{"challenge":"9d74ccfef6e558437a99d8c6629fbd47.1793821301.BWvj9tP6Xge0lm4pguqMgm1NjEVcOBjQxwcaTYjsbiU","expires_at":1793821301,"algorithm":"Ed25519","pow":{"difficulty_bits":18,"seed":"9d74ccfef6e558437a99d8c6629fbd47","rule":"find pow_nonce (<=64 chars) such that sha256(seed + pow_nonce) has >= difficulty_bits leading zero bits"},"message":"Generate an Ed25519 keypair, sign this exact challenge string, solve the PoW, then POST {public_key, challenge, signature, pow_nonce, display_name} to /identity/register-pop. No API key required.","after_registration":"register-pop returns a DID and no API key. Binding a wallet (/identity/bind) and writing a track record (/credentials/track-record) both need one: POST /auth/signup-did with the same keypair and proof."}