and TransportIndex (locally unique).
This is the first step towards forward secrecy. Also removed the
Writable interface and unnecessary user-defined types, moved various
constants to ProtocolConstants and renamed some classes.
Added TestDatabaseModule so tests can specify their own DB
configuration. The modules are currently too tightly coupled - see
whether any dependencies can be removed.
The flag is used to distinguish between the initiator and responder
directions of a stream-mode connection, allowing them to use the same
connection number without risking IV reuse.
The flag is also raised for batch-mode connections, which only have
one direction.
authenticate each frame before parsing its contents. Each connection
starts with a tag, followed by any number of frames, each starting
with the frame number (32 bits) and payload length (16 bits), and
ending with a MAC (256 bits).
Tags have the following format: 32 bits reserved, 16 bits for the
transport ID, 32 bits for the connection number, 32 bits (set to zero
in the tag) for the frame number, and 16 bits (set to zero in the tag)
for the block number. The tag is encrypted with the tag key in
ECB mode.
Frame numbers for each connection must start from zero and must be
contiguous and strictly increasing. Each frame is encrypted with the
frame key in CTR mode, using the plaintext tag with the appropriate
frame number to initialise the counter.
The maximum frame size is 64 KiB, including header and footer. The
maximum amount of data that can be sent over a connection is 2^32
frames - roughly 2^48 bytes, or 8 terabytes, with the maximum frame
size of 64 KiB. If that isn't sufficient we can add another 16 bits to
the frame counter.
