What are the Possible reason that I am getting this Encryption error for changing in PHP Version?

Question

I have changed my Php version from 7 to 5.
I got this error ==>

mcrypt_encrypt(): Key of size 10 not supported by this algorithm. Only keys of sizes 16, 24 or 32 supported

How to fix this?

Answer 1

In previous versions keys and IVs were padded with '\0' bytes to the next valid size which is not in the later versions. Try the following solutions -

1) Pad the key with "\0" which previous versions were doing for you

$key=$key."\0";

2) in case option 1 does not work try the following functions

function pad_key($key){
    // key is too large
    if(strlen($key) > 32) return false;

    // set sizes
    $sizes = array(16,24,32);

    // loop through sizes and pad key
    foreach($sizes as $s){
        while(strlen($key) < $s) $key = $key."\0";
        if(strlen($key) == $s) break; // finish if the key matches a size
    }

    // return
    return $key;
}