rich1.0Rusty Russell [ARCHIVE] (npub1zw…hkhpx)https://yabu.me/npub1zw7cc8z78v6s3grujfvcv3ckpvg6kr0w7nz9yzvwyglyg0qu5sjsqhkhpxnjumphttps://yabu.me📅 Original date posted:2019-12-02 📝 Original message: Conner Fromknecht <conner at lightning.engineering> writes: > Hi all, > > I recently revisited the eltoo paper and noticed some things related > watchtowers that might affect channel construction. > > Due to NOINPUT, any update transaction _can_ spend from any other, so > in theory the tower only needs the most recent update txn to resolve > any dispute. > > In order to spend, however, the tower must also produce a witness > script which when hashed matches the witness program of the input. To > ensure settlement txns can only spend from exactly one update txn, > each update txn uses unique keys for the settlement clause, meaning > that each state has a _unique_ witness program. I didn't think this was the design. The update transaction can spend any prior, with a fixed script, due to NOINPUT. The settlement transaction does *not* use NOINPUT, and thus can only spend the matching update. Cheers, Rusty.