[Resolved] [Resolved] Encryption method --- too slow!

silent

I need to write a good encryption method for my project
(symmetrical is fine - as the key would have to be in the script
in some way to decode it anyway)

But it seems to be pretty slow right now, because I have to
do byte-by-byte encoding of the input stream.
(and since it's characters, it's even slower because in order
to perform math operations on them, I need to use ord() and chr())

Does anybody have any suggestions?

drawmack

Look into AES
http://csrc.nist.gov/CryptoToolkit/aes/rijndael/

For speed though public key is uaually faster

laserlight

Yeah, Rijndael should be good.

For speed though public key is uaually faster

I had the impression that the converse was true, which is why say, PGP uses an asymmetric cryptosystem to encrypt the key for a symmetric cryptosystem.

silent

Originally posted by laserlight

I had the impression that the converse was true, which is why say, PGP uses an asymmetric cryptosystem to encrypt the key for a symmetric cryptosystem. [/B]

Yeah, that's how PGP works. It encrypts the symmetric key with the public key and puts it in the ciphertext.
Ok, I'll look into implementing those in PHP.

Thanks!

drawmack

Originally posted by laserlight
Yeah, Rijndael should be good.

I had the impression that the converse was true, which is why say, PGP uses an asymmetric cryptosystem to encrypt the key for a symmetric cryptosystem.

I could be mistaken, but I thought that was a security feature for authentication purposes.

silent

Originally posted by drawmack
I could be mistaken, but I thought that was a security feature for authentication purposes.

I believe that PGP uses the asymmetric encryption on the key only
because using that cipher on long pieces of text could be very
costly (in CPU terms)

BTW:
Here's what I have, and it crashes :

function enc_rijn($input,$key,$mode = 'cfb') {
  $td = mcrypt_module_open('rijndael-128','',$mode,'');
  $iv = mcrypt_create_iv(mcrypt_enc_get_iv_size($td), MCRYPT_RAND);
  mcrypt_generic_init($td,$key,$iv);
  $ciphertext = mcrypt_generic($td,$input);
  mcrypt_generic_deinit($td);
  mcrypt_module_close($td);
  return $ciphertext;
}


function dec_rijn($input,$key,$mode = 'cfb') {
  $td = mcrypt_module_open('rijndael-128','',$mode,'');
  $iv = mcrypt_create_iv(mcrypt_enc_get_iv_size($td), MCRYPT_RAND);
  mcrypt_generic_init($td,$key,$iv);
  $plaintext = mdecrypt_generic($td,$input);
  mcrypt_generic_deinit($td);
  mcrypt_module_close($td);
  return $plaintext;
}

$test = 'This is the message to be encrypted';
$key = 'this is the key';
$ciphertext = enc_rijn($test,$key);
echo dec_rijn($ciphertext,$key);

Any ideas?

silent

I fixed the problem with mcrypt, and thought I would share this
info with other people who have problems with mcrypt on windows.

I was using php 4.3.5 - which apparently has issues with mcrypt.
All I had to do was upgrade to 4.3.7, and everything is fine now.