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98 lines
3.0 KiB
98 lines
3.0 KiB
5 years ago
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// oaep.cpp - written and placed in the public domain by Wei Dai
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#include "pch.h"
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#ifndef CRYPTOPP_IMPORTS
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#include "oaep.h"
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#include <functional>
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NAMESPACE_BEGIN(CryptoPP)
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// ********************************************************
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size_t OAEP_Base::MaxUnpaddedLength(size_t paddedLength) const
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{
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return SaturatingSubtract(paddedLength/8, 1+2*DigestSize());
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}
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void OAEP_Base::Pad(RandomNumberGenerator &rng, const byte *input, size_t inputLength, byte *oaepBlock, size_t oaepBlockLen, const NameValuePairs ¶meters) const
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{
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assert (inputLength <= MaxUnpaddedLength(oaepBlockLen));
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// convert from bit length to byte length
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if (oaepBlockLen % 8 != 0)
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{
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oaepBlock[0] = 0;
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oaepBlock++;
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}
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oaepBlockLen /= 8;
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std::auto_ptr<HashTransformation> pHash(NewHash());
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const size_t hLen = pHash->DigestSize();
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const size_t seedLen = hLen, dbLen = oaepBlockLen-seedLen;
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byte *const maskedSeed = oaepBlock;
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byte *const maskedDB = oaepBlock+seedLen;
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ConstByteArrayParameter encodingParameters;
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parameters.GetValue(Name::EncodingParameters(), encodingParameters);
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// DB = pHash || 00 ... || 01 || M
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pHash->CalculateDigest(maskedDB, encodingParameters.begin(), encodingParameters.size());
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memset(maskedDB+hLen, 0, dbLen-hLen-inputLength-1);
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maskedDB[dbLen-inputLength-1] = 0x01;
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memcpy(maskedDB+dbLen-inputLength, input, inputLength);
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rng.GenerateBlock(maskedSeed, seedLen);
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std::auto_ptr<MaskGeneratingFunction> pMGF(NewMGF());
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pMGF->GenerateAndMask(*pHash, maskedDB, dbLen, maskedSeed, seedLen);
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pMGF->GenerateAndMask(*pHash, maskedSeed, seedLen, maskedDB, dbLen);
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}
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DecodingResult OAEP_Base::Unpad(const byte *oaepBlock, size_t oaepBlockLen, byte *output, const NameValuePairs ¶meters) const
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{
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bool invalid = false;
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// convert from bit length to byte length
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if (oaepBlockLen % 8 != 0)
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{
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invalid = (oaepBlock[0] != 0) || invalid;
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oaepBlock++;
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}
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oaepBlockLen /= 8;
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std::auto_ptr<HashTransformation> pHash(NewHash());
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const size_t hLen = pHash->DigestSize();
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const size_t seedLen = hLen, dbLen = oaepBlockLen-seedLen;
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invalid = (oaepBlockLen < 2*hLen+1) || invalid;
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SecByteBlock t(oaepBlock, oaepBlockLen);
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byte *const maskedSeed = t;
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byte *const maskedDB = t+seedLen;
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std::auto_ptr<MaskGeneratingFunction> pMGF(NewMGF());
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pMGF->GenerateAndMask(*pHash, maskedSeed, seedLen, maskedDB, dbLen);
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pMGF->GenerateAndMask(*pHash, maskedDB, dbLen, maskedSeed, seedLen);
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ConstByteArrayParameter encodingParameters;
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parameters.GetValue(Name::EncodingParameters(), encodingParameters);
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// DB = pHash' || 00 ... || 01 || M
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byte *M = std::find(maskedDB+hLen, maskedDB+dbLen, 0x01);
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invalid = (M == maskedDB+dbLen) || invalid;
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invalid = (std::find_if(maskedDB+hLen, M, std::bind2nd(std::not_equal_to<byte>(), 0)) != M) || invalid;
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invalid = !pHash->VerifyDigest(maskedDB, encodingParameters.begin(), encodingParameters.size()) || invalid;
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if (invalid)
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return DecodingResult();
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M++;
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memcpy(output, M, maskedDB+dbLen-M);
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return DecodingResult(maskedDB+dbLen-M);
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}
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NAMESPACE_END
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#endif
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