Triple DES Encryption of String To 8 byte hex - php

Question

I have to encrypt a string to an 8 byte hex using TDES. Below are the values (modified for reference)
key = 636948778095358323114731
pin=1234
Code for encryption :
function encryptText_3des($plainText, $key) {
$key = hash("md5", $key, TRUE);
for ($x=0;$x<8;$x++) {
$key = $key.substr($key, $x, 1);
}
$padded = pkcs5_pad($plainText,mcrypt_get_block_size(MCRYPT_3DES, MCRYPT_MODE_CBC));
$encrypted = base64_encode(mcrypt_encrypt(MCRYPT_3DES, $key, $padded, MCRYPT_MODE_CBC));
return $encrypted;
}
function pkcs5_pad ($text, $blocksize) {
$pad = $blocksize - (strlen($text) % $blocksize);
return $text . str_repeat(chr($pad), $pad);
}
However when i do this :
//outputs 3des encrypted data
echo encryptText_3des($data, $encryption_key);
I get this error :
Warning: mcrypt_encrypt(): Encryption mode requires an initialization
vector of size 8
How can i get the value ?..(please i also need it as a 8 byte hex..)
Thanks

Answer 1

You miss initialization vector for encryption function:
function encryptText_3des($plainText, $key)
{
$key = hash("md5", $key, TRUE);
for ($x = 0; $x < 8; $x++) {
$key = $key . substr($key, $x, 1);
}
$padded = pkcs5_pad($plainText,mcrypt_get_block_size(MCRYPT_3DES, MCRYPT_MODE_CBC));
// CBC initialization vector
$iv_size = mcrypt_get_iv_size(MCRYPT_3DES, MCRYPT_MODE_CBC);
$iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
$encrypted = base64_encode(mcrypt_encrypt(MCRYPT_3DES, $key, $padded, MCRYPT_MODE_CBC, $iv));
return $encrypted;
}
Also do not forget to save $iv string somewhere (include in encrypted string for example), because IV bytes are required for TDES decryption procedure later.
See also