<?php

  /* 
     Copyright: hkmaly@matfyz.cz
     Licence: GPL or ask me
     No warranty
     
     Version 0.2, backward-compatible, safer for files > 4KB

     arch-tag: symetric cryptography using md5

     For peoples who find this using google:
        homepage of this "project" is on http://www.karlin.mff.cuni.cz/~hkmaly/php/
        (including documentation)
   */

  function bytexor($a,$b,$l)
  {
    $c="";
    for($i=0;$i<$l;$i++) {
      $c.=$a{$i}^$b{$i};
    }
    return($c);
  }

  function binmd5($val)
  {
    return(pack("H*",md5($val)));
  }

  function decrypt_md5($msg,$heslo,$time)
  {
    $key=$heslo.$time;$sifra="";
    $key1=binmd5($key);
    while($msg) {
      $m=substr($msg,0,16);
      $msg=substr($msg,16);
      echo ".";
      $sifra.=$m=bytexor($m,$key1,16);
      $key1=binmd5($key.$key1.$m);
    }
    echo "\n";
    return($sifra);
  }

  function crypt_md5($msg,$heslo,$time)
  {
    $key=$heslo.$time;$sifra="";
    $key1=binmd5($key);
    while($msg) {
      $m=substr($msg,0,16);
      $msg=substr($msg,16);
      echo ".";
      $sifra.=bytexor($m,$key1,16);
      $key1=binmd5($key.$key1.$m);
    }
    echo "\n";
    return($sifra);
  }

  if(!($key=$_SERVER['argv'][2])) exit("Usage: ".$_SERVER['argv'][0]." mode password file ...\n\tAvailable modes: c - crypt, d - decrypt\n");
  $mode=$_SERVER['argv'][1];
  for($i=3;$i<$_SERVER['argc'];$i++) {
    $name=$_SERVER['argv'][$i];
    $fdi=fopen($name,"r");
    if($name=="php://stdin") $name="stdin";
    if($mode=='c') {
      $fdo=fopen($name.".md5crypted","w");
      $time=time();
      $ver=2;
      fwrite($fdo,$time."-".$ver."\n");
      $fce="crypt_md5";
    } else if($mode=='d') {
      $fdo=fopen($name.".plain","w");
      $time=trim(fgets($fdi,100));
      if($ver=strrchr($time,"-")) {
        $ver=0-$ver;
	$time=explode("-",$time);
	$time=$time['0'];
      }
      $fce="decrypt_md5";
    } else exit("Usage: ".$_SERVER['argv'][0]." mode password file ...\n\tAvailable modes: c - crypt, d - decrypt\n");
    while(!feof($fdi)) {
      $buf=fread($fdi,4096);
      fwrite($fdo,$fce($buf,$key,$time));
      if($ver) $time++;
    }
    fclose($fdi);
    fclose($fdo);
  }

 ?>