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// pubkey.cpp - written and placed in the public domain by Wei Dai
#include "pch.h"
#include "pubkey.h"
NAMESPACE_BEGIN(CryptoPP)
void TF_DigestSignerBase::SignDigest(RandomNumberGenerator &rng, const byte *digest, unsigned int digestLen, byte *signature) const
{
assert(digestLen <= MaxDigestLength());
SecByteBlock paddedBlock(PaddedBlockByteLength());
GetPaddingAlgorithm().Pad(rng, digest, digestLen, paddedBlock, PaddedBlockBitLength());
GetTrapdoorFunctionInterface().CalculateRandomizedInverse(rng, Integer(paddedBlock, paddedBlock.size())).Encode(signature, DigestSignatureLength());
}
bool TF_DigestVerifierBase::VerifyDigest(const byte *digest, unsigned int digestLen, const byte *signature) const
{
SecByteBlock paddedBlock(PaddedBlockByteLength());
Integer x = GetTrapdoorFunctionInterface().ApplyFunction(Integer(signature, DigestSignatureLength()));
if (x.ByteCount() > paddedBlock.size())
x = Integer::Zero(); // don't return false here to prevent timing attack
x.Encode(paddedBlock, paddedBlock.size());
if (GetPaddingAlgorithm().IsReversible())
{
SecByteBlock recoveredDigest(MaxDigestLength());
DecodingResult result = GetPaddingAlgorithm().Unpad(paddedBlock, PaddedBlockBitLength(), recoveredDigest);
return result == DecodingResult(digestLen) && memcmp(digest, recoveredDigest, digestLen) == 0;
}
else
{
SecByteBlock paddedBlock2(PaddedBlockByteLength());
GetPaddingAlgorithm().Pad(NullRNG(), digest, digestLen, paddedBlock2, PaddedBlockBitLength());
return paddedBlock == paddedBlock2;
}
}
DecodingResult TF_DecryptorBase::FixedLengthDecrypt(const byte *cipherText, byte *plainText) const
{
SecByteBlock paddedBlock(PaddedBlockByteLength());
Integer x = GetTrapdoorFunctionInterface().CalculateInverse(Integer(cipherText, FixedCiphertextLength()));
if (x.ByteCount() > paddedBlock.size())
x = Integer::Zero(); // don't return false here to prevent timing attack
x.Encode(paddedBlock, paddedBlock.size());
return GetPaddingAlgorithm().Unpad(paddedBlock, PaddedBlockBitLength(), plainText);
}
void TF_EncryptorBase::Encrypt(RandomNumberGenerator &rng, const byte *plainText, unsigned int plainTextLength, byte *cipherText) const
{
if (plainTextLength > FixedMaxPlaintextLength())
throw InvalidArgument(AlgorithmName() + ": message too long for this public key");
SecByteBlock paddedBlock(PaddedBlockByteLength());
GetPaddingAlgorithm().Pad(rng, plainText, plainTextLength, paddedBlock, PaddedBlockBitLength());
GetTrapdoorFunctionInterface().ApplyRandomizedFunction(rng, Integer(paddedBlock, paddedBlock.size())).Encode(cipherText, FixedCiphertextLength());
}
NAMESPACE_END
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