Hi,
Wednesday, December 4, 2002, 3:39:10 PM, you wrote:
>>Is there a minimum field size for using mcrypt?
SY> Boy I feel dumb now. :) My answer was in my post. Mcrypt returns a
SY> string that is usually longer than the original string, since the return has
SY> to be a multiple of the block size used. So a 2-character string takes
SY> "blocksize" characters when encrypted. Mcrypt also apparently needs the
SY> extra characters when decrypting.
SY> - Steve Yates
SY> - If at first you don't succeed, lower your standards.
SY> ~ Taglines by Taglinator - www.srtware.com ~
Here is a class I made that will handle any size string and always returns the
same string that was encoded.
class encrypt_class{
var $secret;
function encrypt_class(){
$this->secret = 'this is a very long key, even too long for me';
}
Function encode($id){
$eid = $iv = 0;
$len = strlen($id);
$id = $len.'-'.$id;
$td = mcrypt_module_open(MCRYPT_TripleDES, "", MCRYPT_MODE_ECB, "");
$key = substr($this->secret, 0, mcrypt_enc_get_key_size ($td));
$iv = pack("a".mcrypt_enc_get_iv_size($td),$iv);
mcrypt_generic_init ($td, $key, $iv);
$eid = base64_encode(mcrypt_generic ($td, $id));
mcrypt_generic_deinit($td);
return $eid;
}
Function decode($eid){
$id = $iv = 0;
$td = mcrypt_module_open (MCRYPT_TripleDES, "", MCRYPT_MODE_ECB, "");
$key = substr($this->secret, 0, mcrypt_enc_get_key_size ($td));
$iv = pack("a".mcrypt_enc_get_iv_size($td),$iv);
mcrypt_generic_init ($td, $key, $iv);
$id = mdecrypt_generic ($td, base64_decode($eid));
$len = strtok($id,'-');
$id = substr($id,(strlen($len)+1),$len);
mcrypt_generic_deinit($td);
return $id;
}
}
--
regards,
Tom
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