> In contrast, for a well-designed hash function there should not be any way to save work when computing... This property, that making a small change at the fr

> In contrast, for a well-designed hash function there should not be any way to save work when computing... This property, that making a small change at the front of the message requires repeating almost all of the work to re-hash the whole message, doesn't apply to K12 or BLAKE3. Their tree structures make it possible to reuse most of the work you did the first time. (This is essentially the same thing as being able to hash different parts of the message in parallel, which is the design goal of both algorithms.) With BLAKE3, if you wanted to force someone to repeat all the work, the cleanest way to do it would be to change the key.