Investigate Liquid BTC as a DID registry

[macterra]

Summary

Explore adding Liquid Network (Blockstream's Bitcoin sidechain) as a DID registry alongside the existing BTC/BTCS/BTCT registries.

Feasibility

Liquid supports OP_RETURN and uses an Elements RPC interface that is a superset of Bitcoin Core's, so the existing satoshi-mediator pattern maps almost directly.

Advantages over mainnet:

• ~1 minute block times (vs ~10 min)
• Very low fees (~0.1 sat/vB)
• Still Bitcoin-anchored (federated 2-way peg)

What would need to change

• RPC endpoint config — point at elementsd instead of bitcoind
• Fee logic — Liquid fees are near-zero, fee estimation/RBF can be simplified
• Asset handling — Liquid uses L-BTC, may need to specify asset ID in transaction construction
• New registry name (e.g. LBTC)
• New compose file (docker-compose.btc-liquid.yml)

Files

• services/mediators/satoshi/src/satoshi-mediator.ts — existing OP_RETURN anchoring logic
• services/mediators/satoshi/src/config.ts — RPC and fee configuration

[macterra]

For future reference, syncing liquid requires 62G of disk