Re: I-D ACTION:draft-laganier-ipv6-khi-00.txt

[Francis Dupont <Francis.Dupont at enst-bretagne.fr>]

 In your previous mail you wrote:

   I am supportive of the genral idea of reserving a prefix for
   "statistically unique identifiers" that are derived from some kind of
   cryptographic ID.

=> thanks

   However, I have a problem with the specified syntax:
   
      Input      :=  any bitstring
      Hash Input :=  Context ID | Input
      Hash       :=  SHA1( Expand( Hash Input ) )
      KHI        :=  Prefix | Encode_n( Hash )
   
   This syntax includes a static reference to the SHA1 hash function and to
   the "encode_n" extraction function. As a general rule, hard coding a
   specific cryptographic algorithm in a standard is a very bad idea. In
   fact, SHA1 is already suspect.

=> security considerations explain that:
 - SHA1 can be replaced by something else
 - SHA1 is still good for this usage
 - if SHA1 or another important detail is changed then another prefix
   must be used.

   The syntax should allow for an
   identification of the algorithm as part of the "hash input".
   
=> the document explains why this is a bad idea.

Thanks

Francis.Dupont at enst-bretagne.fr

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