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.