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Internet Engineering Task Force                               D. Kuptsov
Internet-Draft                                                 A. Gurtov
Intended status: Informational        Helsinki Institute for Information
Expires: September 15, 2011                 Technology, Aalto University
                                                                D. Zhang
                                             Huawei Technologies Co.,Ltd
                                                          March 14, 2011


    Hierarchical Host Identity Tags (HHIT) Verification Architecture
                         draft-kuptsov-hhit-05

Abstract

   This document describes the architecture for hierarchical host
   identity tags (HHIT) vrification for HIP protocol.

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   publication of this document.  Please review these documents
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Structure of HHIT . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Use case  . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
   4.  Experimental observations . . . . . . . . . . . . . . . . . . . 7
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
   6.  Normative References  . . . . . . . . . . . . . . . . . . . . . 8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 8


































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1.  Introduction

   This document describes the architecture for hierarchical host
   identity tags (HHIT) vrification for Host Identity Protocol (HIP) RFC
   5201 [RFC5201].

   The purpose of HHIT architecture is to enable online verification of
   flat identifiers (in a scalable way), such as Host Identity Tags
   (HIT), by corresponding organizations that are responsible for
   clients holding such identifiers.  While one way of verifying whether
   HIT belongs to a client that is affiliated with some organization (or
   unit within organization) is to use certificates; such approach can
   be undesired because it (i) introduces high cost for certificate
   verification, and (ii) does not directly allow certificate status
   verification (consider the situation when private key of a particular
   host was stolen and firewall enforcing certificate verification does
   not check the revocation status of host's certificate).


2.  Structure of HHIT

   The following are the goals of HHIT: (i) allow any on the path
   security gateway to distinguish to which authority the identifier
   belongs, and later ask corresponding authority whether given HHIT is
   valid; (ii) prevent misuse of HHIT by attackers (specifically, the
   design allows to prevent replaying and constructing "fake" HHITs that
   will enable attackers to bypass the security gateways).

   The structure of hierarchical HHIT:






















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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                            OID                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                            HHIT                               |
   +                                                               |
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Type            |C|             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        ENC_HHIT_TIMESTAMP                     |
   +                                                               +
   |                                                               |
   +                                                               +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Padding (4 bytes)                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 1

   o  OID is organization identifier that depending of the application
      of HHIT can be globally unique (e.g., assigned by Internet
      Assigned Numbers Authority (IANA)), or unique within certain scope
      (e.g., within organization and assigned on per department or unit
      granularity).  Length of OID is 32 bits.

   o  HHIT is an output of a pseudo-random function (PRF) under one-time
      secret key and input taken as a concatenation of OID and flat
      identifier (HIT): HHIT=PRF(OID || HIT, secret) The length of HHIT
      field is 96 bits to guarantee sufficient level of security.

   o  ENC_HHIT_TIMESTAMP parameter guarantees freshness of HHIT, it
      contains the timestamp when particular HHIT was generated.  This
      field is encrypted (using symmetric encryption function) under the
      same one-time secret as HHIT: ENC_HHIT_TIMESTAMP = ENC(HHIT ||
      #epoch || padding (96 bits), secret), where HHIT is as described
      above, #epoch is a timestamp indicating the time when HHIT was
      constructed, and secret is the next yet unused secret key from a
      key pull, assigned to a client by its authority.  Because the



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      usage of block cipher is assumed for encryption, the length of
      ENC_HHIT_TIMESTAMP field is a multiple of the block size of a
      particular encryption algorithm.  Length of #epoch is 64 bits to
      allow encode timestamp in microseconds.  As a result, the length
      of ENC_HHIT_TIMESTAMP when used together with AES-CBC algorithm,
      is 2*128 bits.

   Because total length of OID||HHIT||ENC_HHIT_TIMESTAMP exceeds
   reserved 128 bits for source address in HIP protocol, the Sender's
   Host Identity Tag should contain only OID||HHIT, while
   ENC_HHIT_TIMESTAMP should be carried as mandatory HIP parameter in I1
   packet.


3.  Use case

   Next we describe a possible use case - access control with HHIT:

                          Register HHIT (offline)
   +----------------------+------------------>+-------------+
   |                      |                   |  Domain 1   |
   |Client (from domain 1)|    Secret keys    |  authority  |
   +----------------------+<------------------+-------+-----+
                          |                  HHIT /\  | OK
                          |                       |   v
                          |   I1              +---+---------+
                          +------------------>|  Security   |-->...
                          +------------------>|  gateway    |
                          |   I1              +---+---+-----+
                          |                  HHIT |   /\
                          |   Register HHIT       v   |  Ok
   +----------------------+------------------>+-------------+
   |Client (from domain 2)|                   |  Domain 2   |
   |                      |    Secret keys    |  authority  |
   +----------------------+<------------------+-------+-----+

                                 Figure 2

   We outline the protocol interaction:

   o  Each end-host that belongs to some organization, or organizational
      unit, constructs its HIT (using the procedure described in RFC
      5201 [RFC5201]), and registers it in an offline manner in its
      organizational repository.  Depending on the application, the
      registration itself can involve authentication, e.g. using
      passwords, certificates, biometric information, passport, etc.
      Upon verification, domain authority generates set of one-time-
      passwords (the number of such passwords again depends on the



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      application needs), and for each secret s populates its database
      with the following records: HHIT = PRF(OID || HIT, s) Domain
      authority then returns list of secrets to client over secure
      channel (how this is achieved is out of scope).

   o  When a client wants to access the service that is behind security
      gateway, it chooses next unused one-time secret "unused secret"
      and constructs the HHIT as PRF(OID || HIT, "unused secret"), it
      also takes the current #epoch "now" and constructs
      ENC_HHIT_TIMESTAMP parameter as ENC(HHIT || "now", "unused
      secret").

   o  Every I1 packet then contains: sender's Host Identity Tag field as
      (OID || HHIT), also parameter ENC_HHIT_TIMESTAMP is added such
      that domain authority can verify the freshness of HHIT.

   o  When security gateway receives such I1 packet, it will look-up the
      domain authority using OID found in the sender's Host Identity
      Tag, and submit OID, HHIT, and ENC_HHIT_TIMESTAMP to corresponding
      domain authority.  Security gateway will buffer I1 until it will
      receive (positive or negative) response from corresponding domain
      authority.

   o  Last, when domain authority receives OID, HHIT, and
      ENC_HHIT_TIMESTAMP for verification it looks up for the proper
      secret using HHIT as index.  If the record was not found, the
      domain authority immediately responds to a gateway that
      information is not valid.  Else, domain authority attempts to
      decrypt ENC_HHIT_TIMESTAMP field to find #epoch.  It also
      retrieves the last registered I1 timestamp (if any) -- "#epoch
      last".  To mitigate possible replays, for every received I1 packet
      domain authority should check the timestamp found in
      ENC_HHIT_TIMESTAMP, and the timestamp of previously seen I1 packet
      for the same source.  Optimally, timestamp found in received I1
      packet should be grater then the last registered timestamp, i.e.,
      the timestamps for the same source should be monotonically
      increasing #epoch > "#epoch last".  However, consecutive I1s can
      be reordered, i.e., #epoch < "#epoch last".  In this case if
      "#epoch last" - #epoch > Delta, the HHIT will be considered as
      invalid, and negative response will be sent to security gateway.

   o  Security gateway will make a forwarding decision regarding
      particular buffered I1 packet based on the response it receives
      from domain authority: if the response is negative I1 packet is
      dropped, otherwise the state will be created and I1 will be
      forwarded.  Note, for consequent R1, I2, R2 packets the forwarding
      decisions by security gateway are done solely based on the stored
      internal state: if it exists the packets are forwarded, otherwise



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      dropped.


4.  Experimental observations

   To grasp what would be the performance implications, we measured HHIT
   verification using 2 DHTs deployed in the Internet and single
   security gateway.  Each DHT was mimic single domain authority.  We
   generated storms of I1 packets towards security gateway, using
   exponential distribution for interarrival times with different lambda
   parameter 1,10,100,1000 which corresponded to average interarrival
   times 1000, 100, 10, 1 (ms) respectively.  We then measured 3
   parameters: (a) drop rate (due to failed verification when I1 arrived
   out off order, or connection timeout), (b) HHIT verification duration
   (ms) and (c) queue buildup (number of I1 packets waiting for
   verification request completion).  We present mean and median
   statistics for these parameters in the table below.

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Experimental results (mean/median)               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Parameter   | lambda=1  | lambda=10 | lambda=100| lambda=1000 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Droprate(%) |0.016/0.014|0.017/0.015| 0.68/0.76 | 0.909/0.901 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Verification|1304/902.6 | 1339/896.7| 1586/982.2| 3826/2204   |
   | duration(ms)|           |           |           |             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Queue size  |   2.4/2   | 18.04/17.0|301.5/283.0|  1009/1022  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 3


5.  Security Considerations

   We mentioned earlier that for every sent I1 packet, sender picks next
   unused one-time secret to produce HHIT and ENC_HHIT_TIMESTAMP.
   However, it can be sufficient for domain authority and particular
   client to share a single secret which is rotated every time T (where
   T can be on the scale of days).

   The Delta threshold should be relatively small to prevent replays.
   Thus, Delta should be of order of few hundred milliseconds to
   guarantee sufficient level of security.






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6.  Normative References

   [RFC5201]  Moskowitz, R., Nikander, P., Jokela, P., and T. Henderson,
              "Host Identity Protocol", RFC 5201, April 2008.


Authors' Addresses

   Dmitriy Kuptsov
   Helsinki Institute for Information Technology, Aalto University
   PO Box 19215
   Espoo  00076 Aalto
   Finland

   Phone:
   Email: dmitriy.kuptsov@hiit.fi


   Andrei Gurtov
   Helsinki Institute for Information Technology, Aalto University
   PO Box 19215
   Espoo  00076 Aalto
   Finland

   Phone:
   Email: gurtov@hiit.fi


   Dacheng Zhang
   Huawei Technologies Co.,Ltd
   PO Box 19215
   Beijing
   China

   Phone:
   Email: zhangdacheng@huawei.com















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