Right. There are minor trade-offs to be made with regards to that design point of OP_CHECKSIGFROMSTACKVERIFY. Fortunately this covenant construction isn't sensitive to that choice and can be made to work with either implementation of OP_CHECKSIGFROMSTACKVERIFY. On Wed, Nov 2, 2016 at 11:35 PM, Johnson Lau wrote: > Interesting. I have implemented OP_CHECKSIGFROMSTACKVERIFY in a different > way from the Elements. Instead of hashing the data on stack, I directly put > the 32 byte hash to the stack. This should be more flexible as not every > system are using double-SHA256 > > https://github.com/jl2012/bitcoin/commits/mast_v3_master > > > On 3 Nov 2016, at 01:30, Russell O'Connor via bitcoin-dev < > bitcoin-dev@lists.linuxfoundation.org> wrote: > > Hi all, > > It is possible to implement covenants using two script extensions: OP_CAT > and OP_CHECKSIGFROMSTACKVERIFY. Both of these op codes are already > available in the Elements Alpha sidechain, so it is possible to construct > covenants in Elements Alpha today. I have detailed how the construction > works in a blog post at 11/02/covenants-in-elements-alpha.html>. As an example, I've constructed > scripts for the Moeser-Eyal-Sirer vault. > > I'm interested in collecting and implementing other useful covenants, so > if people have ideas, please post them. > > If there are any questions, I'd be happy to answer. > > -- > Russell O'Connor > _______________________________________________ > bitcoin-dev mailing list > bitcoin-dev@lists.linuxfoundation.org > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev > > >