encryption decryption function in php

Question

import gnupg, urllib

retk = urllib.urlopen("http://keyserver.pramberger.at/pks/"
"lookup?op=get&search=userid for the key is required")
pub_key = retk.read()
#print pub_key
gpg = gnupg.GPG(gnupghome="/tmp/foldername", verbose=True)
print "Import the Key :", gpg.import_keys(pub_key).summary()
print "Encrypt the Message:"
msg = "Hellllllllllo"
uid = "userid that has the key on public key server"
enc = gpg.encrypt(msg, uid,always_trust=True)
print "*The enc content***************************== ", enc

this function written in python gives me encrypted message.The encryption is done using the public key which i am getting from public key server(pramberger.at).

Now how can i implement the same functionality (getting the key from any public key server and using that key encrypt the message) in php.

Answer 1

Have a look at mcrypt here: PHP.NET Mcrypt

Tutorials are as follows:

• An Introduction to mcrypt in PHP
• Two-way encryption using PHP and Mcrypt
• PHP Encryption / MCrypt Library

Code example using Mcrypt:

<?php  

/*  
 * phpFreaksCrypto.class.php4 -> phpFreaksCrypto Class (PHP4)  
 */  

/**  
  * @author Dustin Whittle  
  * @version 0.01  
  */  

if (realpath(__FILE__) == realpath($_SERVER['SCRIPT_FILENAME']))  
{  
  // tell people trying to access this file directly goodbye...  
  exit('This file can not be accessed directly...');  
}  

class phpFreaksCrypto  
{  

  var $td;  

  // this gets called when class is instantiated  
  function phpFreaksCrypto($key = 'MyRandomStringThatWillAlwaysBeTheSame', $iv = false, $algorithm = 'tripledes', $mode = 'ecb') 
  {  

    if(extension_loaded('mcrypt') === FALSE)  
    {  
      $prefix = (PHP_SHLIB_SUFFIX == 'dll') ? 'php_' : '';  
      dl($prefix . 'mcrypt.' . PHP_SHLIB_SUFFIX) or die('The Mcrypt module could not be loaded.');  
    }  

    if($mode != 'ecb' && $iv === false)  
    {  
      /*  
        the iv must remain the same from encryption to decryption and is usually  
        passed into the encrypted string in some form, but not always.  
      */  
      die('In order to use encryption modes other then ecb, you must specify a unique and consistent initialization vector.');  
    }  

    // set mcrypt mode and cipher  
    $this->td = mcrypt_module_open($algorithm, '', $mode, '') ;  

    // Unix has better pseudo random number generator then mcrypt, so if it is available lets use it!  
    $random_seed = strstr(PHP_OS, "WIN") ? MCRYPT_RAND : MCRYPT_DEV_RANDOM;  

    // if initialization vector set in constructor use it else, generate from random seed  
    $iv = ($iv === false) ? mcrypt_create_iv(mcrypt_enc_get_iv_size($this->td), $random_seed) : substr($iv, 0, mcrypt_enc_get_iv_size($this->td));  

    // get the expected key size based on mode and cipher  
    $expected_key_size = mcrypt_enc_get_key_size($this->td);  

    // we dont need to know the real key, we just need to be able to confirm a hashed version  
    $key = substr(md5($key), 0, $expected_key_size);  

    // initialize mcrypt library with mode/cipher, encryption key, and random initialization vector  
    mcrypt_generic_init($this->td, $key, $iv);  
  }  

  function encrypt($plain_string)  
  {  
    /*  
      encrypt string using mcrypt and then encode any special characters  
      and then return the encrypted string  
    */  
    return base64_encode(mcrypt_generic($this->td, $plain_string));  
  }  

  function decrypt($encrypted_string)  
  {  
    /*  
      remove any special characters then decrypt string using mcrypt and then trim null padding  
      and then finally return the encrypted string  
    */  
    return trim(mdecrypt_generic($this->td, base64_decode($encrypted_string)));  
  }  

  // since php 4 does not have deconstructors, we will need to manually call this function  
  function __destruct()  
  {  
    // shutdown mcrypt  
    mcrypt_generic_deinit($this->td);  

    // close mcrypt cipher module  
    mcrypt_module_close($this->td);  
  }  

}  
?>

Answer 2

The PHP equivalent should be the GnuPG extension. Take a look at the manual for gnupg_encrypt() and gnupg_decrypt().