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use 226 bits private keys for non-x64

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orignal 2016-04-06 15:49:46 -04:00
parent 405aa906c5
commit 8657226594
1 changed files with 18 additions and 7 deletions
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25
Crypto.cpp
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@ -146,6 +146,10 @@ namespace crypto
}
// DH/ElGamal
const int ELGAMAL_SHORT_EXPONENT_NUM_BITS = 226;
const int ELGAMAL_FULL_EXPONENT_NUM_BITS = 2048;
#define elgp GetCryptoConstants ().elgp
#define elgg GetCryptoConstants ().elgg
@ -169,6 +173,10 @@ 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
m_DH->priv_key = BN_new ();
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);
if (pub) bn2buf (m_DH->pub_key, pub, 256);
@ -201,9 +209,9 @@ namespace crypto
// select random k
BIGNUM * k = BN_new ();
#if defined(__x86_64__)
BN_rand (k, 2048, -1, 1); // full exponent for x64
BN_rand (k, ELGAMAL_FULL_EXPONENT_NUM_BITS, -1, 1); // full exponent for x64
#else
BN_rand (k, 226, -1, 1); // short exponent of 226 bits
BN_rand (k, ELGAMAL_SHORT_EXPONENT_NUM_BITS, -1, 1); // short exponent of 226 bits
#endif
// caulculate a
a = BN_new ();
@ -282,6 +290,14 @@ namespace crypto
{
#if defined(__x86_64__) || defined(__i386__) || defined(_MSC_VER)
RAND_bytes (priv, 256);
#else
// lower 226 bits (28 bytes and 2 bits) only. short exponent
auto numBytes = (ELGAMAL_SHORT_EXPONENT_NUM_BITS)/8 + 1; // 29
auto numZeroBytes = 256 - numBytes;
RAND_bytes (priv + numZeroBytes, numBytes);
memset (priv, 0, numZeroBytes);
priv[numZeroBytes] &= 0x04;
#endif
BN_CTX * ctx = BN_CTX_new ();
BIGNUM * p = BN_new ();
BN_bin2bn (priv, 256, p);
@ -289,11 +305,6 @@ namespace crypto
bn2buf (p, pub, 256);
BN_free (p);
BN_CTX_free (ctx);
#else
DHKeys dh;
dh.GenerateKeys (priv, pub);
#endif
}
// HMAC