Is there a way to have the prepopulated data encrypted

is there a way to have the prepopulated data encrypted so that people filling in the forms cannot spoof data?

Unfortunately, we do not have a mechanism to protect prepopulated data.

Could you please provide us with more details on your use case? What data is supposed to be pre-populated?

when you prepopulate the fields it is "clear text"

e.g. if I want to send someone a form prepopulated with their details I could send them the following -

https://cdn.jotfor.ms/81117533752858?employeeid=1234&firstName=Bob&lastName=Smith

However, if they wanted to, they could modify the link and impersonate someone e.g. -

https://cdn.jotfor.ms/81117533752858?employeeid=9876&firstName=The&lastName=Boss

Is there a way to encrypt the prepopulated fields to prevent this?

Unfortunately, that is not possible. 

If each of your users has its own unique ID, instead of pre-populating the fields using URL parameters, you can use Spreadsheet to Form widget.

How to Use the Spreadsheet to Form Widget

Or you can use conditional logic to populate form fields based on Unique ID. 

How to Insert Text or Calculation into a Field Using Conditional Logic