If you saw Imitation Game, which title is suggestive of the Turing Machine's mission, you know lives depend on keeping secrets and/or finding them out, and once mathematics became something "engines" could do on an industrial scale, the art of cryptography really took off.
Above you'll hear me babbling away, fairly coherently, about the difference between private key and public key cryptography, and the difference it made.
Buzz Hill is tracking Bitcoin and the whole idea of cryptographic systems built to enable secure transactions. He just sent me a PDF of Bitcoin: A Peer-to-Peer Electronic Cash System, by Satoshi Nakamoto. I'm looking forward to studying it more.
Cryptography came up recently around Python.org as well, where we went into the topic of tie-breaking algorithms on elections-wg, a new working group. I summarized some of what I took away from that thread on edu-sig, also a Python community listserv.