specification.

   o  An OSB definition MUST provide a canonicalization algorithm if the
      default non-primary-block canonicalization algorithm cannot be
      used to generate a deterministic input for a cipher suite.  This
      requirement MAY be waived if the OSB is defined so as to never be
      the security target of a BIB or a BCB.

   o  An OSB definition MAY NOT require any behavior of a BPSEC-BPA that
      is in conflict with the behavior identified in this specification.
      In particular, the security processing requirements imposed by
      this specification MUST be consistent across all BPSEC-BPAs in a
      network.

   o  The behavior of an OSB when dealing with fragmentation MUST be
      specified and MUST NOT lead to ambiguous processing states.  In
      particular, an OSB definition should address how to receive and
      process an OSB in a bundle fragment that may or may not also
      contain its security target.  An OSB definition should also
      address whether an OSB may be added to a bundle marked as a
      fragment.

   Additionally, policy considerations for the management, monitoring,
   and configuration associated with blocks SHOULD be included in any
   OSB definition.

   NOTE: The burden of showing compliance with processing rules is
   placed upon the standards defining new security blocks and the
   identification of such blocks shall not, alone, require maintenance
   of this specification.

11.  Conformance

   All implementations are strongly RECOMMENDED to provide some method
   of hop-by-hop verification by generating a hash to some canonical
   form of the bundle and placing an integrity signature on that form
   using a BIB.

12.  IANA Considerations

   This protocol has fields that have been registered by IANA.

12.1.  Bundle Block Types

   This specification allocates three block types from the existing
   "Bundle Block Types" registry defined in [RFC6255] .

       Additional Entries for the Bundle Block-Type Codes Registry:

          +-------+-----------------------------+---------------+
          | Value |         Description         |   Reference   |
          +-------+-----------------------------+---------------+
          |   2   |    Block Integrity Block    | This document |
          |   3   | Block Confidentiality Block | This document |
          +-------+-----------------------------+---------------+

                                  Table 2

12.2.  Cipher Suite Flags

   This protocol has a cipher suite flags field and certain flags are
   defined.  An IANA registry has been set up as follows.

   The registration policy for this registry is: Specification Required

   The Value range is: Variable Length
                        Cipher Suite Flag Registry:

   +--------------------------+-------------------------+--------------+
   |  Bit Position (right to  |       Description       |  Reference   |
   |          left)           |                         |              |
   +--------------------------+-------------------------+--------------+
   |            0             |  Block contains result  |     This     |
   |                          |                         |   document   |
   |            1             |      Block Contains     |     This     |
   |                          |        parameters       |   document   |
   |            2             |  Source EID ref present |     This     |
   |                          |                         |   document   |
   |            >3            |         Reserved        |     This     |
   |                          |                         |   document   |
   +--------------------------+-------------------------+--------------+

                                  Table 3

12.3.  Parameters and Results

   This protocol has fields for cipher suite parameters and results. configuration associated with blocks SHOULD be included in any
   OSB definition.

   NOTE: The field burden of showing compliance with processing rules is a type-length-value triple
   placed upon the standards defining new security blocks and a registry is required
   for the "type" sub-field.  The values for "type" apply
   identification of such blocks shall not, alone, require maintenance
   of this specification.

11.  Conformance

   All implementations are strongly RECOMMENDED to both provide some method
   of hop-by-hop verification by generating a hash to some canonical
   form of the
   cipher suite parameters bundle and the cipher suite results fields.  Certain
   values are defined.  An placing an integrity signature on that form
   using a BIB.

12.  IANA registry has been set up as follows.

   The registration policy for this registry is: Specification Required

   The Value range is: 8-bit unsigned integer. Considerations

   Registries of Cipher Suite Parameters IDs, Cipher Suite Flags, Cipher Suite
   Parameter Types, and Results Type Security Result Types will be required.

12.1.  Bundle Block Types

   This specification allocates two block types from the existing
   "Bundle Block Types" registry defined in [RFC6255] .

       Additional Entries for the Bundle Block-Type Codes Registry:

   +---------+-------------------------------------------+-------------+

          +-------+-----------------------------+---------------+
          | Value |         Description         |   Reference   |
   +---------+-------------------------------------------+-------------+
   |    0    |                  reserved                 | Section 3.6 |
   |    1    |         initialization vector (IV)        | Section 3.6 |
   |    2    |                  reserved                 | Section 3.6 |
   |    3    |              key information              | Section 3.6 |
   |    4    | content-range (pair of Unsigned Integers) | Section 3.6 |
   |    5    |            integrity signature            | Section 3.6 |
   |    6    |                 unassigned                | Section 3.6 |
   |    7    |                    salt                   | Section 3.6 |
   |    8    |      BCB integrity check value (ICV)      | Section 3.6 |
   |  9-191  |                  reserved                 | Section 3.6 |
          +-------+-----------------------------+---------------+
          | 192-250  TBD  |                private use    Block Integrity Block    | Section 3.6 This document |
          | 251-255  TBD  |                  reserved Block Confidentiality Block | Section 3.6 This document |
   +---------+-------------------------------------------+-------------+
          +-------+-----------------------------+---------------+

                                  Table 4 3

13.  References

13.1.  Normative References

   [BPBIS]    Burleigh, S., Fall, K., and E. Birrane, "Bundle Protocol",
              draft-ietf-dtn-bpbis-04
              draft-ietf-dtn-bpbis-06 (work in progress), July 2016.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3552]  Rescorla, E. and B. Korver, "Guidelines for Writing RFC
              Text on Security Considerations", BCP 72, RFC 3552,
              DOI 10.17487/RFC3552, July 2003,
              <http://www.rfc-editor.org/info/rfc3552>.

   [RFC6255]  Blanchet, M., "Delay-Tolerant Networking Bundle Protocol
              IANA Registries", RFC 6255, May 2011.

13.2.  Informative References

   [BPBISCBOR]
              Burleigh, S., "Bundle Protocol CBOR Representation
              Specification", draft-burleigh-dtn-rs-cbor-01 (work in
              progress), April 2016.

   [RFC4838]  Cerf, V., Burleigh, S., Hooke, A., Torgerson, L., Durst,
              R., Scott, K., Fall, K., and H. Weiss, "Delay-Tolerant
              Networking Architecture", RFC 4838, April 2007.

   [RFC6257]  Symington, S., Farrell, S., Weiss, H., and P. Lovell,
              "Bundle Security Protocol Specification", RFC 6257, May
              2011.

   [SBSP]     Birrane, E., "Streamlined Bundle Security Protocol",
              draft-birrane-dtn-sbsp-01 (work in progress), October
              2015.

Appendix A.  Acknowledgements

   The following participants contributed technical material, use cases,
   and useful thoughts on the overall approach to this security
   specification: Scott Burleigh of the Jet Propulsion Laboratory, Amy
   Alford and Angela Hennessy of the Laboratory for Telecommunications
   Sciences, and Angela Dalton and Cherita Corbett of the Johns Hopkins
   University Applied Physics Laboratory.

Authors' Addresses

   Edward J. Birrane, III
   The Johns Hopkins University Applied Physics Laboratory
   11100 Johns Hopkins Rd.
   Laurel, MD  20723
   US

   Phone: +1 443 778 7423
   Email: Edward.Birrane@jhuapl.edu

   Kenneth McKeever
   The Johns Hopkins University Applied Physics Laboratory
   11100 Johns Hopkins Rd.
   Laurel, MD  20723
   US

   Phone: +1 443 778 2237
   Email: Ken.McKeever@jhuapl.edu