BlockHost

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Supported Chains ​

BlockHost is chain-agnostic. The blockchain engine is a pluggable component — each engine implements the same interface, and the rest of the system doesn't know or care which chain is running.

All four engines below are working end-to-end on their respective testnets. None have been exercised on mainnet yet — the broker doesn't currently listen on any mainnet, and no economic activity has flowed through the contracts in production. Treat the engines as production-grade code, but assume mainnet operation is unverified territory.

Engines ​

EVM (Ethereum, Polygon, Base, Arbitrum, …) ​

  • Engine: blockhost-engine-evm
  • Wallet: MetaMask or any injected Ethereum provider
  • Contracts: Solidity (ERC-721 NFT + subscription manager)
  • Signing: secp256k1 (ECDSA)
  • Tested on: Sepolia testnet

The original engine. EVM-compatible chains share the same contract bytecode — deploy once, works on any EVM chain.

OPNet (Bitcoin L1) ​

  • Engine: blockhost-engine-opnet
  • Wallet: OPWallet browser extension
  • Contracts: AssemblyScript (OPNet smart contracts via Tapscript)
  • Signing: Schnorr / ML-DSA
  • Tested on: OPNet Signet

Smart contracts on Bitcoin L1 without sidechains or bridges. Subscriptions and NFTs live directly on Bitcoin. Uses OPNet's Tapscript-encoded calldata — valid Bitcoin transactions paying valid fees.

Cardano ​

  • Engine: blockhost-engine-cardano
  • Wallet: Nami, Eternl, Lace (CIP-30 compatible)
  • Contracts: Aiken validators
  • Signing: Ed25519
  • Tested on: Preprod

Uses a UTXO-native subscription model inspired by cardano-swaps. Instead of locking funds in a shared contract, each subscriber creates their own UTXO at a validator address. No custody transfer, no UTXO contention. The validator enforces payment collection and cancellation rules through pure math.

NFTs are Cardano native assets — no smart contract needed for the token itself, just a minting policy tied to the subscription validator. The engine ships at 184KB with zero WASM dependencies (built on cmttk and noble-bip32ed25519 for transaction building and key derivation in pure TypeScript).

Ergo ​

  • Engine: blockhost-engine-ergo
  • Wallet: Nautilus (EIP-12 dApp connector)
  • Contracts: ErgoScript validators
  • Signing: Schnorr (ProveDlog sigma protocol)
  • Tested on: Ergo testnet

UTXO-native like Cardano, but on a chain with native Sigma protocols and storage rent. Subscriptions, NFTs, and admin operations all use ErgoScript validators. The engine bundles ergo-relay, a small Rust P2P broadcast binary (developed alongside ergo-node-rust, an independent full Rust Ergo node), so the host can submit transactions without depending on a centralized API. Schnorr signature verification in the libpam Ergo plugin is a from-scratch sigma-protocol implementation in pure TypeScript — no ergo-lib-wasm.

Adding a New Chain ​

Building an engine requires implementing:

  1. Engine manifest (engine.json) — identity, wizard module, finalization steps, constraints
  2. Wizard plugin — Flask blueprint for the installer's blockchain configuration page
  3. Finalization steps — wallet generation, contract deployment, chain config
  4. Monitor — blockchain event watcher that detects new subscriptions
  5. CLI tools — bw (wallet ops), ab (addressbook), is (identity predicates), mint_nft
  6. Signing page — wallet connect + signature capture for SSH authentication
  7. Signup page — subscription purchase flow

See the Building an Engine guide for the full walkthrough.