Date: 15. Okt 1999
Version: 0.1
Algorithm: Described in "Applied Cryptography" from Bruce Schneider
(p. 353 / "Karn" )
Usage:
$key = "My Secryt Key";
$rand = "A Shared Random String ...";
$abcd = "Pleas Encrypt Me ....";
// These Functions work with mime decoded Data
$cryptomime = new HCEMD5 ($key, $rand);
$encrypt = $cryptomime->hce_block_encode_mime($abcd);
$abcd = $cryptomime->hce_block_decode_mime($encrypt);
// These Functions work with binary Data
$cryptobin = new HCEMD5 ($key, $rand);
$encrypt = $cryptobin->hce_block_encode_mime($abcd);
$abcd = $cryptobin->hce_block_decode_mime($encrypt);
Bugs:
Function binmd5 could be done nicer.
Function array2string could be done nicer.
Description:
The MIME Functions are tested and work eitherways with
the Crypt::HCE_MD5 module (0.45) (whithout teh KEYBUG Flag ..).
Shamelessly stolen from Eric Estabrooks, eric@urbanrage.com
Crypt::HCE_MD5 module
This module implements a chaining block cipher using a one
way hash. This method of encryption is the same that is
used by radius (RFC2138) and is also described in Applied
Cryptography.
Two interfaces are provided in the module. The first is
straight block encryption/decryption the second does
base64 mime encoding/decoding of the encrypted/decrypted
blocks.
The idea is the the two sides have a shared secret that
supplies one of the keys and a randomly generated block of
bytes provides the second key. The random key is passed
in cleartext between the two sides.
An example client and server are packaged as modules with
this module. They are used in the tests. They can also
be found in the examples directory.
The 'KEYBUG' flag is for decrypting data encrypted with an
older version of Crypt::HCE_MD5. There was a bug in the
chaining portion that prevented the full 16 bytes of the
previous block from being using in creating the chaining
hash. Decrypt your old data and re-encrypt it without the
KEYBUG flag.
The release after this one will have the KEYBUG feature
removed, but I'll leave this version on CPAN
Thanks to Jake Angerman for pointing out the weakness.
/****************************************************************************\
/****************************************************************************\
/****************************************************************************\
/****************************************************************************/
class HCEMD5 {
var $hce_md5_sec_key;
var $hce_md5_rand;
// Turn on debugging Here
var $hce_md5_debug = "0";
function HCEMD5($key, $rand, $debug="$this->hce_md5_debug") {
// Initalize The Keys ..
if ($key && $rand) {
$this->hce_md5_sec_key = $key;
$this->hce_md5_rand = $rand;
// $this->hce_md5_debug = $debug;
// if ($this->hce_md5_debug) print " xx $this->hce_md5_debug xx
";
return true;
} else {
return false;
}
}
function array2string ($array, $debug="$this->hce_md5_debug"){
// $var = join ( "", $var) does not seem to work
// under php3 If someone knows better please tell me ..
//
$length = count($array);
if ($length < 1) {
return $array;
}
$length++;
$string = $array[1];
for ( $i=2 ; $i < $length ; $i++) {
$string = $string . $array[$i];
}
return $string;
}
function array2pack ($array, $debug="$this->hce_md5_debug"){
// hexadecimal representaion of a string or array ...
$length = count($array);
if ($length == 1) {
return pack('C*', $array);
}
$length++;
for ( $i=0 ; $i < $length ; $i++) {
$pack[$i] = pack('C*', $array[$i]);
}
return $pack;
}
function _new_key($round, $debug="$this->hce_md5_debug") {
/* Ok Punch the Keys togeter .*/
$digest = $this->binmd5($this->hce_md5_sec_key . $round);
$e_block = unpack('C*', $digest);
return $e_block;
}
function binmd5($string, $debug="$this->hce_md5_debug") {
// We have mhash .....
// return mhash("MHASH_MD5", $string);
// We have md5 ...
if ($debug) {
print "
Tohash $string
BinTohex: ";
print bin2hex($string);
}
// return pack('H*',md5($string));
// seems as thisone is fixed
// Someplace here I get my arays terminated with 0x0
// after th first round any help to eliminate this bug would
// be great
return pack('H*',md5(pack('H*', ereg_replace( "00$", "", bin2hex($string)))));
}
function hce_block_decrypt($data,$debug="$this->hce_md5_debug") {
$data = unpack('C*', $data);
unset($ans);
unset($ans1);
$ans = array();
$ans1 = array();
$eblock = 1;
$e_block = $this->_new_key($this->hce_md5_rand);
$data_size = count($data);
// $data_size++;
for($i=0; $i < $data_size; $i++) {
$mod = $i % 16;
/* print "hr $mod"; */
if(($mod == 0) && ($i > 15)) {
$tmparr = array($data[$i - 15], $data[$i - 14], $data[$i - 13], $data[$i - 12], $data[$i - 11], $data[$i - 10], $data[$i - 9], $data[$i - 8], $data[$i - 7], $data[$i - 6], $data[$i - 5], $data[$i - 4], $data[$i - 3], $data[$i - 2], $data[$i - 1], $data[$i] );
if ($debug) {
print "
New round ... Tmparr: $eblock --\n";
print join(" ", $tmparr);
}
$tmparr = $this->array2pack($tmparr);
$tmparr = $this->array2string($tmparr);
$e_block = $this->_new_key($tmparr);
if ($debug) {
print "
New round ... E-block $eblock --\n";
print join(" ", $e_block);
$eblock++;
}
}
$mod++;
$i++;
$ans[$i] = $e_block[$mod] ^ $data[$i];
$ans1[$i] = pack('C*', $ans[$i ]);
if ($debug) {
print "
Decrypt: round: $i e_block: $e_block[$mod] Data: $data[$i] Ans: $ans[$i] Ansunp: $ans1[$i] ";
}
$i--;
}
return $this->array2string($ans1);
}
function hce_block_encrypt($data,$debug="$this->hce_md5_debug") {
$data = unpack('C*', $data);
unset($ans);
unset($ans1);
$ans = array();
$ans1 = array();
$eblock = 1;
$e_block = $this->_new_key($this->hce_md5_rand);
$data_size = count($data);
// $data_size++;
for($i=0; $i < $data_size; $i++) {
$mod = $i % 16;
/* print "hr $mod"; */
if(($mod == 0) && ($i > 15)) {
$tmparr = array($ans[$i - 15], $ans[$i - 14], $ans[$i - 13], $ans[$i - 12], $ans[$i - 11], $ans[$i - 10], $ans[$i - 9], $ans[$i - 8], $ans[$i - 7], $ans[$i - 6], $ans[$i - 5], $ans[$i - 4], $ans[$i - 3], $ans[$i - 2], $ans[$i - 1], $ans[$i] );
if ($debug) {
print "
New round ... Tmparr: $eblock --\n";
print join(" ", $tmparr);
}
$tmparr = $this->array2pack($tmparr);
$tmparr = $this->array2string($tmparr);
$e_block = $this->_new_key($tmparr);
if($debug) {
print "
New round ... E-block: $eblock --\n";
print join(" ", $e_block);
$eblock++;
}
}
$mod++;
$i++;
$ans[$i] = $e_block[$mod] ^ $data[$i];
$ans1[$i] = pack('C*', $ans[$i]);
if ($debug) {
print "
Encrypt: round: $i e_block: $e_block[$mod] Data: $data[$i] Ans: $ans[$i] Ansunp: $ans1[$i] ";
}
$i--;
$mod--;
}
return $this->array2string($ans1);
}
function hce_block_decode_mime ($data,$debug="$this->hce_md5_debug") {
$data = base64_decode($data);
return $this->hce_block_decrypt($data,$debug);
}
function hce_block_encode_mime ($data,$debug="$this->hce_md5_debug") {
$data = $this->hce_block_encrypt($data,$debug);
return base64_encode($data);
}
}
?>