ext-cryptopp/mdc.h

 // 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 BlockCipherBaseTemplate<MDC_Info<T> >
	{
		typedef typename T::HashWordType HashWordType;

	public:
		void UncheckedSetKey(CipherDir direction, const byte *userKey, unsigned int length)
		{
			assert(direction == ENCRYPTION);
			AssertValidKeyLength(length);
			memcpy(Key(), userKey, KEYLENGTH);
			T::CorrectEndianess(Key(), Key(), KEYLENGTH);
		}

		void ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
		{
			T::CorrectEndianess(Buffer(), (HashWordType *)inBlock, BLOCKSIZE);
			T::Transform(Buffer(), Key());
			if (xorBlock)
			{
				T::CorrectEndianess(Buffer(), Buffer(), BLOCKSIZE);
				xorbuf(outBlock, xorBlock, m_buffer, BLOCKSIZE);
			}
			else
				T::CorrectEndianess((HashWordType *)outBlock, Buffer(), 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 BlockCipherTemplate<ENCRYPTION, Enc> Encryption;
};

NAMESPACE_END

#endif