draft-ietf-dtn-bpsec-02.txt   draft-ietf-dtn-bpsec-03.txt 
Delay-Tolerant Networking E. Birrane Delay-Tolerant Networking E. Birrane
Internet-Draft K. McKeever Internet-Draft K. McKeever
Intended status: Experimental JHU/APL Intended status: Standards Track JHU/APL
Expires: January 7, 2017 July 6, 2016 Expires: May 3, 2017 October 30, 2016
Bundle Protocol Security Specification Bundle Protocol Security Specification
draft-ietf-dtn-bpsec-02 draft-ietf-dtn-bpsec-03
Abstract Abstract
This document defines a security protocol providing end to end data This document defines a security protocol providing end to end data
integrity and confidentiality services for the Bundle Protocol. integrity and confidentiality services for the Bundle Protocol.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 7, 2017. This Internet-Draft will expire on May 3, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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2.2. Multiple Security Sources . . . . . . . . . . . . . . . . 7 2.2. Multiple Security Sources . . . . . . . . . . . . . . . . 7
2.3. Mixed Security Policy . . . . . . . . . . . . . . . . . . 8 2.3. Mixed Security Policy . . . . . . . . . . . . . . . . . . 8
2.4. User-Selected Ciphersuites . . . . . . . . . . . . . . . 8 2.4. User-Selected Ciphersuites . . . . . . . . . . . . . . . 8
2.5. Deterministic Processing . . . . . . . . . . . . . . . . 9 2.5. Deterministic Processing . . . . . . . . . . . . . . . . 9
3. Security Block Definitions . . . . . . . . . . . . . . . . . 9 3. Security Block Definitions . . . . . . . . . . . . . . . . . 9
3.1. Block Identification . . . . . . . . . . . . . . . . . . 10 3.1. Block Identification . . . . . . . . . . . . . . . . . . 10
3.2. Block Representation . . . . . . . . . . . . . . . . . . 10 3.2. Block Representation . . . . . . . . . . . . . . . . . . 10
3.3. Block Integrity Block . . . . . . . . . . . . . . . . . . 13 3.3. Block Integrity Block . . . . . . . . . . . . . . . . . . 13
3.4. Block Confidentiality Block . . . . . . . . . . . . . . . 14 3.4. Block Confidentiality Block . . . . . . . . . . . . . . . 14
3.5. Block Interactions . . . . . . . . . . . . . . . . . . . 16 3.5. Block Interactions . . . . . . . . . . . . . . . . . . . 16
3.6. Multi-Target Block Definitions . . . . . . . . . . . . . 17 3.6. Parameters and Result Fields . . . . . . . . . . . . . . 17
3.7. Parameters and Result Fields . . . . . . . . . . . . . . 17 3.7. BSP Block Example . . . . . . . . . . . . . . . . . . . . 18
3.8. BSP Block Example . . . . . . . . . . . . . . . . . . . . 18
4. Canonical Forms . . . . . . . . . . . . . . . . . . . . . . . 20 4. Canonical Forms . . . . . . . . . . . . . . . . . . . . . . . 20
4.1. Technical Notes . . . . . . . . . . . . . . . . . . . . . 20 4.1. Technical Notes . . . . . . . . . . . . . . . . . . . . . 20
4.2. Primary Block Canonicalization . . . . . . . . . . . . . 21 4.2. Primary Block Canonicalization . . . . . . . . . . . . . 21
4.3. Non-Primary-Block Canonicalization . . . . . . . . . . . 22 4.3. Non-Primary-Block Canonicalization . . . . . . . . . . . 22
5. Security Processing . . . . . . . . . . . . . . . . . . . . . 22 5. Security Processing . . . . . . . . . . . . . . . . . . . . . 22
5.1. Bundles Received from Other Nodes . . . . . . . . . . . . 23 5.1. Bundles Received from Other Nodes . . . . . . . . . . . . 23
5.1.1. Receiving BCB Blocks . . . . . . . . . . . . . . . . 23 5.1.1. Receiving BCB Blocks . . . . . . . . . . . . . . . . 23
5.1.2. Receiving BIB Blocks . . . . . . . . . . . . . . . . 23 5.1.2. Receiving BIB Blocks . . . . . . . . . . . . . . . . 23
5.2. Bundle Fragmentation and Reassembly . . . . . . . . . . . 24 5.2. Bundle Fragmentation and Reassembly . . . . . . . . . . . 24
6. Key Management . . . . . . . . . . . . . . . . . . . . . . . 25 6. Key Management . . . . . . . . . . . . . . . . . . . . . . . 25
7. Policy Considerations . . . . . . . . . . . . . . . . . . . . 25 7. Policy Considerations . . . . . . . . . . . . . . . . . . . . 25
8. Security Considerations . . . . . . . . . . . . . . . . . . . 26 8. Security Considerations . . . . . . . . . . . . . . . . . . . 26
8.1. Attacker Capabilities and Objectives . . . . . . . . . . 27 8.1. Attacker Capabilities and Objectives . . . . . . . . . . 27
8.2. Attacker Behaviors and BPSec Mitigations . . . . . . . . 28 8.2. Attacker Behaviors and BPSec Mitigations . . . . . . . . 28
8.2.1. Eavesdropping Attacks . . . . . . . . . . . . . . . . 28 8.2.1. Eavesdropping Attacks . . . . . . . . . . . . . . . . 28
8.2.2. Modification Attacks . . . . . . . . . . . . . . . . 28 8.2.2. Modification Attacks . . . . . . . . . . . . . . . . 28
8.2.3. Topology Attacks . . . . . . . . . . . . . . . . . . 29 8.2.3. Topology Attacks . . . . . . . . . . . . . . . . . . 29
8.2.4. Message Injection . . . . . . . . . . . . . . . . . . 30 8.2.4. Message Injection . . . . . . . . . . . . . . . . . . 30
9. Ciphersuite Authorship Considerations . . . . . . . . . . . . 30 9. Ciphersuite Authorship Considerations . . . . . . . . . . . . 30
10. Conformance . . . . . . . . . . . . . . . . . . . . . . . . . 31 10. Defining Other Security Blocks . . . . . . . . . . . . . . . 31
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31 11. Conformance . . . . . . . . . . . . . . . . . . . . . . . . . 32
11.1. Bundle Block Types . . . . . . . . . . . . . . . . . . . 31 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32
11.2. Cipher Suite Flags . . . . . . . . . . . . . . . . . . . 31 12.1. Bundle Block Types . . . . . . . . . . . . . . . . . . . 32
11.3. Parameters and Results . . . . . . . . . . . . . . . . . 32 12.2. Cipher Suite Flags . . . . . . . . . . . . . . . . . . . 32
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 33 12.3. Parameters and Results . . . . . . . . . . . . . . . . . 33
12.1. Normative References . . . . . . . . . . . . . . . . . . 33 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 34
12.2. Informative References . . . . . . . . . . . . . . . . . 33 13.1. Normative References . . . . . . . . . . . . . . . . . . 34
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 34 13.2. Informative References . . . . . . . . . . . . . . . . . 34
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 34 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 35
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 35
1. Introduction 1. Introduction
This document defines security features for the Bundle Protocol This document defines security features for the Bundle Protocol
[BPBIS] intended for use in delay-tolerant networks, in order to [BPBIS] intended for use in delay-tolerant networks, in order to
provide Delay-Tolerant Networking (DTN) security services. provide Delay-Tolerant Networking (DTN) security services.
1.1. Motivation 1.1. Motivation
The Bundle Protocol is used in DTNs that overlay multiple networks, The Bundle Protocol is used in DTNs that overlay multiple networks,
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If node BN2 originates a bundle (for example, a bundle status report 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 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 to BN4, then BN2 is the source of the bundle (as well as being the
first forwarder of the bundle) and BN4 is the destination of the first forwarder of the bundle) and BN4 is the destination of the
bundle (as well as being the final intermediate receiver). bundle (as well as being the final intermediate receiver).
The following security-specific terminology is also defined to The following security-specific terminology is also defined to
clarify security operations in this specifiation. clarify security operations in this specifiation.
o Security-Service - the security features supported by this o Security Service - the security features supported by this
specification: integrity and confidentiality. specification: integrity and confidentiality.
o Security-Source - a bundle node that adds a security block to a o Security Source - a bundle node that adds a security block to a
bundle. bundle.
o Security-Target - the block within a bundle that receives a o Security Target - the block within a bundle that receives a
security-service as part of a security-operation. security-service as part of a security-operation.
o Security Block - a BPSec extension block in a bundle. o Security Block - a BPSec extension block in a bundle.
o Security-Operation - the application of a security-service to a o Security Operation - the application of a security service to a
security-target, notated as OP(security-service, security-target). security target, notated as OP(security service, security target).
For example, OP(confidentiality, payload). Every security- For example, OP(confidentiality, payload). Every security
operation in a bundle MUST be unique, meaning that a 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. service can only be applied to a security target once in a bundle.
A security operation is implemented by a security block. A security operation is implemented by a security block.
2. Key Properties 2. Key Properties
The application of security services in a DTN is a complex endeavor The application of security services in a DTN is a complex endeavor
that must consider physical properties of the network, policies at that must consider physical properties of the network, policies at
each node, and various application security requirements. Rather each node, and various application security requirements. Rather
than enumerate all potential security implementations in all than enumerate all potential security implementations in all
potential DTN topologies, this specification defines a set of key potential DTN topologies, this specification defines a set of key
properties of a security system. The security primitives outlined in properties of a security system. The security primitives outlined in
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granularity where applicable such that different blocks within a granularity where applicable such that different blocks within a
bundle may have different security services applied to them. bundle may have different security services applied to them.
For example, within a bundle, a payload might be encrypted to protect For example, within a bundle, a payload might be encrypted to protect
its contents, whereas an extension block containing summary its contents, whereas an extension block containing summary
information related to the payload might be integrity signed but information related to the payload might be integrity signed but
otherwise unencrypted to provide certain nodes access to payload- otherwise unencrypted to provide certain nodes access to payload-
related data without providing access to the payload. related data without providing access to the payload.
Each security block in a bundle will be associated with a specific Each security block in a bundle will be associated with a specific
security-operation. security operation.
2.2. Multiple Security Sources 2.2. Multiple Security Sources
A bundle MAY have multiple security blocks and these blocks MAY have A bundle MAY have multiple security blocks and these blocks MAY have
different security-sources. different security sources.
The Bundle Protocol allows extension blocks to be added to a bundle 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 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 adds a new extension block to a bundle, that extension block may have
security services applied to it by that waypoint. Similarly, a security services applied to it by that waypoint. Similarly, a
waypoint node may add a security service to an existing extension waypoint node may add a security service to an existing extension
block, consistent with its security policy. For example, a node block, consistent with its security policy. For example, a node
representing a boundary between a trusted part of the network and an representing a boundary between a trusted part of the network and an
untrusted part of the network may wish to apply payload encryption untrusted part of the network may wish to apply payload encryption
for bundles leaving the trusted portion of the network. for bundles leaving the trusted portion of the network.
In each case, a node other than the bundle originator may add a In each case, a node other than the bundle originator may add a
security service to the bundle and, as such, the source for the security service to the bundle and, as such, the source for the
security service will be different than the source of the bundle security service will be different than the source of the bundle
itself. Security services MUST track their orginating node so as to itself. Security services MUST track their orginating node so as to
properly apply policy and key selection associated with processing properly apply policy and key selection associated with processing
the security service at the bundle destination. the security service at the bundle destination.
Referring to Figure 1, if the bundle that originates at BN1 is given Referring to Figure 1, if the bundle that originates at BN1 is given
security blocks by BN1, then BN1 is the security-source for those security blocks by BN1, then BN1 is the security source for those
blocks as well as being the source of the bundle. If the bundle that blocks as well as being the source of the bundle. If the bundle that
originates at BN1 is then given a security block by BN2, then BN2 is originates at BN1 is then given a security block by BN2, then BN2 is
the security-source for that block even though BN1 remains the bundle the security source for that block even though BN1 remains the bundle
source. source.
2.3. Mixed Security Policy 2.3. Mixed Security Policy
Different nodes in a DTN may have different security-related Different nodes in a DTN may have different security related
capabilities. Some nodes may not be security-aware and will not capabilities. Some nodes may not be security aware and will not
understand any security-related extension blocks. Other nodes may understand any security related extension blocks. Other nodes may
have security policies that require evaluation of security services have security policies that require evaluation of security services
at places other than the bundle destination (such as verifying at places other than the bundle destination (such as verifying
integrity signatures at certain waypoint nodes). Other nodes may integrity signatures at certain waypoint nodes). Other nodes may
ignore any security processing if they are not the destination of the ignore any security processing if they are not the destination of the
bundle. The security services described in this specification must bundle. The security services described in this specification must
allow each of these scenarios. allow each of these scenarios.
Extension blocks representing security services MUST have their block Extension blocks representing security services MUST have their block
processing flags set such that the block will be treated processing flags set such that the block will be treated
appropriately by non-security-aware nodes. appropriately by non-security-aware nodes.
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destination. This specification MUST provide determinism in the destination. This specification MUST provide determinism in the
application and evaluation of security services, even when doing so application and evaluation of security services, even when doing so
results in a loss of flexibility. results in a loss of flexibility.
3. Security Block Definitions 3. Security Block Definitions
There are two types of security blocks that may be included in a There are two types of security blocks that may be included in a
bundle. These are the Block Integrity Block (BIB) and the Block bundle. These are the Block Integrity Block (BIB) and the Block
Confidentiality Block (BCB). Confidentiality Block (BCB).
The BIB is used to ensure the integrity of its security-target(s). The BIB is used to ensure the integrity of its security target(s).
The integrity information in the BIB MAY (when possible) be The integrity information in the BIB MAY (when possible) be
verified by any node in between the BIB security-source and the verified by any node in between the BIB security source and the
bundle destination. BIBs MAY be added to, and removed from, bundle destination. BIBs MAY be added to, and removed from,
bundles as a matter of security policy. bundles as a matter of security policy.
The BCB indicates that the security-target(s) has been encrypted, The BCB indicates that the security target(s) has been encrypted,
in whole or in part, at the BCB security-source in order to 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 protect its content while in transit. The BCB may be decrypted by
appropriate nodes in the network, up to and including the bundle appropriate nodes in the network, up to and including the bundle
destination, as a matter of security policy. destination, as a matter of security policy.
A security-operation MUST NOT be applied more than once in a bundle. A security operation MUST NOT be applied more than once in a bundle.
For example, the two security-operations: OP(integrity, payload) and For example, the two security operations: OP(integrity, payload) and
OP(integrity, payload) are considered redundant and MUST NOT appear OP(integrity, payload) are considered redundant and MUST NOT appear
together in a bundle. However, the two security operations together in a bundle. However, the two security operations
OP(integrity, payload) and OP(integrity, extension_block_1) MAY both OP(integrity, payload) and OP(integrity, extension_block_1) MAY both
be present in the bundle. Also, the two security operations be present in the bundle. Also, the two security operations
OP(integrity, extension_block_1) and OP(integrity, extension_block_2) OP(integrity, extension_block_1) and OP(integrity, extension_block_2)
are unique and may both appear in the same bundle. are unique and may both appear in the same bundle.
If the same security-service is to be applied to multiple security- If the same security service is to be applied to multiple security
targets, and cipher suite parameters for each security service are targets, and cipher suite parameters for each security service are
identical, then the set of security-operations can be represented as identical, then the set of security operations can be represented as
a single security-block with multiple security-targets. In such a a single security block with multiple security targets. In such a
case, all security-operations represented in the security-block MUST case, all security operations represented in the security block MUST
be applied/evaluated together. be applied/evaluated together.
3.1. Block Identification 3.1. Block Identification
This specification requires that every target block of a security This specification requires that every target block of a security
operation be uniquely identifiable. The definition of the extension operation be uniquely identifiable. The definition of the extension
block header from [BPBIS] provides such a mechanism in the "Block block header from [BPBIS] provides such a mechanism in the "Block
Number" field, which provides a unique identifier for a block within Number" field, which provides a unique identifier for a block within
a bundle. Within this specification, a security-target will be a bundle. Within this specification, a security target will be
identified by its unique Block Number. 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 a case, the security
block MUST contain security results for each covered security target.
The use of multiple security targets 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 3.2. Block Representation
Each security block uses the Canonical Bundle Block Format as defined Each security block uses the Canonical Bundle Block Format as defined
in [BPBIS]. That is, each security block is comprised of the in [BPBIS]. That is, each security block is comprised of the
following elements: following elements:
o Block Type Code o Block Type Code
o Block Number o Block Number
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| Security Result | Byte Array | | Security Result | Byte Array |
+---------------------+--------------------------+ +---------------------+--------------------------+
Figure 2: BIB and BCB Block Structure Figure 2: BIB and BCB Block Structure
Where the block fields are identified as follows. Where the block fields are identified as follows.
o # Security Targets - The number of security targets for this o # Security Targets - The number of security targets for this
security block. This value MUST be at least 1. security block. This value MUST be at least 1.
o Security-Targets - This array contains the unique identifier of o Security Targets - This array contains the unique identifier of
the blocks targetted by this security operation. Each security- the blocks targetted by this security operation. Each security
target MUST represent a block present in the bundle. A security- target MUST represent a block present in the bundle. A security
target MUST NOT be repeated in this array. target MUST NOT be repeated in this array.
o Cipher suite ID - Identifies the cipher suite used to implement o Cipher suite ID - Identifies the cipher suite used to implement
the security service represented by this block and applied to each the security service represented by this block and applied to each
security-target. security target.
o Cipher suite flags - Identifies which optional security block o Cipher suite flags - Identifies which optional security block
fields are present in the block. The structure of the Cipher fields are present in the block. The structure of the Cipher
Suite Flags field is shown in Figure 3. The presence of an Suite Flags field is shown in Figure 3. The presence of an
optional field is indicated by setting the value of the optional field is indicated by setting the value of the
corresponding flag to one. A value of zero indicates the corresponding flag to one. A value of zero indicates the
corresponding optional field is not present. The BPSEC Cipher corresponding optional field is not present. The BPSEC Cipher
Suite Flags are defined as follows. Suite Flags are defined as follows.
Bit Bit Bit Bit Bit Bit Bit Bit Bit Bit Bit Bit Bit Bit Bit Bit
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| reserved | src |parm | | reserved | src |parm |
+-----------------------------------+-----+-----+ +-----------------------------------+-----+-----+
MSB LSB MSB LSB
Figure 3: Cipher Suite Flags Figure 3: Cipher Suite Flags
Where: Where:
* bits 7-2 are reserved for future use. * bits 7-2 are reserved for future use.
* src - bit 1 indicates whether the Security Source EID is * src - bit 1 indicates whether the Security Source is present in
present in the block. the block.
* parm - bit 0 indicates whether or not the Cipher Suite * parm - bit 0 indicates whether or not the Cipher Suite
Parameters field is present in the block. Parameters field is present in the block.
o (OPTIONAL) Security Source (URI) - This identifies the EID that o (OPTIONAL) Security Source (URI) - This identifies the node that
inserted the security service in the bundle. If the security inserted the security service in the bundle. If the security
source is not present then the souce of the block MAY be taken to source is not present then the source MAY be inferred from the
be the bundle source, the previous hop, or some other EID as bundle source, the previous hop, or some other node as defined by
defined by security policy. security policy.
o (OPTIONAL) Parameters (Byte Array) - Compound field of the o (OPTIONAL) Parameters (Byte Array) - Compound field of the
following two items. following two items.
* Length (Unsigned Integer) - specifies the length of the next * Length (Unsigned Integer) - specifies the length of the next
field, which captures the parameters data. field, which captures the parameters data.
* Data (Byte Array) - A byte array encoding one or more cipher * Data (Byte Array) - A byte array encoding one or more cipher
suite parameters, with each parameter represented as a Type- suite parameters, with each parameter represented as a Type-
Length-Value (TLV) triplet, defined as follows. Length-Value (TLV) triplet, defined as follows.
+ Type (Byte) - The parameter type. + Type (Byte) - The parameter type.
+ Length (Unsigned Integer) - The length of the parameter. + Length (Unsigned Integer) - The length of the parameter.
+ Value (Byte Array) - The parameter value. + Value (Byte Array) - The parameter value.
See Section 3.7 for a list of parameter types that MUST be See Section 3.6 for a list of parameter types that MUST be
supported by BPSEC implementations. BPSEC cipher suite supported by BPSEC implementations. BPSEC cipher suite
specifications MAY define their own parameters to be specifications MAY define their own parameters to be
represented in this byte array. represented in this byte array.
o Security Result (Byte Array) - Compound field of the next two o Security Result (Byte Array) - A security result is the output of
items. an appropriate cipher suite specific calculation (e.g., a
signature, Message Authentication Code (MAC), or cipher-text block
key). There MUST exist one security result for each security
target in the security block. A security result is a multi-field
component, described as follows.
* Length (Unsigned Integer) - specifies the length of the next * Total Length (Unsigned Integer) - specifies the length, in
field, which is the security-result data. bytes, of the remaining security result information.
* Data (Byte Array) - A byte array encoding a security result for * Results (Byte Array) - This field captures each of the security
each security-target covered by the security-block, with each results, catenated together, one for each security target
entry represented as a TLV and optionally prepended with covered by the security block. Each result is captured by the
information on which security-target is referenced by the four-tuple of (Target, Type, Len, Value). The meaning of each
result, as follows. is given below.
+ Target (Optional Unsigned Integer) - If the security-block + Target (Optional) (Unsigned Integer) - If the security block
has multiple security-targets, the target field is the Block has multiple security targets, the target field is the Block
Number of the security-target to which this result field Number of the security target to which this result field
applies. If the security-block only has a single security- applies. If the security block only has a single security
target, this field is omitted. target, this field is omitted.
+ Type (Unsigned Integer)(Byte) - The type of security result + Type (Unsigned Integer) - The type of security result field.
field.
+ Length (Unsigned Integer) - The length of the result field. + Length (Unsigned Integer) - The length of the result field.
+ Value (Byte Array) - The results of the appropriate cipher + Value (Byte Array) - The results of the cipher suite
suite specific calculation (e.g., a signature, Message specific calculation.
Authentication Code (MAC), or cipher-text block key).
3.3. Block Integrity Block 3.3. Block Integrity Block
A BIB is an ASB with the following characteristics: A BIB is an ASB with the following characteristics:
The Block Type Code value MUST be 0x02. The Block Type Code value MUST be 0x02.
The Block Processing Control flags value can be set to whatever The Block Processing Control flags value can be set to whatever
values are required by local policy. Cipher suite designers values are required by local policy. Cipher suite designers
should carefully consider the effect of setting flags that either should carefully consider the effect of setting flags that either
discard the block or delete the bundle in the event that this discard the block or delete the bundle in the event that this
block cannot be processed. block cannot be processed.
A security-target for a BIB MUST NOT reference a security-block A security target for a BIB MUST NOT reference a security block
defined in this specification (e.g., a BIB or a BCB). defined in this specification (e.g., a BIB or a BCB).
The cipher suite ID MUST be documented as an end-to-end The cipher suite ID MUST be documented as an end-to-end
authentication-cipher suite or as an end-to-end error-detection- authentication-cipher suite or as an end-to-end error-detection-
cipher suite. cipher suite.
An EID-reference to the security-source MAY be present. If this An EID-reference to the security source MAY be present. If this
field is not present, then the security-source of the block SHOULD field is not present, then the security source of the block SHOULD
be inferred according to security policy and MAY default to the be inferred according to security policy and MAY default to the
bundle source. The security-source may also be specified as part bundle source. The security source may also be specified as part
of key-information described in Section 3.7. of key information described in Section 3.6.
The security-result captures the result of applying the cipher The security result captures the result of applying the cipher
suite calculation (e.g., the MAC or signature) to the relevant suite calculation (e.g., the MAC or signature) to the relevant
parts of the security-target, as specified in the cipher suite parts of the security target, as specified in the cipher suite
definition. This field MUST be present. definition. This field MUST be present.
The cipher suite MAY process less than the entire security-target. The cipher suite MAY process less than the entire security target.
If the cipher suite processes less than the complete, original If the cipher suite processes less than the complete, original
security-target, the cipher suite parameters MUST specify which security target, the cipher suite parameters MUST specify which
bytes of the security-target are protected. bytes of the security target are protected.
Notes: Notes:
o Since OP(integrity, target) is allowed only once in a bundle per o Since OP(integrity, target) is allowed only once in a bundle per
target, it is RECOMMENDED that users wishing to support multiple target, it is RECOMMENDED that users wishing to support multiple
integrity signatures for the same target define a multi-signature integrity signatures for the same target define a multi-signature
cipher suite. cipher suite.
o For some cipher suites, (e.g., those using asymmetric keying to o For some cipher suites, (e.g., those using asymmetric keying to
produce signatures or those using symmetric keying with a group produce signatures or those using symmetric keying with a group
skipping to change at page 14, line 48 skipping to change at page 15, line 5
The Block Processing Control flags value can be set to whatever The Block Processing Control flags value can be set to whatever
values are required by local policy, except that this block MUST values are required by local policy, except that this block MUST
have the "replicate in every fragment" flag set if the target of have the "replicate in every fragment" flag set if the target of
the BCB is the Payload Block. Having that BCB in each fragment the BCB is the Payload Block. Having that BCB in each fragment
indicates to a receiving node that the payload portion of each indicates to a receiving node that the payload portion of each
fragment represents cipher-text. Cipher suite designers should fragment represents cipher-text. Cipher suite designers should
carefully consider the effect of setting flags that either discard carefully consider the effect of setting flags that either discard
the block or delete the bundle in the event that this block cannot the block or delete the bundle in the event that this block cannot
be processed. be processed.
A security-target for a BCB MAY reference the payload block, a A security target for a BCB MAY reference the payload block, a
non-security extension block, or a BIB block. A security-target non-security extension block, or a BIB block. A security target
in a BCB MUST NOT be another BCB. in a BCB MUST NOT be another BCB.
The cipher suite ID MUST be documented as a confidentiality cipher The cipher suite ID MUST be documented as a confidentiality cipher
suite. suite.
Any additional bytes generated as a result of encryption and/or Any additional bytes generated as a result of encryption and/or
authentication processing of the security-target SHOULD be placed authentication processing of the security target SHOULD be placed
in an "integrity check value" field (see Section 3.7) or other in an "integrity check value" field (see Section 3.6) or other
such appropriate area in the security-result of the BCB. such appropriate area in the security result of the BCB.
An EID-reference to the security-source MAY be present. If this An EID-reference to the security source MAY be present. If this
field is not present, then the security-source of the block SHOULD field is not present, then the security source of the block SHOULD
be inferred according to security policy and MAY default to the be inferred according to security policy and MAY default to the
bundle source. The security-source may also be specified as part bundle source. The security source may also be specified as part
of key-information described in Section 3.7. of key information described in Section 3.6.
The security-result MUST be present in the BCB. This compound The security result MUST be present in the BCB. This compound
field normally contains fields such as an encrypted bundle field normally contains fields such as an encrypted bundle
encryption key and/or authentication tag. encryption key and/or authentication tag.
The BCB modifies the contents of its security-target. When a BCB is The BCB modifies the contents of its security target. When a BCB is
applied, the security-target body data are encrypted "in-place". applied, the security target body data are encrypted "in-place".
Following encryption, the security-target body data contains cipher- Following encryption, the security target body data contains cipher-
text, not plain-text. Other security-target block fields (such as text, not plain-text. Other security target block fields (such as
type, processing control flags, and length) remain unmodified. type, processing control flags, and length) remain unmodified.
Fragmentation, reassembly, and custody transfer are adversely Fragmentation, reassembly, and custody transfer are adversely
affected by a change in size of the payload due to ambiguity about affected by a change in size of the payload due to ambiguity about
what byte range of the block is actually in any particular fragment. what byte range of the block is actually in any particular fragment.
Therefore, when the security-target of a BCB is the bundle payload, 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. the BCB MUST NOT alter the size of the payload block body data.
Cipher suites SHOULD place any block expansion, such as Cipher suites SHOULD place any block expansion, such as
authentication tags (integrity check values) and any padding authentication tags (integrity check values) and any padding
generated by a block-mode cipher, into an integrity check value item generated by a block-mode cipher, into an integrity check value item
in the security-result field (see Section 3.7) of the BCB. This "in- in the security result field (see Section 3.6) of the BCB. This "in-
place" encryption allows fragmentation, reassembly, and custody place" encryption allows fragmentation, reassembly, and custody
transfer to operate without knowledge of whether or not encryption transfer to operate without knowledge of whether or not encryption
has occurred. has occurred.
Notes: Notes:
o The cipher suite MAY process less than the entire original o The cipher suite MAY process less than the entire original
security-target body data. If the cipher suite processes less security target body data. If the cipher suite processes less
than the complete, original security-target body data, the BCB for than the complete, original security target body data, the BCB for
that security-target MUST specify, as part of the cipher suite that security target MUST specify, as part of the cipher suite
parameters, which bytes of the body data are protected. parameters, which bytes of the body data are protected.
o The BCB's "discard" flag may be set independently from its o The BCB's "discard" flag may be set independently from its
security-target's "discard" flag. Whether or not the BCB's security target's "discard" flag. Whether or not the BCB's
"discard" flag is set is an implementation/policy decision for the "discard" flag is set is an implementation/policy decision for the
encrypting node. (The "discard" flag is more properly called the encrypting node. (The "discard" flag is more properly called the
"Discard if block cannot be processed" flag.) "Discard if block cannot be processed" flag.)
o A BCB MAY include information as part of additional authenticated o A BCB MAY include information as part of additional authenticated
data to address parts of the target block, such as EID references, data to address parts of the target block, such as EID references,
that are not converted to cipher-text. that are not converted to cipher-text.
3.5. Block Interactions 3.5. Block Interactions
The security-block types defined in this specification are designed The security block types defined in this specification are designed
to be as independent as possible. However, there are some cases to be as independent as possible. However, there are some cases
where security blocks may share a security-target creating processing where security blocks may share a security target creating processing
dependencies. dependencies.
If confidentiality is being applied to a target that already has If confidentiality is being applied to a target that already has
integrity applied to it, then an undesirable condition occurs where a integrity applied to it, then an undesirable condition occurs where a
security-aware intermediate node would be unable to check the security aware intermediate node would be unable to check the
integrity result of a block because the block contents have been integrity result of a block because the block contents have been
encrypted after the integrity signature was generated. To address encrypted after the integrity signature was generated. To address
this concern, the following processing rules MUST be followed. this concern, the following processing rules MUST be followed.
o If confidentiality is to be applied to a target, it MUST also be o If confidentiality is to be applied to a target, it MUST also be
applied to any integrity operation already defined for that applied to any integrity operation already defined for that
target. This means that if a BCB is added to encrypt a block, 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 another BCB MUST also be added to encrypt a BIB also targeting
that block. that block.
o An integrity operation MUST NOT be applied to a security-target if o An integrity operation MUST NOT be applied to a security target if
a BCB in the bundle shares the same security-target. This a BCB in the bundle shares the same security target. This
prevents ambiguity in the order of evaluation when receiving a BIB prevents ambiguity in the order of evaluation when receiving a BIB
and a BCB for a given security-target. and a BCB for a given security target.
o An integrity value MUST NOT be evaluated if the BIB providing the 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 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 the bundle. In such a case, the BIB data contains cipher-text as
it has been encrypted. it has been encrypted.
o An integrity value MUST NOT be evaluated if the security-target of 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 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 such a case, the security target data contains cipher-text as it
has been encrypted. has been encrypted.
o As mentioned in Section 3.3, a BIB MUST NOT have a BCB as its o As mentioned in Section 3.3, a BIB MUST NOT have a BCB as its
security target. BCBs may embed integrity results as part of security target. BCBs may embed integrity results as part of
cipher suite parameters. cipher suite parameters.
These restrictions on block interactions impose a necessary ordering These restrictions on block interactions impose a necessary ordering
when applying security operations within a bundle. Specifically, for when applying security operations within a bundle. Specifically, for
a given security-target, BIBs MUST be added before BCBs. This a given security target, BIBs MUST be added before BCBs. This
ordering MUST be preserved in cases where the current BPA is adding 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 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 waypoint adding new security blocks to a bundle that already contains
security blocks. security blocks.
3.6. Multi-Target Block Definitions 3.6. Parameters and Result Fields
A security-block MAY target multiple security-targets if and only if
all cipher suite parameters, security source, and key information are
common for each security operation. The following processing
directives apply for these multi-target blocks.
o If a security-block has more than one security-target, then each
type identifier in the security result TLV MUST be interpretted as
a tuple with the first entry being the security-target for which
the security result applies and the second entry being the type
value enumeration of the security result value.
o If the security-block has a single security-target, the type field
of every entry in the security result array MUST simply be the
type field and MUST NOT be a tuple as described above.
3.7. Parameters and Result Fields
Various cipher suites include several items in the cipher suite Various cipher suites include several items in the cipher suite
parameters and/or security-result fields. Which items MAY appear is parameters and/or security result fields. Which items MAY appear is
defined by the particular cipher suite description. A cipher suite defined by the particular cipher suite description. A cipher suite
MAY support several instances of the same type within a single block. MAY support several instances of the same type within a single block.
Each item is represented as a type-length-value. Type is a single Each item is represented as a type-length-value. Type is a single
byte indicating the item. Length is the count of data bytes to byte indicating the item. Length is the count of data bytes to
follow, and is an Unsigned Integer. Value is the data content of the follow, and is an Unsigned Integer. Value is the data content of the
item. item.
Item types, name, and descriptions are defined as follows. Item types, name, and descriptions are defined as follows.
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| 4 | Content Range | Pair of Unsigned Integers | Cipher | | 4 | Content Range | Pair of Unsigned Integers | Cipher |
| | | (offset,length) specifying | Suite | | | | (offset,length) specifying | Suite |
| | | the range of payload bytes | Parameters | | | | the range of payload bytes | Parameters |
| | | to which an operation | | | | | to which an operation | |
| | | applies. The offset MUST be | | | | | applies. The offset MUST be | |
| | | the offset within the | | | | | the offset within the | |
| | | original bundle, even if | | | | | original bundle, even if | |
| | | the current bundle is a | | | | | the current bundle is a | |
| | | fragment. | | | | | fragment. | |
+-------+----------------+-----------------------------+------------+ +-------+----------------+-----------------------------+------------+
| 5 | Integrity | Result of BAB or BIB digest | Security | | 5 | Integrity | Result of BIB digest or | Security |
| | Signatures | or other signing operation. | Results | | | Signatures | other signing operation. | Results |
+-------+----------------+-----------------------------+------------+ +-------+----------------+-----------------------------+------------+
| 6 | Unassigned | | | | 6 | Unassigned | | |
+-------+----------------+-----------------------------+------------+ +-------+----------------+-----------------------------+------------+
| 7 | Salt | An IV-like value used by | Cipher | | 7 | Salt | An IV-like value used by | Cipher |
| | | certain confidentiality | Suite | | | | certain confidentiality | Suite |
| | | suites. | Parameters | | | | suites. | Parameters |
+-------+----------------+-----------------------------+------------+ +-------+----------------+-----------------------------+------------+
| 8 | BCB Integrity | Output from certain | Security | | 8 | BCB Integrity | Output from certain | Security |
| | Check Value | confidentiality cipher | Results | | | Check Value | confidentiality cipher | Results |
| | (ICV) / | suite operations to be used | | | | (ICV) / | suite operations to be used | |
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| | | data has not been modified. | | | | | data has not been modified. | |
| | | This value MAY contain | | | | | This value MAY contain | |
| | | padding if required by the | | | | | padding if required by the | |
| | | cipher suite. | | | | | cipher suite. | |
+-------+----------------+-----------------------------+------------+ +-------+----------------+-----------------------------+------------+
| 9-255 | Reserved | | | | 9-255 | Reserved | | |
+-------+----------------+-----------------------------+------------+ +-------+----------------+-----------------------------+------------+
Table 1 Table 1
3.8. BSP Block Example 3.7. BSP Block Example
An example of BPSec blocks applied to a bundle is illustrated in An example of BPSec blocks applied to a bundle is illustrated in
Figure 4. In this figure the first column represents blocks within a Figure 4. In this figure the first column represents blocks within a
bundle and the second column represents a unique identifier for each bundle and the second column represents a unique identifier for each
block, suitable for use as the security-target of a BPSec security- block, suitable for use as the security target of a BPSec security
block. Since the mechanism and format of a security-target is not block. Since the mechanism and format of a security target is not
specified in this document, the terminology B1...Bn is used to specified in this document, the terminology B1...Bn is used to
identify blocks in the bundle for the purposes of illustration. identify blocks in the bundle for the purposes of illustration.
Block in Bundle ID Block in Bundle ID
+===================================+====+ +===================================+====+
| Primary Block | B1 | | Primary Block | B1 |
+-----------------------------------+----+ +-----------------------------------+----+
| BIB | B2 | | BIB | B2 |
| OP(integrity, target=B1) | | | OP(integrity, target=B1) | |
+-----------------------------------+----+ +-----------------------------------+----+
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5. Security Processing 5. Security Processing
This section describes the security aspects of bundle processing. This section describes the security aspects of bundle processing.
5.1. Bundles Received from Other Nodes 5.1. Bundles Received from Other Nodes
Security blocks MUST be processed in a specific order when received Security blocks MUST be processed in a specific order when received
by a security-aware node. The processing order is as follows. by a security-aware node. The processing order is as follows.
o All BCB blocks in the bundle MUST be evaluated prior to evaluating 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- any BIBs in the bundle. When BIBs and BCBs share a security
target, BCBs MUST be evaluated first and BIBs second. target, BCBs MUST be evaluated first and BIBs second.
5.1.1. Receiving BCB Blocks 5.1.1. Receiving BCB Blocks
If a received bundle contains a BCB, the receiving node MUST If a received bundle contains a BCB, the receiving node MUST
determine whether it has the responsibility of decrypting the BCB determine whether it has the responsibility of decrypting the BCB
security target and removing the BCB prior to delivering data to an security target and removing the BCB prior to delivering data to an
application at the node or forwarding the bundle. application at the node or forwarding the bundle.
If the receiving node is the destination of the bundle, the node MUST 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 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 not the destination of the bundle, the node MAY decrypt the BCB if
directed to do so as a matter of security policy. directed to do so as a matter of security policy.
If the relevant parts of an encrypted payload block cannot be If the relevant parts of an encrypted payload block cannot be
decrypted (i.e., the decryption key cannot be deduced or decryption decrypted (i.e., the decryption key cannot be deduced or decryption
fails), then the bundle MUST be discarded and processed no further. fails), then the bundle MUST be discarded and processed no further.
If an encrypted security-target other than the payload block cannot If an encrypted security target other than the payload block cannot
be decrypted then the associated security-target and all security be decrypted then the associated security target and all security
blocks associated with that target MUST be discarded and processed no blocks associated with that target MUST be discarded and processed no
further. In both cases, requested status reports (see [BPBIS]) MAY further. In both cases, requested status reports (see [BPBIS]) MAY
be generated to reflect bundle or block deletion. be generated to reflect bundle or block deletion.
When a BCB is decrypted, the recovered plain-text MUST replace the When a BCB is decrypted, the recovered plain-text MUST replace the
cipher-text in the security-target body data cipher-text in the security target body data
If a BCB contains multiple security-targets, all security-targets If a BCB contains multiple security targets, all security targets
MUST be processed if the BCB is processed by the Node. The effect of MUST be processed if the BCB is processed by the Node. The effect of
this is to be the same as if each security-target had been this is to be the same as if each security target had been
represented by an individual BCB with a single security-target. represented by an individual BCB with a single security target.
5.1.2. Receiving BIB Blocks 5.1.2. Receiving BIB Blocks
If a received bundle contains a BIB, the receiving node MUST If a received bundle contains a BIB, the receiving node MUST
determine whether it has the responsibility of verifying the BIB determine whether it has the responsibility of verifying the BIB
security target and whether to remove the BIB prior to delivering security target and whether to remove the BIB prior to delivering
data to an application at the node or forwarding the bundle. data to an application at the node or forwarding the bundle.
A BIB MUST NOT be processed if the security-target of the BIB is also 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 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 operations mandated by this specification, when both a BIB and a BCB
share a security-target, it means that the security-target MUST have share a security target, it means that the security target MUST have
been encrypted after it was integrity signed and, therefore, the BIB been encrypted after it was integrity signed and, therefore, the BIB
cannot be verified until the security-target has been decrypted by cannot be verified until the security target has been decrypted by
processing the BCB. processing the BCB.
If the security policy of a security-aware node specifies that a If the security policy of a security-aware node specifies that a
bundle should have applied integrity to a specific security-target bundle should have applied integrity to a specific security target
and no such BIB is present in the bundle, then the node MUST process and no such BIB is present in the bundle, then the node MUST process
this security-target in accordance with the security policy. This this security target in accordance with the security policy. This
MAY involve removing the security-target from the bundle. If the MAY involve removing the security target from the bundle. If the
removed security-target is the payload or primary block, the bundle removed security target is the payload or primary block, the bundle
MAY be discarded. This action may occur at any node that has the MAY be discarded. This action may occur at any node that has the
ability to verify an integrity signature, not just the bundle ability to verify an integrity signature, not just the bundle
destination. destination.
If the bundle has a BIB and the receiving node is the destination for If the bundle has a BIB and the receiving node is the destination for
the bundle, the node MUST verify the security-target in accordance the bundle, the node MUST verify the security target in accordance
with the cipher suite specification. If a BIB check fails, the with the cipher suite specification. If a BIB check fails, the
security-target has failed to authenticate and the security-target security target has failed to authenticate and the security target
SHALL be processed according to the security policy. A bundle status SHALL be processed according to the security policy. A bundle status
report indicating the failure MAY be generated. Otherwise, if the report indicating the failure MAY be generated. Otherwise, if the
BIB verifies, the security-target is ready to be processed for BIB verifies, the security target is ready to be processed for
delivery. delivery.
If the bundle has a BIB and the receiving node is not the bundle 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 destination, the receiving node MAY attempt to verify the value in
the security-result field. If the check fails, the node SHALL the security result field. If the check fails, the node SHALL
process the security-target in accordance to local security policy. process the security target in accordance to local security policy.
It is RECOMMENDED that if a payload integrity check fails at a 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 waypoint that it is processed in the same way as if the check fails
at the destination. at the destination.
If a BIB contains multiple security-targets, all security-targets If a BIB contains multiple security targets, all security targets
MUST be processed if the BIB is processed by the Node. The effect of MUST be processed if the BIB is processed by the Node. The effect of
this is to be the same as if each security-target had been this is to be the same as if each security target had been
represented by an individual BIB with a single security-target. represented by an individual BIB with a single security target.
5.2. Bundle Fragmentation and Reassembly 5.2. Bundle Fragmentation and Reassembly
If it is necessary for a node to fragment a bundle and security If it is necessary for a node to fragment a bundle and security
services have been applied to that bundle, the fragmentation rules services have been applied to that bundle, the fragmentation rules
described in [BPBIS] MUST be followed. As defined there and repeated described in [BPBIS] MUST be followed. As defined there and repeated
here for completeness, only the payload may be fragmented; security here for completeness, only the payload may be fragmented; security
blocks, like all extension blocks, can never be fragmented. blocks, like all extension blocks, can never be fragmented.
Due to the complexity of bundle fragmentation, including the Due to the complexity of bundle fragmentation, including the
possibility of fragmenting bundle fragments, integrity and possibility of fragmenting bundle fragments, integrity and
confidentiality operations are not to be applied to a bundle confidentiality operations are not to be applied to a bundle
representing a fragment (i.e., a bundle whose "bundle is a Fragment" representing a fragment (i.e., a bundle whose "bundle is a Fragment"
flag is set in the Bundle Processing Control Flags field). flag is set in the Bundle Processing Control Flags field).
Specifically, a BCB or BIB MUST NOT be added to a bundle fragment, Specifically, a BCB or BIB MUST NOT be added to a bundle fragment,
even if the security-target of the security block is not the payload. even if the security target of the security block is not the payload.
When integrity and confidentiality must be applied to a fragment, we When integrity and confidentiality must be applied to a fragment, we
RECOMMEND that encapsulation be used instead. RECOMMEND that encapsulation be used instead.
6. Key Management 6. Key Management
Key management in delay-tolerant networks is recognized as a Key management in delay-tolerant networks is recognized as a
difficult topic and is one that this specification does not attempt difficult topic and is one that this specification does not attempt
to solve. to solve.
7. Policy Considerations 7. Policy Considerations
When implementing BPSec, several policy decisions must be considered. When implementing BPSec, several policy decisions must be considered.
This section describes key policies that affect the generation, This section describes key policies that affect the generation,
forwarding, and receipt of bundles that are secured using this forwarding, and receipt of bundles that are secured using this
specification. specification.
o If a bundle is received that contains more than one security- o If a bundle is received that contains more than one security
operation, in violation of BPSec, then the BPA must determine how operation, in violation of BPSec, then the BPA must determine how
to handle this bundle. The bundle may be discarded, the block to handle this bundle. The bundle may be discarded, the block
affected by the security-operation may be discarded, or one affected by the security operation may be discarded, or one
security-operation may be favored over another. security operation may be favored over another.
o BPAs in the network MUST understand what security-operations they o BPAs in the network MUST understand what security operations they
should apply to bundles. This decision may be based on the source should apply to bundles. This decision may be based on the source
of the bundle, the destination of the bundle, or some other of the bundle, the destination of the bundle, or some other
information related to the bundle. information related to the bundle.
o If an intermediate receiver has been configured to add a security- o If an intermediate receiver has been configured to add a security
operation to a bundle, and the received bundle already has the operation to a bundle, and the received bundle already has the
security-operation applied, then the receiver MUST understand what security operation applied, then the receiver MUST understand what
to do. The receiver may discard the bundle, discard the security- to do. The receiver may discard the bundle, discard the security
target and associated BPSec blocks, replace the security- target and associated BPSec blocks, replace the security
operation, or some other action. operation, or some other action.
o It is recommended that security operations only be applied to the o It is recommended that security operations only be applied to the
payload block, the primary block, and any block-types specifically payload block, the primary block, and any block-types specifically
identified in the security policy. If a BPA were to apply identified in the security policy. If a BPA were to apply
security operations such as integrity or confidentiality to every security operations such as integrity or confidentiality to every
block in the bundle, regardless of the block type, there could be block in the bundle, regardless of the block type, there could be
downstream errors processing blocks whose contents must be downstream errors processing blocks whose contents must be
inspected at every hop in the network path. inspected at every hop in the network path.
o Adding a BIB to a security-target that has already been encrypted 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 by a BCB is not allowed. Therefore, we recommend three methods to
add an integrity signature to an encrypted security-target. add an integrity signature to an encrypted security target.
1. At the time of encryption, an integrity signature may be 1. At the time of encryption, an integrity signature may be
generated and added to the BCB for the security-target as generated and added to the BCB for the security target as
additional information in the security-result field. additional information in the security result field.
2. The encrypted block may be replicated as a new block and 2. The encrypted block may be replicated as a new block and
integrity signed. integrity signed.
3. An encapsulation scheme may be applied to encapsulate the 3. An encapsulation scheme may be applied to encapsulate the
security-target (or the entire bundle) such that the security target (or the entire bundle) such that the
encapsulating structure is, itself, no longer the security- encapsulating structure is, itself, no longer the security
target of a BCB and may therefore be the security-target of a target of a BCB and may therefore be the security target of a
BIB. BIB.
8. Security Considerations 8. Security Considerations
Given the nature of delay-tolerant networking applications, it is Given the nature of delay-tolerant networking applications, it is
expected that bundles may traverse a variety of environments and expected that bundles may traverse a variety of environments and
devices which each pose unique security risks and requirements on the devices which each pose unique security risks and requirements on the
implementation of security within BPSEC. For these reasons, it is implementation of security within BPSEC. For these reasons, it is
important to introduce key threat models and describe the roles and important to introduce key threat models and describe the roles and
responsibilities of the BPSEC protocol in protecting the responsibilities of the BPSEC protocol in protecting the
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from one of the endpoints. from one of the endpoints.
8.2. Attacker Behaviors and BPSec Mitigations 8.2. Attacker Behaviors and BPSec Mitigations
8.2.1. Eavesdropping Attacks 8.2.1. Eavesdropping Attacks
Once Mallory has received a bundle, she is able to examine the Once Mallory has received a bundle, she is able to examine the
contents of that bundle and attempt to recover any protected data or contents of that bundle and attempt to recover any protected data or
cryptographic keying material from the blocks contained within. The cryptographic keying material from the blocks contained within. The
protection mechanism that BPSec provides against this action is the protection mechanism that BPSec provides against this action is the
BCB, which encrypts the contents of its security-target, providing BCB, which encrypts the contents of its security target, providing
confidentiality of the data. Of course, it should be assumed that confidentiality of the data. Of course, it should be assumed that
Mallory is able to attempt offline recovery of encrypted data, so the Mallory is able to attempt offline recovery of encrypted data, so the
cryptographic mechanisms selected to protect the data should provide cryptographic mechanisms selected to protect the data should provide
a suitable level of protection. a suitable level of protection.
When evaluating the risk of eavesdropping attacks, it is important to When evaluating the risk of eavesdropping attacks, it is important to
consider the lifetime of bundles on a DTN. Depending on the network, 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 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 on the network for years and the cipher suite used for a BCB provides
inadequate protection, Mallory may be able to recover the protected inadequate protection, Mallory may be able to recover the protected
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will also be able to modify the received bundle, including non-BPSec will also be able to modify the received bundle, including non-BPSec
data such as the primary block, payload blocks, or block processing data such as the primary block, payload blocks, or block processing
control flags as defined in [BPBIS]. Mallory will be able to control flags as defined in [BPBIS]. Mallory will be able to
undertake activities which include modification of data within the undertake activities which include modification of data within the
blocks, replacement of blocks, addition of blocks, or removal of blocks, replacement of blocks, addition of blocks, or removal of
blocks. Within BPSec, both the BIB and BCB provide integrity blocks. Within BPSec, both the BIB and BCB provide integrity
protection mechanisms to detect or prevent data manipulation attempts protection mechanisms to detect or prevent data manipulation attempts
by Mallory. by Mallory.
The BIB provides that protection to another block which is its The BIB provides that protection to another block which is its
security-target. The cryptographic mechansims used to generate the security target. The cryptographic mechansims used to generate the
BIB should be strong against collision attacks and Mallory should not BIB should be strong against collision attacks and Mallory should not
have access to the cryptographic material used by the originating have access to the cryptographic material used by the originating
node to generate the BIB (e.g., K_A). If both of these conditions 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 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 BIB and lead Bob to validate the security target as originating from
Alice. Alice.
Since BPSec security operations are implemented by placing blocks in Since BPSec security operations are implemented by placing blocks in
a bundle, there is no in-band mechanism for detecting or correcting a bundle, there is no in-band mechanism for detecting or correcting
certain cases where Mallory removes blocks from a bundle. If Mallory certain cases where Mallory removes blocks from a bundle. If Mallory
removes a BCB block, but keeps the security-target, the security- removes a BCB block, but keeps the security target, the security
target remains encrypted and there is a possibility that there may no target remains encrypted and there is a possibility that there may no
longer be sufficient information to decrypt the block at its longer be sufficient information to decrypt the block at its
destination. If Mallory removes both a BCB (or BIB) and its destination. If Mallory removes both a BCB (or BIB) and its security
security-target there is no evidence left in the bundle of the target there is no evidence left in the bundle of the security
security operation. Similarly, if Mallory removes the BIB but not operation. Similarly, if Mallory removes the BIB but not the
the security-target there is no evidence left in the bundle of the security target there is no evidence left in the bundle of the
security operation. In each of these cases, the implementation of security operation. In each of these cases, the implementation of
BPSec MUST be combined with policy configuration at endpoints in the BPSec MUST be combined with policy configuration at endpoints in the
network which describe the expected and required security operations network which describe the expected and required security operations
that must be applied on transmission and are expected to be present that must be applied on transmission and are expected to be present
on receipt. This or other similar out-of-band information is on receipt. This or other similar out-of-band information is
required to correct for removal of security information in the required to correct for removal of security information in the
bundle. bundle.
A limitation of the BIB may exist within the implementation of BIB A limitation of the BIB may exist within the implementation of BIB
validation at the destination node. If Mallory is a legitimate node 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 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 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 only validating that the BIB was generated by a legitimate user, Bob
will acknowledge the message as originating from Mallory instead of will acknowledge the message as originating from Mallory instead of
Alice. In order to provide verifiable integrity checks, both a BIB Alice. In order to provide verifiable integrity checks, both a BIB
and BCB should be used. Alice creates a BIB with the protected data 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 block as the security target and then creates a BCB with both the BIB
and protected data block as its security-targets. In this and protected data block as its security targets. In this
configuration, since Mallory is only a legitimate node and does not 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 have access to Alice's key K_A, Mallory is unable to decrypt the BCB
and replace the BIB. and replace the BIB.
8.2.3. Topology Attacks 8.2.3. Topology Attacks
If Mallory is in a MITM position within the DTN, she is able to 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 influence how any bundles that come to her may pass through the
network. Upon receiving and processing a bundle that must be routed network. Upon receiving and processing a bundle that must be routed
elsewhere in the network, Mallory has three options as to how to elsewhere in the network, Mallory has three options as to how to
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time may be extremely large. This may limit the utility of time may be extremely large. This may limit the utility of
session key generation mechanisms, such as Diffie-Hellman, as a session key generation mechanisms, such as Diffie-Hellman, as a
two-way handshake may not be feasible or reliable. two-way handshake may not be feasible or reliable.
o Opportunistic Access: Depending on the application environment, a o Opportunistic Access: Depending on the application environment, a
given endpoint may not be guaranteed to be accessible within a given endpoint may not be guaranteed to be accessible within a
certain amount of time. This may make asymmetric cryptographic certain amount of time. This may make asymmetric cryptographic
architectures which rely on a key distribution center or other architectures which rely on a key distribution center or other
trust center impractical under certain conditions. trust center impractical under certain conditions.
10. Conformance 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 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 All implementations are strongly RECOMMENDED to provide some method
of hop-by-hop verification by generating a hash to some canonical of hop-by-hop verification by generating a hash to some canonical
form of the bundle and placing an integrity signature on that form form of the bundle and placing an integrity signature on that form
using a BIB. using a BIB.
11. IANA Considerations 12. IANA Considerations
This protocol has fields that have been registered by IANA. This protocol has fields that have been registered by IANA.
11.1. Bundle Block Types 12.1. Bundle Block Types
This specification allocates three block types from the existing This specification allocates three block types from the existing
"Bundle Block Types" registry defined in [RFC6255] . "Bundle Block Types" registry defined in [RFC6255] .
Additional Entries for the Bundle Block-Type Codes Registry: Additional Entries for the Bundle Block-Type Codes Registry:
+-------+-----------------------------+---------------+ +-------+-----------------------------+---------------+
| Value | Description | Reference | | Value | Description | Reference |
+-------+-----------------------------+---------------+ +-------+-----------------------------+---------------+
| 2 | Block Integrity Block | This document | | 2 | Block Integrity Block | This document |
| 3 | Block Confidentiality Block | This document | | 3 | Block Confidentiality Block | This document |
+-------+-----------------------------+---------------+ +-------+-----------------------------+---------------+
Table 2 Table 2
11.2. Cipher Suite Flags 12.2. Cipher Suite Flags
This protocol has a cipher suite flags field and certain flags are This protocol has a cipher suite flags field and certain flags are
defined. An IANA registry has been set up as follows. defined. An IANA registry has been set up as follows.
The registration policy for this registry is: Specification Required The registration policy for this registry is: Specification Required
The Value range is: Variable Length The Value range is: Variable Length
Cipher Suite Flag Registry: Cipher Suite Flag Registry:
+--------------------------+-------------------------+--------------+ +--------------------------+-------------------------+--------------+
skipping to change at page 32, line 22 skipping to change at page 33, line 22
| 1 | Block Contains | This | | 1 | Block Contains | This |
| | parameters | document | | | parameters | document |
| 2 | Source EID ref present | This | | 2 | Source EID ref present | This |
| | | document | | | | document |
| >3 | Reserved | This | | >3 | Reserved | This |
| | | document | | | | document |
+--------------------------+-------------------------+--------------+ +--------------------------+-------------------------+--------------+
Table 3 Table 3
11.3. Parameters and Results 12.3. Parameters and Results
This protocol has fields for cipher suite parameters and results. This protocol has fields for cipher suite parameters and results.
The field is a type-length-value triple and a registry is required The field is a type-length-value triple and a registry is required
for the "type" sub-field. The values for "type" apply to both the for the "type" sub-field. The values for "type" apply to both the
cipher suite parameters and the cipher suite results fields. Certain cipher suite parameters and the cipher suite results fields. Certain
values are defined. An IANA registry has been set up as follows. values are defined. An IANA registry has been set up as follows.
The registration policy for this registry is: Specification Required The registration policy for this registry is: Specification Required
The Value range is: 8-bit unsigned integer. The Value range is: 8-bit unsigned integer.
Cipher Suite Parameters and Results Type Registry: Cipher Suite Parameters and Results Type Registry:
+---------+-------------------------------------------+-------------+ +---------+-------------------------------------------+-------------+
| Value | Description | Reference | | Value | Description | Reference |
+---------+-------------------------------------------+-------------+ +---------+-------------------------------------------+-------------+
| 0 | reserved | Section 3.7 | | 0 | reserved | Section 3.6 |
| 1 | initialization vector (IV) | Section 3.7 | | 1 | initialization vector (IV) | Section 3.6 |
| 2 | reserved | Section 3.7 | | 2 | reserved | Section 3.6 |
| 3 | key-information | Section 3.7 | | 3 | key information | Section 3.6 |
| 4 | content-range (pair of Unsigned Integers) | Section 3.7 | | 4 | content-range (pair of Unsigned Integers) | Section 3.6 |
| 5 | integrity signature | Section 3.7 | | 5 | integrity signature | Section 3.6 |
| 6 | unassigned | Section 3.7 | | 6 | unassigned | Section 3.6 |
| 7 | salt | Section 3.7 | | 7 | salt | Section 3.6 |
| 8 | BCB integrity check value (ICV) | Section 3.7 | | 8 | BCB integrity check value (ICV) | Section 3.6 |
| 9-191 | reserved | Section 3.7 | | 9-191 | reserved | Section 3.6 |
| 192-250 | private use | Section 3.7 | | 192-250 | private use | Section 3.6 |
| 251-255 | reserved | Section 3.7 | | 251-255 | reserved | Section 3.6 |
+---------+-------------------------------------------+-------------+ +---------+-------------------------------------------+-------------+
Table 4 Table 4
12. References 13. References
12.1. Normative References 13.1. Normative References
[BPBIS] Burleigh, S., Fall, K., and E. Birrane, "Bundle Protocol", [BPBIS] Burleigh, S., Fall, K., and E. Birrane, "Bundle Protocol",
draft-ietf-dtn-bpbis-04 (work in progress), July 2016. draft-ietf-dtn-bpbis-04 (work in progress), July 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC [RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552, Text on Security Considerations", BCP 72, RFC 3552,
DOI 10.17487/RFC3552, July 2003, DOI 10.17487/RFC3552, July 2003,
<http://www.rfc-editor.org/info/rfc3552>. <http://www.rfc-editor.org/info/rfc3552>.
[RFC6255] Blanchet, M., "Delay-Tolerant Networking Bundle Protocol [RFC6255] Blanchet, M., "Delay-Tolerant Networking Bundle Protocol
IANA Registries", RFC 6255, May 2011. IANA Registries", RFC 6255, May 2011.
12.2. Informative References 13.2. Informative References
[BPBISCBOR] [BPBISCBOR]
Burleigh, S., "Bundle Protocol CBOR Representation Burleigh, S., "Bundle Protocol CBOR Representation
Specification", draft-burleigh-dtn-rs-cbor-01 (work in Specification", draft-burleigh-dtn-rs-cbor-01 (work in
progress), April 2016. progress), April 2016.
[RFC4838] Cerf, V., Burleigh, S., Hooke, A., Torgerson, L., Durst, [RFC4838] Cerf, V., Burleigh, S., Hooke, A., Torgerson, L., Durst,
R., Scott, K., Fall, K., and H. Weiss, "Delay-Tolerant R., Scott, K., Fall, K., and H. Weiss, "Delay-Tolerant
Networking Architecture", RFC 4838, April 2007. Networking Architecture", RFC 4838, April 2007.
 End of changes. 104 change blocks. 
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