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use precalculated table for DH

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orignal 2016-04-10 21:16:18 -04:00
parent 34a8d4a57d
commit 6a9d2ba653
1 changed files with 15 additions and 10 deletions
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23
Crypto.cpp
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@ -156,26 +156,26 @@ namespace crypto
#if !defined(__x86_64__) // use precalculated table
static BN_MONT_CTX * g_MontCtx = nullptr;
static void PrecalculateElggTable (BIGNUM * table[][255], int len) // table is len's array of array of 255 bignums
{
if (len <= 0) return;
BN_CTX * ctx = BN_CTX_new ();
BN_MONT_CTX * montCtx = BN_MONT_CTX_new ();
BN_MONT_CTX_set (montCtx, elgp, ctx);
g_MontCtx = BN_MONT_CTX_new ();
BN_MONT_CTX_set (g_MontCtx, elgp, ctx);
for (int i = 0; i < len; i++)
{
table[i][0] = BN_new ();
if (!i)
BN_to_montgomery (table[0][0], elgg, montCtx, ctx);
BN_to_montgomery (table[0][0], elgg, g_MontCtx, ctx);
else
BN_mod_mul_montgomery (table[i][0], table[i-1][254], table[i-1][0], montCtx, ctx);
BN_mod_mul_montgomery (table[i][0], table[i-1][254], table[i-1][0], g_MontCtx, ctx);
for (int j = 1; j < 255; j++)
{
table[i][j] = BN_new ();
BN_mod_mul_montgomery (table[i][j], table[i][j-1], table[i][0], montCtx, ctx);
BN_mod_mul_montgomery (table[i][j], table[i][j-1], table[i][0], g_MontCtx, ctx);
}
}
BN_MONT_CTX_free (montCtx);
BN_CTX_free (ctx);
}
@ -187,15 +187,16 @@ namespace crypto
BN_free (table[i][j]);
table[i][j] = nullptr;
}
BN_MONT_CTX_free (g_MontCtx);
}
static BIGNUM * ElggPow (const uint8_t * exp, int len, BIGNUM * table[][255], BN_CTX * ctx)
// exp is in Big Endian
{
if (len <= 0) return nullptr;
auto montCtx = BN_MONT_CTX_new ();
BN_MONT_CTX_copy (montCtx, g_MontCtx);
BIGNUM * res = nullptr;
BN_MONT_CTX * montCtx = BN_MONT_CTX_new ();
BN_MONT_CTX_set (montCtx, elgp, ctx);
for (int i = 0; i < len; i++)
{
if (res)
@ -249,8 +250,12 @@ namespace crypto
#if !defined(__x86_64__) // use short exponent for non x64
m_DH->priv_key = BN_new ();
BN_rand (m_DH->priv_key, ELGAMAL_SHORT_EXPONENT_NUM_BITS, 0, 1);
#endif
auto ctx = BN_CTX_new ();
m_DH->pub_key = ElggPow (m_DH->priv_key, g_ElggTable, ctx);
BN_CTX_free (ctx);
#else
DH_generate_key (m_DH);
#endif
if (priv) bn2buf (m_DH->priv_key, priv, 256);
if (pub) bn2buf (m_DH->pub_key, pub, 256);
m_IsUpdated = true;