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.

-- 
Russell O'Connor