dmac.h

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// dmac.h - originally written and placed in the public domain by Wei Dai
 
/// \file dmac.h
/// \brief Classes for DMAC message authentication code
 
#ifndef CRYPTOPP_DMAC_H
#define CRYPTOPP_DMAC_H
 
#include "cbcmac.h"
 
NAMESPACE_BEGIN(CryptoPP)
 
/// \brief DMAC message authentication code base class
/// \tparam T class derived from BlockCipherDocumentation
/// \since Crypto++ 3.1
template <class T>
class CRYPTOPP_NO_VTABLE DMAC_Base : public SameKeyLengthAs<T>, public MessageAuthenticationCode
{
public:
    CRYPTOPP_CONSTANT(DIGESTSIZE=T::BLOCKSIZE);
    static std::string StaticAlgorithmName() {return std::string("DMAC(") + T::StaticAlgorithmName() + ")";}
 
    virtual~DMAC_Base() {}
    DMAC_Base() : m_subkeylength(0), m_counter(0) {}
 
    void UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params);
    void Update(const byte *input, size_t length);
    void TruncatedFinal(byte *mac, size_t size);
    unsigned int DigestSize() const {return DIGESTSIZE;}
 
    std::string AlgorithmProvider() const;
 
private:
    byte *GenerateSubKeys(const byte *key, size_t keylength);
 
    size_t m_subkeylength;
    SecByteBlock m_subkeys;
    CBC_MAC<T> m_mac1;
    typename T::Encryption m_f2;
    unsigned int m_counter;
};
 
template <class T>
std::string DMAC_Base<T>::AlgorithmProvider() const
{
    return m_f2.AlgorithmProvider();
}
 
/// \brief DMAC message authentication code
/// \tparam T class derived from BlockCipherDocumentation
/// \sa <A HREF="https://eprint.iacr.org/1997/010">CBC MAC for Real-Time Data Sources (08.15.1997)</A>
///   by Erez Petrank and Charles Rackoff
/// \since Crypto++ 3.1
template <class T>
class DMAC : public MessageAuthenticationCodeFinal<DMAC_Base<T> >
{
public:
    /// \brief Construct a DMAC
    DMAC() {}
 
    /// \brief Construct a DMAC
    /// \param key a byte array used to key the cipher
    /// \param length the size of the byte array, in bytes
    DMAC(const byte *key, size_t length=DMAC_Base<T>::DEFAULT_KEYLENGTH)
        {this->SetKey(key, length);}
};
 
template <class T>
void DMAC_Base<T>::UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params)
{
    m_subkeylength = T::StaticGetValidKeyLength(T::BLOCKSIZE);
    m_subkeys.resize(2*UnsignedMin((unsigned int)T::BLOCKSIZE, m_subkeylength));
    m_mac1.SetKey(GenerateSubKeys(key, length), m_subkeylength, params);
    m_f2.SetKey(m_subkeys+m_subkeys.size()/2, m_subkeylength, params);
    m_counter = 0;
    m_subkeys.resize(0);
}
 
template <class T>
void DMAC_Base<T>::Update(const byte *input, size_t length)
{
    m_mac1.Update(input, length);
    m_counter = (unsigned int)((m_counter + length) % T::BLOCKSIZE);
}
 
template <class T>
void DMAC_Base<T>::TruncatedFinal(byte *mac, size_t size)
{
    ThrowIfInvalidTruncatedSize(size);
 
    byte pad[T::BLOCKSIZE];
    byte padByte = byte(T::BLOCKSIZE-m_counter);
    memset(pad, padByte, padByte);
    m_mac1.Update(pad, padByte);
    m_mac1.TruncatedFinal(mac, size);
    m_f2.ProcessBlock(mac);
 
    m_counter = 0;  // reset for next message
}
 
template <class T>
byte *DMAC_Base<T>::GenerateSubKeys(const byte *key, size_t keylength)
{
    typename T::Encryption cipher(key, keylength);
    memset(m_subkeys, 0, m_subkeys.size());
    cipher.ProcessBlock(m_subkeys);
    m_subkeys[m_subkeys.size()/2 + T::BLOCKSIZE - 1] = 1;
    cipher.ProcessBlock(m_subkeys+m_subkeys.size()/2);
    return m_subkeys;
}
 
NAMESPACE_END
 
#endif