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ElGamalEncryptor added

pull/46/head
orignal 11 years ago
parent
commit
b14cdc8052
  1. 66
      ElGamal.h

66
ElGamal.h

@ -12,25 +12,48 @@ namespace i2p
{ {
namespace crypto namespace crypto
{ {
inline void ElGamalEncrypt (const uint8_t * key, const uint8_t * data, int len,
uint8_t * encrypted, bool zeroPadding = false) // 514 with padding and 512 without class ElGamalEncryptor
{ {
CryptoPP::AutoSeededRandomPool rnd; public:
CryptoPP::Integer y(key, 256), k(rnd, CryptoPP::Integer::One(), elgp-1);
if (zeroPadding) ElGamalEncryptor (const uint8_t * key, bool zeroPadding = false):
y (key, 256), k (rnd, CryptoPP::Integer::One(), elgp-1),
a (a_exp_b_mod_c (elgg, k, elgp)), b1 (a_exp_b_mod_c (y, k, elgp)),
m_ZeroPadding (zeroPadding)
{ {
encrypted[0] = 0;
encrypted[257] = 0;
} }
a_exp_b_mod_c (elgg, k, elgp).Encode (zeroPadding ? encrypted + 1 : encrypted, 256);
void Encrypt (const uint8_t * data, int len, uint8_t * encrypted)
{
// calculate b = b1*m mod p
uint8_t m[255]; uint8_t m[255];
m[0] = 0xFF; m[0] = 0xFF;
memcpy (m+33, data, len); memcpy (m+33, data, len);
CryptoPP::SHA256().CalculateDigest(m+1, m+33, 222); CryptoPP::SHA256().CalculateDigest(m+1, m+33, 222);
a_times_b_mod_c (a_exp_b_mod_c (y, k, elgp), CryptoPP::Integer b (a_times_b_mod_c (b1, CryptoPP::Integer (m, 255), elgp));
CryptoPP::Integer (m, 255), elgp).Encode (zeroPadding ? encrypted + 258 : encrypted + 256, 256);
// copy a and b
if (m_ZeroPadding)
{
encrypted[0] = 0;
a.Encode (encrypted + 1, 256);
encrypted[257] = 0;
b.Encode (encrypted + 258, 256);
} }
else
{
a.Encode (encrypted, 256);
b.Encode (encrypted + 256, 256);
}
}
private:
CryptoPP::AutoSeededRandomPool rnd;
CryptoPP::Integer y, k, a, b1;
bool m_ZeroPadding;
};
inline bool ElGamalDecrypt (const uint8_t * key, const uint8_t * encrypted, inline bool ElGamalDecrypt (const uint8_t * key, const uint8_t * encrypted,
uint8_t * data, bool zeroPadding = false) uint8_t * data, bool zeroPadding = false)
@ -49,6 +72,29 @@ namespace crypto
memcpy (data, m + 33, 222); memcpy (data, m + 33, 222);
return true; return true;
} }
// deprecated
inline void ElGamalEncrypt (const uint8_t * key, const uint8_t * data, int len,
uint8_t * encrypted, bool zeroPadding = false) // 514 with padding and 512 without
{
CryptoPP::AutoSeededRandomPool rnd;
CryptoPP::Integer y(key, 256), k(rnd, CryptoPP::Integer::One(), elgp-1);
if (zeroPadding)
{
encrypted[0] = 0;
encrypted[257] = 0;
}
a_exp_b_mod_c (elgg, k, elgp).Encode (zeroPadding ? encrypted + 1 : encrypted, 256);
uint8_t m[255];
m[0] = 0xFF;
memcpy (m+33, data, len);
CryptoPP::SHA256().CalculateDigest(m+1, m+33, 222);
a_times_b_mod_c (a_exp_b_mod_c (y, k, elgp),
CryptoPP::Integer (m, 255), elgp).Encode (zeroPadding ? encrypted + 258 : encrypted + 256, 256);
}
} }
} }

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