[FRIAM] codes

[Jon Zingale]

I meant to post this a bit ago when we were posting on ciphers,
cryptography, and codes:

The algorithm was run on the prison text. A portion of the final result is
shown in Figure 4. It gives a useful decoding that seemed to work on
additional texts...I like this example because a) it is real, b) there is
no question the algorithm found the correct answer, and c) the procedure
works despite the implausible underlying assumptions. In fact, the message
is in a mix of English, Spanish and prison jargon. The plausibility measure
is based on first-order transitions only. A preliminary attempt with
single-letter frequencies failed. To be honest, several practical details
have been omitted: we allowed an unspecified “?” symbol in the deviation
(with transitions to and from “?” being initially uniform). The display in
Figure 4 was ‘cleaned up’ by a bit of human tinkering. I must also add that
the algorithm described has a perfectly natural derivation as Bayesian
statistics.


https://math.uchicago.edu/~shmuel/Network-course-readings/MCMCRev.pdf
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