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[分享]XOR_MAC
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发表于: 2009-5-27 23:32 3637
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// xormac.h - written and placed in the public domain by Wei Dai #ifndef CRYPTOPP_XORMAC_H #define CRYPTOPP_XORMAC_H #include "iterhash.h" NAMESPACE_BEGIN(CryptoPP) template <class T> class XMACC : public IteratedHash<typename T::HashWordType>, public MessageAuthenticationCode { public: typedef typename T::HashWordType HashWordType; // If you need to generate MACs with XMACC (instead of just verifying them), // you must save the counter before destroying an XMACC object // and reinitialize it the next time you create an XMACC with the same key. // Start counter at 0 when using a key for the first time. XMACC(const byte *userKey, word32 counter=0xffffffff); word32 CurrentCounter() const {return counter;} void Final(byte *mac); bool Verify(const byte *mac); unsigned int DigestSize() const {return DIGESTSIZE;} enum {KEYLENGTH=T::DIGESTSIZE-4, DIGESTSIZE = 4+T::DIGESTSIZE, DATASIZE = T::DATASIZE}; private: void Init(); void HashBlock(const HashWordType *input); static void WriteWord32(byte *output, word32 value); static void XorDigest(HashWordType *digest, const HashWordType *buffer); SecByteBlock key; SecBlock<HashWordType> buffer; word32 counter, index; }; template <class T> XMACC<T>::XMACC(const byte *userKey, word32 counter) : IteratedHash<T::HashWordType>(DATASIZE, T::DIGESTSIZE) , key(KEYLENGTH) , buffer(T::DIGESTSIZE/sizeof(HashWordType)) , counter(counter) { memcpy(key, userKey, KEYLENGTH); Init(); } template <class T> void XMACC<T>::Init() { countLo = countHi = 0; index = 0x80000000; memset(digest, 0, T::DIGESTSIZE); } template <class T> inline void XMACC<T>::WriteWord32(byte *output, word32 value) { output[0] = byte(value >> 24); output[1] = byte(value >> 16); output[2] = byte(value >> 8); output[3] = byte(value); } template <class T> inline void XMACC<T>::XorDigest(HashWordType *digest, const HashWordType *buffer) { for (unsigned i=0; i<(T::DIGESTSIZE/sizeof(HashWordType)); i++) digest[i] ^= buffer[i]; } template <class T> void XMACC<T>::HashBlock(const HashWordType *input) { memcpy(buffer, key, KEYLENGTH); WriteWord32((byte *)buffer.ptr+KEYLENGTH, ++index); T::CorrectEndianess(buffer, buffer, T::DIGESTSIZE); T::CorrectEndianess(data, input, DATASIZE); T::Transform(buffer, data); XorDigest(digest, buffer); } template <class T> void XMACC<T>::Final(byte *mac) { assert(counter != 0xffffffff); PadLastBlock(DATASIZE-8); WriteWord32((byte *)data.ptr+DATASIZE-8, countHi); WriteWord32((byte *)data.ptr+DATASIZE-4, countLo); HashBlock(data); memcpy(buffer, key, KEYLENGTH); WriteWord32((byte *)buffer.ptr+KEYLENGTH, 0); memset(data, 0, DATASIZE-4); WriteWord32((byte *)data.ptr+DATASIZE-4, ++counter); T::CorrectEndianess(buffer, buffer, T::DIGESTSIZE); T::CorrectEndianess(data, data, DATASIZE); T::Transform(buffer, data); XorDigest(digest, buffer); WriteWord32(mac, counter); T::CorrectEndianess(digest, digest, T::DIGESTSIZE); memcpy(mac+4, digest, T::DIGESTSIZE); Init(); // reinit for next use } template <class T> bool XMACC<T>::Verify(const byte *mac) { PadLastBlock(DATASIZE-8); WriteWord32((byte *)data.ptr+DATASIZE-8, countHi); WriteWord32((byte *)data.ptr+DATASIZE-4, countLo); HashBlock(data); memcpy(buffer, key, KEYLENGTH); WriteWord32((byte *)buffer.ptr+KEYLENGTH, 0); memset(data, 0, DATASIZE-4); memcpy((byte *)data.ptr+DATASIZE-4, mac, 4); T::CorrectEndianess(buffer, buffer, T::DIGESTSIZE); T::CorrectEndianess(data, data, DATASIZE); T::Transform(buffer, data); XorDigest(digest, buffer); T::CorrectEndianess(digest, digest, T::DIGESTSIZE); bool macValid = (memcmp(mac+4, digest, T::DIGESTSIZE) == 0); Init(); // reinit for next use return macValid; } NAMESPACE_END #endif
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