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[EDIT] FILE: jCryption.php

<?php
	/**
	* jCryption
	*
	* PHP versions 4 and 5
	*
	* LICENSE: This source file is subject to version 3.0 of the PHP license
	* that is available through the world-wide-web at the following URI:
	* http://www.php.net/license/3_0.txt.  If you did not receive a copy of
	* the PHP License and are unable to obtain it through the web, please
	* send a note to license@php.net so we can mail you a copy immediately.
	*
	* Many of the functions in this class are from the PEAR Crypt_RSA package ...
	* So most of the credits goes to the original creator of this package Alexander Valyalkin
	* you can get the package under http://pear.php.net/package/Crypt_RSA
	*
	* I just changed, added, removed and improved some functions to fit the needs of jCryption
	*
	* @author     Daniel Griesser <daniel.griesser@jcryption.org>
	* @copyright  2010 Daniel Griesser
	* @license    http://www.php.net/license/3_0.txt  PHP License 3.0
	* @version    1.1
	* @link       http://jcryption.org/
	*/
	class jCryption
	{

public $_key_len;
		public $_e;

/**
		* Constructor
		*
		* @access public
		*/
        public function __construct($e = "\x01\x00\x01")
        {
            $this->_e = $e;
        }

/**
		* Generates the Keypair with the given keyLength the encryption key e ist set staticlly
		* set to 65537 for faster encryption.
		*
		* @param int $keyLength
		* @return array
		* @access public
		*/
		public function generateKeypair($keyLength) {
			$this->_key_len = intval($keyLength);
			if ($this->_key_len < 8) {
				$this->_key_len = 8;
			}

// set [e] to 0x10001 (65537)
			$e = $this->bin2int($this->_e);

// generate [p], [q] and [n]
			$p_len = intval(($this->_key_len + 1) / 2);
			$q_len = $this->_key_len - $p_len;
			$p1 = $q1 = 0;
			do {
				// generate prime number [$p] with length [$p_len] with the following condition:
				// GCD($e, $p - 1) = 1

do {
					$p = $this->getPrime($p_len);
					$p1 = $this->dec($p);
					$tmp = $this->GCD($e, $p1);
				} while (!$this->isOne($tmp));
				// generate prime number [$q] with length [$q_len] with the following conditions:
				// GCD($e, $q - 1) = 1
				// $q != $p

do {
					$q = $this->getPrime($q_len);
					//$q = 102238965184417281201422828818276460200050705922822343263269460146519295919831;
					$q1 = $this->dec($q);
					$tmp = $this->GCD($e, $q1);
				} while (!$this->isOne($tmp) && !$this->cmpAbs($q, $p));

// if (p < q), then exchange them
				if ($this->cmpAbs($p, $q) < 0) {
					$tmp = $p;
					$p = $q;
					$q = $tmp;
					$tmp = $p1;
					$p1 = $q1;
					$q1 = $tmp;
				}
				// calculate n = p * q
				$n = $this->mul($p, $q);

} while ($this->bitLen($n) != $this->_key_len);

// calculate d = 1/e mod (p - 1) * (q - 1)
			$pq = $this->mul($p1, $q1);
			$d = $this->invmod($e, $pq);

// store RSA keypair attributes
			$keypair = array('n'=>$n, 'e'=>$e, 'd'=>$d, 'p'=>$p, 'q'=>$q);

return $keypair;
		}

public function useKeys($keys,$keyLength) {
			$this->_key_len = intval($keyLength);
			if ($this->_key_len < 8) {
				$this->_key_len = 8;
			}

// set [e] to 0x10001 (65537)
			$e = $this->bin2int($this->_e);

// generate [p], [q] and [n]
			$p_len = intval(($this->_key_len + 1) / 2);
			$q_len = $this->_key_len - $p_len;
			$p1 = $q1 = 0;
			do {
				do {
					$q = $keys[rand(0,count($keys))];
					$p = $keys[rand(0,count($keys))];
					$p1 = $this->dec($p);
					$q1 = $this->dec($q);
				} while (!$this->cmpAbs($q, $p));

} while ($this->bitLen($n) != $this->_key_len);

// calculate d = 1/e mod (p - 1) * (q - 1)
			$pq = $this->mul($p1, $q1);
			$d = $this->invmod($e, $pq);

// store RSA keypair attributes
			$keypair = array('n'=>$n, 'e'=>$e, 'd'=>$d, 'p'=>$p, 'q'=>$q);

return $keypair;
		}

/**
		* Finds greatest common divider (GCD) of $num1 and $num2
		*
		* @param string $num1
		* @param string $num2
		* @return string
		* @access public
		*/
		public function GCD($num1, $num2) {
			do {
				$tmp = bcmod($num1, $num2);
				$num1 = $num2;
				$num2 = $tmp;
			} while (bccomp($num2, '0'));
			return $num1;
		}

/**
		* Performs Miller-Rabin primality test for number $num
		* with base $base. Returns true, if $num is strong pseudoprime
		* by base $base. Else returns false.
		*
		* @param string $num
		* @param string $base
		* @return bool
		* @access private
		*/
		public function _millerTest($num, $base) {
			if (!bccomp($num, '1')) {
				// 1 is not prime ;)
				return false;
			}
			$tmp = bcsub($num, '1');

$zero_bits = 0;
			while (!bccomp(bcmod($tmp, '2'), '0')) {
				$zero_bits++;
				$tmp = bcdiv($tmp, '2');
			}

$tmp = $this->powmod($base, $tmp, $num);
			if (!bccomp($tmp, '1')) {
				// $num is probably prime
				return true;
			}

while ($zero_bits--) {
				if (!bccomp(bcadd($tmp, '1'), $num)) {
					// $num is probably prime
					return true;
				}
				$tmp = $this->powmod($tmp, '2', $num);
			}
			// $num is composite
			return false;
		}

/**
		* Transforms binary representation of large integer into its native form.
		*
		* Example of transformation:
		*    $str = "\x12\x34\x56\x78\x90";
		*    $num = 0x9078563412;
		*
		* @param string $str
		* @return string
		* @access public
		*/
		public function bin2int($str) {
			$result = '0';
			$n = strlen($str);
			do {
				$result = bcadd(bcmul($result, '256'), ord($str {--$n} ));
			} while ($n > 0);
			return $result;
		}

/**
		* Transforms large integer into binary representation.
		*
		* Example of transformation:
		*    $num = 0x9078563412;
		*    $str = "\x12\x34\x56\x78\x90";
		*
		* @param string $num
		* @return string
		* @access public
		*/
		public function int2bin($num) {
			$result = '';
			do {
				$result .= chr(bcmod($num, '256'));
				$num = bcdiv($num, '256');
			} while (bccomp($num, '0'));
			return $result;
		}

/**
		* Calculates pow($num, $pow) (mod $mod)
		*
		* @param string $num
		* @param string $pow
		* @param string $mod
		* @return string
		* @access public
		*/
		public function powmod($num, $pow, $mod) {
			if (function_exists('bcpowmod')) {
				// bcpowmod is only available under PHP5
				return bcpowmod($num, $pow, $mod);
			}

// emulate bcpowmod
			$result = '1';
			do {
				if (!bccomp(bcmod($pow, '2'), '1')) {
					$result = bcmod(bcmul($result, $num), $mod);
				}
				$num = bcmod(bcpow($num, '2'), $mod);
				$pow = bcdiv($pow, '2');
			} while (bccomp($pow, '0'));
			return $result;
		}

/**
		* Calculates $num1 * $num2
		*
		* @param string $num1
		* @param string $num2
		* @return string
		* @access public
		*/
		public function mul($num1, $num2) {
			return bcmul($num1, $num2);
		}

/**
		* Calculates $num1 % $num2
		*
		* @param string $num1
		* @param string $num2
		* @return string
		* @access public
		*/
		public function mod($num1, $num2) {
			return bcmod($num1, $num2);
		}

/**
		* Compares abs($num1) to abs($num2).
		* Returns:
		*   -1, if abs($num1) < abs($num2)
		*   0, if abs($num1) == abs($num2)
		*   1, if abs($num1) > abs($num2)
		*
		* @param string $num1
		* @param string $num2
		* @return int
		* @access public
		*/
		public function cmpAbs($num1, $num2) {
			return bccomp($num1, $num2);
		}

/**
		* Tests $num on primality. Returns true, if $num is strong pseudoprime.
		* Else returns false.
		*
		* @param string $num
		* @return bool
		* @access private
		*/
		public function isPrime($num) {
			static $primes = null;
			static $primes_cnt = 0;
			if (is_null($primes)) {
				// generate all primes up to 10000
				$primes = [];
				for ($i = 0; $i < 10000; $i++) {
					$primes[] = $i;
				}
				$primes[0] = $primes[1] = 0;
				for ($i = 2; $i < 100; $i++) {
					while (!$primes[$i]) {
						$i++;
					}
					$j = $i;
					for ($j += $i; $j < 10000; $j += $i) {
						$primes[$j] = 0;
					}
				}
				$j = 0;
				for ($i = 0; $i < 10000; $i++) {
					if ($primes[$i]) {
						$primes[$j++] = $primes[$i];
					}
				}
				$primes_cnt = $j;
			}

// try to divide number by small primes
			for ($i = 0; $i < $primes_cnt; $i++) {
				if (bccomp($num, $primes[$i]) <= 0) {
					// number is prime
					return true;
				}
				if (!bccomp(bcmod($num, $primes[$i]), '0')) {
					// number divides by $primes[$i]
					return false;
				}
			}

/*
			try Miller-Rabin's probable-primality test for first
			7 primes as bases
			*/
			for ($i = 0; $i < 7; $i++) {
				if (!$this->_millerTest($num, $primes[$i])) {
					// $num is composite
					return false;
				}
			}
			// $num is strong pseudoprime
			return true;
		}

/**
		* Produces a better random number
		* for seeding mt_rand()
		*
		* @access private
		*/
		public function _makeSeed() {
			return hexdec(sha1(sha1(microtime(true)*mt_rand()).md5(microtime(true)*mt_rand())));
		}

/**
		* Generates prime number with length $bits_cnt
		*
		* @param int $bits_cnt
		* @access public
		*/
		public function getPrime($bits_cnt) {
			$bytes_n = intval($bits_cnt / 8);
			$bits_n = $bits_cnt % 8;
			do {
				$str = '';
				mt_srand((int)$this->_makeSeed());
				for ($i = 0; $i < $bytes_n; $i++) {
					$str .= chr((int)sha1(mt_rand() * microtime(true)) & 0xff);
				}
				$n = mt_rand() * microtime(true) & 0xff;

$n |= 0x80;
				$n >>= 8 - $bits_n;
				$str .= chr($n);
				$num = $this->bin2int($str);

// search for the next closest prime number after [$num]
				if (!bccomp(bcmod($num, '2'), '0')) {
					$num = bcadd($num, '1');
				}
				while (!$this->isPrime($num)) {
					$num = bcadd($num, '2');
				}

} while ($this->bitLen($num) != $bits_cnt);
			return $num;
		}

/**
		* Calculates $num - 1
		*
		* @param string $num
		* @return string
		* @access public
		*/
		public function dec($num) {
			return bcsub($num, '1');
		}

/**
		* Returns true, if $num is equal to one. Else returns false
		*
		* @param string $num
		* @return bool
		* @access public
		*/
		public function isOne($num) {
			return !bccomp($num, '1');
		}

/**
		* Finds inverse number $inv for $num by modulus $mod, such as:
		*     $inv * $num = 1 (mod $mod)
		*
		* @param string $num
		* @param string $mod
		* @return string
		* @access public
		*/
		public function invmod($num, $mod) {
			$x = '1';
			$y = '0';
			$num1 = $mod;
			do {
				$tmp = bcmod($num, $num1);
				$q = bcdiv($num, $num1);
				$num = $num1;
				$num1 = $tmp;

$tmp = bcsub($x, bcmul($y, $q));
				$x = $y;
				$y = $tmp;
			} while (bccomp($num1, '0'));
			if (bccomp($x, '0') < 0) {
				$x = bcadd($x, $mod);
			}
			return $x;
		}

/**
		* Returns bit length of number $num
		*
		* @param string $num
		* @return int
		* @access public
		*/
		public function bitLen($num) {
			$tmp = $this->int2bin($num);
			$bit_len = strlen($tmp) * 8;
			$tmp = ord($tmp {strlen($tmp) - 1} );
			if (!$tmp) {
				$bit_len -= 8;
			} else {
				while (!($tmp & 0x80)) {
					$bit_len--;
					$tmp <<= 1;
				}
			}
			return $bit_len;
		}

/**
		* Calculates bitwise or of $num1 and $num2,
		* starting from bit $start_pos for number $num1
		*
		* @param string $num1
		* @param string $num2
		* @param int $start_pos
		* @return string
		* @access public
		*/
		public function bitOr($num1, $num2, $start_pos) {
			$start_byte = intval($start_pos / 8);
			$start_bit = $start_pos % 8;
			$tmp1 = $this->int2bin($num1);

$num2 = bcmul($num2, 1 << $start_bit);
			$tmp2 = $this->int2bin($num2);
			if ($start_byte < strlen($tmp1)) {
				$tmp2 |= substr($tmp1, $start_byte);
				$tmp1 = substr($tmp1, 0, $start_byte).$tmp2;
			} else {
				$tmp1 = str_pad($tmp1, $start_byte, "\0").$tmp2;
			}
			return $this->bin2int($tmp1);
		}

/**
		* Returns part of number $num, starting at bit
		* position $start with length $length
		*
		* @param string $num
		* @param int start
		* @param int length
		* @return string
		* @access public
		*/
		public function subint($num, $start, $length) {
			$start_byte = intval($start / 8);
			$start_bit = $start % 8;
			$byte_length = intval($length / 8);
			$bit_length = $length % 8;
			if ($bit_length) {
				$byte_length++;
			}
			$num = bcdiv($num, 1 << $start_bit);
			$tmp = substr($this->int2bin($num), $start_byte, $byte_length);
			$tmp = str_pad($tmp, $byte_length, "\0");
			$tmp = substr_replace($tmp, $tmp {$byte_length - 1} & chr(0xff >> (8 - $bit_length)), $byte_length - 1, 1);
			return $this->bin2int($tmp);
		}

/**
		* Converts a hex string to bigint string
		*
		* @param string $hex
		* @return string
		* @access public
		*/
		public function hex2bint($hex) {
			$result = '0';
			for ($i = 0; $i < strlen($hex); $i++) {
				$result = bcmul($result, '16');
				if ($hex[$i] >= '0' && $hex[$i] <= '9') {
					$result = bcadd($result, $hex[$i]);
				} else if ($hex[$i] >= 'a' && $hex[$i] <= 'f') {
						$result = bcadd($result, '1'.('0' + (ord($hex[$i]) - ord('a'))));
					} else if ($hex[$i] >= 'A' && $hex[$i] <= 'F') {
							$result = bcadd($result, '1'.('0' + (ord($hex[$i]) - ord('A'))));
						}
			}
			return $result;
		}

/**
		* Converts a hex string to int
		*
		* @param string $hex
		* @return int
		* @access public
		*/
		public function hex2int($hex) {
			$result = 0;
			for ($i = 0; $i < strlen($hex); $i++) {
				$result *= 16;
				if ($hex[$i] >= '0' && $hex[$i] <= '9') {
					$result += ord($hex[$i]) - ord('0');
				} else if ($hex[$i] >= 'a' && $hex[$i] <= 'f') {
						$result += 10 + (ord($hex[$i]) - ord('a'));
					} else if ($hex[$i] >= 'A' && $hex[$i] <= 'F') {
							$result += 10 + (ord($hex[$i]) - ord('A'));
						}
			}
			return $result;
		}

/**
		* Converts a bigint string to the ascii code
		*
		* @param string $bigint
		* @return string
		* @access public
		*/
		public function bint2char($bigint) {
			$message = '';
			while (bccomp($bigint, '0') != 0) {
				$ascii = bcmod($bigint, '256');
				$bigint = bcdiv($bigint, '256', 0);
				$message .= chr($ascii);
			}
			return $message;
		}

/**
		* Removes the redundacy in den encrypted string
		*
		* @param string $string
		* @return mixed
		* @access public
		*/
		public function redundacyCheck($string) {
			$r1 = substr($string, 0, 2);
			$r2 = substr($string, 2);
			$check = $this->hex2int($r1);
			$value = $r2;
			$sum = 0;
			for ($i = 0; $i < strlen($value); $i++) {
				$sum += ord($value[$i]);
			}
			if ($check == ($sum & 0xFF)) {
				return $value;
			} else {
				return NULL;
			}
		}

/**
		* Decrypts a given string with the $dec_key and the $enc_mod
		*
		* @param string $encrypted
		* @param int $dec_key
		* @param int $enc_mod
		* @return string
		* @access public
		*/
		public function decrypt($encrypted, $dec_key, $enc_mod) {
			//replaced split with explode
			$blocks = explode(' ', $encrypted);
			$result = "";
			$max = count($blocks);
			for ($i = 0; $i < $max; $i++) {
				$dec = $this->hex2bint($blocks[$i]);
				$dec = $this->powmod($dec, $dec_key, $enc_mod);
				$ascii = $this->bint2char($dec);
				$result .= $ascii;
			}
			return $this->redundacyCheck($result);
		}

/**
		* Converts a given decimal string to any base between 2 and 36
		*
		* @param string $decimal
		* @param int $base
		* @return string
		*/
		public function dec2string($decimal, $base) {

$string = null;

$base = (int) $base;
			if ($base < 2 | $base > 36 | $base == 10) {
				echo 'BASE must be in the range 2-9 or 11-36';
				exit;
			}

$charset = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';

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

do {
				$remainder = bcmod($decimal, $base);
				$char = substr($charset, $remainder, 1);
				$string = "$char$string";
				$decimal = bcdiv(bcsub($decimal, $remainder), $base);
			} while ($decimal > 0);

return strtolower($string);
		}

public function getE() {
			return $this->_e;
		}

public function generatePrime($length) {
			$this->_key_len = intval($length);
			if ($this->_key_len < 8) {
				$this->_key_len = 8;
			}

$e = $this->bin2int("\x01\x00\x01");

$p_len = intval(($this->_key_len + 1) / 2);
			do {
				$p = $this->getPrime($p_len);
				$p1 = $this->dec($p);
				$tmp = $this->GCD($e, $p1);
			} while (!$this->isOne($tmp));

return $p;
		}

}

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