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Implement fixed-window exponentiation to mitigate hyper-threading

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timing attacks.

BN_FLG_EXP_CONSTTIME requests this algorithm, and this done by default for
RSA/DSA/DH private key computations unless
RSA_FLAG_NO_EXP_CONSTTIME/DSA_FLAG_NO_EXP_CONSTTIME/
DH_FLAG_NO_EXP_CONSTTIME is set.

Submitted by: Matthew D Wood
Reviewed by: Bodo Moeller
This commit is contained in:
Bodo Möller
2005-05-16 01:26:08 +00:00
parent 64c32bf9eb
commit ecb1445ce2
20 changed files with 598 additions and 33 deletions
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4
crypto/dsa/dsa_ossl.c
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@@ -197,6 +197,10 @@ static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp)
do
if (!BN_rand_range(&k, dsa->q)) goto err;
while (BN_is_zero(&k));
if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)
{
BN_set_flags(&k, BN_FLG_EXP_CONSTTIME);
}
if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
{