A warrant canary is a statement that a site or company has not received any secret warrant request. According to Wikipedia, the idea was first proposed by Steven Schear in 2002. Then the idea hit its peak around 2013-2014 when big companies like Apple started using them.
How they work?
The idea is that a subpoena or gag order could prevent someone from talking about a warrant. But that it did not stop someone from “not” saying they did not have a warrant. So if a warrant was served the warrant canary statement would go away. Implying that a warrant might have been served to the site or company.
What did they look like?
Well, they could be a lot of things. A simple text statement, a picture, a PDF, almost anything. A site called https://canarywatch.org/ used to try to keep up with them but the site is no longer maintained.
The problems with warrant canaries
Warrant canaries are not a perfect system. For example, can a court order demand that you keep your warrant canary in place? That’s up for debate. Can a government demand that you lie and say things that are not true? I’m not a lawyer so I’ve no idea. But that brings up all kinds of issues including violating religious beliefs.
I do know that in Australia warrant canary’s were outlawed. Making it illegal to disclose if you have or have not been issued a warrant.
So do they still work?
It’s hard to say. Most of the big players that had them no longer do and lots of people say they don’t work anymore.
But some people have come up with clever ways to prevent the government from interfering with them. I wish I could find it now but I’ve not had much luck. But I remember reading about one system that had to be signed with something like GPG by 2 people in different countries. The idea was if a government got to 1 person then the other would be outside that government’s jurisdiction. Then they could refuse to sign it.
I’d say if you really want one then you should talk to a lawyer. It’s a neat idea but is it worth the legal cost? I guess that depends on what you’re trying to protect.