LOCK: security considerations?

[antbryan]

1. You need to answer at least the security questions of how a client is
   protected from a malicious server, and how a server is protected from a
   malicious client, as well as how the connection (client and server) is
   protected against a malicious file. Consider what happens if a file contains
   a number of predicted boundary values, and the server or client is not good
   at picking random numbers for those boundaries. Note, for instance, how SMTP
   does this in the DATA command - the DATA ends with a line containing only
   ".". Any line beginning with a "." in the data has to be prefixed by another
   ".". The receiver then simply strips out the first dot on each line. Don't
   give in to the idea that "random numbers can't be guessed", or that
   accidental occurrences or malicious action won't ever successfully reproduce
   the boundary condition. Make it IMPOSSIBLE.