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55 lines
1.5 KiB
55 lines
1.5 KiB
#ifndef EL_GAMAL_H__ |
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#define EL_GAMAL_H__ |
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#include <inttypes.h> |
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#include <cryptopp/integer.h> |
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#include <cryptopp/osrng.h> |
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#include <cryptopp/sha.h> |
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#include "CryptoConst.h" |
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#include "Log.h" |
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namespace i2p |
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{ |
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namespace crypto |
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{ |
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inline void ElGamalEncrypt (const uint8_t * key, const uint8_t * data, int len, |
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uint8_t * encrypted, bool zeroPadding = false) // 514 with padding and 512 without |
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{ |
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CryptoPP::AutoSeededRandomPool rnd; |
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CryptoPP::Integer y(key, 256), k(rnd, CryptoPP::Integer::One(), elgp-1); |
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if (zeroPadding) |
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{ |
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encrypted[0] = 0; |
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encrypted[257] = 0; |
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} |
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a_exp_b_mod_c (elgg, k, elgp).Encode (zeroPadding ? encrypted + 1 : encrypted, 256); |
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uint8_t m[255]; |
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m[0] = 0xFF; |
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memcpy (m+33, data, len); |
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CryptoPP::SHA256().CalculateDigest(m+1, m+33, 222); |
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a_times_b_mod_c (a_exp_b_mod_c (y, k, elgp), |
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CryptoPP::Integer (m, 255), elgp).Encode (zeroPadding ? encrypted + 258 : encrypted + 256, 256); |
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} |
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inline bool ElGamalDecrypt (const uint8_t * key, const uint8_t * encrypted, |
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uint8_t * data, bool zeroPadding = false) |
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{ |
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CryptoPP::Integer x(key, 256), a(zeroPadding? encrypted +1 : encrypted, 256), |
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b(zeroPadding? encrypted + 258 :encrypted + 256, 256); |
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uint8_t m[255], hash[32]; |
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a_times_b_mod_c (b, a_exp_b_mod_c (a, elgp - x - 1, elgp), elgp).Encode (m, 255); |
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CryptoPP::SHA256().CalculateDigest(hash, m+33, 222); |
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for (int i = 0; i < 32; i++) |
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if (hash[i] != m[i+1]) |
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{ |
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LogPrint ("ElGamal decrypt hash doesn't match"); |
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return false; |
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} |
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memcpy (data, m + 33, 222); |
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return true; |
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} |
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} |
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} |
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#endif
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