SkipJack32

skipjack.php

<?php
/**
 * A 32-bit block cipher based on skipjack.
 * In common: F-table, G-permutation, key schedule.
 * Different: 24 round feistel structure.
 * 
 * Ported to PHP from C implementation at:
 * 	http://www.qualcomm.com.au/PublicationsDocs/skip32.c
 * 
 * Might not work as expected on 32-bit processors due to PHP lacking a unsigned 32-bit integer.
 * 
 * @author Panu Rissanen <[email protected]>
 * @author Greg Rose, QUALCOMM Australia
 * @author Hans Duedal <[email protected]>
 * 
 * @license Without copyright, no rights reserved.
 */
class SkipJack32
{
	private static $ftable = array (
		0xa3,0xd7,0x09,0x83,0xf8,0x48,0xf6,0xf4,0xb3,0x21,0x15,0x78,0x99,0xb1,0xaf,0xf9,
		0xe7,0x2d,0x4d,0x8a,0xce,0x4c,0xca,0x2e,0x52,0x95,0xd9,0x1e,0x4e,0x38,0x44,0x28,
		0x0a,0xdf,0x02,0xa0,0x17,0xf1,0x60,0x68,0x12,0xb7,0x7a,0xc3,0xe9,0xfa,0x3d,0x53,
		0x96,0x84,0x6b,0xba,0xf2,0x63,0x9a,0x19,0x7c,0xae,0xe5,0xf5,0xf7,0x16,0x6a,0xa2,
		0x39,0xb6,0x7b,0x0f,0xc1,0x93,0x81,0x1b,0xee,0xb4,0x1a,0xea,0xd0,0x91,0x2f,0xb8,
		0x55,0xb9,0xda,0x85,0x3f,0x41,0xbf,0xe0,0x5a,0x58,0x80,0x5f,0x66,0x0b,0xd8,0x90,
		0x35,0xd5,0xc0,0xa7,0x33,0x06,0x65,0x69,0x45,0x00,0x94,0x56,0x6d,0x98,0x9b,0x76,
		0x97,0xfc,0xb2,0xc2,0xb0,0xfe,0xdb,0x20,0xe1,0xeb,0xd6,0xe4,0xdd,0x47,0x4a,0x1d,
		0x42,0xed,0x9e,0x6e,0x49,0x3c,0xcd,0x43,0x27,0xd2,0x07,0xd4,0xde,0xc7,0x67,0x18,
		0x89,0xcb,0x30,0x1f,0x8d,0xc6,0x8f,0xaa,0xc8,0x74,0xdc,0xc9,0x5d,0x5c,0x31,0xa4,
		0x70,0x88,0x61,0x2c,0x9f,0x0d,0x2b,0x87,0x50,0x82,0x54,0x64,0x26,0x7d,0x03,0x40,
		0x34,0x4b,0x1c,0x73,0xd1,0xc4,0xfd,0x3b,0xcc,0xfb,0x7f,0xab,0xe6,0x3e,0x5b,0xa5,
		0xad,0x04,0x23,0x9c,0x14,0x51,0x22,0xf0,0x29,0x79,0x71,0x7e,0xff,0x8c,0x0e,0xe2,
		0x0c,0xef,0xbc,0x72,0x75,0x6f,0x37,0xa1,0xec,0xd3,0x8e,0x62,0x8b,0x86,0x10,0xe8,
		0x08,0x77,0x11,0xbe,0x92,0x4f,0x24,0xc5,0x32,0x36,0x9d,0xcf,0xf3,0xa6,0xbb,0xac,
		0x5e,0x6c,0xa9,0x13,0x57,0x25,0xb5,0xe3,0xbd,0xa8,0x3a,0x01,0x05,0x59,0x2a,0x46
	);

	private static function g($key, $k, $w) {
		$g1 = ($w>>8)&0xff;
		$g2 = $w&0xff;

		$g3 = self::$ftable[$g2 ^ $key[(4*$k)%10]] ^ $g1;
		$g4 = self::$ftable[$g3 ^ $key[(4*$k+1)%10]] ^ $g2;
		$g5 = self::$ftable[$g4 ^ $key[(4*$k+2)%10]] ^ $g3;
		$g6 = self::$ftable[$g5 ^ $key[(4*$k+3)%10]] ^ $g4;

		return (($g5<<8) + $g6);
	}

	private static function skip32($key, $value, $encrypt=true) {
		// direction
		$k = null;
		$kstep = null;
		if ($encrypt) {
			$kstep = 1;
			$k = 0;
		} else {
			$kstep = -1;
			$k = 23;
		}

		// pack into two 16-bit words
		$wl = (($value >> 16) & 0xFFFF);
		$wr = ($value & 0xFFFF);

		// 24 feistel rounds, doubled up
		for ($i=0;$i<24/2;++$i) {
			$wr = $wr ^ (self::g($key, $k, $wl) ^ $k);
			$k += $kstep;
			$wl = $wl ^ (self::g($key, $k, $wr) ^ $k);
			$k += $kstep;
		}
		$wr = $wr << 16;
		return $wr + $wl;
	}

	/**
	 * Encrypt a 32-bit integer using the skipjack algo.
	 * Returns an integer, if you want the data convert it with pack('N').
	 * Ie: var_dump(bin2hex(pack('N',SkipJack32::encrypt('0123456789', 0xdeadbeef))));
	 * 
	 * @param string $key 10-byte key string
	 * @param integer $value
	 * @return number
	 */
	public static function encrypt($key, $value) {
		return self::skip32(array_slice(unpack("C10",$key),0),$value,true);
	}

	/**
	 * Decrypt a 32-bit integer encrypted with SkipJack32.
	 * Returns an integer, use pack('N') to get the binary data instead.
	 * Ie. var_dump(bin2hex(pack('N',SkipJack32::decrypt('0123456789', 0x8de4f05a))));
	 * 
	 * @param string $key 10-byte key string
	 * @param integer $value
	 * @return number
	 */
	public static function decrypt($key, $value) {
		return self::skip32(array_slice(unpack("C10",$key),0),$value,false);
	}
}