Good questions, the core doesn't need a blockchain at all. AC2 is just an approval/signing layer (DIDComm + WebAuthn/FIDO2 + WebRTC), so most use cases like API access, git commits, and client comms never touch a chain. Blockchain only enters when what's being signed is a transaction, like an x402 payment.

For that case we use Algorand, but AC2 is chain-agnostic, meaning any chain could plug in. Algorand fit because of instant finality (no forking), low predictable fees for frequent small agent payments, and post-quantum resilient signatures. zCash optimizes for privacy, which isn't really our problem, we care about speed/finality for agent-authorized actions, not hiding the payment.

So the blockchain piece is more of a plugin for one use case than the foundation of the protocol. Hope that answers your questions!