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// trunhash.h - originally written and placed in the public domain by Wei Dai
/// \file trunhash.h
/// \brief Classes for truncated hashes
#ifndef CRYPTOPP_TRUNHASH_H
#define CRYPTOPP_TRUNHASH_H
#include "cryptlib.h"
NAMESPACE_BEGIN(CryptoPP)
/// \brief Null hash
/// \details A null hash that conforms to HashTransformation interface
class NullHash : public HashTransformation
{
public:
void Update(const byte *input, size_t length)
{CRYPTOPP_UNUSED(input);CRYPTOPP_UNUSED(length);}
unsigned int DigestSize() const
{return 0;}
void TruncatedFinal(byte *digest, size_t digestSize)
{CRYPTOPP_UNUSED(digest);CRYPTOPP_UNUSED(digestSize);}
bool TruncatedVerify(const byte *digest, size_t digestLength)
{CRYPTOPP_UNUSED(digest);CRYPTOPP_UNUSED(digestLength);return true;}
};
/// \brief Construct new HashModule with smaller digest size from an existing one
/// \tparam T HashTransformation derived class
template <class T>
class TruncatedHashTemplate : public HashTransformation
{
public:
/// \brief Construct a TruncatedHashTemplate
TruncatedHashTemplate(T hm, unsigned int digestSize)
: m_hm(hm), m_digestSize(digestSize) {}
/// \brief Construct a TruncatedHashTemplate
TruncatedHashTemplate(const byte *key, size_t keyLength, unsigned int digestSize)
: m_hm(key, keyLength), m_digestSize(digestSize) {}
/// \brief Construct a TruncatedHashTemplate
TruncatedHashTemplate(size_t digestSize)
: m_digestSize(digestSize) {}
void Restart()
{m_hm.Restart();}
void Update(const byte *input, size_t length)
{m_hm.Update(input, length);}
unsigned int DigestSize() const {return m_digestSize;}
void TruncatedFinal(byte *digest, size_t digestSize)
{m_hm.TruncatedFinal(digest, digestSize);}
bool TruncatedVerify(const byte *digest, size_t digestLength)
{return m_hm.TruncatedVerify(digest, digestLength);}
private:
T m_hm;
unsigned int m_digestSize;
};
typedef TruncatedHashTemplate<HashTransformation &> TruncatedHashModule;
NAMESPACE_END
#endif
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