Recently I blogged about steganography and my (very) simple experiment to see how it works. If that piqued your interest, you may be interested in just how useful steganography can be: Anticensorship in the Internet's Infrastructure.
Telex is a way of using public-key steganography to circumvent censorship:
"The client secretly marks the connection as a Telex request by inserting a cryptographic tag into the headers. We construct this tag using a mechanism called public-key steganography. This means anyone can tag a connection using only publicly available information, but only the Telex service (using a private key) can recognize that a connection has been tagged."
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