Can't use MD5 or mcrypt Please help!

Atiq

I have searched forums for this and didn't find any answer.

I want an encryption algorithm with the following requirements:

1) It can be decrypted and should have the key feature like mcrypt function.

2) I also want that if the string to be encrypted is 9 chars long then encrypted string should also be 9 chars long.

3) String input should result in string output and integer inputs should result in integer outputs.

MD5 and mcrypt both doesn't support length feature.

Following is the link that meet most of my requierments but not very secure.

http://www.hansanderson.com/php/crypto/

Regards,

Atiq

laserlight

As far as I know, there are no cryptographically secure algorithms that meet your criteria.

jpmoriarty

it's your requirements that make it insecure. encrypting to the same length, and alpha to alpha, numeric to numeric, mean that any decent hacker would be able to break it in minutes. it's a bit like asking for a padlock with a 10 digit code to open it - but making the lock out of paper.

laserlight

Actually, it might be possible with a specially designed one time pad cryptosystem, but a one time pad doesnt fit the key criterion.

onion2k

Originally posted by Atiq
Following is the link that meet most of my requierments but not very secure.

http://www.hansanderson.com/php/crypto/

What makes you think thats insecure? Polyalphabetic transposition cyphers (which is what that does) will defeat 95% of people. What are you doing that requires more than that?

Kudose

How about the crypto system I use.

It turns:

account

into

½Ð<žÈ

and has a key like you require.

🙂

Atiq

Originally posted by Kudose
How about the crypto system I use.

It turns:

account

into

½Ð<žÈ

and has a key like you require.

🙂

What is that system please explain. It looks like it has the length feature.
There are 7 chars in account and 7 chars in the encrypted string.
I think this will help me.

Thanks for the help to all of you guys!

slak

Aes_encrypt & Aes_decrypt work well for me in MySQL if that helps you any.

Kudose

functions.inc.php

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

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

you encrypt and decrypt like this

$password = crypt_md5($password, $key);
$password = decrypt_md5($password, $key);

Hope that helps.