Question How can the server in a Relay alter the values of other player's cloud save data?

I don't want to exactly use this method but here's my logic:

We have a board game. After each move the Server checks if someone has won the game. Once that returns true, the server sends a cloud code execution request. The cloud code adds currency X to the winning player and deducts some from the losing players.

The problem with this method is, of course, player A can't access/alter the currency amounts of other players.

How should I go about doing this so it is the most cheat-proof?

Bonus question: Any ETA on when we'll be able to access other players' values?

 

Awesome, exactly what I was looking for. Thanks!
A side question, do you also have any docs on encrypting the data you send between the devices and cloud code? Maybe you don't want to be sending the playerID as a simple string but rather in some encrypted format and decrypt it on the Cloud Code end. Concerned about the processing this will take on the latter but still curious.