[Cryptography] RFC7540 (HTTP/2) easter egg: "PRISM"

[Henry Baker]

FYI -- Thank you, Edward!

http://blog.jgc.org/2015/11/the-secret-message-hidden-in-every.html

If you spy on an HTTP/2 connection starting up you'll notice that it sends an almost-but-not-quite valid HTTP request at the very start of the connection.  Like this:

http://3.bp.blogspot.com/-q5wtbZUhRD0/VlxWqJ4iH1I/AAAAAAAAC8Q/XeUgvbxSQzY/s320/Screen%2BShot%2B2015-11-30%2Bat%2B14.00.55.png

Written a little more clearly that's:

    PRI * HTTP2.0

    SM

The HTTP verb is PRI and the body contains just SM.  Put them together and you get... *PRISM.*  This occurs right at the start of the connection to ensure that the server really supports HTTP/2.0.  It is detailed in Section 3.5 of RFC7540 as follows:

https://tools.ietf.org/html/rfc7540#section-3.5