Mycrypt Blowfish Block Chaining Cipher

Blowfish Cipher Tutorials - Herong's Tutorial Examples

∟Mycrypt Blowfish Block Chaining Cipher

This section provides a tutorial example on how to write Blowfish block chaining cipher by calling the PHP Mcrypt function, mcrypt_encrypt() in a given operation mode and IV (Initial Vector0).

If we want to perform Blowfish block chaining cipher in CBC, CFB or OFB operation modes, we need to call the PHP Mcrypt mcrypt_encrypt() function with the IV argument.

Here is my simple Blowfish block chaining cipher in PHP:

<?php
#- Blowfish-Block-Chaining-Cipher.php
#- Copyright (c) 2018 HerongYang.com, All Rights Reserved.

   $key = hex2bin('0000000000000000');
   $cleartext = hex2bin('4EF997456198DD78E1C030E74C14D261');
   $mode = "cbc";
   $iv = hex2bin('0000000000000000');
   $ciphertext = hex2bin('e1c030e74c14d2614ef997456198dd78');

   if (count($argv)>1) $key = hex2bin($argv[1]);
   if (count($argv)>2) $cleartext = hex2bin($argv[2]);
   if (count($argv)>3) $mode = $argv[3];
   if (count($argv)>4) $iv = hex2bin($argv[4]);
   if (count($argv)>5) $ciphertext = hex2bin($argv[5]);

   // mcrypt_ecb() was DEPRECATED in PHP 5.5.0, and REMOVED in PHP 7.0.0 
   // $result = 
   //    mcrypt_ecb(MCRYPT_BLOWFISH, $key, $cleartext, MCRYPT_ENCRYPT); 
   
   // mcrypt_encrypt() has been DEPRECATED as of PHP 7.1.0
   $result = 
      mcrypt_encrypt(MCRYPT_BLOWFISH, $key, $cleartext, $mode, $iv);

   $validation = $result==$ciphertext;
   print("Secret Key: ".bin2hex($key)." + IV: ".bin2hex($iv)."\n");
   print("Plaintext: ".bin2hex($cleartext)."\n");
   print("Oper. Mode: ".$mode."\n");
   print("Ciphertext: ".bin2hex($ciphertext)."\n");
   print("PHP Result: ".bin2hex($result)."\n");
   print("Validation: ".$validation."\n");
?>

Test 1: Run it without argument. The default test will be performed in CBC mode. The result should match the expected ciphertext:

C:\herong>php Blowfish-Block-Chaining-Cipher.php

Secret Key: 0000000000000000 + IV: 0000000000000000
Plaintext: 4ef997456198dd78e1c030e74c14d261
Oper. Mode: cbc
Ciphertext: e1c030e74c14d2614ef997456198dd78
PHP Result: e1c030e74c14d2614ef997456198dd78
Validation: 1

Test 2: Run a CFB 2-block test vector provided earlier in the book.

C:\herong>php Blowfish-Block-Chaining-Cipher.php \
   0000000000000000 E1C030E74C14D2614EF997456198DD78 cfb \
   0000000000000000 af39a7a22d8c0f19ce94e96f7a22ac91
   
Secret Key: 0000000000000000 + IV: 0000000000000000
Plaintext: e1c030e74c14d2614ef997456198dd78
Oper. Mode: cfb
Ciphertext: af39a7a22d8c0f19ce94e96f7a22ac91
PHP Result: af3c08c3657ab473564bf52dc19d78ac
Validation:

Surprisingly, the result of CFB mode does not match the expected ciphertext! I need to do some research in the next tutorial.

Test 3: Run an OFB 2-block test vector provided earlier in the book.

C:\herong>php Blowfish-Block-Chaining-Cipher.php \
   0000000000000000 E1C030E74C14D2614EF997456198DD78 ofb \
   0000000000000000 af39a7a22d8c0f19af39a7a22d8c0f19

Secret Key: 0000000000000000 + IV: 0000000000000000
Plaintext: e1c030e74c14d2614ef997456198dd78
Oper. Mode: ofb
Ciphertext: af39a7a22d8c0f19af39a7a22d8c0f19
PHP Result: af08be64e49a94be35829afefd3d699b
Validation: