ASCII stereograms 101

In the 1990s, text email (without pictures) was the main channel for person-to-person communication. Mimicking early text printer graphics, arrays of evenly spaced characters could serve as simple pixels inside an email. Imaginative emailers followed this method to adorn their messages with emojis and ASCII pictures.

Amongst such text-based imagery you can find ASCII stereograms, arrangements of symbols on a page that when viewed in the right way reveal 3d pictures. (See previous post: What ever happened to autostereograms.) The Wikipedia entry for ASCII stereograms links to a short online article by computer scientist Jonathan Bowen that demonstrated the practice.

ASCII stereograms offer a low-tech means of hiding messages. Here’s my attempt to deliver a secret message via a block of text repeated in two columns. What might be taken as careless typing serves to highlight certain words and parts of words by bringing them into relief, as if on a layer above the main text. The secret command here is from Flash Gordon to Earth!

In digital communications, encryption that is useful needs to be fast, foolproof and scalable. The practical use of ASCII stereograms is unclear. But to hide secret messages in plain sight brings cryptography into the realm of the human visual system, and hence the senses. It also brings the challenges of cryptography into alignment with optical illusions which are also more useful in shedding light on questions of perception and reality than they are practical. 😉


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