Show HN: Arken – cryptographic identity for AI agents calling MCP servers/APIs

ArkenForge's arken-core is a Rust library providing ECDSA secp256k1 signature verification, did:key identity parsing per the W3C spec, and 60-second-TTL nonce challenge generation, compiled to a native shared library loaded by higher-level packages via FFI. It exports three C-compatible functions that write JSON output, and implements a flow where an unsigned request receives a 401 with a one-time nonce that the client signs and returns in an Authorization: Signature header. The project is described as not production-ready, with in-memory nonces, no key recovery, and a Rust toolchain required to build.