pubkey.cpp

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

#include "pch.h"
#include "config.h"

#ifndef CRYPTOPP_IMPORTS

#include "pubkey.h"
#include "integer.h"
#include "filters.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(), NULLPTR, 0, hash, hashIdentifier, messageEmpty, computedRepresentative, representativeBitLength);
    return VerifyBufsEqual(representative, computedRepresentative, computedRepresentative.size());
}

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 message 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,
        NULLPTR, 0, ma.m_semisignature);
}

size_t TF_SignerBase::SignAndRestart(RandomNumberGenerator &rng, PK_MessageAccumulator &messageAccumulator, byte *signature, bool restart) const
{
    CRYPTOPP_UNUSED(restart);

    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
{
    if (ciphertextLength != FixedCiphertextLength())
            throw InvalidArgument(AlgorithmName() + ": ciphertext length of " + IntToString(ciphertextLength) + " doesn't match the required length of " + IntToString(FixedCiphertextLength()) + " for this key");

    SecByteBlock paddedBlock(PaddedBlockByteLength());
    Integer x = GetTrapdoorFunctionInterface().CalculateInverse(rng, Integer(ciphertext, ciphertextLength));
    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())
    {
        if (FixedMaxPlaintextLength() < 1)
            throw InvalidArgument(AlgorithmName() + ": this key is too short to encrypt any messages");
        else
            throw InvalidArgument(AlgorithmName() + ": message length of " + IntToString(plaintextLength) + " exceeds the maximum of " + IntToString(FixedMaxPlaintextLength()) + " 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