TOC 
Mobile Ad hoc Networking (MANET)U. Herberg
Internet-DraftT. Clausen
Intended status: Standards TrackLIX, Ecole Polytechnique
Expires: January 14, 2010July 13, 2009


MANET Cryptographical Signature TLV Definition
draft-herberg-manet-packetbb-sec-01

Status of this Memo

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Abstract

This document describes a general and flexible TLV (type-length-value structure) for representing cryptographic signatures as well as timestamps, using the generalized MANET packet/message format [RFC5444] (Clausen, T., Dearlove, C., Dean, J., and C. Adjih, “Generalized MANET Packet/Message Format,” February 2009.). It defines two Message TLVs and two Packet TLVs, for affixing a cryptographic signature and a timestamp to a packet and message, respectively.



Table of Contents

1.  Introduction
2.  Terminology
3.  Applicability Statement
4.  Protocol Overview and Functioning
5.  General SIGNATURE TLV Structure
6.  General TIMESTAMP TLV Structure
7.  Message TLVs
    7.1.  Message SIGNATURE TLV
    7.2.  Message TIMESTAMP TLV
8.  Packet TLVs
    8.1.  Packet SIGNATURE TLV
        8.1.1.  Packet TIMESTAMP TLV
9.  IANA Considerations
    9.1.  TLV Registrations
        9.1.1.  Expert Review: Evaluation Guidelines
        9.1.2.  Message TLV Type Registrations
        9.1.3.  Packet TLV Type Registrations
    9.2.  New IANA registries
        9.2.1.  Expert Review: Evaluation Guidelines
        9.2.2.  Hash-Function Registry
        9.2.3.  Cryptographic Algorithm Registry
10.  Security Considerations
11.  Acknowledgements
12.  References
    12.1.  Normative References
    12.2.  Informative References
Appendix A.  Examples
    A.1.  Example Signed Message
§  Authors' Addresses




 TOC 

1.  Introduction

This document:

This document does not stipulate how to sign, validate, or encrypt messages. A specification of a routing protocol or routing protocol extension, using the security representation of this document, MUST specify appropriate interpretation of the TLVs. This document does specifically not suggest specific cryptographic algorithms or hash functions, but rather establishes IANA registries for such.



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2.  Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.).

This document uses the terminology and notation defined in [RFC5444] (Clausen, T., Dearlove, C., Dean, J., and C. Adjih, “Generalized MANET Packet/Message Format,” February 2009.). Additionally, it defines the following terminology:



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3.  Applicability Statement

The packet and message format defined in [RFC5444] (Clausen, T., Dearlove, C., Dean, J., and C. Adjih, “Generalized MANET Packet/Message Format,” February 2009.) accords MANET routing protocols using this format the ability to carry additional information in control messages, through inclusion of TLVs. Information so included in a control message MAY be used by the routing protocol, or an extension of the routing protocol, according to its specification.

This document specifies how to include a cryptographic signature for a packet or message by way of TLVs, as specified in [RFC5444] (Clausen, T., Dearlove, C., Dean, J., and C. Adjih, “Generalized MANET Packet/Message Format,” February 2009.). This document also specifies how to treat "mutable" fields (<msg-hop-count> and <msg-hop-limit>) in the message header when calculating the signature, such that the resulting signature can be correctly verified by any recipient, and how to include this signature. A MANET routing protocol, or an extension of a MANET routing protocol, MAY use such included cryptographic signatures for, for example, rejecting messages where signature verification fails.

Basic MANET routing protocol specifications are often "oblivious to security", however have a clause allowing a control message to be rejected as "badly formed" prior to it being processed or forwarded. Protocols such as [NHDP] (Clausen, T., Dean, J., and C. Dearlove, “MANET Neighborhood Discovery Protocol (NHDP),” July 2009.) recognize external reasons (such as failure to verify a signature) as being reasons for rejecting a message as "badly formed" and there "invalid for processing". This is the result of the observation that with respect to security in MANETs, "one size rarely fits all" and that MANET routing protocol deployment domains have varying security requirements ranging from "unbreakable" to "virtually none". The virtue of this approach is that MANET routing protocol specifications (and implementations) can remain "generic", with extensions providing proper deployment-domain specific security mechanisms.

The MANET routing protocol "security architecture", in which this specification situates itself, can therefore be summarized as follows:

This document addresses the last of these issues, by specifying a common exchange format for cryptographic signatures. This document also makes reservations from within the Message TLV and Packet TLV registries of [RFC5444] (Clausen, T., Dearlove, C., Dean, J., and C. Adjih, “Generalized MANET Packet/Message Format,” February 2009.), to be used (and shared) among MANET routing protocol security extensions. Finally, this document establishes two IANA registries for code-points for hash functions and signature functions for use by protocols adhering to [RFC5444] (Clausen, T., Dearlove, C., Dean, J., and C. Adjih, “Generalized MANET Packet/Message Format,” February 2009.).

With respect to [RFC5444] (Clausen, T., Dearlove, C., Dean, J., and C. Adjih, “Generalized MANET Packet/Message Format,” February 2009.), this document:



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4.  Protocol Overview and Functioning

This specification does not describe a protocol, nor does it mandate specific router or protocol behavior. It represents a purely syntactical representation of security related information for use with [RFC5444] (Clausen, T., Dearlove, C., Dean, J., and C. Adjih, “Generalized MANET Packet/Message Format,” February 2009.) messages and packets, as well as sets up IANA registrations and registries.



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5.  General SIGNATURE TLV Structure

The following data structure allows the representation of a cryptographic signature, including specification of the appropriate hash function and cryptographic algorithm used for calculating the signature. This <signature> data structure is specified, using the regular expression syntax of [RFC5444] (Clausen, T., Dearlove, C., Dean, J., and C. Adjih, “Generalized MANET Packet/Message Format,” February 2009.), as:

          <signature> := <hash-function>
                         <cryptographic-algorithm>
                         <signature-value>

where:

<hash-function>
is an 8-bit unsigned integer field specifying the hash function according to Table 3 (Hash-Function registry).
<cryptographic-algorithm>
is an 8-bit unsigned integer field specifying the cryptographic function according to Table 4 (Cryptographic algorithm registry).
<signature-value>
is an unsigned integer field, whose length is <tlv-length>-2, and which contains the cryptographic signature.

The rationale for separating the hash function and the cryptographic function into two octets instead of having all combinations in a single octet -- possibly as TLV type extension -- is twofold: First, if further hash or cryptographic functions are added in the future, the number space might not be continuous any more. More importantly, the number space of 256 possible combinations is rapidly exhausted. For example, having only 16 different hash functions and 16 different cryptographic functions would lead to exhaustion. As new or improved cryptographic mechanism are continuously being developed and introduced, this format should be able to accommodate such for the foreseeable future.

The rationale for not including a field that lists parameters of the cryptographic signature in the TLV is the following: Before being able to to validate a cryptographic signature, routers have to exchange keys (e.g. public keys). Any additional parameters can be exchanged together with the keys in this bootstrap process. It is therefore not necessary, and would even entail an extra overhead, to transmit the parameters within every message.

The basic version of this TLV assumes that calculating the signature can be decomposed into:

signature-value = cryptographic-function(hash-function(message))

with cryptographic-function and hash-function being selected from Table 3 (Hash-Function registry) and Table 4 (Cryptographic algorithm registry) respectively (where either of them can be the identity function -- indicated by "none" in the registry). The type extension 0 is assumed to indicate this decomposition. Otherwise, if this decomposition is not possible, the type extension field can be used for indication how signatures are to be calculated.

The algorithm that is used for calculating the hash function MUST be selected from one of those listed in Table 3 (Hash-Function registry). Furthermore, <hash-function> MUST correspond to the number in that table assigned by IANA.

The algorithm that is used for calculating the cryptographic algorithm MUST be selected from one of those listed in Table 4 (Cryptographic algorithm registry). Furthermore, <cryptographic-algorithm> MUST correspond to the number in that table assigned by IANA. If the selected hash function is "none" (0), the cryptographic function MUST NOT be "none" (0).



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6.  General TIMESTAMP TLV Structure

The following data structure allows the representation of a timestamp. This <timestamp> data structure is specified as:

       <timestamp> := <time-value>

where:

<time-value>
is an unsigned integer field, whose length is <tlv-length>, and which contains the timestamp. The value of this variable is to be interpreted by the routing protocol as specified by the type extension of the TIMESTAMP TLV (refer to Table 2 (Packet TLV types)).

A timestamp is essentially "freshness information". As such, its setting and interpretation is to be determined by the routing protocol (or the extension) that uses it, and may e.g. correspond to a UNIX-timestamp, GPS timestamp or a simple sequence number. This is out of the scope of this specification.



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7.  Message TLVs

Two Message TLVs are defined, for including the cryptographic signature of a message, and for including the timestamp indicating the time at which the cryptographic signature was calculated.



 TOC 

7.1.  Message SIGNATURE TLV

A Message SIGNATURE TLV is an example of a SIGNATURE TLV as described in Section 5 (General SIGNATURE TLV Structure). When determining the <signature-value> for a message, the signature is calculated over the entire message with the following considerations:



 TOC 

7.2.  Message TIMESTAMP TLV

A Message TIMESTAMP TLV is an example of a TIMESTAMP TLV as described in Section 6 (General TIMESTAMP TLV Structure).



 TOC 

8.  Packet TLVs

Two Packet TLVs are defined, for including the cryptographic signature of a packet, and for including the timestamp indicating the time at which the cryptographic signature was calculated.



 TOC 

8.1.  Packet SIGNATURE TLV

A Packet SIGNATURE TLV is an example of a SIGNATURE TLV as described in Section 5 (General SIGNATURE TLV Structure). When calculating the <signature-value> for a Packet, the signature is calculated over the entire Packet, including the packet header, all Packet TLVs (other than Packet SIGNATURE TLVs) and all included Messages and their message headers.



 TOC 

8.1.1.  Packet TIMESTAMP TLV

A Packet TIMESTAMP TLV is an example of a TIMESTAMP TLV as described in Section 6 (General TIMESTAMP TLV Structure).



 TOC 

9.  IANA Considerations



 TOC 

9.1.  TLV Registrations

This specification defines two Message TLV types which must be allocated from the 0-127 range of the "Assigned Message TLV Types" repository of [RFC5444] (Clausen, T., Dearlove, C., Dean, J., and C. Adjih, “Generalized MANET Packet/Message Format,” February 2009.) as specified in Table 1 (Message TLV types) and two Packet TLV types which must be allocated from the 0-223 range of the "Assigned Packet TLV Types" repository of [RFC5444] (Clausen, T., Dearlove, C., Dean, J., and C. Adjih, “Generalized MANET Packet/Message Format,” February 2009.) as specified in Table 2 (Packet TLV types).

IANA is requested to assign the same numerical value to the Message TLV and Packet TLV types with the same name.



 TOC 

9.1.1.  Expert Review: Evaluation Guidelines

For the registries for TLV type extensions where an Expert Review is required, the designated expert SHOULD take the same general recommendations into consideration as are specified by [RFC5444] (Clausen, T., Dearlove, C., Dean, J., and C. Adjih, “Generalized MANET Packet/Message Format,” February 2009.).



 TOC 

9.1.2.  Message TLV Type Registrations

The Message TLVs as specified in Table 1 (Message TLV types) must be allocated from the "Message TLV Types" namespace of [RFC5444] (Clausen, T., Dearlove, C., Dean, J., and C. Adjih, “Generalized MANET Packet/Message Format,” February 2009.).



NameTypeType ExtensionDescription
SIGNATURE TBD1 0 Signature of a message
    1-223 Expert Review
    224-255 Experimental Use
TIMESTAMP TBD2 0 Unsigned timestamp of arbitrary length, given by the tlv-length field. The MANET routing protocol has to define how to interpret this timestamp
    1 Unsigned 32-bit timestamp (POSIX) representing the number of seconds elapsed since January 1, 1970
    2 NTP timestamp format as defined in [RFC4330] (Mills, D., “Simple Network Time Protocol (SNTP) Version 4 for IPv4, IPv6 and OSI,” January 2006.)
    3-223 Expert Review
    224-255 Experimental Use

 Table 1: Message TLV types 



 TOC 

9.1.3.  Packet TLV Type Registrations

The Packet TLVs as specified in Table 2 (Packet TLV types) must be allocated from the "Packet TLV Types" namespace of [RFC5444] (Clausen, T., Dearlove, C., Dean, J., and C. Adjih, “Generalized MANET Packet/Message Format,” February 2009.).



NameTypeType ExtensionDescription
SIGNATURE TBD3 0 Signature of a packet
    1-223 Expert Review
    224-255 Experimental Use
TIMESTAMP TBD4 0 Unsigned timestamp of arbitrary length, given by the tlv-length field. The MANET routing protocol has to define how to interpret this timestamp
    1 Unsigned 32-bit timestamp (POSIX) representing the number of seconds elapsed since January 1, 1970
    2 NTP timestamp format as defined in [RFC4330] (Mills, D., “Simple Network Time Protocol (SNTP) Version 4 for IPv4, IPv6 and OSI,” January 2006.)
    3-223 Expert Review
    224-255 Experimental Use

 Table 2: Packet TLV types 



 TOC 

9.2.  New IANA registries

This document specifies some values where IANA registries are required.



 TOC 

9.2.1.  Expert Review: Evaluation Guidelines

For the registries for the following tables where an Expert Review is required, the designated expert SHOULD take the same general recommendations into consideration as are specified by [RFC5444] (Clausen, T., Dearlove, C., Dean, J., and C. Adjih, “Generalized MANET Packet/Message Format,” February 2009.).



 TOC 

9.2.2.  Hash-Function Registry

IANA is requested to create a new registry for the hash functions that can be used when creating a signature. The initial assignments and allocation policies are specified in Table 3 (Hash-Function registry).



Hash function valueAlgorithmDescription
0 none The "identity function": the hash value of a message is the message itself
1 MD5 The hash function as specified in [RFC1321] (Rivest, R., “The MD5 Message-Digest Algorithm,” April 1992.)
2 SHA1 The hash function as specified in [RFC3174] (Eastlake, D. and P. Jones, “US Secure Hash Algorithm 1 (SHA1),” September 2001.)
3 SHA256 The hash function as specified in [SHA256] (, “Secure Hash Algorithm,” August 2002.)
4-223   Expert Review
224-255   Experimental Use

 Table 3: Hash-Function registry 



 TOC 

9.2.3.  Cryptographic Algorithm Registry

IANA is requested to create a new registry for the cryptographic function. Initial assignments and allocation policies are specified in Table 4 (Cryptographic algorithm registry).



Cryptographic algorithm valueAlgorithmDescription
0 none The "identity function": the value of an encrypted hash is the hash itself
1 RSA RSA as specified in [RFC2437] (Kaliski, B. and J. Staddon, “PKCS #1: RSA Cryptography Specifications Version 2.0,” October 1998.)
2 DSA DSA as specified in [DSA] (, “Digital Signature Standard,” May 1994.)
3 HMAC HMAC as specified in [RFC2104] (Krawczyk, H., Bellare, M., and R. Canetti, “HMAC: Keyed-Hashing for Message Authentication,” February 1997.)
4 3DES 3DES as specified in [3DES] (, “Triple Data Encryption Algorithm Modes of Operation,” 1998.)
5 AES AES as specified in [AES] (, “Advanced Encryption Standard (AES),” November 2001.)
6-223   Expert Review
224-255   Experimental Use

 Table 4: Cryptographic algorithm registry 



 TOC 

10.  Security Considerations

This document does not specify a protocol itself. However, it provides a syntactical component for cryptographic signatures of messages and packets as defined in [RFC5444] (Clausen, T., Dearlove, C., Dean, J., and C. Adjih, “Generalized MANET Packet/Message Format,” February 2009.). It can be used to address security issues of a protocol or extension that uses the component specified in this document. As such, it has the same security considerations as [RFC5444] (Clausen, T., Dearlove, C., Dean, J., and C. Adjih, “Generalized MANET Packet/Message Format,” February 2009.).

In addition, a protocol that includes this component MUST specify the usage as well as the security that is attained by the cryptographic signatures of a message or a packet.

As an example, a routing protocol that uses this component to reject "badly formed" messages if a control message does not contain a valid signature, should indicate the security assumption that if the signature is valid, the message is considered valid. It also should indicate the security issues that are counteracted by this measure (e.g. link or identity spoofing) as well as the issues that are not counteracted (e.g. compromised keys, replay attacks).



 TOC 

11.  Acknowledgements

The authors would like to thank Jerome Milan (Ecole Polytechnique) for his advice as cryptographer. In addition, many thanks to Alan Cullen (BAE), Justin Dean (NRL), Christopher Dearlove (BAE), and Henning Rogge (FGAN) for their constructive comments on the document.



 TOC 

12.  References



 TOC 

12.1. Normative References

[RFC2119] Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” RFC 2119, BCP 14, March 1997.
[RFC5444] Clausen, T., Dearlove, C., Dean, J., and C. Adjih, “Generalized MANET Packet/Message Format,” RFC 5444, February 2009.


 TOC 

12.2. Informative References

[3DES] “Triple Data Encryption Algorithm Modes of Operation,” ANSI X9.52-1998 , 1998.
[AES] “Advanced Encryption Standard (AES),” FIPS 197 , November 2001.
[DSA] “Digital Signature Standard,” NIST, FIPS PUB 186 , May 1994.
[NHDP] Clausen, T., Dean, J., and C. Dearlove, “MANET Neighborhood Discovery Protocol (NHDP),” work in progress draft-ietf-manet-nhdp-10.txt, July 2009.
[RFC1321] Rivest, R., “The MD5 Message-Digest Algorithm,” RFC 1321, April 1992 (TXT).
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, “HMAC: Keyed-Hashing for Message Authentication,” RFC 2104, February 1997 (TXT).
[RFC2437] Kaliski, B. and J. Staddon, “PKCS #1: RSA Cryptography Specifications Version 2.0,” RFC 2437, October 1998 (TXT, HTML, XML).
[RFC3174] Eastlake, D. and P. Jones, “US Secure Hash Algorithm 1 (SHA1),” RFC 3174, September 2001 (TXT).
[RFC4330] Mills, D., “Simple Network Time Protocol (SNTP) Version 4 for IPv4, IPv6 and OSI,” RFC 4330, January 2006 (TXT).
[SHA256] “Secure Hash Algorithm,” NIST FIPS 180-2 , August 2002.


 TOC 

Appendix A.  Examples



 TOC 

A.1.  Example Signed Message

The sample message depicted in Figure 1 (Example message with signature) is taken from the appendix of [RFC5444] (Clausen, T., Dearlove, C., Dean, J., and C. Adjih, “Generalized MANET Packet/Message Format,” February 2009.). However, a SIGNATURE Message TLV has been added. It is assumed that the SIGNATURE TLV type is lesser than the TLV type of the second message TLV (i.e. it comes first in the order of Message TLVs). The TLV has the thasvalue flags set ('1'). The TLV value represents a 15 octet long signature of the whole message.



      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 1 0 0 0|    Packet Sequence Number     | Message Type  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |1 1 1 1 0 0 0 0|0 0 0 0 0 0 0 0 0 1 0 0 1 0 1 0|   Orig Addr   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |           Originator Address (cont)           |   Hop Limit   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Hop Count   |    Message Sequence Number    |0 0 0 0 0 0 0 0|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 1 1 1 0 1|   SIGNATURE   |0 0 0 1 0 0 0 0| hash-function |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |crypto-function|0 0 0 0 1 1 1 1|     Signature Value           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      Signature Value (cont)                   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      Signature Value (cont)                   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      Signature Value (cont)                   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |Sig. Val (cont)|   TLV Type    |0 0 0 1 0 0 0 0|0 0 0 0 0 1 1 0|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                             Value                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Value (cont)          |0 0 0 0 0 0 1 0|0 0 1 1 0 0 0 0|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 0 0 1 0|              Mid              |      Mid      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Mid (cont)   | Prefix Length |0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 0 0 1 1|1 0 0 0 0 0 0 0|0 0 0 0 0 0 1 0|     Head      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Head (cont)  |              Mid              |      Mid      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Mid (cont)   |              Mid              |0 0 0 0 0 0 0 0|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 1 0 0 1|   TLV Type    |0 0 0 1 0 0 0 0|0 0 0 0 0 0 1 0|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |             Value             |   TLV Type    |0 0 1 0 0 0 0 0|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Index Start  |  Index Stop   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 Figure 1: Example message with signature 



 TOC 

Authors' Addresses

  Ulrich Herberg
  LIX, Ecole Polytechnique
  91128 Palaiseau Cedex,
  France
Phone:  +33-1-6933-4126
Email:  ulrich@herberg.name
URI:  http://www.herberg.name/
  
  Thomas Heide Clausen
  LIX, Ecole Polytechnique
  91128 Palaiseau Cedex,
  France
Phone:  +33 6 6058 9349
Email:  T.Clausen@computer.org
URI:  http://www.thomasclausen.org/