Basic RSA example. : RSA algorithm « Security « Java Tutorial

import java.math.BigInteger;

import javax.crypto.Cipher;

public class MainClass {
  public static void main(String[] args) throws Exception {
    Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());

    byte[] input = new byte[] { (byte) 0xbe, (byte) 0xef };
    Cipher cipher = Cipher.getInstance("RSA/None/NoPadding", "BC");

    KeyFactory keyFactory = KeyFactory.getInstance("RSA", "BC");
    RSAPublicKeySpec pubKeySpec = new RSAPublicKeySpec(new BigInteger(
        "12345678", 16), new BigInteger("11", 16));
    RSAPrivateKeySpec privKeySpec = new RSAPrivateKeySpec(new BigInteger(
        "12345678", 16), new BigInteger("12345678",

    RSAPublicKey pubKey = (RSAPublicKey) keyFactory.generatePublic(pubKeySpec);
    RSAPrivateKey privKey = (RSAPrivateKey) keyFactory.generatePrivate(privKeySpec);

    cipher.init(Cipher.ENCRYPT_MODE, pubKey);

    byte[] cipherText = cipher.doFinal(input);
    System.out.println("cipher: " + new String(cipherText));

    cipher.init(Cipher.DECRYPT_MODE, privKey);
    byte[] plainText = cipher.doFinal(cipherText);
    System.out.println("plain : " + new String(plainText));

36.38.RSA algorithm
36.38.1.Basic RSA example.
36.38.2.RSA example with random key generation.
36.38.3.RSA example with PKCS #1 Padding.
36.38.4.RSA example with OAEP Padding and random key generation.
36.38.5.An example of using RSA to encrypt a single asymmetric key.
36.38.6.Simple Digital Signature Example
36.38.7.Creates a 1024 bit RSA key pair and stores it to the filesystem as two files
36.38.8.RSA Signature Generation
36.38.9.An RSA sample application