ciphermacexample.java

来自「Examples using Message Authentication Co」· Java 代码 · 共 61 行

package chapter3;

import java.security.Key;
import java.security.MessageDigest;
import java.security.SecureRandom;

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

/**
 * Message without tampering with MAC (DES), encryption AES in CTR mode
 */
public class CipherMacExample
{   
    public static void main(
        String[]    args)
        throws Exception
    {
        SecureRandom	random = new SecureRandom();
        IvParameterSpec ivSpec = Utils.createCtrIvForAES(1, random);
        Key             key = Utils.createKeyForAES(256, random);
        Cipher          cipher = Cipher.getInstance("AES/CTR/NoPadding", "BC");
        String          input = "Transfer 0000100 to AC 1234-5678";
        Mac             mac = Mac.getInstance("DES", "BC");
        byte[]          macKeyBytes = new byte[] { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08 };
        Key             macKey = new SecretKeySpec(macKeyBytes, "DES");
        
        System.out.println("input : " + input);
        
        // encryption step
        
        cipher.init(Cipher.ENCRYPT_MODE, key, ivSpec);
        
        byte[] cipherText = new byte[cipher.getOutputSize(input.length() + mac.getMacLength())];

        int ctLength = cipher.update(Utils.toByteArray(input), 0, input.length(), cipherText, 0);
        
        mac.init(macKey);
        mac.update(Utils.toByteArray(input));
        
        ctLength += cipher.doFinal(mac.doFinal(), 0, mac.getMacLength(), cipherText, ctLength);
        
        // decryption step
        
        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 : " + Utils.toString(plainText, messageLength) + " verified: " + MessageDigest.isEqual(mac.doFinal(), messageHash));
    }
}