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