mdc.h

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

#ifndef CRYPTOPP_MDC_H
#define CRYPTOPP_MDC_H

/** \file
*/

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

NAMESPACE_BEGIN(CryptoPP)

//! _
template <class T>
struct MDC_Info : public FixedBlockSize<T::DIGESTSIZE>, public FixedKeyLength<T::BLOCKSIZE>
{
        static std::string StaticAlgorithmName() {return std::string("MDC/")+T::StaticAlgorithmName();}
};

//! <a href="http://www.weidai.com/scan-mirror/cs.html#MDC">MDC</a>
/*! a construction by Peter Gutmann to turn an iterated hash function into a PRF */
template <class T>
class MDC : public MDC_Info<T>
{
        class CRYPTOPP_NO_VTABLE Enc : public BlockCipherImpl<MDC_Info<T> >
        {
                typedef typename T::HashWordType HashWordType;

        public:
                void UncheckedSetKey(const byte *userKey, unsigned int length, const NameValuePairs &params)
                {
                        this->AssertValidKeyLength(length);
                        memcpy_s(m_key, m_key.size(), userKey, this->KEYLENGTH);
                        T::CorrectEndianess(Key(), Key(), this->KEYLENGTH);
                }

                void ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
                {
                        T::CorrectEndianess(Buffer(), (HashWordType *)inBlock, this->BLOCKSIZE);
                        T::Transform(Buffer(), Key());
                        if (xorBlock)
                        {
                                T::CorrectEndianess(Buffer(), Buffer(), this->BLOCKSIZE);
                                xorbuf(outBlock, xorBlock, m_buffer, this->BLOCKSIZE);
                        }
                        else
                                T::CorrectEndianess((HashWordType *)outBlock, Buffer(), this->BLOCKSIZE);
                }

                bool IsPermutation() const {return false;}

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

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

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

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

NAMESPACE_END

#endif

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