MainClass.java Source code

Introduction

Here is the source code for MainClass.java

Source

import java.security.Key;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.SecureRandom;
import java.security.Security;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.Mac;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

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

        SecureRandom random = new SecureRandom();
        IvParameterSpec ivSpec = createCtrIvForAES();
        Key key = createKeyForAES(256, random);
        Cipher cipher = Cipher.getInstance("AES/CTR/NoPadding", "BC");
        String input = "12345678";
        Mac mac = Mac.getInstance("DES", "BC");
        byte[] macKeyBytes = new byte[] { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08 };
        Key macKey = new SecretKeySpec(macKeyBytes, "DES");

        cipher.init(Cipher.ENCRYPT_MODE, key, ivSpec);

        byte[] cipherText = new byte[cipher.getOutputSize(input.length() + mac.getMacLength())];

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

        mac.init(macKey);
        mac.update(input.getBytes());

        ctLength += cipher.doFinal(mac.doFinal(), 0, mac.getMacLength(), cipherText, ctLength);

        cipher.init(Cipher.DECRYPT_MODE, key, ivSpec);

        byte[] plainText = cipher.doFinal(cipherText, 0, ctLength);
        int messageLength = plainText.length - mac.getMacLength();

        mac.init(macKey);
        mac.update(plainText, 0, messageLength);

        byte[] messageHash = new byte[mac.getMacLength()];
        System.arraycopy(plainText, messageLength, messageHash, 0, messageHash.length);

        System.out.println("plain : " + new String(plainText) + " verified: "
                + MessageDigest.isEqual(mac.doFinal(), messageHash));

    }

    public static SecretKey createKeyForAES(int bitLength, SecureRandom random)
            throws NoSuchAlgorithmException, NoSuchProviderException {
        KeyGenerator generator = KeyGenerator.getInstance("AES", "BC");

        generator.init(128, random);

        return generator.generateKey();
    }

    public static IvParameterSpec createCtrIvForAES() {
        return new IvParameterSpec("1234567812345678".getBytes());
    }

}