A canary trap is a method for exposing an information leak, that involves giving different versions of sensitive information to each of a group of suspects and seeing which version gets leaked.

The term was coined by Tom Clancy in his novel Patriot Games. The hero, Jack Ryan, describes the technique he devised for identifying the sources of leaked classified documents: Tom Clancy Thomas Leo Clancy Jr. ... Patriot Games (1987) is a book by Tom Clancy. ... Spoiler warning: Jack Ryan (full name John Patrick Ryan, Lt. ...

Each summary paragraph has six different versions, and the mixture of those paragraphs is unique to each numbered copy of the paper. There are over a thousand possible permutations, but only ninety-six numbered copies of the actual document. The reason the summary paragraphs are so—well, lurid, I guess—is to entice a reporter to quote them verbatim in the public media. If he quotes something from two or three of those paragraphs, we know which copy he saw and, therefore, who leaked it. They've got an even more refined version of the trap working now. You can do it by computer. You use a thesaurus program to shuffle through synonyms, and you can make every copy of the document totally unique.

By making sure that each copy of the document differs slightly in its wording, if any copy is leaked then it is possible to determine who 'sang'.

The technique of embedding significant information in a hidden form in a medium has been used in many ways, which are usually classified according to intent:

• Watermarks are used to show that items are authentic and not forged.
• Steganography is used to hide a secret message in an apparently innocuous message, in order to escape detection
• A canary trap hides information in a document that uniquely identifies it, so that copies of it can be traced.

This Crown & CA (for Crown Agent) watermark was standard for postage stamps of the British colonies from the 1880s to the 1920s. ... Steganography is the art and science of writing hidden messages in such a way that no one apart from the intended recipient knows of the existence of the message; this is in contrast to cryptography, where the existence of the message is clear, but the meaning is obscured. ...

See also

• Watermark
• Steganography
• Honeypot

This Crown & CA (for Crown Agent) watermark was standard for postage stamps of the British colonies from the 1880s to the 1920s. ... Steganography is the art and science of writing hidden messages in such a way that no one apart from the intended recipient knows of the existence of the message; this is in contrast to cryptography, where the existence of the message is clear, but the meaning is obscured. ... In computer terminology, a honeypot is a trap set to detect or deflect attempts at unauthorized use of information systems. ...

External link

• Fingerprinting gives a good overview of different kinds of Canary trap techniques.