bbs.cpp

#include "bbs.h"

// default constructor
BBS::BBS()
{
	// default insecure params
	this->p = 11;
	this->q = 19;
	// seed
	this->x0 = 4;
	// product of P & Q
	this->n = p * q;
}

/*
	set object parameters
	@param blum prime number p
	@param blum prime number q
	@param integer seed
*/
void BBS::setParams(unsigned long long p, unsigned long long q, unsigned long long seed)
{
	// choose p and q such that gcd(p, q) = 1
	this->p = p;
	this->q = q;
	// random seed should be netween 1 & n-1
	this->x0 = seed;
	// blum integer
	this->n = p * q;
}

/*
	overloaded constructor
	@param blum prime number p
	@param blum prime number q
	@param integer seed
*/
BBS::BBS(unsigned long long p, unsigned long long q, unsigned long long seed)
{
	this->setParams(p, q, seed);
}

/*
	Get next random number
*/
unsigned long long BBS::getRandNum()
{
	unsigned long long nextRandNum = (this->x0 * this->x0) % this->n;
	this->x0 = nextRandNum;
	return nextRandNum;
}

/*
	Get next random bit
*/
unsigned long long BBS::getRandBit()
{
	return this->getRandNum() % 2;
}

void BBS::setP(unsigned long long p)
{
	this->p = p;
}

void BBS::setQ(unsigned long long q)
{
	this->q = q;
}

void BBS::setSeed(unsigned long long seed)
{
	this->x0 = seed;
}

BBS::~BBS() {}