Fixed read loop not breaking out for invalid signatures

Reported by Mark Wallace

Signed-off-by: Ozan Turgut <ozanturgut@gmail.com>
Removed concept of protocol signature

After a talk with jsilland, I determined that there is
minimal benefit to having the protocol probabilistically
protect itself at the expense of clients who are using it
correctly. Therefore, a signature is no longer required
when opening a stream.

Signed-off-by: Ozan Turgut <ozanturgut@gmail.com>