mdc.h

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// mdc.h - originally written and placed in the public domain by Wei Dai

/// \file mdc.h
/// \brief Classes for the MDC message digest

#ifndef CRYPTOPP_MDC_H
#define CRYPTOPP_MDC_H

#include "seckey.h"
#include "secblock.h"
#include "misc.h"

// GCC cast warning
#define HashWordPtr(x) ((HashWordType*)(void*)(x))
#define ConstHashWordPtr(x) ((const HashWordType*)(const void*)(x))

NAMESPACE_BEGIN(CryptoPP)

/// \tparam B BlockCipher derived class
/// \brief MDC_Info cipher information
template <class B>
struct MDC_Info : public FixedBlockSize<B::DIGESTSIZE>, public FixedKeyLength<B::BLOCKSIZE>
{
    static std::string StaticAlgorithmName() {return std::string("MDC/")+B::StaticAlgorithmName();}
};

/// \brief MDC cipher
/// \tparam H HashTransformation derived class
/// \details MDC() is a construction by Peter Gutmann to turn an iterated hash function into a PRF
/// \sa <a href="http://www.cryptopp.com/wiki/MDC">MDC</a>
template <class H>
class MDC : public MDC_Info<H>
{
    /// \brief MDC cipher encryption operation
    class CRYPTOPP_NO_VTABLE Enc : public BlockCipherImpl<MDC_Info<H> >
    {
        typedef typename H::HashWordType HashWordType;

    public:
        void UncheckedSetKey(const byte *userKey, unsigned int length, const NameValuePairs &params)
        {
            CRYPTOPP_UNUSED(params);
            this->AssertValidKeyLength(length);
            ConditionalByteReverse(BIG_ENDIAN_ORDER, Key(), ConstHashWordPtr(userKey), this->KEYLENGTH);
        }

        void ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
        {
            ConditionalByteReverse(BIG_ENDIAN_ORDER, Buffer(), ConstHashWordPtr(inBlock), this->BLOCKSIZE);
            H::Transform(Buffer(), Key());

            if (xorBlock)
            {
                ConditionalByteReverse(BIG_ENDIAN_ORDER, Buffer(), Buffer(), this->BLOCKSIZE);
                xorbuf(outBlock, xorBlock, m_buffer, this->BLOCKSIZE);
            }
            else
            {
                ConditionalByteReverse(BIG_ENDIAN_ORDER, HashWordPtr(outBlock), Buffer(), this->BLOCKSIZE);
            }
        }

        bool IsPermutation() const {return false;}

        unsigned int OptimalDataAlignment() const {return sizeof(HashWordType);}

    private:
        HashWordType *Key() {return HashWordPtr(m_key.data());}
        const HashWordType *Key() const {return ConstHashWordPtr(m_key.data());}
        HashWordType *Buffer() const {return HashWordPtr(m_buffer.data());}

        // VC60 workaround: bug triggered if using FixedSizeAllocatorWithCleanup
        FixedSizeSecBlock<byte, MDC_Info<H>::KEYLENGTH, AllocatorWithCleanup<byte> > m_key;
        mutable FixedSizeSecBlock<byte, MDC_Info<H>::BLOCKSIZE, AllocatorWithCleanup<byte> > m_buffer;
    };

public:
    // use BlockCipher interface
    typedef BlockCipherFinal<ENCRYPTION, Enc> Encryption;
};

NAMESPACE_END

#endif