This document attempts to describe the cryptographic techniques used on MySky to provide the users with secure, encrypted storage on Skynet, which is otherwise a very public system. When users are storing private data on MySky, we wish to provide the following guarantees: The contents of a file cannot be viewed by an attacker The metadata of a file is not uniquely identifying The file itself cannot be linked to the user Multiple files uploaded together cannot be linked to each other Side channel attacks such as timing analysis are inhibited We also wish to provide the following features to the user