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  • Committer: weidai
  • Date: 2004-09-03 10:57:31 UTC
  • Revision ID: svn-v4:57ff6487-cd31-0410-9ec3-f628ee90f5f0:trunk/c5:193
changes related to the next FIPS validation

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// 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