Encode your message as a hostname, like “the-answer-is-42.yourdomain.com” Buy or request a SSL certificate for that CN. it’ll be from a notarized source, with

Encode your message as a hostname, like “the-answer-is-42.yourdomain.com” Buy or request a SSL certificate for that CN. it’ll be from a notarized source, with a date on it, proving you knew that info at least as early as that, and recorded in the certificate transparency streams. Also encode today’s lottery numbers to prove you knew the info after that date.