[Java] RSA Implementierung

public class Bezout
{
	int a = 0;
	int b = 0;
		
	public Bezout(int a, int b)
	{
		this.a = a;
		this.b = b;
	}
		
	private int ggT(int a, int b)
	{
		if (a == 0) return b;
		else if (b == 0) return a;
		else
		{
			int remainder = 0;
			do
			{
				remainder = a % b;
				a = b;
				b = remainder;
			} while (remainder != 0);
		}
			
		return a;
	}
		
	public int getD()
	{
		if (a == 0) return 0;
		else if (b == 0) return 1;
		else
		{
			int s1 = 1, s2 = 0, s = 0;
			int t1 = 0, t2 = 1, t = 1;
				
			while (a % b != 0)
			{
				int q = a / b;
				int r = a % b;
					
				s = s1 - q * s2;
				t = t1 - q * t2;
					
				s1 = s2; s2 = s;
				t1 = t2; t2 = t;
				
				a = b;
				b = r;
			}
				
			return s;
		}
	}
}

public class PublicKey
{
	public int n;
	public int e;
}
	
public class PrivateKey
{
	public int n;
	public int e;
	public int p;
	public int q;
	public int d;
	public int phi;
}

public class RSA {
	
	private PublicKey pk = new PublicKey();
	private PrivateKey sk = new PrivateKey();
	
	public RSA()
	{
		generate();
	}
	
	public List<Integer> encrypt(String m)
	{
		List<Integer> c = new ArrayList<Integer>();
		
		for (char ch : m.toCharArray())
		{			
			BigInteger i = BigInteger.valueOf(ch);
			i = i.modPow(BigInteger.valueOf(pk.e), BigInteger.valueOf(pk.n));

			c.add(i.intValue());
		}
		
		return c;
	}
	
	public String decrypt(List<Integer> c)
	{
		StringBuilder m = new StringBuilder();
		
		for (int ch : c)
		{		
			BigInteger i = BigInteger.valueOf(ch);
			i = i.modPow(BigInteger.valueOf(sk.d), BigInteger.valueOf(sk.n));
			m.append((char)i.intValue());
		}
		
		return m.toString();
	}
	
	private void generate()
	{	
		SecureRandom sr = new SecureRandom(String.valueOf(new Date().getTime()).getBytes());
		int random_1 = Math.abs(BigInteger.valueOf(Math.abs(sr.nextInt()) % 0x7FFF).nextProbablePrime().intValue());
		int random_2 = Math.abs(BigInteger.valueOf(Math.abs(sr.nextInt()) % 0x7FFF).nextProbablePrime().intValue());
		int random_3 = Math.abs(BigInteger.valueOf(Math.abs(sr.nextInt()) % 0x7FFF).nextProbablePrime().intValue());
			
		while (random_3 == random_1 || random_3 == random_2)
		{
			random_3 = Math.abs(BigInteger.valueOf(Math.abs(sr.nextInt()) % 0x7FFF).nextProbablePrime().intValue());
		}
		
		sk.p = random_1;
		sk.q = random_2;
		
		sk.n = sk.p * sk.q;
		pk.n = sk.n;
		
		sk.phi = (sk.p - 1) * (sk.q - 1);
		sk.e = random_3;
		pk.e = sk.e;

		sk.d = new Bezout(sk.e, sk.phi).getD();
	}
}