PERPLEX CITY, SEASON ZERO
A bit of context for the "AADAA" string and the firstname.lastname@example.org 'exchange' emails.
Courtesy of Bruce via #syzygy:
"In 'Cryptonomicon' there's a set of punch cards containing some very important information encrypted with a cipher called Arethusa.
An NSA chief spends years banging his head against this cipher - and the encrypted text starts AADAA FGTAA ...
You learn near the end of the book that its not a cipher. The string that begins AADAA is actually a hoax. A convincing string of randomness that someone switched with the real encrypts to protect them.
In fact, the sequence is the output of a function called the Riemann-Zeta function.
So, if it starts with "AADAA..." you've got the wrong cipher text.
All you've got is noise.
In all likelihood it's a quick nod to say that the 'Dinah' emails are OOG."