diff --git a/lib/openpgp_crypt_symmetric.php b/lib/openpgp_crypt_symmetric.php
index a8b52d6..9833a46 100644
--- a/lib/openpgp_crypt_symmetric.php
+++ b/lib/openpgp_crypt_symmetric.php
@@ -2,6 +2,7 @@
 
 require_once dirname(__FILE__).'/openpgp.php';
 @include_once dirname(__FILE__).'/openpgp_crypt_rsa.php';
+@include_once dirname(__FILE__).'/openpgp_mcrypt_wrapper.php';
 @include_once 'Crypt/AES.php';
 @include_once 'Crypt/TripleDES.php';
 require_once 'Crypt/Random.php'; // part of phpseclib is absolutely required
@@ -148,6 +149,11 @@ class OpenPGP_Crypt_Symmetric {
           $key_block_bytes = 8;
         }
         break;
+      case 3:
+        if(defined('MCRYPT_CAST_128')) {
+          $cipher = new MCryptWrapper(MCRYPT_CAST_128);
+        }
+        break;
       case 7:
         if(class_exists('Crypt_AES')) {
           $cipher = new Crypt_AES(CRYPT_AES_MODE_CFB);
diff --git a/lib/openpgp_mcrypt_wrapper.php b/lib/openpgp_mcrypt_wrapper.php
new file mode 100644
index 0000000..1030700
--- /dev/null
+++ b/lib/openpgp_mcrypt_wrapper.php
@@ -0,0 +1,31 @@
+<?php
+
+if(function_exists('mcrypt_encrypt') && defined('MCRYPT_MODE_CFB')) {
+  class MCryptWrapper {
+    public $cipher, $key, $iv, $key_size, $block_size;
+
+
+    function __construct($cipher) {
+      $this->cipher = $cipher;
+      $this->key_size = mcrypt_module_get_algo_key_size($cipher);
+      $this->block_size = mcrypt_module_get_algo_block_size($cipher);
+      $this->iv = str_repeat("\0", mcrypt_get_iv_size($cipher, 'ncfb'));
+    }
+
+    function setKey($key) {
+      $this->key = $key;
+    }
+
+    function setIV($iv) {
+      $this->iv = $iv;
+    }
+
+    function encrypt($data) {
+      return mcrypt_encrypt($this->cipher, $this->key, $data, 'ncfb', $this->iv);
+    }
+
+    function decrypt($data) {
+      return mcrypt_decrypt($this->cipher, $this->key, $data, 'ncfb', $this->iv);
+    }
+  }
+}
diff --git a/tests/data/symmetric-cast5.gpg b/tests/data/symmetric-cast5.gpg
new file mode 100644
index 0000000..950b791
--- /dev/null
+++ b/tests/data/symmetric-cast5.gpg
@@ -0,0 +1 @@
+�
�9��F�-`�2
�萗w��D���0q�,���z��}Zϲ֣�#־��	aٛ!�!�
\ No newline at end of file
diff --git a/tests/phpseclib_suite.php b/tests/phpseclib_suite.php
index 90e5f7d..0f6ae30 100644
--- a/tests/phpseclib_suite.php
+++ b/tests/phpseclib_suite.php
@@ -84,6 +84,10 @@ class Decryption extends PHPUnit_Framework_TestCase {
     $this->oneSymmetric("hello", "PGP\n", "symmetric-3des.gpg");
   }
 
+  public function testDecryptCAST5() { // Requires mcrypt
+    $this->oneSymmetric("hello", "PGP\n", "symmetric-cast5.gpg");
+  }
+
   public function testDecryptSessionKey() {
     $this->oneSymmetric("hello", "PGP\n", "symmetric-with-session-key.gpg");
   }