Hi ZmnSCPxj,

Just to clarify, my design does not specify the source of voting power, so it is agnostic to whatever system you want to derive stake or valdiator set membership from.

Your idea of timelocking Bitcoin is interesting, I am eager to find a solution where holding Bitcoin is enough to get voting power. It's possible there may be an issue with the fact that the Bitcoin is not slashable (although their voting power is), meaning a validator who double-signs cannot have their Bitcoin removed from them. However their UTXO can be blacklisted which does make their attack costly since they lose out on the time-value of their stake.

Our current thinking for the source of stake is to pay out stake to Bitcoin merged-miners although I'll definitely do some more thinking about timelocked Bitcoin as stake.

On Fri, Jan 18, 2019, 5:42 PM ZmnSCPxj <ZmnSCPxj@protonmail.com wrote:

Good morning Matt,

It seems to me much more interesting if the stakes used to weigh voting power are UTXOs on the Bitcoin blockchain.
This idea is what I call "mainstake"; rather than a blockchain having its own token that is self-attesting (which is insecure).
It seems to me, naively, that the same script you propose here can be used for mainstake.

For instance, the sidechain network might accept potential stakers on the mainchain, if the staker proves the existence of a mainchain transaction whose output is for example:

<sidechain identifier> OP_DROP
"1 year" OP_CHECKSEQUENCEVERIFY OP_DROP
<pubkey> OP_CHECKSIG

The sidechain network could accept this and use the value of the output as the weight of the vote of that stake.

Regards,
ZmnSCPxj

Sent with ProtonMail Secure Email.

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Saturday, January 19, 2019 6:59 AM, Matt Bell via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> wrote:

> I have been working on a design for Bitcoin sidechains using the Tendermint BFT consensus protocol, which is commonly used to build proof-of-stake networks (Cosmos is the notable one).
>
> The design ends up being very similar to Blockstream's Liquid sidechain, since Tendermint consensus is not far off from Liquid's "strong federation" consensus.
>
> Any feedback about improvements or critical flaws would be greatly appreciated. The design document is here: https://github.com/mappum/bitcoin-peg/blob/master/bitcoinPeg.md (that repo also contains a simplified implementation of this sidechain design).
>
> Thanks for your feedback,
> Matt Bell