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use precalculated table for ElGamal encryption

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This commit is contained in:
orignal 2016-04-10 17:06:02 -04:00
parent ffc666eaaa
commit 34a8d4a57d
1 changed files with 34 additions and 9 deletions
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43
Crypto.cpp
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@ -148,12 +148,15 @@ namespace crypto
// DH/ElGamal
const int ELGAMAL_SHORT_EXPONENT_NUM_BITS = 226;
const int ELGAMAL_SHORT_EXPONENT_NUM_BYTES = ELGAMAL_SHORT_EXPONENT_NUM_BITS/8+1;
const int ELGAMAL_FULL_EXPONENT_NUM_BITS = 2048;
#define elgp GetCryptoConstants ().elgp
#define elgg GetCryptoConstants ().elgg
void PrecalculateElggTable (BIGNUM * table[][255], int len) // table is len's array of array of 255 bignums
#if !defined(__x86_64__) // use precalculated table
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 ();
@ -176,7 +179,17 @@ namespace crypto
BN_CTX_free (ctx);
}
BIGNUM * ElggPow (const uint8_t * exp, int len, BIGNUM * table[][255], BN_CTX * ctx)
static void DestroyElggTable (BIGNUM * table[][255], int len)
{
for (int i = 0; i < len; i++)
for (int j = 0; j < 255; j++)
{
BN_free (table[i][j]);
table[i][j] = nullptr;
}
}
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;
@ -199,7 +212,7 @@ namespace crypto
return res;
}
BIGNUM * ElggPow (const BIGNUM * exp, BIGNUM * table[][255], BN_CTX * ctx)
static BIGNUM * ElggPow (const BIGNUM * exp, BIGNUM * table[][255], BN_CTX * ctx)
{
auto len = BN_num_bytes (exp);
uint8_t * buf = new uint8_t[len];
@ -208,6 +221,10 @@ namespace crypto
delete[] buf;
return ret;
}
BIGNUM * g_ElggTable[ELGAMAL_SHORT_EXPONENT_NUM_BYTES][255];
#endif
// DH
@ -229,9 +246,9 @@ namespace crypto
{
if (m_DH->priv_key) { BN_free (m_DH->priv_key); m_DH->priv_key = NULL; };
if (m_DH->pub_key) { BN_free (m_DH->pub_key); m_DH->pub_key = NULL; };
#if !defined(__x86_64__) // use short exponent for non x64
#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);
BN_rand (m_DH->priv_key, ELGAMAL_SHORT_EXPONENT_NUM_BITS, 0, 1);
#endif
DH_generate_key (m_DH);
if (priv) bn2buf (m_DH->priv_key, priv, 256);
@ -266,12 +283,14 @@ namespace crypto
BIGNUM * k = BN_new ();
#if defined(__x86_64__)
BN_rand (k, ELGAMAL_FULL_EXPONENT_NUM_BITS, -1, 1); // full exponent for x64
#else
BN_rand (k, ELGAMAL_SHORT_EXPONENT_NUM_BITS, -1, 1); // short exponent of 226 bits
#endif
// caulculate a
// calculate a
a = BN_new ();
BN_mod_exp (a, elgg, k, elgp, ctx);
#else
BN_rand (k, ELGAMAL_SHORT_EXPONENT_NUM_BITS, -1, 1); // short exponent of 226 bits
// calculate a
a = ElggPow (k, g_ElggTable, ctx);
#endif
BIGNUM * y = BN_new ();
BN_bin2bn (key, 256, y);
// calculate b1
@ -772,10 +791,16 @@ namespace crypto
for (int i = 0; i < numLocks; i++)
m_OpenSSLMutexes.emplace_back (new std::mutex);
CRYPTO_set_locking_callback (OpensslLockingCallback);*/
#if !defined(__x86_64__)
PrecalculateElggTable (g_ElggTable, ELGAMAL_SHORT_EXPONENT_NUM_BYTES);
#endif
}
void TerminateCrypto ()
{
#if !defined(__x86_64__)
DestroyElggTable (g_ElggTable, ELGAMAL_SHORT_EXPONENT_NUM_BYTES);
#endif
/* CRYPTO_set_locking_callback (nullptr);
m_OpenSSLMutexes.clear ();*/
}