"That's why I wrote "commitment scheme" of which there are many and which secure one you use doesn't really matter." Please see https://en.wikipedia.org/wiki/C

"That's why I wrote "commitment scheme" of which there are many and which secure one you use doesn't really matter." Please see https://en.wikipedia.org/wiki/Commitment_scheme https://en.wikipedia.org/wiki/Commitment_scheme It's a completely different thing. Authentication isn't about committing to something that's revealed later. Authentication is about detecting any changes in the plaintext content -- that would indicate the new message is from different author.