audio file encryption and decryption using rsa

import java.math.BigInteger;
import java.util.Random;
import java.io.*;

public class RSA {

private BigInteger p;
private BigInteger q;
private BigInteger N;
private BigInteger phi;
private BigInteger e;
private BigInteger d;
private int bitlength = 1024;
private int blocksize = 256; //blocksize in byte

private Random r;
public RSA() {
r = new Random();
p = BigInteger.probablePrime(bitlength, r);
q = BigInteger.probablePrime(bitlength, r);
N = p.multiply(q);

phi = p.subtract(BigInteger.ONE).multiply(q.subtract(BigInteger.ONE));
e = BigInteger.probablePrime(bitlength/2, r);

while (phi.gcd(e).compareTo(BigInteger.ONE) > 0 && e.compareTo(phi) < 0 ) {
e.add(BigInteger.ONE);
}
d = e.modInverse(phi);
}

public RSA(BigInteger e, BigInteger d, BigInteger N) {
this.e = e;
this.d = d;
this.N = N;
}

public static void main (String[] args) throws IOException
{
RSA rsa = new RSA();
DataInputStream in=new DataInputStream(System.in);
String teststring ;
System.out.println("Enter the plain text:");
teststring=in.readLine();
System.out.println("Encrypting String: " + teststring);
System.out.println("String in Bytes: " + bytesToString(teststring.getBytes()));

// encrypt
byte[] encrypted = rsa.encrypt(teststring.getBytes());
System.out.println("Encrypted String in Bytes: " + bytesToString(encrypted));

// decrypt
byte[] decrypted = rsa.decrypt(encrypted);
System.out.println("Decrypted String in Bytes: " + bytesToString(decrypted));

System.out.println("Decrypted String: " + new String(decrypted));

}

private static String bytesToString(byte[] encrypted) {
String test = "";
for (byte b : encrypted) {
test += Byte.toString(b);
}
return test;
}

//Encrypt message
public byte[] encrypt(byte[] message) {
return (new BigInteger(message)).modPow(e, N).toByteArray();
}

// Decrypt message
public byte[] decrypt(byte[] message) {
return (new BigInteger(message)).modPow(d, N).toByteArray();
}
}

I want a source code to encrypt and decrypt a text file using rsa algorithm.it should do it using the random funtion.