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# mdc.h

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    00001  // mdc.h - written and placed in the public domain by Wei Dai
    00002
    00003 #ifndef CRYPTOPP_MDC_H
    00004 #define CRYPTOPP_MDC_H
    00005
    00006 /** \file
    00007 */
    00008
    00009 #include "seckey.h"
    00010 #include "misc.h"
    00011
    00012 NAMESPACE_BEGIN(CryptoPP)
    00013
    00014 template <class T>
    00015 struct MDC_Info : public FixedBlockSize<T::DIGESTSIZE>, public FixedKeyLength<T::BLOCKSIZE>
    00016 {
    00017         static std::string StaticAlgorithmName() {return std::string("MDC/")+T::StaticAlgorithmName();}
    00018 };
    00019
    00020 //! <a href="http://www.weidai.com/scan-mirror/cs.html#MDC">MDC</a>
    00021 /*! a construction by Peter Gutmann to turn an iterated hash function into a PRF */
    00022 template <class T>
    00023 class MDC : public MDC_Info<T>
    00024 {
    00025         class Enc : public BlockCipherBaseTemplate<MDC_Info<T> >
    00026         {
    00027                 typedef typename T::HashWordType HashWordType;
    00028
    00029         public:
    00030                 void UncheckedSetKey(CipherDir direction, const byte *userKey, unsigned int length)
    00031                 {
    00032                         assert(direction == ENCRYPTION);
    00033                         AssertValidKeyLength(length);
    00034                         memcpy(Key(), userKey, KEYLENGTH);
    00035                         T::CorrectEndianess(Key(), Key(), KEYLENGTH);
    00036                 }
    00037
    00038                 void ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
    00039                 {
    00040                         T::CorrectEndianess(Buffer(), (HashWordType *)inBlock, BLOCKSIZE);
    00041                         T::Transform(Buffer(), Key());
    00042                         if (xorBlock)
    00043                         {
    00044                                 T::CorrectEndianess(Buffer(), Buffer(), BLOCKSIZE);
    00045                                 xorbuf(outBlock, xorBlock, m_buffer, BLOCKSIZE);
    00046                         }
    00047                         else
    00048                                 T::CorrectEndianess((HashWordType *)outBlock, Buffer(), BLOCKSIZE);
    00049                 }
    00050
    00051                 bool IsPermutation() const {return false;}
    00052
    00053                 unsigned int GetAlignment() const {return sizeof(HashWordType);}
    00054
    00055         private:
    00056                 HashWordType *Key() {return (HashWordType *)m_key.data();}
    00057                 const HashWordType *Key() const {return (const HashWordType *)m_key.data();}
    00058                 HashWordType *Buffer() const {return (HashWordType *)m_buffer.data();}
    00059
    00060                 // VC60 workaround: bug triggered if using FixedSizeAllocatorWithCleanup
    00061                 FixedSizeSecBlock<byte, MDC_Info<T>::KEYLENGTH, AllocatorWithCleanup<byte> > m_key;
    00062                 mutable FixedSizeSecBlock<byte, MDC_Info<T>::BLOCKSIZE, AllocatorWithCleanup<byte> > m_buffer;
    00063         };
    00064
    00065 public:
    00066         //! use BlockCipher interface
    00067         typedef BlockCipherTemplate<ENCRYPTION, Enc> Encryption;
    00068 };
    00069
    00070 NAMESPACE_END
    00071
    00072 #endif