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dmac.h

#ifndef CRYPTOPP_DMAC_H
#define CRYPTOPP_DMAC_H

#include "cbcmac.h"

NAMESPACE_BEGIN(CryptoPP)


template <class T> class DMAC : public MessageAuthenticationCode, SameKeyLengthAs<T>
{
public:
        enum {DIGESTSIZE=T::BLOCKSIZE};

#ifdef __MWERKS__       // CW50 workaround: can't use DEFAULT_KEYLENGTH here
        DMAC(const byte *key, unsigned int keylength = T::DEFAULT_KEYLENGTH);
#else
        DMAC(const byte *key, unsigned int keylength = DEFAULT_KEYLENGTH);
#endif

        void Update(const byte *input, unsigned int length);
        void Final(byte *mac);
        unsigned int DigestSize() const {return DIGESTSIZE;}

private:
        byte *GenerateSubKeys(const byte *key, unsigned int keylength);

        unsigned int subkeylength;
        SecByteBlock subkeys;
        CBC_MAC<T> mac1;
        T f2;
        unsigned int counter;
};

template <class T>
DMAC<T>::DMAC(const byte *key, unsigned int keylength)
        : subkeylength(T::KeyLength(T::BLOCKSIZE))
        , subkeys(2*STDMAX((unsigned int)T::BLOCKSIZE, subkeylength))
        , mac1(GenerateSubKeys(key, keylength), subkeylength)
        , f2(subkeys+subkeys.size/2, subkeylength)
        , counter(0)
{
        subkeys.Resize(0);
}

template <class T>
void DMAC<T>::Update(const byte *input, unsigned int length)
{
        mac1.Update(input, length);
        counter = (counter + length) % T::BLOCKSIZE;
}

template <class T>
void DMAC<T>::Final(byte *mac)
{
        byte pad[T::BLOCKSIZE];
        byte padByte = byte(T::BLOCKSIZE-counter);
        memset(pad, padByte, padByte);
        mac1.Update(pad, padByte);
        mac1.Final(mac);
        f2.ProcessBlock(mac);
}

template <class T>
byte *DMAC<T>::GenerateSubKeys(const byte *key, unsigned int keylength)
{
        T cipher(key, keylength);
        memset(subkeys, 0, subkeys.size);
        cipher.ProcessBlock(subkeys);
        subkeys[subkeys.size/2 + T::BLOCKSIZE - 1] = 1;
        cipher.ProcessBlock(subkeys+subkeys.size/2);
        return subkeys;
}

NAMESPACE_END

#endif

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