Hi there, great idea. Sort of like text stenography.

Is the message really hidden in this message? Or are you just doing the lookup your database of hidden messages based on the hash of the public message?

Regarding the website UX - after I pasted the message to your text field I thought the hidden message is the youtube video. But that didn't make sense to me and only later I understood the message is above the video.

If you are interested in more UX feedback, feel free to visit https://usability.testing.exchange which is a free community platform built exactly for this purpose.

Also, looking at the payment options - I'm missing a pay-per-message approach. For your consideration.