envoys

Cryptographic identity for AI agents. Ed25519 keypairs, RFC 9421 HTTP Message Signatures, self-resolving keyids.

Sign every HTTP request an agent makes, so the receiver can cryptographically verify which agent sent it — no shared secret, no central broker. Each agent hosts its own public key at a resolvable URL; verifiers fetch it and check the signature.

Python SDK, requires Python 3.10+. Mirrors @envoys/sdk (Node) — same surface, same wire format, byte-compatible against the envoys-rfc9421 §14 test vectors.

Install

pip install envoys

Quick start

Register an agent

import asyncio
from envoys import Envoys, RegisterOptions

async def main():
    client, result = await Envoys.register(RegisterOptions(
        account_key = "ak_...",        # from envoys.me dashboard
        name        = "scout",
    ))
    print(result.address)       # scout@your-handle.envoys.me
    print(result.private_key)   # PEM PKCS8 — store securely, shown once

asyncio.run(main())

Sign an outgoing HTTP request

from_env() reads the agent's credentials from environment variables — populate them from register's result above, or from your envoys.me dashboard.

from envoys import Envoys
import httpx

envoys = Envoys.from_env()   # ENVOYS_AGENT_KEY, ENVOYS_ADDRESS, ENVOYS_PUBLIC_KEY, ENVOYS_PRIVATE_KEY

body    = {"task": "summarize", "url": "https://example.com/doc"}
headers = envoys.sign_request("POST", "/api/task", body)

with httpx.Client() as http:
    r = http.post("https://other-agent.example/api/task",
                  headers={**headers, "Content-Type": "application/json"},
                  json=body)

Verify an incoming request

import asyncio
from envoys import Envoys, VerifyRequestOptions

async def verify(method, path, headers, body):
    result = await Envoys.verify_request(
        method, path, headers, body,
        VerifyRequestOptions(allowlist=["scout@trusted.envoys.me"]),
    )
    if not result.verified:
        return None, result.error
    return result.address, None

The verifier enforces component coverage per spec §5.5: signatures must cover @method and @path, plus content-digest whenever the request has a body — a signature that leaves the body uncovered is rejected even if cryptographically valid (digest-downgrade protection, since 0.2.0).

Optional: bind the signature to the target host (@authority)

headers = envoys.sign_request("POST", "/rpc", body, authority="receiver.example.com")

Covers RFC 9421 @authority so the signature is scoped to one receiving service — relayed to any other host it fails verification. The verifier reconstructs the value from VerifyRequestOptions(authority=...) (set this behind a proxy that rewrites Host) or the request's Host header. Opt-in: verifiers older than 0.2.0 reject signatures covering components they don't reconstruct. Spec v1.6.0 §4.2.

keyid resolution is SSRF-guarded (since 0.3.0)

The keyid is sender-controlled, so resolving it is an untrusted outbound request. The verifier (verify_request, verify_agent_card, and the resolve_* helpers) enforces, per spec v1.6.3 §5.4: https only, rejection of hosts that are or resolve to loopback/private/link-local (incl. the 169.254.169.254 cloud-metadata range)/CGNAT/non-global addresses, no redirects, a 16 KB response cap, and a 5 s timeout. Override via ResolverGuardOptions:

from envoys import ResolverGuardOptions, VerifyRequestOptions

await Envoys.verify_request(method, path, headers, body, VerifyRequestOptions(
    resolver=ResolverGuardOptions(timeout_s=3.0, max_response_bytes=8192),
))
# Local testing only — re-enables private hosts / http:
await Envoys.resolve_key_from_keyid(
    url, ResolverGuardOptions(allow_private_hosts=True, allow_insecure_http=True),
)

DNS rebinding is closed too: resolution is pinned to the validated public address at connect time (a custom httpx transport resolves once, rejects any non-public address, and connects to that IP while preserving the original Host header and TLS SNI), so the address connected to is the address validated. For hard isolation, also constrain egress at the network layer.

Surface

Mirrors @envoys/sdk one-to-one with Python-idiomatic naming. Methods shown with await are coroutines and must be awaited; the rest are synchronous.

Spec & conformance

The wire format is published at https://envoys.me/specs/signature/v1. Every operation in this SDK byte-matches the §14 reference vectors at envoys-rfc9421, and cross-implementation interop is verified bidirectionally against @envoys/sdk (Node) — Python signs / Node verifies, and Node signs / Python verifies. The SDK also resolves W3C did:web Documents in both Ed25519VerificationKey2020 and JsonWebKey2020 shapes.

License

Apache-2.0