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# dmac.h

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