I'll try to get that in with the next release (along with include payments and multiplayer rooms).
It does require some sort of backend though, so with the current set of Construct 2 plugins, that'll probably end up being AJAX for most people. The big thing encryption prevents is the falsified leaderboard scores. However, a simple implementation of a backend isn't really going to do the trick - if you send the score over via AJAX to encrypt it, then send the encrypted object to Clay.io, the user can still fake sending a higher score over via AJAX. The best way to do it is keep track of the score with server-side logic, and verify what the client is sending is legitimate :)
There are some interesting use cases for this. For example, in Word Wars, we generate the 4x4 board on the server, then run through all possible combinations of words - each possible word is hashed, then sent to the client along with a unique salt for each game.
The client then hashes each word that is typed, and checks it against the array of hashes to see if it's a match, then updates the score for the client to see (so they know it was a valid word).
At the end of the game, the list of non-hashed words the user came up with is passed to the server, and the server checks those against the list of all possible words and generates a score from that (the scoring algorithm is the same as the client side, so the scores will be the same).
So basically my point is, it takes a bit of extra work to completely stop faked scores, but it's definitely not impossible with JavaScript :)