inlineivcbcexample.java

sip CMSEnvelopedData

package chapter2;

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

/**
 * Symmetric encryption example with padding and CBC using DES
 * with the initialization vector inline.
 */
public class InlineIvCBCExample
{   
    public static void main(
        String[]    args)
        throws Exception
    {
        byte[]          input = new byte[] { 
                0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 
                0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
                0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07 };
        byte[]		    keyBytes = new byte[] { 
                0x01, 0x23, 0x45, 0x67, (byte)0x89, (byte)0xab, (byte)0xcd, (byte)0xef };
        byte[]		    ivBytes = new byte[] { 
                0x07, 0x06, 0x05, 0x04, 0x03, 0x02, 0x01, 0x00 };
        
        SecretKeySpec   key = new SecretKeySpec(keyBytes, "DES");
        IvParameterSpec ivSpec = new IvParameterSpec(new byte[8]);
        Cipher          cipher = Cipher.getInstance("DES/CBC/PKCS7Padding", "BC");
        

        System.out.println("input : " + Utils.toHex(input));
        
        // encryption pass
        
        cipher.init(Cipher.ENCRYPT_MODE, key, ivSpec);
        
        byte[] cipherText = new byte[cipher.getOutputSize(ivBytes.length + input.length)];
        
        int ctLength = cipher.update(ivBytes, 0, ivBytes.length, cipherText, 0);
        
        ctLength += cipher.update(input, 0, input.length, cipherText, ctLength);
        
        ctLength += cipher.doFinal(cipherText, ctLength);
        
        System.out.println("cipher: " + Utils.toHex(cipherText, ctLength) + " bytes: " + ctLength);
        
        // decryption pass
        
        cipher.init(Cipher.DECRYPT_MODE, key, ivSpec);
        
        byte[] buf = new byte[cipher.getOutputSize(ctLength)];
        
        int bufLength = cipher.update(cipherText, 0, ctLength, buf, 0);
        
        bufLength += cipher.doFinal(buf, bufLength);
        
        // remove the iv from the start of the message
        
        byte[] plainText = new byte[bufLength - ivBytes.length];
        
        System.arraycopy(buf, ivBytes.length, plainText, 0, plainText.length);
        
        System.out.println("plain : " + Utils.toHex(plainText, plainText.length) + " bytes: " + plainText.length);
    }
}