Mega Code Archive
CBC using DES with an IV based on a nonce
<![CDATA[
import java.security.Security;
import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
/**
* CBC using DES with an IV based on a nonce. In this case a hypothetical
* message number.
*/
public class MainClass {
public static void main(String[] args) throws Exception {
Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());
byte[] input = "www.rntsoft.com".getBytes();
byte[] keyBytes = new byte[] { 0x01, 0x23, 0x45, 0x67, (byte) 0x89, (byte) 0xab, (byte) 0xcd,
(byte) 0xef };
byte[] msgNumber = new byte[] { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
IvParameterSpec zeroIv = new IvParameterSpec(new byte[8]);
SecretKeySpec key = new SecretKeySpec(keyBytes, "DES");
Cipher cipher = Cipher.getInstance("DES/CBC/PKCS7Padding", "BC");
System.out.println("input : " + new String(input));
// encryption pass
cipher.init(Cipher.ENCRYPT_MODE, key, zeroIv);
IvParameterSpec encryptionIv = new IvParameterSpec(cipher.doFinal(msgNumber), 0, 8);
// encrypt message
cipher.init(Cipher.ENCRYPT_MODE, key, encryptionIv);
byte[] cipherText = new byte[cipher.getOutputSize(input.length)];
int ctLength = cipher.update(input, 0, input.length, cipherText, 0);
ctLength += cipher.doFinal(cipherText, ctLength);
System.out.println("cipher: " + new String(cipherText) + " bytes: " + ctLength);
cipher.init(Cipher.ENCRYPT_MODE, key, zeroIv);
IvParameterSpec decryptionIv = new IvParameterSpec(cipher.doFinal(msgNumber), 0, 8);
// decrypt message
cipher.init(Cipher.DECRYPT_MODE, key, decryptionIv);
byte[] plainText = new byte[cipher.getOutputSize(ctLength)];
int ptLength = cipher.update(cipherText, 0, ctLength, plainText, 0);
ptLength += cipher.doFinal(plainText, ptLength);
System.out.println("plain : " + new String(plainText) + " bytes: " + ptLength);
}
}
CBCusingDESwithanIVbasedonanonce.zip( 1,199 k)
]]>