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Aloha!
I took a look at the code in sha256.c and have a couple of small comments.
(1) The K table is not zero extended. This just makes the table look weird:
K[64] =
{
0x428a2f98UL, 0x71374491UL, 0xb5c0fbcfUL, 0xe9b5dba5UL,
0x3956c25bUL, 0x59f111f1UL, 0x923f82a4UL, 0xab1c5ed5UL,
0xd807aa98UL, 0x12835b01UL, 0x243185beUL, 0x550c7dc3UL,
0x72be5d74UL, 0x80deb1feUL, 0x9bdc06a7UL, 0xc19bf174UL,
0xe49b69c1UL, 0xefbe4786UL, 0xfc19dc6UL, 0x240ca1ccUL,
0x2de92c6fUL, 0x4a7484aaUL, 0x5cb0a9dcUL, 0x76f988daUL,
0x983e5152UL, 0xa831c66dUL, 0xb00327c8UL, 0xbf597fc7UL,
0xc6e00bf3UL, 0xd5a79147UL, 0x6ca6351UL, 0x14292967UL,
0x27b70a85UL, 0x2e1b2138UL, 0x4d2c6dfcUL, 0x53380d13UL,
0x650a7354UL, 0x766a0abbUL, 0x81c2c92eUL, 0x92722c85UL,
0xa2bfe8a1UL, 0xa81a664bUL, 0xc24b8b70UL, 0xc76c51a3UL,
0xd192e819UL, 0xd6990624UL, 0xf40e3585UL, 0x106aa070UL,
0x19a4c116UL, 0x1e376c08UL, 0x2748774cUL, 0x34b0bcb5UL,
0x391c0cb3UL, 0x4ed8aa4aUL, 0x5b9cca4fUL, 0x682e6ff3UL,
0x748f82eeUL, 0x78a5636fUL, 0x84c87814UL, 0x8cc70208UL,
0x90befffaUL, 0xa4506cebUL, 0xbef9a3f7UL, 0xc67178f2UL,
};
I would suggest zero extending the table to get the same textual width
of all elements.
(2) Pretty cool that you actually generate the constants from the FIPS
180 specification! Good verification.
(3) The SHA-224 H0-table refers to the _SHA256_DIGEST_LENGTH. This imho
should be a separate define _SHA224_DIGEST_LENGTH. Yes, it is the same
length in practice but it looks weird esp since the generated digest for
SHA-224 is in fact not the same even though the internal diget state
vector H is the same length as SHA-256.
(4) I'll think I'm going to ask on the SHA-3 maillist (hosted by NIST)
if John Kelsey & Co can provide an explanation for the H0-constants used
in SHA-224 and SHA-1 in the same way as for SHA-256, SHA-512 etc. It
really is a bit peculiar that they don't.
- --
Med vänlig hälsning, Yours
Joachim Strömbergson - Alltid i harmonisk svängning.
========================================================================
Joachim Strömbergson Secworks AB [email protected]
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