PHP MCRYPT encrypt/decrypt returns invisible stran

Question

mcrypt_decrypt is giving me additional invisible characters which are NOT VISIBLE by just echoing out on the page. Can ONLY BE SEEN by writing it to the text file. Means, just displaying on the page is OK and hard to be noticed.

Here is the code sample by Googling. Please guide me what is the correct usage is there's something wrong:

function encrypt ($pure_string, $key) {
    $iv_size = mcrypt_get_iv_size(MCRYPT_BLOWFISH, MCRYPT_MODE_ECB);
    $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
    $encrypted_string = mcrypt_encrypt(MCRYPT_BLOWFISH, $encryption_key, $pure_string, MCRYPT_MODE_ECB, $iv);
    return $encrypted_string;
}

function decrypt ($encrypted_string, $key) {
    $iv_size = mcrypt_get_iv_size(MCRYPT_BLOWFISH, MCRYPT_MODE_ECB);
    $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
    $decrypted_string = mcrypt_decrypt(MCRYPT_BLOWFISH, $encryption_key, $encrypted_string, MCRYPT_MODE_ECB, $iv);
    return $decrypted_string;
}

but when i try it:

$encrypted_string = encrypt("This is the original string.", "ABC123");
echo decrypt($encrypted_string, "ABC123");

.. i am getting something like:

This is the original string.�������

This strange characters ������� are actually not visible when you/ i just echo it. Can only be seen by writing into the text file.

• So what am i missing please?
• Is there any perfect way to achieve this encrypt/decrypt?

Thank you.

Answer 1

rtrim() will remove the padding that mcrypt added...

Answer 2

function encrypt ($pure_string, $key) {

=> $key

$encrypted_string = mcrypt_encrypt(MCRYPT_BLOWFISH, $encryption_key, $pure_string, MCRYPT_MODE_ECB, $iv);

=> $encryption_key

not equal

Answer 3

This is padding. ECB mode requires input to be multiple of cipher block size, so additional bytes are added (most likely it is PKCS#5 padding).

To remove PKCS#5 padding you can use following code:

$dec_s = strlen($decrypted);
$padding = ord($decrypted[$dec_s-1]);
$decrypted = substr($decrypted, 0, -$padding); 

Answer 4

You can use trim($string, "\0\4") to cut out these characters.