blumshub.h

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// blumshub.h - originally written and placed in the public domain by Wei Dai
 
/// \file blumshub.h
/// \brief Classes for Blum Blum Shub generator
 
#ifndef CRYPTOPP_BLUMSHUB_H
#define CRYPTOPP_BLUMSHUB_H
 
#include "cryptlib.h"
#include "modarith.h"
#include "integer.h"
 
NAMESPACE_BEGIN(CryptoPP)
 
/// \brief BlumBlumShub without factorization of the modulus
/// \details You should reseed the generator after a fork() to avoid multiple generators
///  with the same internal state.
class PublicBlumBlumShub : public RandomNumberGenerator,
                           public StreamTransformation
{
public:
    virtual ~PublicBlumBlumShub() {}
 
    /// \brief Construct a PublicBlumBlumShub
    /// \param n the modulus
    /// \param seed the seed for the generator
    /// \details seed is the secret key and should be about as large as n.
    PublicBlumBlumShub(const Integer &n, const Integer &seed);
 
    unsigned int GenerateBit();
    byte GenerateByte();
    void GenerateBlock(byte *output, size_t size);
    void ProcessData(byte *outString, const byte *inString, size_t length);
 
    bool IsSelfInverting() const {return true;}
    bool IsForwardTransformation() const {return true;}
 
protected:
    ModularArithmetic modn;
    Integer current;
    word maxBits, bitsLeft;
};
 
/// \brief BlumBlumShub with factorization of the modulus
/// \details You should reseed the generator after a fork() to avoid multiple generators
///  with the same internal state.
class BlumBlumShub : public PublicBlumBlumShub
{
public:
    virtual ~BlumBlumShub() {}
 
    /// \brief Construct a BlumBlumShub
    /// \param p the first prime factor
    /// \param q the second prime factor
    /// \param seed the seed for the generator
    /// \details Esure p and q are both primes congruent to 3 mod 4 and at least 512 bits long.
    ///  seed is the secret key and should be about as large as p*q.
    BlumBlumShub(const Integer &p, const Integer &q, const Integer &seed);
 
    bool IsRandomAccess() const {return true;}
    void Seek(lword index);
 
protected:
    const Integer p, q;
    const Integer x0;
};
 
NAMESPACE_END
 
#endif