blumshub.h

#ifndef CRYPTOPP_BLUMSHUB_H
#define CRYPTOPP_BLUMSHUB_H

#include "modarith.h"

NAMESPACE_BEGIN(CryptoPP)

class BlumGoldwasserPublicKey;
class BlumGoldwasserPrivateKey;

//! BlumBlumShub without factorization of the modulus
class PublicBlumBlumShub : public RandomNumberGenerator,
                                                   public StreamTransformation
{
public:
        PublicBlumBlumShub(const Integer &n, const Integer &seed);

        unsigned int GenerateBit();
        byte GenerateByte();

        void ProcessData(byte *outString, const byte *inString, size_t length)
        {
                while (length--)
                        *outString++ = *inString ^ GenerateByte();
        }

        bool IsSelfInverting() const {return true;}
        bool IsForwardTransformation() const {return true;}

protected:
        ModularArithmetic modn;
        word maxBits, bitsLeft;
        Integer current;

        friend class BlumGoldwasserPublicKey;
        friend class BlumGoldwasserPrivateKey;
};

//! BlumBlumShub with factorization of the modulus
class BlumBlumShub : public PublicBlumBlumShub
{
public:
        // Make sure 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 big 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

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