RSA.java

public class RSA {
	
	public static void main(String[] args){

		KulcsPar jSzereplo = new KulcsPar();


		String tisztaSzoveg = "Hello,Vilag!";

		byte[] buffer = tisztaSzoveg.getBytes();
		java.math.BigInteger[] titkos = new java.math.BigInteger[buffer.length];

		for (int i = 0; i < titkos.length; ++i){
			titkos[i] = new java.math.BigInteger(new byte[]{buffer[i]});
			titkos[i] = titkos[i].modPow(jSzereplo.e, jSzereplo.m);
		}

		for (int i = 0; i < titkos.length; ++i){
			titkos[i] = titkos[i].modPow(jSzereplo.d, jSzereplo.m);
			buffer[i] = titkos[i].byteValue();
		}

		System.out.println(new String(buffer));
		
	}
}

class KulcsPar {

	java.math.BigInteger d, e, m;

	public KulcsPar(){

        int meretBitekben = 700 * (int) (java.lang.Math.log ((double) 10)/ java.lang.Math.log((double)2));
        System.out.println("Méret bitekben: ");
        System.out.println(meretBitekben);

        java.math.BigInteger p = new java.math.BigInteger(meretBitekben, 100, new java.util.Random());
        System.out.println("p");
        System.out.println(p);    

        java.math.BigInteger q = new java.math.BigInteger(meretBitekben, 100, new java.util.Random());
        System.out.println("q");
        System.out.println(q);

        m = p.multiply(q);
        System.out.println("m");
        System.out.println(m);

        java.math.BigInteger z = p.subtract(java.math.BigInteger.ONE).multiply(q.subtract(java.math.BigInteger.ONE));
        System.out.println("z");
        System.out.println(z);
        


        do{
            do{
                d = new java.math.BigInteger(meretBitekben, new java.util.Random());
            }while(d.equals(java.math.BigInteger.ONE));

        }while(!z.gcd(d).equals(java.math.BigInteger.ONE));

        e = d.modInverse(z);
        System.out.println("e");
        System.out.println(e);
	}
}