Why are these strange characters appearing in mcrypt?

Question

I encrypt and decrypt successfully, but when I decrypt the value, there appears strange characters at the end of the string, "���". The initial $_POST['value'] do not have any blank space or any strange character.

How can I solve this?

I encrypt with this:

$key = 'my key';
$td = mcrypt_module_open('tripledes', '', 'ecb', '');
$iv = mcrypt_create_iv(mcrypt_enc_get_iv_size($td), MCRYPT_RAND);
mcrypt_generic_init($td, $key, $iv);        
$id = mcrypt_generic($td, $_POST['value']);
mcrypt_generic_deinit($td);
mcrypt_module_close($td);

I decrypt with this:

$key = 'my key';
$td = mcrypt_module_open('tripledes', '', 'ecb', '');
$iv = mcrypt_create_iv (mcrypt_enc_get_iv_size($td), MCRYPT_RAND);
mcrypt_generic_init($td, $key, $iv);
$id = mdecrypt_generic($td, $_COOKIE['value']);
mcrypt_generic_deinit($td);
mcrypt_module_close($td);

Answer 1

It is just padding the result based on the block size used. If you use rtrim(), you will get rid of them.