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Add references for the Diffie-Hellman fixed primes.

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I ran across their defining RFCs recently and noticed that each one
provides an explicit mathematical expression for the prime (since each
one is derived from the expansion of pi, with framing FFs and a
correction term to make it actually prime).

Those expressions can be re-evaluated trivially by spigot, so it seems
reasonable to add those spigot commands in comments. This also means
the comments contain citations for these primes in actual standards,
including both the hex digits and the mathematical expressions.
This commit is contained in:
Simon Tatham 2021-08-28 10:25:09 +01:00
parent e0f9c42b0f
commit 5bb869dd22
1 changed files with 6 additions and 0 deletions
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6
crypto/diffie-hellman.c
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@ -19,12 +19,18 @@ struct dh_extra {
static void dh_group1_construct(dh_ctx *ctx)
{
/* Command to recompute, from the expression in RFC 2412 section E.2:
spigot -B16 '2^1024 - 2^960 - 1 + 2^64 * ( floor(2^894 pi) + 129093 )'
*/
ctx->p = MP_LITERAL(0xFFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE649286651ECE65381FFFFFFFFFFFFFFFF);
ctx->g = mp_from_integer(2);
}
static void dh_group14_construct(dh_ctx *ctx)
{
/* Command to recompute, from the expression in RFC 3526 section 3:
spigot -B16 '2^2048 - 2^1984 - 1 + 2^64 * ( floor(2^1918 pi) + 124476 )'
*/
ctx->p = MP_LITERAL(0x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
ctx->g = mp_from_integer(2);
}