HMAC-SHA1 with an MD5 key

[johnbrizard51]

Hi all,
I would like to recover the key used to sign a message with HMAC-SHA1. I know the key was generated using MD5: 

PHP Code:

$hash = hash_hmac('sha1', $message, hash('md5', $key, false)) // Sample php code that generated the hash 


Lets say the original key is 5 characters long alpha only. That would be 26^5 combinations instead of 2^128.
Is it possible to use hashcat in that way ?

Thanks for your time.