Md5 or sha1 formula

Suggest to add this to the formulas, it should be pretty trivial. This would allow to check for manipulation of externally filled forms (e.g. forms filled with jotform I sent out to customers) by using a hash digest. If I have a secret customer_id field on the form and an expiration date,

e.g. fields customer_id and valid_to (as unix timestamp), I could hash those values with a secret, e.g. md5(“mysecret”, customer_id, valid_to) and pass the hmac digest along as a secret field as well. I could check for expiration and valid customer id.

Anyone trying to mess with the customer id would get caught in the next service where I would process the form data, since the message digest would not match and can not be created properly without the secret.