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RSAKeyGenerator.java
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RSAKeyGenerator.java
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import java.math.BigInteger;
import java.security.SecureRandom;
public class RSAKeyGenerator {
private Key privateKey, publicKey;
private class Key {
private BigInteger x,y;
Key (BigInteger x, BigInteger y) {
this.x = x;
this.y = y;
}
@Override
public String toString() {
return "(" + x + "," + y + ")";
}
}
RSAKeyGenerator(int bits) {
BigInteger p = BigInteger.probablePrime(bits, new SecureRandom());
BigInteger q;
do {
q = BigInteger.probablePrime(bits, new SecureRandom());
} while (q.equals(p));
BigInteger n = p.multiply(q);
BigInteger phi = p.subtract(BigInteger.ONE).multiply(q.subtract(BigInteger.ONE));
BigInteger e, d;
do {
e = BigInteger.probablePrime(bits, new SecureRandom());
} while ((e.compareTo(BigInteger.ONE) != 1) || (e.compareTo(phi) != -1) || (e.gcd(phi).compareTo(BigInteger.ONE) != 0));
d = e.modInverse(phi);
privateKey = new Key(d, n);
publicKey = new Key(e, n);
//below is a testing code for the keys.
/*
System.out.println("p: " + p);
System.out.println("q: " + q);
System.out.println("privateKey: " + this.getPrivateKey().toString());
System.out.println("publicKey: " + this.getPublicKey().toString());
BigInteger msg = BigInteger.valueOf(100);
System.out.println("message: " + msg);
BigInteger trans = msg.modPow(e, n);
System.out.println("trans: " + trans);
System.out.println("decoded message: " + trans.modPow(d, n));
*/
}
public Key getPrivateKey() {
return privateKey;
}
public Key getPublicKey() {
return publicKey;
}
public static void main(String[] args) {
RSAKeyGenerator test = new RSAKeyGenerator(5);
System.out.println(test.getPrivateKey().toString());
System.out.println(test.getPublicKey().toString());
}
}