modes.cpp

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

#include "pch.h"

#ifndef CRYPTOPP_IMPORTS

#include "modes.h"

#ifndef NDEBUG
#include "des.h"
#endif

NAMESPACE_BEGIN(CryptoPP)

#ifndef NDEBUG
void Modes_TestInstantiations()
{
        CFB_Mode<DES>::Encryption m0;
        CFB_Mode<DES>::Decryption m1;
        OFB_Mode<DES>::Encryption m2;
        CTR_Mode<DES>::Encryption m3;
        ECB_Mode<DES>::Encryption m4;
        CBC_Mode<DES>::Encryption m5;
}
#endif

void CTR_ModePolicy::SeekToIteration(lword iterationCount)
{
        int carry=0;
        for (int i=BlockSize()-1; i>=0; i--)
        {
                unsigned int sum = m_register[i] + byte(iterationCount) + carry;
                m_counterArray[i] = (byte) sum;
                carry = sum >> 8;
                iterationCount >>= 8;
        }
}

inline void CTR_ModePolicy::ProcessMultipleBlocks(byte *output, const byte *input, size_t n)
{
        unsigned int s = BlockSize(), j = 0;
        for (unsigned int i=1; i<n; i++, j+=s)
                IncrementCounterByOne(m_counterArray + j + s, m_counterArray + j, s);
        m_cipher->ProcessAndXorMultipleBlocks(m_counterArray, input, output, n);
        IncrementCounterByOne(m_counterArray, m_counterArray + s*(n-1), s);
}

void CTR_ModePolicy::OperateKeystream(KeystreamOperation operation, byte *output, const byte *input, size_t iterationCount)
{
        assert(m_cipher->IsForwardTransformation());    // CTR mode needs the "encrypt" direction of the underlying block cipher, even to decrypt
        unsigned int maxBlocks = m_cipher->OptimalNumberOfParallelBlocks();
        if (maxBlocks == 1)
        {
                unsigned int sizeIncrement = BlockSize();
                while (iterationCount)
                {
                        m_cipher->ProcessAndXorBlock(m_counterArray, input, output);
                        IncrementCounterByOne(m_counterArray, sizeIncrement);
                        output += sizeIncrement;
                        input += sizeIncrement;
                        iterationCount -= 1;
                }
        }
        else
        {
                unsigned int sizeIncrement = maxBlocks * BlockSize();
                while (iterationCount >= maxBlocks)
                {
                        ProcessMultipleBlocks(output, input, maxBlocks);
                        output += sizeIncrement;
                        input += sizeIncrement;
                        iterationCount -= maxBlocks;
                }
                if (iterationCount > 0)
                        ProcessMultipleBlocks(output, input, iterationCount);
        }
}

void CTR_ModePolicy::CipherResynchronize(byte *keystreamBuffer, const byte *iv)
{
        unsigned int s = BlockSize();
        CopyOrZero(m_register, iv, s);
        m_counterArray.New(s * m_cipher->OptimalNumberOfParallelBlocks());
        CopyOrZero(m_counterArray, iv, s);
}

void BlockOrientedCipherModeBase::UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params)
{
        m_cipher->SetKey(key, length, params);
        ResizeBuffers();
        if (IsResynchronizable())
                Resynchronize(GetIVAndThrowIfInvalid(params));
}

void BlockOrientedCipherModeBase::ProcessData(byte *outString, const byte *inString, size_t length)
{
        if (!length)
                return;

        unsigned int s = BlockSize();
        assert(length % s == 0);

        if (!RequireAlignedInput() || IsAlignedOn(inString, m_cipher->BlockAlignment()))
                ProcessBlocks(outString, inString, length / s);
        else
        {
                do
                {
                        memcpy(m_buffer, inString, s);
                        ProcessBlocks(outString, m_buffer, 1);
                        inString += s;
                        outString += s;
                        length -= s;
                } while (length > 0);
        }
}

void CBC_Encryption::ProcessBlocks(byte *outString, const byte *inString, size_t numberOfBlocks)
{
        unsigned int blockSize = BlockSize();
        xorbuf(m_register, inString, blockSize);
        while (--numberOfBlocks)
        {
                m_cipher->ProcessBlock(m_register, outString);
                inString += blockSize;
                xorbuf(m_register, inString, outString, blockSize);
                outString += blockSize;
        }
        m_cipher->ProcessBlock(m_register);
        memcpy(outString, m_register, blockSize);
}

void CBC_CTS_Encryption::ProcessLastBlock(byte *outString, const byte *inString, size_t length)
{
        if (length <= BlockSize())
        {
                if (!m_stolenIV)
                        throw InvalidArgument("CBC_Encryption: message is too short for ciphertext stealing");

                // steal from IV
                memcpy(outString, m_register, length);
                outString = m_stolenIV;
        }
        else
        {
                // steal from next to last block
                xorbuf(m_register, inString, BlockSize());
                m_cipher->ProcessBlock(m_register);
                inString += BlockSize();
                length -= BlockSize();
                memcpy(outString+BlockSize(), m_register, length);
        }

        // output last full ciphertext block
        xorbuf(m_register, inString, length);
        m_cipher->ProcessBlock(m_register);
        memcpy(outString, m_register, BlockSize());
}

void CBC_Decryption::ProcessBlocks(byte *outString, const byte *inString, size_t numberOfBlocks)
{
        unsigned int blockSize = BlockSize();
        do
        {
                memcpy(m_temp, inString, blockSize);    // make copy in case we're doing in place decryption
                m_cipher->ProcessAndXorBlock(m_temp, m_register, outString);
                m_register.swap(m_temp);
                inString += blockSize;
                outString += blockSize;
        } while (--numberOfBlocks);
}

void CBC_CTS_Decryption::ProcessLastBlock(byte *outString, const byte *inString, size_t length)
{
        const byte *pn, *pn1;
        bool stealIV = length <= BlockSize();

        if (stealIV)
        {
                pn = inString;
                pn1 = m_register;
        }
        else
        {
                pn = inString + BlockSize();
                pn1 = inString;
                length -= BlockSize();
        }

        // decrypt last partial plaintext block
        memcpy(m_temp, pn1, BlockSize());
        m_cipher->ProcessBlock(m_temp);
        xorbuf(m_temp, pn, length);

        if (stealIV)
                memcpy(outString, m_temp, length);
        else
        {
                memcpy(outString+BlockSize(), m_temp, length);
                // decrypt next to last plaintext block
                memcpy(m_temp, pn, length);
                m_cipher->ProcessBlock(m_temp);
                xorbuf(outString, m_temp, m_register, BlockSize());
        }
}

NAMESPACE_END

#endif

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