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/*
* Created on 02/04/2005
*
* JRandTest package
*
* Copyright (c) 2005, Zur Aougav, [email protected]
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification,
* are permitted provided that the following conditions are met:
*
* Redistributions of source code must retain the above copyright notice, this list
* of conditions and the following disclaimer.
*
* Redistributions in binary form must reproduce the above copyright notice, this
* list of conditions and the following disclaimer in the documentation and/or
* other materials provided with the distribution.
*
* Neither the name of the JRandTest nor the names of its contributors may be
* used to endorse or promote products derived from this software without specific
* prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
* ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package com.fasteasytrade.jrandtest.algo;
import java.math.BigInteger;
import java.util.Random;
/**
* QuadraidResidue1 Prng algorithm from NIST test package
*
* Fix random p, prime, length 512 bits.
*
* Fix random g, prime, length 512 bits. g < p.
*
* Each prng iteration calculate g = g**2 mod p.
* The lowest 64 bits of g are the prng result.
*
* @author Zur Aougav
*/
public class QuadraticResidue1Prng extends Cipher {
/**
* n's length/num of bits
*/
public final int bit_length = 512;
/**
* prime (with probability < 2 ** -100).
*
* Length of p is bit_length = 512 bits = 64 bytes.
*/
BigInteger p;
/**
* Initial g is a random prime (with probability < 2 ** -100)
*
* Length of g is bit_length = 512 bits = 64 bytes.
*
* g is the "state" of the prng.
*
* g = take 64 lowr bits of ( g**2 mod n ).
*/
BigInteger g;
/**
* g0 is the "initial state" of the prng.
*
* reset method set g to g0.
*/
BigInteger g0;
QuadraticResidue1Prng() {
setup(bit_length);
}
QuadraticResidue1Prng(int x) {
if (x < bit_length) {
setup(bit_length);
} else {
setup(x);
}
}
QuadraticResidue1Prng(BigInteger p, BigInteger g) {
this.p = p;
this.g = g;
g0 = g;
}
QuadraticResidue1Prng(BigInteger p, BigInteger g, BigInteger g0) {
this.p = p;
this.g = g;
this.g0 = g0;
}
/**
* Generate the key and seed for Quadratic Residue Prng.
*
* Select random primes - p, g. g < p.
*
* @param len
* length of p and g, num of bits.
*/
void setup(int len) {
Random rand = new Random();
p = BigInteger.probablePrime(len, rand);
g = BigInteger.probablePrime(len, rand);
/**
* if g >= p swap(g, p).
*/
if (g.compareTo(p) > -1) {
BigInteger temp = g;
g = p;
p = temp;
}
/**
* here for sure g < p
*/
g0 = g;
}
/**
* calculate g**2 mod p and returns lowest 64 bits, long.
*
*/
public long nextLong() {
g = g.multiply(g).mod(p);
/**
* set g to 2 if g <= 1.
*/
if (g.compareTo(BigInteger.ONE) < 1) {
g = BigInteger.valueOf(2);
}
return g.longValue();
}
/**
* Public key.
*
* @return p prime (with probability < 2 ** -100)
*/
public BigInteger getP() {
return p;
}
/**
* Secret key
*
* @return g prime (with probability < 2 ** -100)
*/
public BigInteger getG() {
return g;
}
/**
* Reset "state" of prng by setting g to g0 (initial g).
*
*/
public void reset() {
g = g0;
}
}