int
__ops_elgamal_public_encrypt(uint8_t *g_to_k, uint8_t *encm,
const uint8_t *in,
size_t size,
const __ops_elgamal_pubkey_t *pubkey)
{
int ret = 0;
int k_bits;
BIGNUM *m;
BIGNUM *p;
BIGNUM *g;
BIGNUM *y;
BIGNUM *k;
BIGNUM *yk;
BIGNUM *c1;
BIGNUM *c2;
BN_CTX *tmp;
m = BN_bin2bn(in, (int)size, NULL);
p = pubkey->p;
g = pubkey->g;
y = pubkey->y;
k = BN_new();
yk = BN_new();
c1 = BN_new();
c2 = BN_new();
tmp = BN_CTX_new();
if (!m || !p || !g || !y || !k || !yk || !c1 || !c2 || !tmp) {
goto done;
}
/*
* generate k
*/
k_bits = decide_k_bits(BN_num_bits(p));
if (!BN_rand(k, k_bits, 0, 0)) {
goto done;
}
/*
* c1 = g^k c2 = m * y^k
*/
if (!BN_mod_exp(c1, g, k, p, tmp)) {
goto done;
}
if (!BN_mod_exp(yk, y, k, p, tmp)) {
goto done;
}
if (!BN_mod_mul(c2, m, yk, p, tmp)) {
goto done;
}
/* result */
BN_bn2bin(c1, g_to_k);
ret = BN_num_bytes(c1); /* c1 = g^k */
BN_bn2bin(c2, encm);
ret += BN_num_bytes(c2); /* c2 = m * y^k */
done:
if (tmp) {
BN_CTX_free(tmp);
}
if (c2) {
BN_clear_free(c2);
}
if (c1) {
BN_clear_free(c1);
}
if (yk) {
BN_clear_free(yk);
}
if (k) {
BN_clear_free(k);
}
if (g) {
BN_clear_free(g);
}
return ret;
}
int
pgp_elgamal_encrypt(PGP_PubKey * pk, PGP_MPI * _m,
PGP_MPI ** c1_p, PGP_MPI ** c2_p)
{
int res = PXE_PGP_MATH_FAILED;
int k_bits;
BIGNUM *m = mpi_to_bn(_m);
BIGNUM *p = mpi_to_bn(pk->pub.elg.p);
BIGNUM *g = mpi_to_bn(pk->pub.elg.g);
BIGNUM *y = mpi_to_bn(pk->pub.elg.y);
BIGNUM *k = BN_new();
BIGNUM *yk = BN_new();
BIGNUM *c1 = BN_new();
BIGNUM *c2 = BN_new();
BN_CTX *tmp = BN_CTX_new();
if (!m || !p || !g || !y || !k || !yk || !c1 || !c2 || !tmp)
goto err;
/*
* generate k
*/
k_bits = decide_k_bits(BN_num_bits(p));
if (!BN_rand(k, k_bits, 0, 0))
goto err;
/*
* c1 = g^k c2 = m * y^k
*/
if (!BN_mod_exp(c1, g, k, p, tmp))
goto err;
if (!BN_mod_exp(yk, y, k, p, tmp))
goto err;
if (!BN_mod_mul(c2, m, yk, p, tmp))
goto err;
/* result */
*c1_p = bn_to_mpi(c1);
*c2_p = bn_to_mpi(c2);
if (*c1_p && *c2_p)
res = 0;
err:
if (tmp)
BN_CTX_free(tmp);
if (c2)
BN_clear_free(c2);
if (c1)
BN_clear_free(c1);
if (yk)
BN_clear_free(yk);
if (k)
BN_clear_free(k);
if (y)
BN_clear_free(y);
if (g)
BN_clear_free(g);
if (p)
BN_clear_free(p);
if (m)
BN_clear_free(m);
return res;
}
