pubkey.cpp

// pubkey.cpp - written and placed in the public domain by Wei Dai

#include "pch.h"

#ifndef CRYPTOPP_IMPORTS

#include "pubkey.h"

NAMESPACE_BEGIN(CryptoPP)

void P1363_MGF1KDF2_Common(HashTransformation &hash, byte *output, size_t outputLength, const byte *input, size_t inputLength, const byte *derivationParams, size_t derivationParamsLength, bool mask, unsigned int counterStart)
{
        ArraySink *sink;
        HashFilter filter(hash, sink = mask ? new ArrayXorSink(output, outputLength) : new ArraySink(output, outputLength));
        word32 counter = counterStart;
        while (sink->AvailableSize() > 0)
        {
                filter.Put(input, inputLength);
                filter.PutWord32(counter++);
                filter.Put(derivationParams, derivationParamsLength);
                filter.MessageEnd();
        }
}

bool PK_DeterministicSignatureMessageEncodingMethod::VerifyMessageRepresentative(
        HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
        byte *representative, size_t representativeBitLength) const
{
        SecByteBlock computedRepresentative(BitsToBytes(representativeBitLength));
        ComputeMessageRepresentative(NullRNG(), NULL, 0, hash, hashIdentifier, messageEmpty, computedRepresentative, representativeBitLength);
        return memcmp(representative, computedRepresentative, computedRepresentative.size()) == 0;
}

bool PK_RecoverableSignatureMessageEncodingMethod::VerifyMessageRepresentative(
        HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
        byte *representative, size_t representativeBitLength) const
{
        SecByteBlock recoveredMessage(MaxRecoverableLength(representativeBitLength, hashIdentifier.second, hash.DigestSize()));
        DecodingResult result = RecoverMessageFromRepresentative(
                hash, hashIdentifier, messageEmpty, representative, representativeBitLength, recoveredMessage);
        return result.isValidCoding && result.messageLength == 0;
}

void TF_SignerBase::InputRecoverableMessage(PK_MessageAccumulator &messageAccumulator, const byte *recoverableMessage, size_t recoverableMessageLength) const
{
        PK_MessageAccumulatorBase &ma = static_cast<PK_MessageAccumulatorBase &>(messageAccumulator);
        HashIdentifier id = GetHashIdentifier();
        const MessageEncodingInterface &encoding = GetMessageEncodingInterface();

        if (MessageRepresentativeBitLength() < encoding.MinRepresentativeBitLength(id.second, ma.AccessHash().DigestSize()))
                throw PK_SignatureScheme::KeyTooShort();

        size_t maxRecoverableLength = encoding.MaxRecoverableLength(MessageRepresentativeBitLength(), GetHashIdentifier().second, ma.AccessHash().DigestSize());

        if (maxRecoverableLength == 0)
                {throw NotImplemented("TF_SignerBase: this algorithm does not support messsage recovery or the key is too short");}
        if (recoverableMessageLength > maxRecoverableLength)
                throw InvalidArgument("TF_SignerBase: the recoverable message part is too long for the given key and algorithm");

        ma.m_recoverableMessage.Assign(recoverableMessage, recoverableMessageLength);
        encoding.ProcessRecoverableMessage(
                ma.AccessHash(), 
                recoverableMessage, recoverableMessageLength,
                NULL, 0, ma.m_semisignature);
}

size_t TF_SignerBase::SignAndRestart(RandomNumberGenerator &rng, PK_MessageAccumulator &messageAccumulator, byte *signature, bool restart) const
{
        PK_MessageAccumulatorBase &ma = static_cast<PK_MessageAccumulatorBase &>(messageAccumulator);
        HashIdentifier id = GetHashIdentifier();
        const MessageEncodingInterface &encoding = GetMessageEncodingInterface();

        if (MessageRepresentativeBitLength() < encoding.MinRepresentativeBitLength(id.second, ma.AccessHash().DigestSize()))
                throw PK_SignatureScheme::KeyTooShort();

        SecByteBlock representative(MessageRepresentativeLength());
        encoding.ComputeMessageRepresentative(rng, 
                ma.m_recoverableMessage, ma.m_recoverableMessage.size(), 
                ma.AccessHash(), id, ma.m_empty,
                representative, MessageRepresentativeBitLength());
        ma.m_empty = true;

        Integer r(representative, representative.size());
        size_t signatureLength = SignatureLength();
        GetTrapdoorFunctionInterface().CalculateRandomizedInverse(rng, r).Encode(signature, signatureLength);
        return signatureLength;
}

void TF_VerifierBase::InputSignature(PK_MessageAccumulator &messageAccumulator, const byte *signature, size_t signatureLength) const
{
        PK_MessageAccumulatorBase &ma = static_cast<PK_MessageAccumulatorBase &>(messageAccumulator);
        HashIdentifier id = GetHashIdentifier();
        const MessageEncodingInterface &encoding = GetMessageEncodingInterface();

        if (MessageRepresentativeBitLength() < encoding.MinRepresentativeBitLength(id.second, ma.AccessHash().DigestSize()))
                throw PK_SignatureScheme::KeyTooShort();

        ma.m_representative.New(MessageRepresentativeLength());
        Integer x = GetTrapdoorFunctionInterface().ApplyFunction(Integer(signature, signatureLength));
        if (x.BitCount() > MessageRepresentativeBitLength())
                x = Integer::Zero();    // don't return false here to prevent timing attack
        x.Encode(ma.m_representative, ma.m_representative.size());
}

bool TF_VerifierBase::VerifyAndRestart(PK_MessageAccumulator &messageAccumulator) const
{
        PK_MessageAccumulatorBase &ma = static_cast<PK_MessageAccumulatorBase &>(messageAccumulator);
        HashIdentifier id = GetHashIdentifier();
        const MessageEncodingInterface &encoding = GetMessageEncodingInterface();

        if (MessageRepresentativeBitLength() < encoding.MinRepresentativeBitLength(id.second, ma.AccessHash().DigestSize()))
                throw PK_SignatureScheme::KeyTooShort();

        bool result = encoding.VerifyMessageRepresentative(
                ma.AccessHash(), id, ma.m_empty, ma.m_representative, MessageRepresentativeBitLength());
        ma.m_empty = true;
        return result;
}

DecodingResult TF_VerifierBase::RecoverAndRestart(byte *recoveredMessage, PK_MessageAccumulator &messageAccumulator) const
{
        PK_MessageAccumulatorBase &ma = static_cast<PK_MessageAccumulatorBase &>(messageAccumulator);
        HashIdentifier id = GetHashIdentifier();
        const MessageEncodingInterface &encoding = GetMessageEncodingInterface();

        if (MessageRepresentativeBitLength() < encoding.MinRepresentativeBitLength(id.second, ma.AccessHash().DigestSize()))
                throw PK_SignatureScheme::KeyTooShort();

        DecodingResult result = encoding.RecoverMessageFromRepresentative(
                ma.AccessHash(), id, ma.m_empty, ma.m_representative, MessageRepresentativeBitLength(), recoveredMessage);
        ma.m_empty = true;
        return result;
}

DecodingResult TF_DecryptorBase::Decrypt(RandomNumberGenerator &rng, const byte *ciphertext, size_t ciphertextLength, byte *plaintext, const NameValuePairs &parameters) const
{
        SecByteBlock paddedBlock(PaddedBlockByteLength());
        Integer x = GetTrapdoorFunctionInterface().CalculateInverse(rng, 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 GetMessageEncodingInterface().Unpad(paddedBlock, PaddedBlockBitLength(), plaintext, parameters);
}

void TF_EncryptorBase::Encrypt(RandomNumberGenerator &rng, const byte *plaintext, size_t plaintextLength, byte *ciphertext, const NameValuePairs &parameters) const
{
        if (plaintextLength > FixedMaxPlaintextLength())
                throw InvalidArgument(AlgorithmName() + ": message too long for this public key");

        SecByteBlock paddedBlock(PaddedBlockByteLength());
        GetMessageEncodingInterface().Pad(rng, plaintext, plaintextLength, paddedBlock, PaddedBlockBitLength(), parameters);
        GetTrapdoorFunctionInterface().ApplyRandomizedFunction(rng, Integer(paddedBlock, paddedBlock.size())).Encode(ciphertext, FixedCiphertextLength());
}

NAMESPACE_END

#endif

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