packet traffic analysis

[Travis H.]

> I assume that the length is
> explicitly encoded in the legitimate packet.  Then the peer for the
> link ignores everything until the next "escape sequence" introducing a
> legitimate packet.

I should point out that encrypting PRNG output may be pointless, and
perhaps one optimization is to stop encrypting when switching on the
chaff.  The peer can then encrypt the escape sequence as it would
appear in the encrypted stream, and do a simple string match on that. 
In this manner the peer does not have to do any decryption until the
[encrypted] escape sequence re-appears.  Another benefit of this is to
limit the amount of material encrypted under the key to legitimate
traffic and the escape sequences prefixing them.  Some minor details
involving resynchronizing when the PRNG happens to produce the same
output as the expected encrypted escape sequence is left as an
exercise for the reader.
--
http://www.lightconsulting.com/~travis/  -><-
"We already have enough fast, insecure systems." -- Schneier & Ferguson
GPG fingerprint: 50A1 15C5 A9DE 23B9 ED98 C93E 38E9 204A 94C2 641B