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 <
https://blockstream.com/2016/11/02/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.
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Russell O'Connor