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eliminate some BIGNUM allocation overhead

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orignal 2017-03-07 14:24:19 -05:00
parent 92fc736cfa
commit 0e8d80e055
1 changed files with 8 additions and 8 deletions
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16
Crypto.cpp
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@ -275,8 +275,13 @@ namespace crypto
void ElGamalEncrypt (const uint8_t * key, const uint8_t * data, uint8_t * encrypted, bool zeroPadding)
{
BN_CTX * ctx = BN_CTX_new ();
BN_CTX_start (ctx);
// everything, but a, because a might come from table
BIGNUM * k = BN_CTX_get (ctx);
BIGNUM * y = BN_CTX_get (ctx);
BIGNUM * b1 = BN_CTX_get (ctx);
BIGNUM * b = BN_CTX_get (ctx);
// select random k
BIGNUM * k = BN_new ();
#if defined(__x86_64__)
BN_rand (k, ELGAMAL_FULL_EXPONENT_NUM_BITS, -1, 1); // full exponent for x64
#else
@ -292,23 +297,18 @@ namespace crypto
BN_mod_exp (a, elgg, k, elgp, ctx);
}
BIGNUM * y = BN_new ();
// restore y from key
BN_bin2bn (key, 256, y);
// calculate b1
BIGNUM * b1 = BN_new ();
BN_mod_exp (b1, y, k, elgp, ctx);
BN_free (y);
BN_free (k);
// create m
uint8_t m[255];
m[0] = 0xFF;
memcpy (m+33, data, 222);
SHA256 (m+33, 222, m+1);
// calculate b = b1*m mod p
BIGNUM * b = BN_new ();
BN_bin2bn (m, 255, b);
BN_mod_mul (b, b1, b, elgp, ctx);
BN_free (b1);
// copy a and b
if (zeroPadding)
{
@ -322,8 +322,8 @@ namespace crypto
bn2buf (a, encrypted, 256);
bn2buf (b, encrypted + 256, 256);
}
BN_free (b);
BN_free (a);
BN_CTX_end (ctx);
BN_CTX_free (ctx);
}