Warrant canary
Encyclopedia
A warrant canary is a method used by an Internet service provider to inform their customers that the provider has not been served with a secret government subpoena. Such subpoenas, including those covered under the USA Patriot Act
USA PATRIOT Act
The USA PATRIOT Act is an Act of the U.S. Congress that was signed into law by President George W. Bush on October 26, 2001...

, provide criminal penalties for revealing the warrant to a third party, such as the customers. A warrant canary may be posted by the provider to inform customers of dates that they haven't been served a secret subpoena. If the canary has not been updated in the time period specified by the host, customers are to assume that they have been served with such a subpoena. Theoretically, this allows the provider to inform customers of subpoenas without violating any laws. The legality of this has not been tested in any court, however, and the results of the Doe v. Ashcroft lawsuit as well as subsequent changes to the USA PATRIOT Act may obviate the tool for the time being.

A warrant canary may include a digital signature
Digital signature
A digital signature or digital signature scheme is a mathematical scheme for demonstrating the authenticity of a digital message or document. A valid digital signature gives a recipient reason to believe that the message was created by a known sender, and that it was not altered in transit...

 as proof that the message was written by the hosting provider.

The idea of such a negative pronouncement being used to thwart secret warrants was first proposed on the cypherpunks mailing list, and was first implemented by public libraries in response to the USA Patriot Act
USA PATRIOT Act
The USA PATRIOT Act is an Act of the U.S. Congress that was signed into law by President George W. Bush on October 26, 2001...

.

The first commercial use of a warrant canary was by rsync.net. In addition to a digital signature
Digital signature
A digital signature or digital signature scheme is a mathematical scheme for demonstrating the authenticity of a digital message or document. A valid digital signature gives a recipient reason to believe that the message was created by a known sender, and that it was not altered in transit...

, they provide a recent news headline as proof that the warrant canary was recently posted as well as mirroring the posting internationally.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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