Messaging service Signal may be unusual in its deployment of credible end-to-end encryption, but it shares a common availability vulnerability with many other internet services – dependence on Amazon Web Services (AWS). Signal, like many other internet services, failed briefly during the sizable AWS outage that occurred on October 19 and 20. The cause, as AWS explained in its paragraph-starved post-mortem last week, was an error in AWS' automated DNS management system. And the loss of availabili...