Question

I’m trying to use RSA encryption on Blackberry with their native API’s. I made a public/private key pair in Java and saved the Modulus and Exponents of the keys as strings so i can generate the keys from this for encryption and decryption. The following code is from the client side and i’m getting a InvalidKeyException and the backtrace is null so I don’t know what’s happening:

public byte[] Encrypt(byte[] data)
  {
      try {
            RSACryptoSystem cryptoSystem = new RSACryptoSystem(1024);
            RSAPublicKey publicKey = new RSAPublicKey(cryptoSystem, _publicKeyExponent.getBytes(), _publicKeyModulus.getBytes());
            RSAEncryptorEngine encryptorEngine = new RSAEncryptorEngine(publicKey);

            PKCS5FormatterEngine formatterEngine = new PKCS5FormatterEngine( encryptorEngine );

            ByteArrayOutputStream output = new ByteArrayOutputStream();
            BlockEncryptor encryptor = new BlockEncryptor( formatterEngine, output );

            encryptor.write(data);
            encryptor.close();
            output.close();

            return output.toByteArray();
        } catch (InvalidKeyException e) {
            // TODO Auto-generated catch block
            System.out.println();
            e.printStackTrace();
        } catch (CryptoTokenException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (CryptoUnsupportedOperationException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (UnsupportedCryptoSystemException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
      return null;
  } 

And this is what i did server side to generate my keys:

try {
            keyPairGenerator = KeyPairGenerator.getInstance("RSA");
            keyPairGenerator.initialize(1024);
            keyFactory = KeyFactory.getInstance("RSA");
        } catch (NoSuchAlgorithmException ex) {
            Logger.getLogger(EncryptorDecryptor.class.getName()).log(Level.SEVERE, null, ex);
        }

        keyPair = keyPairGenerator.generateKeyPair();
        publicKey = keyPair.getPublic();
        privateKey = keyPair.getPrivate();

        try {
            publicKeySpec = keyFactory.getKeySpec(publicKey, RSAPublicKeySpec.class);
            privateKeySpec = keyFactory.getKeySpec(privateKey, RSAPrivateKeySpec.class);
        } catch (InvalidKeySpecException ex) {
            Logger.getLogger(EncryptorDecryptor.class.getName()).log(Level.SEVERE, null, ex);
        }

        privateKeyModulus = privateKeySpec.getModulus().toString();
        privateKeyExponent = privateKeySpec.getPrivateExponent().toString();

        publicKeyModulus = publicKeySpec.getModulus().toString();
        publicKeyExponent = publicKeySpec.getPublicExponent().toString();

Any ideas?

EDIT: i tried doing a simple test on the server by encrypting and decrypting there and when when I try to decrypt I get a IllegalBlockSizeException these are my encrytion and decryption methods (server side):

public byte[] Decrypt(byte[] data)
    {
        try {
            Cipher cipher = Cipher.getInstance("RSA");
            cipher.init(Cipher.DECRYPT_MODE, privateKey);
            byte[] cipherData = cipher.doFinal(data);
            return cipherData;
        } catch (NoSuchAlgorithmException ex) {
            Logger.getLogger(EncryptorDecryptor.class.getName()).log(Level.SEVERE, null, ex);
        } catch (NoSuchPaddingException ex) {
            Logger.getLogger(EncryptorDecryptor.class.getName()).log(Level.SEVERE, null, ex);
        } catch(IllegalBlockSizeException ex) {
            Logger.getLogger(EncryptorDecryptor.class.getName()).log(Level.SEVERE, null, ex);
        } catch(InvalidKeyException ex) {
            Logger.getLogger(EncryptorDecryptor.class.getName()).log(Level.SEVERE, null, ex);
        } catch(BadPaddingException ex) {
            Logger.getLogger(EncryptorDecryptor.class.getName()).log(Level.SEVERE, null, ex);
        }

        return null;
    }

    public byte[] Encrypt(byte[] data)
    {
        try {
            Cipher cipher = Cipher.getInstance("RSA");
            cipher.init(Cipher.ENCRYPT_MODE, publicKey);
            byte[] cipherData = cipher.doFinal(data);
            return cipherData;
        } catch (NoSuchAlgorithmException ex) {
            Logger.getLogger(EncryptorDecryptor.class.getName()).log(Level.SEVERE, null, ex);
        } catch (NoSuchPaddingException ex) {
            Logger.getLogger(EncryptorDecryptor.class.getName()).log(Level.SEVERE, null, ex);
        } catch(IllegalBlockSizeException ex) {
            Logger.getLogger(EncryptorDecryptor.class.getName()).log(Level.SEVERE, null, ex);
        } catch(InvalidKeyException ex) {
            Logger.getLogger(EncryptorDecryptor.class.getName()).log(Level.SEVERE, null, ex);
        } catch(BadPaddingException ex) {
            Logger.getLogger(EncryptorDecryptor.class.getName()).log(Level.SEVERE, null, ex);
        }

        return null;
    }

And this is the simple test i’m trying:

userName = Base64.encode(encryptorDecryptor.Encrypt(userName.getBytes()));
password = Base64.encode(encryptorDecryptor.Encrypt(password.getBytes()));

userName = new String(encryptorDecryptor.Decrypt(Base64.decode(userName)));
password = new String(encryptorDecryptor.Decrypt(Base64.decode(password)));

Answer 1

1. It is a bug to use String as a container for arbitrary random bytes, e.g. userName = new String(encryptorDecryptor.Encrypt(userName.getBytes()));
is wrong.
2. I’m not familiar with Blackberry’s Java API but in usually you cannot encrypt more than one block with RSA
3. the toString() methods on arrays (e.g. publicKeySpec.getModulus().toString()) don’t return anything useful. You should be able to figure this out just by looking at the data. This is really a beginner java mistake more than a cryptography issue.
4. Don’t using the default character set for the String constructor and String.getBytes() methods. Always specify a character set, usually “UTF-8” is perfect.

That’s all I had the patience for.