CODEWITHSUNDEEP
javaencryptionaesbouncycastle
user3077162
user3077162

Reputation: 231

AES Encryption with Bouncy Castle in Java

I have this simply AES encryption code:

public static void main(String[] args) throws Exception
{
    byte[]        input = new byte[] {
                      0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77,
                      (byte)0x88, (byte)0x99, (byte)0xaa, (byte)0xbb,
                      (byte)0xcc, (byte)0xdd, (byte)0xee, (byte)0xff };
    byte[]        keyBytes = new byte[] {
                      0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
                      0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
                      0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17 };

    SecretKeySpec key = new SecretKeySpec(keyBytes, "AES");

    Cipher        cipher = Cipher.getInstance("AES/ECB/NoPadding", "BC");

    System.out.println("input text : " + Utils.toHex(input));

    // encryption pass

    byte[] cipherText = new byte[input.length];

    cipher.init(Cipher.ENCRYPT_MODE, key);

    int ctLength = cipher.update(input, 0, input.length, cipherText, 0);

    ctLength += cipher.doFinal(cipherText, ctLength);

    System.out.println("cipher text: " + Utils.toHex(cipherText)
                                                 + " bytes: " + ctLength);

    // decryption pass

    byte[] plainText = new byte[ctLength];

    cipher.init(Cipher.DECRYPT_MODE, key);

    int ptLength = cipher.update(cipherText, 0, ctLength, plainText, 0);

    ptLength += cipher.doFinal(plainText, ptLength);

    System.out.println("plain text : " + Utils.toHex(plainText)
                                                 + " bytes: " + ptLength);
}

I tried to decompose this void main to 3 methods : keycreation() , encryption(), and decryption(), but I failed because the encryption() method returns 2 values, byte[] cipher and int ctLength... So can someone help me to decompose this code in 3 methods?

Upvotes: 2

Views: 6834

Answers (1)

Buddhima Gamlath
Buddhima Gamlath

Reputation: 2328

I would recommend organizing your methods into a class like this. Then for each encryption/ decryption task with the same key, you can create an object of this class and call methods on it.

class AESEncryption {

    byte[] keyBytes;
    Cipher cipher;
    SecretKeySpec key;

    public AESEncryption() {

        try {
            cipher = Cipher.getInstance("AES/ECB/NoPadding", "BC");
        } catch (NoSuchAlgorithmException | NoSuchProviderException | NoSuchPaddingException e) {
            System.out.println(e.getMessage());
        }
    }

    public void createKey(byte[] keyBytes) {
        this.keyBytes = keyBytes;
        key = new SecretKeySpec(keyBytes, "AES");
    }

    public byte[] encrypt(byte[] plainText) {
        try {
            cipher.init(Cipher.ENCRYPT_MODE, key);
            return cipher.doFinal(plainText);
        } catch (InvalidKeyException | IllegalBlockSizeException | BadPaddingException e) {
            System.out.println(e.getMessage());
            return null;
        }
    }
}

You can create an object and call methods like this.

    AESEncryption aes = new AESEncryption();

    // call this to create the key
    aes.createKey(keyBytes);

    // call this on encrypt button click
    byte[] encrypted = aes.encrypt(input);

    // call this on decrypt button click
    byte[] decrypted = aes.decrypt(encrypted);

Upvotes: 4

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