A bit easier is to simply include a news headline in the signed message: http://www.rsync.net/resources/notices/canary.txt http://www.rsync.net/resources/notic

A bit easier is to simply include a news headline in the signed message: http://www.rsync.net/resources/notices/canary.txt http://www.rsync.net/resources/notices/canary.txt It's not as sophisticated as the blockchain, etc., but about as good - if you pick sensitive pieces of financial news it's clear you could not have known about them in advance. Or sports results.