Arken gives each AI agent its own signed did:key identity for MCP servers and APIs

Shown on HN Nov 2, an unsigned request gets a 401 with a one-time 60-second nonce, the agent signs it with its secp256k1 key and retries, and the server logs exactly which agent called through Express or FastAPI middleware, with a fetch wrapper that handles the retry on the client side. The author calls it early-stage and not production-ready: nonces live in memory, so they don't survive restarts or span instances, and a lost key can't be recovered (write-up).