trunhash.h

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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