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blumshub.h

#ifndef CRYPTOPP_BLUMSHUB_H
#define CRYPTOPP_BLUMSHUB_H

#include "cryptlib.h"
#include "modarith.h"

NAMESPACE_BEGIN(CryptoPP)

class BlumGoldwasserPublicKey;
class BlumGoldwasserPrivateKey;

class PublicBlumBlumShub : public RandomNumberGenerator,
                                                   public virtual StreamCipher
{
public:
        PublicBlumBlumShub(const Integer &n, const Integer &seed);

        unsigned int GenerateBit();
        byte GenerateByte();

        byte ProcessByte(byte input)
                {return (input ^ GetByte());}

protected:
        const ModularArithmetic modn;
        const int maxBits;
        Integer current;
        int bitsLeft;

        friend class BlumGoldwasserPublicKey;
        friend class BlumGoldwasserPrivateKey;
};

class BlumBlumShub : public PublicBlumBlumShub,
                                         public RandomAccessStreamCipher
{
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);
        void Seek(unsigned long index);

protected:
        const Integer p, q;
        const Integer x0;
};

NAMESPACE_END

#endif

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