Technology · Discipline

Applied cryptography

I apply cryptography where it buys attribution and non-repudiation, and I do not invent primitives.

RS256 tokens and JWKSHMAC-signed webhooksX.509 certificate assertions
An agent-to-agent envelope · signed by its sender
The receiver checks before it acts
audience
issuer
payload hash
delegation chain
checked against a cached public key, with no round trip to a central server

Signed agent-to-agent envelopes, certificate-based token minting for Microsoft identities, signed webhooks and signed event feeds. I place each check where it runs on every call, and every construction is standard, RS256, HMAC and X.509 certificate assertions from maintained libraries.

Signed messages between agents

Agent Swarm lets agents delegate to each other, and I wanted every request to carry proof of who sent it. I sign wherever attribution matters, so agent messages, access tokens and event feeds each carry a provable sender. Each agent-to-agent envelope is signed as a JWT with the sending agent's own key, and verification is local, which keeps signature checks off the latency path of stream messaging. The protocol around these envelopes is on the Agent Client Protocol (ACP) page. The router's public certificate and the message bus's internal CA are separate trust anchors, so rotating or losing one leaves the other intact.

public: the router's certificate
internal: the message bus's CA
Secret material sits in types that wipe it from memory when dropped.

Tokens checked offline at the gateway

Auth and access plane issues OAuth 2.0 tokens to commercial AI assistants, and my tool gateway has to accept them on every call without asking the issuer each time. Verifying locally against published keys keeps it cheap enough to run on every message.

Issuers
my OAuth server, RS256, JWKS
Microsoft's platform
At the Rust gateway
checked locally
calls to an issuer
none

For the same server I built a hash-chained audit log, in which each entry commits to the one before it, and privacy-preserving device fingerprints that are HMAC-hashed, with IP addresses anonymised.

Webhooks checked before parsing

FAFOHive receives events from social platforms and must not trust a forged one. The Facebook receiver checks every request before it parses a byte of it.

Inbound event, exactly as received
signature matches
signature mismatch
HMAC over the raw bytes
parsed
rejected, never parsed
Checking before parsing means a parser quirk cannot change what was signed.

In the other direction, the social modules publish a signed event feed, so a consumer can attribute each event to the service that emitted it. The inbound side is on the Webhook ingestion and verification page.

A key the model never holds

Helix acts in Teams meetings as one specific Microsoft 365 digital employee, and the model that decides what to do must never hold that employee's credential. The meeting-action server mints the employee's Graph tokens on the server. The identity work is told in Solving the digital-employee identity.

AI
certificate assertion, Graph token, checked in process; none of it leaves
the model sends an action requestthe meeting-action server, acting as one digital employee

The model asks for an action; the server holds the key.