origin of SHA 224 initial hash values

[Jeroen C.van Gelderen]

On Dec 6, 2003, at 3:26, Jeremiah Rogers wrote:

> I'm having trouble pinpointing the origin of the initial hash values 
> for SHA 224 and, for that matter, 128. These values are defined as hex 
> representations of cube roots of primes for sha-1 of lengths 256, 384 
> and 512, but  I can't find where they were obtained for the shorter 
> lengths.
>
> Thanks and apologies if this is something well known.

I'd like to second this request for clarification.

I noted that 224 yields a security level identical to 2-key Triple DES.

A quick Google search reveals that SHA-224 is mentioned a few times, in
   draft-ietf-pkix-rsa-pkalgs-01.txt
   draft-ietf-smime-cms-rsa-kem-01.txt
among others.

A draft-ietf-pkix-sha224-00.txt is referenced but not yet available 
from the IETF website.



       *  80-bit security. The RSA key size SHOULD be at least 1024 bits,
          the hash function underlying KDF2 SHOULD be SHA-1 or above, and
          the symmetric key-wrapping scheme SHOULD be AES Key Wrap or
          Triple-DES Key Wrap.

       *  112-bit security. The RSA key size SHOULD be at least 2048
          bits, the hash function underlying KDF2 SHOULD be SHA-224 or
          above, and the symmetric key-wrapping scheme SHOULD be AES Key
          Wrap or Triple-DES Key Wrap.

       *  128-bit security. The RSA key size SHOULD be at least 3072
          bits, the hash function underlying KDF2 SHOULD be SHA-256 or
          above, and the symmetric key-wrapping scheme SHOULD be AES Key
          Wrap.

       -- draft-ietf-smime-cms-rsa-kem-01.txt, pg4

-J

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