"java.lang.NullPointerException" when use doFinal(byte[])

Question

My code here:
KeyFactory kf = null;
Cipher cipher = null;
PrivateKey pk = null;
byte[] symKey = null;
try {
Security.addProvider(new BouncyCastleProvider());
catch (Exception e) {
System.err.println("Error loading security provider (" +
e.getMessage() + ")");
try {
kf = KeyFactory.getInstance("RSA");
catch (NoSuchAlgorithmException ex1) {
try {
pk = kf.generatePrivate(priServer);
catch (InvalidKeySpecException ex3) {
try {
cipher = Cipher.getInstance("RSA");
catch (NoSuchAlgorithmException ex2) {
catch (NoSuchPaddingException ex2) {
try {
cipher.init(Cipher.DECRYPT_MODE, pk);
catch (InvalidKeyException ex4) {
try {
symKey = cipher.doFinal(CEK); //get encode of symmetric key
when CEK is byte[].
I got exception :
java.lang.NullPointerException
     at java.math.BigInteger.remainder(BigInteger.java:1239)
     at org.bouncycastle.crypto.engines.RSAEngine.processBlock(RSAEngine.java:133)
     at org.bouncycastle.jce.provider.JCERSACipher.engineDoFinal(JCERSACipher.java:288)
where my code wrong? Please help me!
Note : I use bouncycastle provider.
Thanks

Answer 1

bla bla bla
kf = KeyFactory.getInstance("RSA");
pk = kf.generatePrivate(priServer);
cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.DECRYPT_MODE, pk);IMHO RSA is 2-keys algorithm => you cannot use it in cipher class
If u need encrypt use PBE for example
PBEKeySpec pbeKeySpec;
PBEParameterSpec pbeParamSpec;
SecretKeyFactory keyFac;
// Salt
byte[] salt = ...;
// Iteration count
int count = 20;
// Create PBE parameter set
pbeParamSpec = new PBEParameterSpec(salt, count);
// Prompt user for encryption password.
pbeKeySpec = new PBEKeySpec(pass); //String with
keyFac = SecretKeyFactory.getInstance("PBEWithMD5AndDES");
SecretKey pbeKey = keyFac.generateSecret(pbeKeySpec);
// Create PBE Cipher
Cipher pbeCipher = Cipher.getInstance("PBEWithMD5AndDES");
// Initialize PBE Cipher with key and parameters
pbeCipher.init(Cipher.ENCRYPT_MODE, pbeKey, pbeParamSpec);
// Our cleartext
byte[] cleartext = "This is another example".getBytes();
// Encrypt the cleartext
byte[] ciphertext = pbeCipher.doFinal(cleartext);