<?php

/*

 * Enano - an open-source CMS capable of wiki functions, Drupal-like sidebar blocks, and everything in between

 * Copyright (C) 2006-2009 Dan Fuhry

 * diffiehellman.php - Diffie Hellman key exchange and supporting functions

 *

 * This program is Free Software; you can redistribute and/or modify it under the terms of the GNU General Public License

 * as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied

 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for details.

 */

/**

 * EnanoMath GMP backend

 */

class EnanoMath_GMP

{

	var $api = 'GMP';

	/**

 	* Initializes a number to a GMP integer.

 	* @param string String representation of the number

 	* @param int Base the number is currently in, defaults to 10

 	* @return resource

 	*/

	function init($int, $base = 10)

	{

	}

	/**

 	* Converts a number from a GMP integer to a string

 	* @param resource

 	* @param int Base, default is 10

 	* @return string

 	*/

	function str($int, $base = 10)

	{

		return ( is_string($int) ) ? $int : gmp_strval($int, $base);

	}

	/**

 	* Converts a number between bases.

 	* @param resource BigInt to convert

 	* @param int Base to convert from

 	* @param int Base to convert to

 	*/

	function basecon($int, $from, $to)

	{

		return $this->init(gmp_strval(gmp_init($this->str($int), $from), $to));

	}

	/**

 	* Generates a random integer.

 	* @param int Length

 	* @return resource

 	*/

	function random($len)

	{

		return gmp_random($len / 8);

	}

	/**

 	* Powmod operation (calculates (a ^ b) mod m)

 	* @param resource a

 	* @param resource b

 	* @param resource m

 	* @return resource

 	*/

	function powmod($a, $b, $m)

	{

		$a = $this->init($a);

		$b = $this->init($b);

		$m = $this->init($m);

		return ( function_exists('gmp_powm') ) ? gmp_powm($a, $b, $m) : gmp_mod(gmp_pow($a, $b), $m);

	}

}

/**

 * EnanoMath big_int backend

 */

class EnanoMath_BigInt

{

	var $api = 'big_int';

	/**

 	* Initializes a number to a BigInt integer.

 	* @param string String representation of the number

 	* @param int Base the number is in, defaults to 10

 	* @return resource

 	*/

	function init($int, $base = 10)

	{

		return (is_resource($int)) ? $int : bi_from_str($int, $base);

	}

	/**

 	* Converts a number from a BigInt integer to a string

 	* @param resource

 	* @param int Base, default is 10

 	* @return string

 	*/

	function str($int, $base = 10)

	{

		return ( is_string($int) ) ? $int : bi_to_str($int, $base);

	}

	/**

 	* Generates a random integer

 	* @param int Length (bits)

 	* @return resource

 	*/

	function random($len)

	{

		return bi_rand($len);

	}

	/**

 	* Converts a number between bases.

 	* @param resource BigInt to convert

 	* @param int Base to convert from

 	* @param int Base to convert to

 	*/

	function basecon($int, $from, $to)

	{

		return bi_base_convert($this->str($int, $from), $from, $to);

	}

	/**

 	* Powmod operation (calculates (a ^ b) mod m)

 	* @param resource a

 	* @param resource b

 	* @param resource m

 	* @return resource

 	*/

	function powmod($a, $b, $m)

	{

		$a = $this->init($a);

		$b = $this->init($b);

		$m = $this->init($m);

		return bi_powmod($a, $b, $m);

	}

}

/**

 * EnanoMath BCMath backend

 */

class EnanoMath_BCMath

{

	var $api = 'BCMath';

	/**

 	* Initializes a number to a BCMath integer.

 	* @param string String representation of the number

 	* @param int Base the number is in, defaults to 10

 	* @return resource

 	*/

	function init($int, $base = 10)

	{

		return $this->basecon($int, $base, 10);

	}

	/**

 	* Converts a number from a BCMath integer to a string

 	* @param resource

 	* @param int Base, default is 10

 	* @return string

 	*/

	function str($res)

	{

		return ( is_string($res) ) ? $res : strval($this->basecon($res, 10, $base));

	}

	/**

 	* Generates a random integer

 	* @param int Length in bits

 	* @return resource

 	*/

	function random($len)

	{

		$len = 4 * $len;

		$chars = '0123456789abcdef';

		$ret = '';

		for ( $i = 0; $i < $len; $i++ )

		{

			$chid = mt_rand ( 0, strlen($chars) - 1 );

			$chr = $chars{$chid};

			$ret .= $chr;

		}

		return $this->basecon($this->init($ret), 16, 10);

	}

	/**

 	* Converts a number between bases.

 	* @param resource BigInt to convert

 	* @param int Base to convert from

 	* @param int Base to convert to

 	*/

	function basecon($int, $from, $to)

	{

		if ( $from != 10 )

			$int = $this->_bcmath_base2dec($int, $from);

		if ( $to != 10 )

			$int = $this->_bcmath_dec2base($int, $to);

		return $int;

	}

	/**

 	* Powmod operation (calculates (a ^ b) mod m)

 	* @param resource a

 	* @param resource b

 	* @param resource m

 	* @return resource

 	*/

	function powmod($a, $b, $m)

	{

		$a = $this->init($a);

		$b = $this->init($b);

		$m = $this->init($m);

		return ( function_exists('bcpowmod') ) ? bcpowmod($a, $b, $m) : bcmod( bcpow($a, $b), $m );

	}

	// from us.php.net/bc:

	// convert a decimal value to any other base value

	function _bcmath_dec2base($dec,$base,$digits=FALSE) {

			if($base<2 or $base>256) die("Invalid Base: ".$base);

			bcscale(0);

			$value="";

			if(!$digits) $digits=$this->_bcmath_digits($base);

			while($dec>$base-1) {

					$rest=bcmod($dec,$base);

					$dec=bcdiv($dec,$base);

					$value=$digits[$rest].$value;

			}

			$value=$digits[intval($dec)].$value;

			return (string) $value;

	}

	// convert another base value to its decimal value

	function _bcmath_base2dec($value,$base,$digits=FALSE) {

			if($base<2 or $base>256) die("Invalid Base: ".$base);

			bcscale(0);

			if($base<37) $value=strtolower($value);

			if(!$digits) $digits=$this->_bcmath_digits($base);

			$size=strlen($value);

			$dec="0";

			for($loop=0;$loop<$size;$loop++) {

					$element=strpos($digits,$value[$loop]);

					$power=bcpow($base,$size-$loop-1);

					$dec=bcadd($dec,bcmul($element,$power));

			}

			return (string) $dec;

	}

	function _bcmath_digits($base) {

			if($base>64) {

					$digits="";

					for($loop=0;$loop<256;$loop++) {

							$digits.=chr($loop);

					}

			} else {

					$digits ="0123456789abcdefghijklmnopqrstuvwxyz";

					$digits.="ABCDEFGHIJKLMNOPQRSTUVWXYZ-_";

			}

			$digits=substr($digits,0,$base);

			return (string) $digits;

	}

}

/**

 * Creates a new math object based on what libraries are available.

 * @return object

 */

function enanomath_create()

{

	if ( function_exists('gmp_init') )

		return new EnanoMath_GMP();

	else if ( function_exists('bi_from_str') )

		return new EnanoMath_BigInt();

	else if ( function_exists('bcadd') )

		return new EnanoMath_BCMath();

	else

		throw new Exception('dh_err_not_supported');

}

?>