dmac.h
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// dmac.h - written and placed in the public domain by Wei Dai
//! \file
//! \headerfile dmac.h
//! \brief Classes for DMAC message authentication code
#ifndef CRYPTOPP_DMAC_H
#define CRYPTOPP_DMAC_H
#include "cbcmac.h"
NAMESPACE_BEGIN(CryptoPP)
//! _
template <class T>
class CRYPTOPP_NO_VTABLE DMAC_Base : public SameKeyLengthAs<T>, public MessageAuthenticationCode
{
public:
static std::string StaticAlgorithmName() {return std::string("DMAC(") + T::StaticAlgorithmName() + ")";}
CRYPTOPP_CONSTANT(DIGESTSIZE=T::BLOCKSIZE)
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;}
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;
};
//! DMAC
/*! Based on "CBC MAC for Real-Time Data Sources" by Erez Petrank
and Charles Rackoff. T should be a class derived from BlockCipherDocumentation.
*/
template <class T>
class DMAC : public MessageAuthenticationCodeFinal<DMAC_Base<T> >
{
public:
DMAC() {}
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
DMAC_Base::TruncatedFinal
void TruncatedFinal(byte *mac, size_t size)
Computes the hash of the current message.
Definition: dmac.h:72
MessageAuthenticationCode
Interface for message authentication codes.
Definition: cryptlib.h:1107
DMAC
DMAC.
Definition: dmac.h:45
HashTransformation::TruncatedFinal
virtual void TruncatedFinal(byte *digest, size_t digestSize)=0
Computes the hash of the current message.
DMAC_Base
_
Definition: dmac.h:16
MessageAuthenticationCodeFinal
Provides class member functions to key a message authentication code.
Definition: seckey.h:394
SecByteBlock
SecBlock<byte> typedef.
Definition: secblock.h:731
cbcmac.h
Classes for CBC MAC.
DMAC_Base::DigestSize
unsigned int DigestSize() const
Provides the digest size of the hash.
Definition: dmac.h:28
DMAC_Base::Update
void Update(const byte *input, size_t length)
Updates a hash with additional input.
Definition: dmac.h:65
UnsignedMin
const T1 UnsignedMin(const T1 &a, const T2 &b)
Safe comparison of values that could be neagtive and incorrectly promoted.
Definition: misc.h:503
SameKeyLengthAs
Provides key lengths based on another class&#39;s key length.
Definition: seckey.h:237
DMAC_Base::UncheckedSetKey
void UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params)
Sets the key for this object without performing parameter validation.
Definition: dmac.h:54
CryptoPP
Crypto++ library namespace.
CBC_MAC
CBC-MAC
Definition: cbcmac.h:40
HashTransformation::Update
virtual void Update(const byte *input, size_t length)=0
Updates a hash with additional input.
NameValuePairs
Interface for retrieving values given their names.
Definition: cryptlib.h:277