Thanks, I am planning to use this in a mobile phone application that will run on both Android and iOS. My idea is to let users access the survey through a webview and I want to the survey to collect a unique identifier for each user that does not contain personal information.
I have just been experimenting with the digest function (https://docs.getodk.org/form-operators-functions/#utility). My idea was to have a deviceid field and then calculate the hash of this. But I am getting an error when I try to use digest:
FormLogicError: Could not evaluate: digest( /model/instance[1]/data/this_deviceid , SHA-256, base64), message: Function "{}digest" does not exist.
