WordPress - cipher user_nicename when using get_author_posts_url

gistfile1.php

<?php
/*
Plugin Name: Cipher Author in get_author_posts_url
Plugin URI: http://yoda.neun12.de/artikel-29/2
Description:  Cipher the author nicename when using get_author_posts_url()
Version: 1.0
Author: Ralf Albert
Author URI: http://neun12.de
*/

/**
 * Three easy steps to use this code in your functions.php (instead as a plugin):
 * 
 * 1. Remove the comment block above
 * 2. Include the code with include_once/require_once 'filename.php' (filename.php is the filename under which you have saved this script)
 *	ALTERNATIVELY
 * 2a. Copy & paste the whole code beneath this comment block to your functions.php
 * 3. Remove the line starting with 'add_action...' at the end of this script
 *    and replace it with something like '$cipher_author = new CipherAuthor;'
 *    
 *    That's it.
 */
 
if( !class_exists( 'CipherAuthor') )
{
	class CipherAuthor
	{
		public function __construct()
		{
			// add filter & hooks
			add_filter( 'author_link', array( &$this, 'author_cipher' ) );
			add_filter( 'query', array( &$this, 'author_decipher' ) );
			
		}
		
		/**
		 * Part 1
		 * Cipher the author nicename with md5
		 */
		public function author_cipher( $link )
		{
			global $wp_rewrite;
		
			preg_match( "/.*\/(.*)?\//", $link, $parts );
			$author_nicename = md5( $parts[1] );
		
			$perma_link = $wp_rewrite->get_author_permastruct();
				if( empty( $perma_link ) )
					return $link;	
			
			$link = str_replace('%author%', $author_nicename, $perma_link);
			$link = home_url( user_trailingslashit( $link ) );
		
			return $link;
		}

		
		/**
		 * Part 2
		 * Decipher the author nicename in any query which contains the string 'user_nicename'
		 */
		
		public function author_decipher( $query )
		{
			global $wpdb;
		
			preg_match( "/user_nicename = '(.*)'/", $query, $md5 );
		
			if( !empty( $md5 ) )
			{
				$user_md5 = $md5[1];
				$users = $wpdb->get_col( "SELECT user_nicename FROM {$wpdb->users}" );
			 
				if( in_array( $user_md5, $users ) )
			 		return $query;
			 		
			 	$user_nicename = '';
		
			 	foreach( $users as $user )
			 	{
			 		if( $user_md5 == md5( $user ) ){
			 			$user_nicename = $user;
			 			break;
			 		}
			 	}
			 	
			 	if( '' != $user_nicename )
			 	{
			 		$query = str_replace($user_md5, $user_nicename, $query);
			 	}
			}
		
			return $query;
		}
				
	} // end class
	
	add_action( 'init', create_function( '', 'return new CipherAuthor;' ) );
	
} // end if class exists