install JCE and BouncyCastle software for encryption.
Some days ago I find this information about (I can not remind where did I take it, maybe was from this forum) for install JCE and BouncyCastle software for encryption.

You should first download change the policy of the JCE By downloading this
http://java.sun.com/j2se/1.4.2/download.html just JCE a and unzip in a folder read the read me doc so you should cut that 2 file and put here C:\j2sdk1.4.2_02\jre\lib\security
and here C:\Program Files\Java\j2re1.4.2_02\lib\security

done this then download the bouncy jar file from http://www.bouncycastle.org/latest_releases.html take the bcprov-jdk14-120.jar and put in following directories

C:\j2sdk1.4.2_02\jre\lib\ext
C:\Program Files\Java\j2re1.4.2_02\lib\ext

then you need to change the environment variable so in the following directories open "java.security" in both
C:\j2sdk1.4.2_02\jre\lib\security
C:\Program Files\Java\j2re1.4.2_02\lib\security

and edit it and add the extra line

security.provider.numberProvider=org.bouncycastle.jce.provider.BouncyCastleProv ider
Then you should test if everything is good installed:
import java.security.Provider;
import java.security.Security;
import java.util.Set;
import java.util.Iterator;
 
public class Verifica {
 
 public static void main(String[] args) {
  Provider[] providers = Security.getProviders();
  for (int i = 0; i < providers.length; i++) {
   Provider provider = providers[i];
   System.out.println("Provider name: " + provider.getName());
   System.out.println("Provider information: " + provider.getInfo());
   System.out.println("Provider version: " + provider.getVersion());
   Set entries = provider.entrySet();
   Iterator iterator = entries.iterator();
   /*while (iterator.hasNext()) {
    System.out.println("Property entry: " + iterator.next());
   }*/
  }
 }

And you will see if there is RSA. (It should)

An example:

Encription:
//Object Cipher to encript data.
Cipher encriptDatos = Cipher.getInstance("RSA", "BC");
 
encriptDatos.init(Cipher.ENCRYPT_MODE, servidorPub); //servidorPub is the server public key you should have or generate
 
//data encryption
byte[] datosEncriptados = encriptDatos.doFinal(b);

Desencryption:
Cipher Cipherdesencriptacion = Cipher.getInstance("RSA", "BC");
Cipherdesencriptacion.init(Cipher.DECRYPT_MODE, servidorPriv); //ServidorPriv is the server public key

//data desencryption
byte[] datosClaros = Cipherdesencriptacion.doFinal(datos); //datos = encripted data.

I am sure you can find many examples of encrypt and decrypt. But hope this help as introduction.

- Susana