strciphr.cpp

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

#include "pch.h"

#ifndef CRYPTOPP_IMPORTS

#include "strciphr.h"

NAMESPACE_BEGIN(CryptoPP)

template <class S>
void AdditiveCipherTemplate<S>::UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params)
{
        PolicyInterface &policy = this->AccessPolicy();
        policy.CipherSetKey(params, key, length);
        m_leftOver = 0;
        unsigned int bufferByteSize = policy.CanOperateKeystream() ? GetBufferByteSize(policy) : RoundUpToMultipleOf(1024U, GetBufferByteSize(policy));
        m_buffer.New(bufferByteSize);

        if (this->IsResynchronizable())
        {
                size_t ivLength;
                const byte *iv = this->GetIVAndThrowIfInvalid(params, ivLength);
                policy.CipherResynchronize(m_buffer, iv, ivLength);
        }
}

template <class S>
void AdditiveCipherTemplate<S>::GenerateBlock(byte *outString, size_t length)
{
        if (m_leftOver > 0)
        {
                size_t len = STDMIN(m_leftOver, length);
                memcpy(outString, KeystreamBufferEnd()-m_leftOver, len);
                length -= len;
                m_leftOver -= len;
                outString += len;

                if (!length)
                        return;
        }
        assert(m_leftOver == 0);

        PolicyInterface &policy = this->AccessPolicy();
        unsigned int bytesPerIteration = policy.GetBytesPerIteration();

        if (length >= bytesPerIteration)
        {
                size_t iterations = length / bytesPerIteration;
                policy.WriteKeystream(outString, iterations);
                outString += iterations * bytesPerIteration;
                length -= iterations * bytesPerIteration;
        }

        if (length > 0)
        {
                size_t bufferByteSize = RoundUpToMultipleOf(length, bytesPerIteration);
                size_t bufferIterations = bufferByteSize / bytesPerIteration;

                policy.WriteKeystream(KeystreamBufferEnd()-bufferByteSize, bufferIterations);
                memcpy(outString, KeystreamBufferEnd()-bufferByteSize, length);
                m_leftOver = bufferByteSize - length;
        }
}

template <class S>
void AdditiveCipherTemplate<S>::ProcessData(byte *outString, const byte *inString, size_t length)
{
        if (m_leftOver > 0)
        {
                size_t len = STDMIN(m_leftOver, length);
                xorbuf(outString, inString, KeystreamBufferEnd()-m_leftOver, len);
                length -= len;
                m_leftOver -= len;
                inString += len;
                outString += len;

                if (!length)
                        return;
        }
        assert(m_leftOver == 0);

        PolicyInterface &policy = this->AccessPolicy();
        unsigned int bytesPerIteration = policy.GetBytesPerIteration();

        if (policy.CanOperateKeystream() && length >= bytesPerIteration)
        {
                size_t iterations = length / bytesPerIteration;
                unsigned int alignment = policy.GetAlignment();
                KeystreamOperation operation = KeystreamOperation((IsAlignedOn(inString, alignment) * 2) | (int)IsAlignedOn(outString, alignment));

                policy.OperateKeystream(operation, outString, inString, iterations);

                inString += iterations * bytesPerIteration;
                outString += iterations * bytesPerIteration;
                length -= iterations * bytesPerIteration;

                if (!length)
                        return;
        }

        size_t bufferByteSize = m_buffer.size();
        size_t bufferIterations = bufferByteSize / bytesPerIteration;

        while (length >= bufferByteSize)
        {
                policy.WriteKeystream(m_buffer, bufferIterations);
                xorbuf(outString, inString, KeystreamBufferBegin(), bufferByteSize);
                length -= bufferByteSize;
                inString += bufferByteSize;
                outString += bufferByteSize;
        }

        if (length > 0)
        {
                bufferByteSize = RoundUpToMultipleOf(length, bytesPerIteration);
                bufferIterations = bufferByteSize / bytesPerIteration;

                policy.WriteKeystream(KeystreamBufferEnd()-bufferByteSize, bufferIterations);
                xorbuf(outString, inString, KeystreamBufferEnd()-bufferByteSize, length);
                m_leftOver = bufferByteSize - length;
        }
}

template <class S>
void AdditiveCipherTemplate<S>::Resynchronize(const byte *iv, int length)
{
        PolicyInterface &policy = this->AccessPolicy();
        m_leftOver = 0;
        m_buffer.New(GetBufferByteSize(policy));
        policy.CipherResynchronize(m_buffer, iv, this->ThrowIfInvalidIVLength(length));
}

template <class BASE>
void AdditiveCipherTemplate<BASE>::Seek(lword position)
{
        PolicyInterface &policy = this->AccessPolicy();
        unsigned int bytesPerIteration = policy.GetBytesPerIteration();

        policy.SeekToIteration(position / bytesPerIteration);
        position %= bytesPerIteration;

        if (position > 0)
        {
                policy.WriteKeystream(KeystreamBufferEnd()-bytesPerIteration, 1);
                m_leftOver = bytesPerIteration - (unsigned int)position;
        }
        else
                m_leftOver = 0;
}

template <class BASE>
void CFB_CipherTemplate<BASE>::UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params)
{
        PolicyInterface &policy = this->AccessPolicy();
        policy.CipherSetKey(params, key, length);

        if (this->IsResynchronizable())
        {
                size_t ivLength;
                const byte *iv = this->GetIVAndThrowIfInvalid(params, ivLength);
                policy.CipherResynchronize(iv, ivLength);
        }

        m_leftOver = policy.GetBytesPerIteration();
}

template <class BASE>
void CFB_CipherTemplate<BASE>::Resynchronize(const byte *iv, int length)
{
        PolicyInterface &policy = this->AccessPolicy();
        policy.CipherResynchronize(iv, this->ThrowIfInvalidIVLength(length));
        m_leftOver = policy.GetBytesPerIteration();
}

template <class BASE>
void CFB_CipherTemplate<BASE>::ProcessData(byte *outString, const byte *inString, size_t length)
{
        assert(length % this->MandatoryBlockSize() == 0);

        PolicyInterface &policy = this->AccessPolicy();
        unsigned int bytesPerIteration = policy.GetBytesPerIteration();
        unsigned int alignment = policy.GetAlignment();
        byte *reg = policy.GetRegisterBegin();

        if (m_leftOver)
        {
                size_t len = STDMIN(m_leftOver, length);
                CombineMessageAndShiftRegister(outString, reg + bytesPerIteration - m_leftOver, inString, len);
                m_leftOver -= len;
                length -= len;
                inString += len;
                outString += len;
        }

        if (!length)
                return;

        assert(m_leftOver == 0);

        if (policy.CanIterate() && length >= bytesPerIteration && IsAlignedOn(outString, alignment))
        {
                if (IsAlignedOn(inString, alignment))
                        policy.Iterate(outString, inString, GetCipherDir(*this), length / bytesPerIteration);
                else
                {
                        memcpy(outString, inString, length);
                        policy.Iterate(outString, outString, GetCipherDir(*this), length / bytesPerIteration);
                }
                inString += length - length % bytesPerIteration;
                outString += length - length % bytesPerIteration;
                length %= bytesPerIteration;
        }

        while (length >= bytesPerIteration)
        {
                policy.TransformRegister();
                CombineMessageAndShiftRegister(outString, reg, inString, bytesPerIteration);
                length -= bytesPerIteration;
                inString += bytesPerIteration;
                outString += bytesPerIteration;
        }

        if (length > 0)
        {
                policy.TransformRegister();
                CombineMessageAndShiftRegister(outString, reg, inString, length);
                m_leftOver = bytesPerIteration - length;
        }
}

template <class BASE>
void CFB_EncryptionTemplate<BASE>::CombineMessageAndShiftRegister(byte *output, byte *reg, const byte *message, size_t length)
{
        xorbuf(reg, message, length);
        memcpy(output, reg, length);
}

template <class BASE>
void CFB_DecryptionTemplate<BASE>::CombineMessageAndShiftRegister(byte *output, byte *reg, const byte *message, size_t length)
{
        for (unsigned int i=0; i<length; i++)
        {
                byte b = message[i];
                output[i] = reg[i] ^ b;
                reg[i] = b;
        }
}

NAMESPACE_END

#endif