RE: [TLS] NIST TLS recomendations (IV generation)

Ray Perlner wrote:
> Page 20-21: Section 6.2.3.2 under IV The document specifies that the
> IV SHOULD be generated by method (1) or (2) and MAY be generated by
> an alternate method. There is, however, no language forbidding the
> generation of IVs by a fourth unlisted method. If a fourth method is
> used, the protocol will not fail but may be insecure. Therefore we
> recommend adding language forbidding the use of an unlisted method
> for IV generation.

Actually the whole text about IVs is quite long, and contains
implementation details that IMHO are likely to confuse rather than
help an implementer.

How about just replacing the whole text about IVs with something
like this?

   IV

       The Initialization Vector (IV) MUST be chosen at random, and
       MUST be unpredictable. See [SP800-38A] Appendix C for
       RECOMMENDED methods for generating unpredictable IVs.

       It is critical that the IV is not sent before the entire
       plaintext of the record is known; otherwise it is possible for
       the attacker to mount the attack described in [CBCATT].

       Note: In versions of TLS prior to 1.1, there was no IV field,
       and the last ciphertext block of the previous record (the "CBC
       residue") was used as the IV. This was changed to prevent the
       attacks described in [CBCATT].

Best regards,
Pasi

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