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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

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