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34 lines
1.2 KiB
34 lines
1.2 KiB
// emsa2.cpp - written and placed in the public domain by Wei Dai |
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#include "pch.h" |
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#include "emsa2.h" |
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#ifndef CRYPTOPP_IMPORTS |
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NAMESPACE_BEGIN(CryptoPP) |
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void EMSA2Pad::ComputeMessageRepresentative(RandomNumberGenerator &rng, |
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const byte *recoverableMessage, size_t recoverableMessageLength, |
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HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty, |
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byte *representative, size_t representativeBitLength) const |
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{ |
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assert(representativeBitLength >= MinRepresentativeBitLength(hashIdentifier.second, hash.DigestSize())); |
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if (representativeBitLength % 8 != 7) |
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throw PK_SignatureScheme::InvalidKeyLength("EMSA2: EMSA2 requires a key length that is a multiple of 8"); |
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size_t digestSize = hash.DigestSize(); |
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size_t representativeByteLength = BitsToBytes(representativeBitLength); |
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representative[0] = messageEmpty ? 0x4b : 0x6b; |
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memset(representative+1, 0xbb, representativeByteLength-digestSize-4); // pad with 0xbb |
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byte *afterP2 = representative+representativeByteLength-digestSize-3; |
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afterP2[0] = 0xba; |
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hash.Final(afterP2+1); |
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representative[representativeByteLength-2] = *hashIdentifier.first; |
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representative[representativeByteLength-1] = 0xcc; |
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} |
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NAMESPACE_END |
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#endif
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