Warrant canary

[3] The idea of using negative pronouncements to thwart the nondisclosure requirements of court orders and served secret warrants was first proposed by Steven Schear on the cypherpunks mailing list,[4] mainly to uncover targeted individuals at ISPs.

[5][6] The term is an allusion to the practice of coal miners bringing canaries into mines to use as an early-warning signal for toxic gases, primarily carbon monoxide and methane.

[11] On November 5, 2013, Apple became the most prominent company to publicly state that it had never received an order for user data under Section 215 of the Patriot Act.

[15] In August 2014, the online cloud service Spider Oak implemented an encrypted warrant canary that publishes an "All Clear!"

[16] In September 2014, U.S. security researcher Moxie Marlinspike wrote that "every lawyer I've spoken to has indicated that having a 'canary' you remove or choose not to update would likely have the same legal consequences as simply posting something that explicitly says you've received something.

[19] Afterwards, computer security and privacy specialist Bruce Schneier wrote in a blog post that "[p]ersonally, I have never believed [warrant canaries] would work.

[21] That said, case law specific to the United States would render the covert continuance of warrant canaries subject to constitutionality challenges.

[29] In February 2024, the Ethereum Foundation removed the warrant canary from their website[30] citing "[a] voluntary enquiry from a state authority that included a requirement for confidentiality" in the commit message.