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hmac.h

// hmac.h - written and placed in the public domain by Wei Dai

#ifndef CRYPTOPP_HMAC_H
#define CRYPTOPP_HMAC_H

#include "cryptlib.h"
#include "misc.h"

NAMESPACE_BEGIN(CryptoPP)


template <class T> class HMAC : public MessageAuthenticationCode, public VariableKeyLength<16, 0, T::BLOCKSIZE>
{
public:
        // put enums here for Metrowerks 4
        enum {DIGESTSIZE=T::DIGESTSIZE, BLOCKSIZE=T::BLOCKSIZE};

        // CW50 workaround: can't use DEFAULT_KEYLENGTH here
        HMAC(const byte *userKey, unsigned int keylength = 16);
        void Update(const byte *input, unsigned int length);
        void Final(byte *mac);
        unsigned int DigestSize() const {return DIGESTSIZE;}

private:
        enum {IPAD=0x36, OPAD=0x5c};

        void Init();

        SecByteBlock k_ipad, k_opad;
        T hash;
};

template <class T>
HMAC<T>::HMAC(const byte *userKey, unsigned int keylength)
        : k_ipad(MAX_KEYLENGTH), k_opad(MAX_KEYLENGTH)
{
        assert(keylength == KeyLength(keylength));

        memset(k_ipad, IPAD, MAX_KEYLENGTH);
        xorbuf(k_ipad, userKey, keylength);

        memset(k_opad, OPAD, MAX_KEYLENGTH);
        xorbuf(k_opad, userKey, keylength);

        Init();
}

template <class T>
void HMAC<T>::Init()
{
        hash.Update(k_ipad, MAX_KEYLENGTH);
}

template <class T>
void HMAC<T>::Update(const byte *input, unsigned int length)
{
        hash.Update(input, length);
}

template <class T>
void HMAC<T>::Final(byte *mac)
{
        hash.Final(mac);

        hash.Update(k_opad, MAX_KEYLENGTH);
        hash.Update(mac, DIGESTSIZE);
        hash.Final(mac);
        Init();
}

NAMESPACE_END

#endif

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