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Share common SAE and EAP-pwd functionality: own scalar generation

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Use a shared helper function for deriving rand, mask, and own scalar.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
This commit is contained in:
Jouni Malinen 2019-04-26 17:33:44 +03:00 • committed by Jouni Malinen
parent c3805fb623
commit 73338db029
4 changed files with 57 additions and 104 deletions
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36
src/common/dragonfly.c
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@ -154,3 +154,39 @@ fail:
crypto_bignum_deinit(qr_or_qnr, 1);
return res;
}
static int dragonfly_get_rand_2_to_r_1(struct crypto_bignum *val,
const struct crypto_bignum *order)
{
return crypto_bignum_rand(val, order) == 0 &&
!crypto_bignum_is_zero(val) &&
!crypto_bignum_is_one(val);
}
int dragonfly_generate_scalar(const struct crypto_bignum *order,
struct crypto_bignum *_rand,
struct crypto_bignum *_mask,
struct crypto_bignum *scalar)
{
int count;
/* Select two random values rand,mask such that 1 < rand,mask < r and
* rand + mask mod r > 1. */
for (count = 0; count < 100; count++) {
if (dragonfly_get_rand_2_to_r_1(_rand, order) &&
dragonfly_get_rand_2_to_r_1(_mask, order) &&
crypto_bignum_add(_rand, _mask, scalar) == 0 &&
crypto_bignum_mod(scalar, order, scalar) == 0 &&
!crypto_bignum_is_zero(scalar) &&
!crypto_bignum_is_one(scalar))
return 0;
}
/* This should not be reachable in practice if the random number
* generation is working. */
wpa_printf(MSG_INFO,
"dragonfly: Unable to get randomness for own scalar");
return -1;
}