versyn

Cryptographic proof for AI decisions. Sign every AI decision with Ed25519, verify it offline against a pinned public key. Signing goes through the API; verification is local and free. 100% verification coverage, zero per-check cost.

pip install versyn

The problem: the "trust tax"

Most AI-monitoring tools audit decisions by sending each one to another large model to judge it. That costs money per check, so teams sample — they audit 1% and hope the other 99% was fine. Every un-audited decision is a blind spot a regulator or a lawsuit can walk into.

versyn removes that tax. Each decision is signed via the Versyn API (the event is sent to be signed). Verification, by contrast, is a signature check on your own machine — no server call, no external model, no per-check fee. You can certify 100% of decisions instead of a sample, at effectively zero marginal cost.

Verify a decision offline

from versyn import VersynClient

client = VersynClient(api_key="vk_...")

event = {
    "kind": "agent.decision",
    "payload": {"agent": "underwriter", "action": "decline", "reason": "DTI_too_high"},
}

cert = client.certify(event)
print(client.verify(cert, original_event=event))   # True — local, no network

verify() runs entirely on your machine. It checks that the signature is valid against the pinned public key, and that the certificate hash binds to your event. Change one field and verification refuses it.

Get a free key

import versyn
key = versyn.register("you@company.com")   # 500 certifications/month, free

It survives outages

If the API is unreachable or credits run out, certify() queues the event to a durable local file (atomic writes, thread-safe) instead of losing it. On restart the client reloads the queue; flush_queue() settles it later. No silent gaps.

Verify against the published key yourself

The pinned key ships in the package and is also published at:

https://versyn.dev/.well-known/versyn-pubkey.txt

What this is — and isn't

A versyn certificate proves a specific decision was signed at a specific time and has not been altered since. It is tamper-evident, independently verifiable evidence.

It does not, by itself, prove the decision was correct or lawful, and it is not regulatory compliance certification. It is the verifiable evidence layer your governance and auditors build on top of.

License

MIT