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97 lines
3.0 KiB
97 lines
3.0 KiB
// 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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