"The first commercial use of a warrant canary was by the US cloud storage provider rsync.net, which began publishing its canary in 2006. In addition to a digital signature, it provides a recent news headline as proof that the warrant canary was recently posted as well as mirroring the posting internationally."[1]
https://www.rsync.net/resources/notices/canary.txt
"The first commercial use of a warrant canary was by the US cloud storage provider rsync.net, which began publishing its canary in 2006. In addition to a digital signature, it provides a recent news headline as proof that the warrant canary was recently posted as well as mirroring the posting internationally."[1]
[1] https://en.wikipedia.org/wiki/Warrant_canary