Laravel : "mcrypt_decrypt(): The IV parameter must be as long as the blocksize"

Question

I ran composer update on a Laravel application, and now I am getting this error:

mcrypt_decrypt(): The IV parameter must be as long as the blocksize

What happened?!

Answer 1

I figured this out. All you have to do is clear your cookies, and everything will be A-okay!

Answer 2

You need to change your cipher at app\config\app.php. Having same cipher name was causing that problem for me. I changed the cipher name uniquely & then it worked fine.