In the current (1.0 and 1.5) versions, the data file is basically a serialized AMF format. This format was created by Adobe (I think) and is used for all kinds of stuff in Flash based applications. In version 2, I am switching to use a local SQLite database. There are lots of benefits for me to doing this but it also opens up the possibilities of other applications being created that can interact with the same data. Obviously users will need to be careful installing other desktop applications that monkey with the Klok data. Changing the data incorrectly could break Klok. It is possible for me to encrypt the local database, but that would eliminate the possibility of other apps using it. So, I am still thinking it all through.