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genopri-shcs/project/PPPServer/src/dgk_crypto/DGK_key_generator.java
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DGK_key_generator.java
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/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package dgk_crypto;
import java.math.BigInteger;
import java.util.Random;
/**
*
* @author raisaro
*/
public class DGK_key_generator {
private BigInteger u;
private BigInteger vpvq;
private BigInteger p;
private BigInteger q;
private BigInteger n;
private BigInteger h;
private BigInteger g;
private BigInteger pp_inv;
private BigInteger qq_inv;
private int k;
private int t;
private int l;
public DGK_key_generator(int dgk_bitlength_n, int dgk_bitlength_v, int dgk_ell) {
this.k = dgk_bitlength_n;
this.t = dgk_bitlength_v;
this.l = dgk_ell;
}
public void generateKeys(){
if (k <= 0 || l <= 0 || t < 2){
System.out.println("Illegal parameter for DGK cryptosystem!");
System.exit(1);
}
if (k % 2 != 0){
System.out.println("Parameter k has to be an even number!");
System.exit(1);
}
if ((k/2 < (l + 5)) || (k/2 < t + 2)){
System.out.println("Parameter k has to be specified by the rules k/2 > l+4 and k/2 > t+1!");
System.exit(1);
}
BigInteger rp, rq;
BigInteger vp, vq;
BigInteger tmp1, tmp2, tmp3;
Random rnd = new Random(System.currentTimeMillis());
//generate u the minimal prime number greater than L+2
l = l*2;
int tmp = l + 2;
u = BigInteger.valueOf(tmp).nextProbablePrime();
// generate vp as a random t bit prime number
vp = BigInteger.probablePrime(t, rnd);
// generate vq as a random t bit prime number
vq = BigInteger.probablePrime(t, rnd);
// store the product vp*vq
vpvq = vp.multiply(vq);
// generation of p and q from u and v
// p is chose as rp*u*vp+1 where rp is randomly chosen such that p has roughly k/2 bits
tmp1 = u.multiply(vp);
int needed_bits = k/2 - tmp1.bitLength();
do{
rp = new BigInteger(needed_bits, rnd);
rp = rp.setBit(needed_bits-1);
p = rp.multiply(tmp1);
p = p.add(BigInteger.ONE);
}while(!p.isProbablePrime(100));
// q is chose as rq*u*vq+1 where rq is randomly chosen such that q has roughly k/2 bits
tmp1 = u.multiply(vq);
needed_bits = k/2 - tmp1.bitLength();
do{
rq = new BigInteger(needed_bits, rnd);
rq = rq.setBit(needed_bits-1);
q = rq.multiply(tmp1);
q = q.add(BigInteger.ONE);
}while(!q.isProbablePrime(100));
// for faster encryption
tmp1 = p.modInverse(q);
pp_inv = p.multiply(tmp1);
tmp1 = q.modInverse(p);
qq_inv = q.multiply(tmp1);
// RSA modulus n
n = p.multiply(q);
/*
h must be random in Zn* and have order vp*vq. We
choose it by setting
h = h' ^{rp * rq * u}.
Seeing h as (hp, hq) and h' as (h'p, h'q) in Zp* x Zq*, we
then have
(hp^vpvq, hq^vpvq) = (h'p^{rp*u*vp}^(rq*vq), h'q^{rq*u*vq}^(rp*vp))
= (1^(rq*vq), 1^(rp*vp)) = (1, 1)
which means that h^(vpvq) = 1 in Zn*.
So we only need to check that h is not 1 and that it really
is in Zn*.
*/
tmp1 = rq.multiply(u);
tmp2 = rp.multiply(tmp1);
int test1 = 1;
int test2 = 1;
do{
long rand;
rand = Math.abs( rnd.nextLong() ) % n.longValue();
tmp1 = BigInteger.valueOf( rand );
h = tmp1.modPow(tmp2, n);
test1 = h.compareTo(BigInteger.ONE);
tmp1 = h.gcd(n);
test2 = tmp1.compareTo(BigInteger.ONE);
}while(test1 == 0 || test2 != 0);
/*
g is chose at random in Zn* such that it has order uv. This
is done in much the same way as for h, but the order of
power of the random number might be u, v or uv. We therefore
also check that gû and g^v are different from 1.
*/
tmp2 = rp.multiply(rq);
test1 = 1;
test2 = 1;
int test3 = 1;
int test4 = 1;
int test5 = 1;
int test6 = 1;
int test7 = 1;
int test8 = 1;
do{
long rand;
rand = Math.abs( rnd.nextLong() ) % n.longValue();
tmp1 = BigInteger.valueOf( rand );
g = tmp1.modPow(tmp2, n);
// test if g is "good":
// test1==0 if gcd(g,n)==1
tmp1 = g.gcd(n);
test1 = tmp1.compareTo(BigInteger.ONE);
// test2==0 if g==1
test2 = g.compareTo(BigInteger.ONE);
// test3==0 if ord(g)==u
tmp1 = g.modPow(u, n);
test3 = tmp1.compareTo(BigInteger.ONE);
//test4==0 if ord(g)==vp
tmp1 = g.modPow(vp, n);
test4 = tmp1.compareTo(BigInteger.ONE);
// test5==0 if ord(g)==vq
tmp1 = g.modPow(vq, n);
test5 = tmp1.compareTo(BigInteger.ONE);
//test6==0 if ord(g)==u*vp
tmp2 = u.multiply(vp);
tmp1 = g.modPow(tmp2, n);
test6 = tmp1.compareTo(BigInteger.ONE);
//test7==0 if ord(g)==u*vq
tmp2 = u.multiply(vq);
tmp1 = g.modPow(tmp2, n);
test7 = tmp1.compareTo(BigInteger.ONE);
//test8==0 if ord(g)==vp*vq
tmp1 = g.modPow(vpvq, n);
test8 = tmp1.compareTo(BigInteger.ONE);
test2 = test2*test3*test4*test5*test6*test7*test8;
}while(test1 != 0 || test2 == 0);
}
public BigInteger getG() {
return g;
}
public BigInteger getH() {
return h;
}
public BigInteger getN() {
return n;
}
public BigInteger getP() {
return p;
}
public BigInteger getPp_inv() {
return pp_inv;
}
public BigInteger getQ() {
return q;
}
public BigInteger getQq_inv() {
return qq_inv;
}
public BigInteger getU() {
return u;
}
public BigInteger getVpvq() {
return vpvq;
}
}
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