Ancient chinese messaging/encryption system
March 9, 2005 6:05 PM   Subscribe

Needed: a photo or at least more information about a particular system of coded communication supposedly used in ancient china along the Great Wall. Either my google-fu is failing me or I dreamed this whole thing up.

I recall seeing a documentary many years ago about cryptography/stenography. In it was the description of a coded communication system supposedly used for transmitting messages along the Great Wall of China. The scheme involved distributing secret rods embedded in cork to outposts located along the length of the wall. When a message needed to be sent, signal fires were held aloft to get the attention of the neighboring sentry. Then, upon showing a second signal fire, both the sender and receiver opened up identical jugs of water above empty buckets that contained the rod and cork floater. The water level would rise until the sender of the message removed the signal fire at which point the receiver plugged his water jug, stopping the water flow. The correct message was then at the brim of the jug.

I can't find any online documentation of this and would love a photo or more details. Anyone know?
posted by fatllama to Science & Nature (2 answers total)
Best answer: You may be confusing Great wall signaling with the hydraulic telegraph.
posted by vacapinta at 7:16 PM on March 9, 2005

Response by poster: Indeed I might be. Thanks vacapinta!
posted by fatllama at 8:24 PM on March 9, 2005

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