<?php
// +----------------------------------------------------------------------
// | ThinkPHP [ WE CAN DO IT JUST THINK IT ]
// +----------------------------------------------------------------------
// | Copyright (c) 2009 http://thinkphp.cn All rights reserved.
// +----------------------------------------------------------------------
// | Licensed ( http://www.apache.org/licenses/LICENSE-2.0 )
// +----------------------------------------------------------------------
// | Author: liu21st <liu21st@gmail.com>
// +----------------------------------------------------------------------
// $Id$

define("BCCOMP_LARGER", 1);
/**
 +------------------------------------------------------------------------------
 * Rsa 加密实现类
 +------------------------------------------------------------------------------
 * @category   ORG
 * @package  ORG
 * @subpackage  Crypt
 * @author    liu21st <liu21st@gmail.com>
 * @version   $Id$
 +------------------------------------------------------------------------------
 */
class Rsa
{

    /**
     +----------------------------------------------------------
     * 加密字符串
     +----------------------------------------------------------
     * @access static
     +----------------------------------------------------------
     * @param string $str 字符串
     * @param string $key 加密key
     +----------------------------------------------------------
     * @return string
     +----------------------------------------------------------
     * @throws ThinkExecption
     +----------------------------------------------------------
     */
	function encrypt($message, $public_key, $modulus, $keylength)
	{
		$padded = self::add_PKCS1_padding($message, true, $keylength / 8);
		$number = self::binary_to_number($padded);
		$encrypted = self::pow_mod($number, $public_key, $modulus);
		$result = self::number_to_binary($encrypted, $keylength / 8);

		return $result;
	}

    /**
     +----------------------------------------------------------
     * 解密字符串
     +----------------------------------------------------------
     * @access static
     +----------------------------------------------------------
     * @param string $str 字符串
     * @param string $key 加密key
     +----------------------------------------------------------
     * @return string
     +----------------------------------------------------------
     * @throws ThinkExecption
     +----------------------------------------------------------
     */
	function decrypt($message, $private_key, $modulus, $keylength)
	{
		$number = self::binary_to_number($message);
		$decrypted = self::pow_mod($number, $private_key, $modulus);
		$result = self::number_to_binary($decrypted, $keylength / 8);

		return self::remove_PKCS1_padding($result, $keylength / 8);
	}

	function sign($message, $private_key, $modulus, $keylength)
	{
		$padded = self::add_PKCS1_padding($message, false, $keylength / 8);
		$number = self::binary_to_number($padded);
		$signed = self::pow_mod($number, $private_key, $modulus);
		$result = self::number_to_binary($signed, $keylength / 8);

		return $result;
	}

	function verify($message, $public_key, $modulus, $keylength)
	{
		return decrypt($message, $public_key, $modulus, $keylength);
	}

	function pow_mod($p, $q, $r)
	{
		// Extract powers of 2 from $q
		$factors = array();
		$div = $q;
		$power_of_two = 0;
		while(bccomp($div, "0") == BCCOMP_LARGER)
		{
			$rem = bcmod($div, 2);
			$div = bcdiv($div, 2);

			if($rem) array_push($factors, $power_of_two);
			$power_of_two++;
		}

		// Calculate partial results for each factor, using each partial result as a
		// starting point for the next. This depends of the factors of two being
		// generated in increasing order.
		$partial_results = array();
		$part_res = $p;
		$idx = 0;
		foreach($factors as $factor)
		{
			while($idx < $factor)
			{
				$part_res = bcpow($part_res, "2");
				$part_res = bcmod($part_res, $r);

				$idx++;
			}

			array_pus($partial_results, $part_res);
		}

		// Calculate final result
		$result = "1";
		foreach($partial_results as $part_res)
		{
			$result = bcmul($result, $part_res);
			$result = bcmod($result, $r);
		}

		return $result;
	}

	//--
	// Function to add padding to a decrypted string
	// We need to know if this is a private or a public key operation [4]
	//--
	function add_PKCS1_padding($data, $isPublicKey, $blocksize)
	{
		$pad_length = $blocksize - 3 - strlen($data);

		if($isPublicKey)
		{
			$block_type = "\x02";

			$padding = "";
			for($i = 0; $i < $pad_length; $i++)
			{
				$rnd = mt_rand(1, 255);
				$padding .= chr($rnd);
			}
		}
		else
		{
			$block_type = "\x01";
			$padding = str_repeat("\xFF", $pad_length);
		}

		return "\x00" . $block_type . $padding . "\x00" . $data;
	}

	//--
	// Remove padding from a decrypted string
	// See [4] for more details.
	//--
	function remove_PKCS1_padding($data, $blocksize)
	{
		assert(strlen($data) == $blocksize);
		$data = substr($data, 1);

		// We cannot deal with block type 0
	if($data{0} == '\0')
			die("Block type 0 not implemented.");

		// Then the block type must be 1 or 2
	assert(($data{0} == "\x01") || ($data{0} == "\x02"));

		// Remove the padding
	$offset = strpos($data, "\0", 1);
		return substr($data, $offset + 1);
	}

	//--
	// Convert binary data to a decimal number
	//--
	function binary_to_number($data)
	{
		$base = "256";
		$radix = "1";
		$result = "0";

		for($i = strlen($data) - 1; $i >= 0; $i--)
		{
			$digit = ord($data{$i});
			$part_res = bcmul($digit, $radix);
			$result = bcadd($result, $part_res);
			$radix = bcmul($radix, $base);
		}

		return $result;
	}

	//--
	// Convert a number back into binary form
	//--
	function number_to_binary($number, $blocksize)
	{
		$base = "256";
		$result = "";

		$div = $number;
		while($div > 0)
		{
			$mod = bcmod($div, $base);
			$div = bcdiv($div, $base);

			$result = chr($mod) . $result;
		}

		return str_pad($result, $blocksize, "\x00", STR_PAD_LEFT);
	}

}
?>