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Versions: 01                                                            
Network Working Group                                 W. Simpson, Editor
Internet Draft                                                DayDreamer
expires in six months                                      November 1995


                          Photuris Extensions
                  draft-ietf-ipsec-photuris-ext-01.txt


Status of this Memo

   This document is a submission to the IP Security Working Group of the
   Internet Engineering Task Force (IETF).  Comments should be submitted
   to the ipsec@ans.net mailing list.

   Distribution of this memo is unlimited.

   This document is an Internet-Draft.  Internet Drafts are working
   documents of the Internet Engineering Task Force (IETF), its Areas,
   and its Working Groups.  Note that other groups may also distribute
   working documents as Internet Drafts.

   Internet Drafts are draft documents valid for a maximum of six
   months, and may be updated, replaced, or obsoleted by other documents
   at any time.  It is not appropriate to use Internet Drafts as
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   To learn the current status of any Internet-Draft, please check the
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Abstract

   Photuris is an experimental session-key management protocol intended
   for use with the IP Security Protocols (AH and ESP).  Extensible
   Exchange Schemes and Attributes are provided to enable future
   implementation changes without affecting the basic protocol.






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1.  Additional Exchange Schemes

   The packet format and basic facilities are already defined for
   Photuris [Firefly].

   Up-to-date values for the Exchange Schemes are specified in the most
   recent "Assigned Numbers" [RFC-1700].  This document defines the
   following values:

   (3)   Implementation Optional.  Modular Exponentiation using a 1024-
         bit strong prime (p), expressed in hex:

         <tbd>

         The recommended generator (g) for this prime is 3.

         Provides 1024 bits of keying material.  The cryptographic
         strength is currently estimated to be equivalent to 86 bits
         (pessimistic) through 98 bits (optimistic).  Exponent lengths
         of 196 to 256 bits are recommended.

         The Identification_Message and Change_Message Privacy-Method is
         DES-CBC-64.

         The Change_Message Validity-Method is MD5.

   (4)   Implementation Optional.  Modular Exponentiation using a 2048-
         bit strong prime (p), expressed in hex:

         <tbd>

         The recommended generator (g) for this prime is 2.

         Provides 2048 bits of keying material.  The cryptographic
         strength is currently estimated to be equivalent to ??? bits
         (pessimistic).  Exponent lengths of ??? to 512 bits are
         recommended.

         The Identification_Message and Change_Message Privacy-Method is
         3DES-CBC-64.

         The Change_Message Validity-Method is MD5.

   (5)   Implementation Optional.  Modular Exponentiation using a 1024-
         bit strong prime (p), expressed in hex:






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            a478 8e21 84b8 d68b  fe02 690e 4dbe 485b
            17a8 0bc5 f21d 680f  1a84 1313 9734 f7f2
            b0db 4e25 3750 018a  ad9e 86d4 9b60 04bb
            bcf0 51f5 2fcb 66d0  c5fc a63f bfe6 3417

            3485 bbbf 7642 e9df  9c74 b85b 6855 e942
            13b8 c2d8 9162 abef  f434 2435 0e96 be41
            edd4 2de9 9a69 6163  8c1d ac59 8bc9 0da0
            69b5 0c41 4d8e b865  2adc ff4a 270d 567f

         The recommended generator (g) for this prime is 5.

         Provides 1024 bits of keying material.  The cryptographic
         strength is currently estimated to be equivalent to 86 bits
         (pessimistic) through 98 bits (optimistic).  Exponent lengths
         of 196 to 256 bits are recommended.

         The Identification_Message and Change_Message Privacy-Method is
         DES-CBC-64.

         The Change_Message Validity-Method is MD5.

         This prime modulus was randomly generated by a freely available
         program written by Phil Karn, verified using the
         mpz_probab_prime() function Miller-Rabin test in the Gnu Math
         Package (GMP) version 1.3.2; and also verified with GMP on
         another platform by Frank A Stevenson.

   (6)   Reserved.

   (7)   Implementation Optional.  Elliptic curve:

         <tbd>

         The Identification_Message and Change_Message Privacy-Method is
         3DES-CBC-64.

         The Change_Message Validity-Method is SHA.

   (8)   Implementation Optional.  Modular Exponentiation using a 4096-
         bit strong prime (p), expressed in hex:

         <tbd>

         The recommended generator (g) for this prime is 2.

         Provides 4096 bits of keying material.  The cryptographic



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         strength is currently estimated to be equivalent to ??? bits
         (pessimistic).  Exponent lengths of ??? to 1024 bits are
         recommended.

         The Identification_Message and Change_Message Privacy-Method is
         3DES-CBC-64.

         The Change_Message Validity-Method is SHA.


2.  Additional Attributes

   The basic Attribute formats are already defined for Photuris
   [Firefly].

   Up-to-date values for the Attribute Type are specified in the most
   recent "Assigned Numbers" [RFC-1700].  This document concerns the
   following values:

      A  I    Type
      +  +       6  SHA
      +         15  RC5
      +         20  Triple DES-CBC, 0-bit IV
      +         21  Triple DES-CBC, 32-bit IV
      +         22  Triple DES-CBC, 64-bit IV
         +      26  PKCS
         +      27  DNS-SIG certificate
         +      28  PGP certificate
         +      29  X.509 certificate chain
      +         32  Sensitivity Label
      +         33  VJ Header Compression
      +         34  LZ77
      +         35  Stac LZS
      +         36  AH-Sequence

      A     Initiator/Responder Attribute-Choice
         I  Identity-Choice
         +  feature must be supported
            when algorithm optionally supported


2.1.  SHA

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+





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   Type             6

   Length           0

   The selected Exchange Scheme SHOULD provide at least 80-bits of
   cryptographic strength.

   Attribute-Choice

      When selected as an Initiator or Responder Attribute-Choice,
      pursuant to [RFC-1852], SHA is also used as the key generation
      cryptographic hash for generating the SPI session-key.  All 160-
      bits of the generated hash are used for the key.

Identity-Choice

   When selected as an Identity-Choice, the resulting Verification field
   is 160-bits (22 octets including Size).

   The SHA hash is calculated as described in "Identity Verification".
   The authentication secret-key (as specified) is selected based on the
   contents of the Identification field.

   The Identification field contains a variable precision number.  Valid
   Identifications and secret-keys are preconfigured by the parties.

   There is no required format or content for the Identification value.
   The value may be a number or string of any kind.

Validity-Method

   When selected as a Validity-Method, the resulting Verification field
   is 160-bits (22 octets including Size).

   The hash is calculated as described in "Change Verification".  The
   leading shared-secret is not padded to any particular alignment.


2.2.  RC5

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |   Version   |    Word-Size    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Rounds     |   Key-Size    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Type             15



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   Length           4

   Version          Indicates the most recent version supported.  All
                    implementations must support version 16 (0x10).

   Word-Size        The number of bits used by internal calculations.
                    All implementations must support at least 32-bits.

   Rounds           The number of rounds used.  All implementations must
                    support at least 12 rounds.

   Key-Size         The number of octets in the session-key.  All
                    implementations must support at least 5 octets.

   When offered as an Attribute, the Version, Word-Size, Rounds, and
   Key-Size are set to the maximum supported.

   When chosen as an Attribute, the Version, Word-Size, Rounds, and
   Key-Size are set to the actual values to be used.

   Note that the Key-Size might be limited by available Exchange
   Schemes.  The selected Exchange Scheme SHOULD provide at least Key-
   Size (in bits) of cryptographic strength.

   Attribute-Choice

      When selected as an Initiator or Responder Attribute-Choice,
      pursuant to [RFC-xxxx], MD5 is used as the key generation
      cryptographic hash for generating the SPI session-key.  The most
      significant Key-Size octets of the generated hash are used for the
      key.

Privacy-Method

   When selected as a Privacy-Method, MD5 is used as the key generation
   cryptographic hash for generating the privacy session-key.  The most
   significant Key-Size octets of the generated hash are used for the
   key.

   The least-significant bits of the ???-bit Initialization Vector (IV)
   are set to the least-significant bits of the Type, LifeTime, and SPI
   fields.  Encryption begins with the next field, and continues to the
   end of the data indicated by the UDP Length.








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2.3.  Triple DES-CBC

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Type             20, 21 or 22

   Length           0

   This attribute indicates EDE encryption (and DED decryption) with
   three 56-bit keys.

   The selected Exchange Scheme SHOULD provide at least 112-bits of
   cryptographic strength.

   Attribute-Choice

      When selected as an Initiator or Responder Attribute-Choice,
      pursuant to [RFC-1851], MD5 is used as the key generation
      cryptographic hash for generating the three SPI session-keys.

      The first MD5 hash is generated as described in [Firefly].

      A second MD5 hash is calculated over the following concatenated
      values:

       + the computed shared-secret,
       + the first 128-bit hash,
       + the computed shared-secret again.

      A third MD5 hash is calculated over the following concatenated
      values:

       + the computed shared-secret,
       + the second 128-bit hash,
       + the computed shared-secret again.

      In all three keys, the most significant 64-bits of the generated
      hash are used for the key.  The least significant bit of each
      octet is ignored (or set to parity).


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Privacy-Method

   When selected as a Privacy-Method, MD5 is used as the key generation
   cryptographic hash for generating the privacy session-keys.  The
   three keys are generated as described above.

   The 64-bit Initialization Vector (IV) is set to the Type, LifeTime,
   and SPI fields.  Encryption begins with the next field, and continues
   to the end of the data indicated by the UDP Length.


2.4.  PGP certificate

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Type             28

   Length           0

   When selected as a Signature-Choice, the resulting Signature field
   size is variable.  PGP certificates include an identification of the
   signature algorithm.  As a minimum, it is required that all
   implementations support MD5 with RSA.

   A Certificate field always follows the Signature field, and contains
   a PGP certificate.  The PGP formats document is distributed with
   every copy of PGP.  If the implementation cannot handle the given
   certificate, an Error_Message indicates Signature Failure.

   PGP certificates include version numbers.  All implementations must
   support version 3 (PGP 2.6) certificates.  A certificate chain can
   include certificates with different version numbers.

   The length of the RSA key is encoded in each certificate.  All
   implementations must support a minimum of 2048-bit keys.


2.5.  X.509 certificate chain

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Type             29



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   Length           0

                    Future extensions to this attribute may add
                    parameter values.  This will be indicated by a non-
                    zero value.

   When selected as a Signature-Choice, the resulting Signature field
   size is variable.  X.509 certificates include an identification of
   the signature algorithm.  As a minimum, it is required that all
   implementations support MD5 with RSA.

   A Certificate field always follows the Signature field, and contains
   a chain of X.509 certificates [??? reference].  If the implementation
   cannot handle the given certificate chain, an Error_Message indicates
   Signature Failure.

   X.509 certificates include version numbers.  All implementations must
   support X.509.v1 (1988) certificates.  A certificate chain can
   include certificates with different version numbers.

   The length of the RSA key is encoded in each certificate.  All
   implementations must support a minimum of 512-bit keys.

   Different certificates in the chain may have different signature
   algorithms and key lengths.

   To improve performance, an implementation can cache the public keys
   for the issuers that frequently sign end-user certificates.  These
   cached public keys can be used to verify the final certificate, and
   avoid the cost of verifying each certificate in the chain.  However,
   the transmitter should always send the entire chain.


2.6.  DNS-SIG

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Type             27

   Length           0








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2.7.  Sensitivity Label

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Type             32

   Length           0



2.8.  VJ Header Compression

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |     Slots     |     Flags     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Type             33

   Length           2

   Slots            indicates the maximum slot identifier.  This is one
                    less than the actual number of slots; the slot
                    identifier has values from zero to Slots.

                    There may be implementations that have problems with
                    small numbers.  The example in [RFC-1144] will only
                    work with 3 through 254 slots.

   Flags            (0)  All compressed TCP packets must set the C bit
                    in every change mask, and must include the slot
                    identifier.

                    (1)  The slot identifer may be compressed.  This
                    requires an ability for the implementation to
                    indicate all errors in reception to the
                    decompression module.  Synchronization after errors
                    depends on waiting for a packet with the slot
                    identifier.  See the discussion in [RFC-1144].

   When selected as an Initiator or Responder Attribute-Choice, all data
   encapsulated in ESP [RFC-1827] is first compressed according to
   [RFC-1144].

   Note that this attribute requires ordered delivery.  Therefore, this



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   attribute is principly used for single network hops.


2.9.  LZ77


2.10.  Stac LZS

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |        History-Count          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Check-Mode  |
   +-+-+-+-+-+-+-+-+


   Type             35

   Length           3

   History-Count    two octets, most significant octet first.  Specifies
                    the maximum number of Compression Histories.

                    (0) the implementation expects the peer to reset the
                    Compression History at the beginning of every
                    packet.

                    (1) only one history is maintained.

                    Other valid values range from 2 to 65535.  The peer
                    is not required to send as many histories as the
                    implementation indicates that it can receive.

   Check-Mode       indicates support of LCB, CRC or Sequence checking.

                       0    None (default)
                       1    LCB
                       2    CRC
                       4    Sequence Number


   When offered as an Attribute, the History-Count is set to the maximum
   histories that can be sent, and the Check-Mode is the XOR of the
   modes supported.

   When selected as an Initiator or Responder Attribute-Choice, the
   History-Count is set to the maximum histories that can be received
   (less than or equal to the number offered), and the Check-Mode is set
   to only one of the modes supported.



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2.11.  AH-Sequence

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Type             36

   Length           0

   When selected as an Initiator or Responder Attribute-Choice, the
   previously Reserved field of the Authentication Header (AH) [RFC-
   1826] contains a 16-bit sequence number.  The SPI Owner (receiver)
   validates this number within an implementation dependent range of
   expected values.  Any AH protected datagram that fails this test is
   silently discarded.

   When the range has been exhausted, the SPI Owner (receiver) expires
   the SPI, despite any remaining SPI LifeTime.  On arrival of an AH
   protected datagram with an expired SPI, an appropriate ICMP Security
   Failures message is generated (Type 40 Code 0), and the datagram is
   discarded.




























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Security Considerations

   Security issues are the primary topic of this memo.


Acknowledgements

   Robert W Baldwin of RSA provided text for RC5 and X.509 Certificates.


References

   [Firefly]
            "Photuris" is the latin name for the firefly.  "Firefly" is
            in turn the name for the USA National Security
            Administration's (classified) key exchange protocol for the
            STU-III secure telephone.  Informed speculation has it that
            Firefly is based on very similar design principles.

   [RFC-1700]
            Reynolds, J., and Postel, J., "Assigned Numbers", STD 2,
            RFC-1700, USC/Information Sciences Institute, October 1994.

   [RFC-1825]
            Atkinson, R., "Security Architecture for the Internet
            Protocol", RFC-1825, Naval Research Laboratory, July 1995.

   [RFC-1826]

   [RFC-1827]

   [RFC-1850]

   [RFC-1851]

   [Schneier94]
            Schneier, B., "Applied Cryptography", John Wiley & Sons, New
            York, NY, 1994.  ISBN 0-471-59756-2.


Author's Address

   Questions about this memo can also be directed to:

      William Allen Simpson
      Daydreamer
      Computer Systems Consulting Services
      1384 Fontaine



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      Madison Heights, Michigan  48071

      Bill.Simpson@um.cc.umich.edu
          bsimpson@MorningStar.com















































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                           Table of Contents


     1.     Additional Exchange Schemes ...........................    1

     2.     Additional Attributes .................................    3
        2.1       SHA .............................................    3
        2.2       RC5 .............................................    4
        2.3       Triple DES-CBC ..................................    6
        2.4       PGP certificate .................................    7
        2.5       X.509 certificate chain .........................    7
        2.6       DNS-SIG .........................................    8
        2.7       Sensitivity Label ...............................    9
        2.8       VJ Header Compression ...........................    9
        2.9       LZ77 ............................................   10
        2.10      Stac LZS ........................................   10
        2.11      AH-Sequence .....................................   11

     SECURITY CONSIDERATIONS ......................................   12

     ACKNOWLEDGEMENTS .............................................   12

     REFERENCES ...................................................   12

     AUTHOR'S ADDRESS .............................................   12