atlas-pca

Reference verifier for Proof-Carrying Authority (PCA), an execution-authentication framework for autonomous agents. With every action the agent presents a self-contained proof-carrying action (PCActn); the resource server verifies the proof offline instead of trusting a bearer token.

Status: 0.2.0, unaudited. Not independently security-reviewed; evaluate before relying on it for production authorization decisions.

Install

pip install atlas-pca

The verifier has no required dependencies. Optional extras: atlas-pca[fast] (native Ed25519 via cryptography), atlas-pca[pq] (ML-DSA-65 post-quantum signatures via dilithium-py), atlas-pca[fastapi], atlas-pca[django].

Use

from atlas_pca import verify_pcactn_core

verdict = verify_pcactn_core(pcactn, grant, audience="https://api.example.com")
if not verdict.allow:
    raise PermissionError(f"authF failed: {verdict.reason}")

Checks

Verification is stateless, fail-closed and runs in a fixed, normative order: wire, version, audience, validity, chain, grant_ref_bound, plan_inclusion, leaf_signature, counter.

grant_ref_bound (new in 0.2.0) requires the signed grant_ref to equal the id of the root capability (cap_chain[0]), so replay state cannot be keyed on an attacker-chosen value.

The package passes the shared 172-vector PCA conformance corpus, which the TypeScript, Rust, Go and other verifiers also pass.

Links

• Source: https://github.com/Atlas-Authorization/pca-python
• Specification and docs: https://github.com/Atlas-Authorization/pca

License: MIT