• Main Page
  • Namespaces
  • Classes
  • Files
  • File List
  • File Members

dmac.h

00001 #ifndef CRYPTOPP_DMAC_H
00002 #define CRYPTOPP_DMAC_H
00003 
00004 #include "cbcmac.h"
00005 
00006 NAMESPACE_BEGIN(CryptoPP)
00007 
00008 //! _
00009 template <class T>
00010 class CRYPTOPP_NO_VTABLE DMAC_Base : public SameKeyLengthAs<T>, public MessageAuthenticationCode
00011 {
00012 public:
00013     static std::string StaticAlgorithmName() {return std::string("DMAC(") + T::StaticAlgorithmName() + ")";}
00014 
00015     CRYPTOPP_CONSTANT(DIGESTSIZE=T::BLOCKSIZE)
00016 
00017     DMAC_Base() {}
00018 
00019     void UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params);
00020     void Update(const byte *input, size_t length);
00021     void TruncatedFinal(byte *mac, size_t size);
00022     unsigned int DigestSize() const {return DIGESTSIZE;}
00023 
00024 private:
00025     byte *GenerateSubKeys(const byte *key, size_t keylength);
00026 
00027     size_t m_subkeylength;
00028     SecByteBlock m_subkeys;
00029     CBC_MAC<T> m_mac1;
00030     typename T::Encryption m_f2;
00031     unsigned int m_counter;
00032 };
00033 
00034 //! DMAC
00035 /*! Based on "CBC MAC for Real-Time Data Sources" by Erez Petrank
00036     and Charles Rackoff. T should be a class derived from BlockCipherDocumentation.
00037 */
00038 template <class T>
00039 class DMAC : public MessageAuthenticationCodeFinal<DMAC_Base<T> >
00040 {
00041 public:
00042     DMAC() {}
00043     DMAC(const byte *key, size_t length=DMAC_Base<T>::DEFAULT_KEYLENGTH)
00044         {this->SetKey(key, length);}
00045 };
00046 
00047 template <class T>
00048 void DMAC_Base<T>::UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params)
00049 {
00050     m_subkeylength = T::StaticGetValidKeyLength(T::BLOCKSIZE);
00051     m_subkeys.resize(2*UnsignedMin((unsigned int)T::BLOCKSIZE, m_subkeylength));
00052     m_mac1.SetKey(GenerateSubKeys(key, length), m_subkeylength, params);
00053     m_f2.SetKey(m_subkeys+m_subkeys.size()/2, m_subkeylength, params);
00054     m_counter = 0;
00055     m_subkeys.resize(0);
00056 }
00057 
00058 template <class T>
00059 void DMAC_Base<T>::Update(const byte *input, size_t length)
00060 {
00061     m_mac1.Update(input, length);
00062     m_counter = (unsigned int)((m_counter + length) % T::BLOCKSIZE);
00063 }
00064 
00065 template <class T>
00066 void DMAC_Base<T>::TruncatedFinal(byte *mac, size_t size)
00067 {
00068     ThrowIfInvalidTruncatedSize(size);
00069 
00070     byte pad[T::BLOCKSIZE];
00071     byte padByte = byte(T::BLOCKSIZE-m_counter);
00072     memset(pad, padByte, padByte);
00073     m_mac1.Update(pad, padByte);
00074     m_mac1.TruncatedFinal(mac, size);
00075     m_f2.ProcessBlock(mac);
00076 
00077     m_counter = 0;  // reset for next message
00078 }
00079 
00080 template <class T>
00081 byte *DMAC_Base<T>::GenerateSubKeys(const byte *key, size_t keylength)
00082 {
00083     typename T::Encryption cipher(key, keylength);
00084     memset(m_subkeys, 0, m_subkeys.size());
00085     cipher.ProcessBlock(m_subkeys);
00086     m_subkeys[m_subkeys.size()/2 + T::BLOCKSIZE - 1] = 1;
00087     cipher.ProcessBlock(m_subkeys+m_subkeys.size()/2);
00088     return m_subkeys;
00089 }
00090 
00091 NAMESPACE_END
00092 
00093 #endif

Generated on Sun Jul 25 2010 14:44:10 for Crypto++ by  doxygen 1.7.1