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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 //! _
00015 template <class T>
00016 struct MDC_Info : public FixedBlockSize<T::DIGESTSIZE>, public FixedKeyLength<T::BLOCKSIZE>
00017 {
00018         static std::string StaticAlgorithmName() {return std::string("MDC/")+T::StaticAlgorithmName();}
00019 };
00020 
00021 //! <a href="http://www.weidai.com/scan-mirror/cs.html#MDC">MDC</a>
00022 /*! a construction by Peter Gutmann to turn an iterated hash function into a PRF */
00023 template <class T>
00024 class MDC : public MDC_Info<T>
00025 {
00026         class CRYPTOPP_NO_VTABLE Enc : public BlockCipherImpl<MDC_Info<T> >
00027         {
00028                 typedef typename T::HashWordType HashWordType;
00029 
00030         public:
00031                 void UncheckedSetKey(CipherDir direction, const byte *userKey, unsigned int length)
00032                 {
00033                         assert(direction == ENCRYPTION);
00034                         this->AssertValidKeyLength(length);
00035                         memcpy(Key(), userKey, this->KEYLENGTH);
00036                         T::CorrectEndianess(Key(), Key(), this->KEYLENGTH);
00037                 }
00038 
00039                 void ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
00040                 {
00041                         T::CorrectEndianess(Buffer(), (HashWordType *)inBlock, this->BLOCKSIZE);
00042                         T::Transform(Buffer(), Key());
00043                         if (xorBlock)
00044                         {
00045                                 T::CorrectEndianess(Buffer(), Buffer(), this->BLOCKSIZE);
00046                                 xorbuf(outBlock, xorBlock, m_buffer, this->BLOCKSIZE);
00047                         }
00048                         else
00049                                 T::CorrectEndianess((HashWordType *)outBlock, Buffer(), this->BLOCKSIZE);
00050                 }
00051 
00052                 bool IsPermutation() const {return false;}
00053 
00054                 unsigned int GetAlignment() const {return sizeof(HashWordType);}
00055 
00056         private:
00057                 HashWordType *Key() {return (HashWordType *)m_key.data();}
00058                 const HashWordType *Key() const {return (const HashWordType *)m_key.data();}
00059                 HashWordType *Buffer() const {return (HashWordType *)m_buffer.data();}
00060 
00061                 // VC60 workaround: bug triggered if using FixedSizeAllocatorWithCleanup
00062                 FixedSizeSecBlock<byte, MDC_Info<T>::KEYLENGTH, AllocatorWithCleanup<byte> > m_key;
00063                 mutable FixedSizeSecBlock<byte, MDC_Info<T>::BLOCKSIZE, AllocatorWithCleanup<byte> > m_buffer;
00064         };
00065 
00066 public:
00067         //! use BlockCipher interface
00068         typedef BlockCipherFinal<ENCRYPTION, Enc> Encryption;
00069 };
00070 
00071 NAMESPACE_END
00072 
00073 #endif

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