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Note that much of check_dh_key is voodoo; make x in DH be only 320 bits for DH speed improvement: this wants auditing. [We have blessing from Ian on this.] (Note that DH in SSL is not yet affected.)

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svn:r5359
This commit is contained in:
Nick Mathewson 2005-11-11 20:18:00 +00:00
parent a3c53e0af9
commit f14743a975
1 changed files with 24 additions and 0 deletions
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24
src/common/crypto.c
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@ -1390,6 +1390,8 @@ crypto_dh_new(void)
return NULL;
}
#define DH_PRIVATE_KEY_BITS 320
/** Return the length of the DH key in <b>dh</b>, in bytes.
*/
int
@ -1405,7 +1407,22 @@ crypto_dh_get_bytes(crypto_dh_env_t *dh)
int
crypto_dh_generate_public(crypto_dh_env_t *dh)
{
int pk_bits = BN_num_bits(dh->dh->p);
if (pk_bits > DH_PRIVATE_KEY_BITS)
pk_bits = DH_PRIVATE_KEY_BITS;
again:
if (!dh->dh->priv_key) {
dh->dh->priv_key = BN_new();
if (!dh->dh->priv_key) {
err(LD_MM, "Unable to allocate BN.");
return -1;
}
}
/* We generate the key ourselves so that we can get a 2-3x speedup by using
* a 320-bit x instead of a 1024-bit x. */
if (!BN_rand(dh->dh->priv_key, pk_bits, 0, 0)) {
crypto_log_errors(LOG_WARN, "Generating DH private key");
}
if (!DH_generate_key(dh->dh)) {
crypto_log_errors(LOG_WARN, "generating DH key");
return -1;
@ -1462,6 +1479,13 @@ tor_check_dh_key(BIGNUM *bn)
#define MIN_DIFFERING_BITS 16
/* This covers another 2^25 keys, which is still negligible. */
#define MIN_DIST_FROM_EDGE (1<<24)
/* XXXX Note that this is basically voodoo. Really, we only care about 0,
* 1, 2, and -1. The "number of bits set" business is inherited from some
* dire warnings in the OpenSSH comments. Real Cryptographers assure us
* that these dire warnings are misplaced.
*
* Still, it can't hurt.
*/
int i, n_bits, n_set;
BIGNUM *x = NULL;
char *s;