Your log proves itself

How it works

When a session ends, Moda generates an HMAC-SHA256 signature. The signed fields: session ID, user ID, start timestamp, end timestamp, duration, supervisor, time category, weather, and road type. These get joined with a pipe separator and the output is base64-encoded. Think of it as a tamper-proof seal on every session.

The secret key is unique to each device and stored in the iOS Keychain — the same secure enclave that holds your passwords and Face ID data. No one can extract it. Not even us.

Edit a session? New signature.

You're allowed to edit sessions. Fix a wrong supervisor name, change the weather, adjust the time. Every edit generates a fresh signature based on the updated fields. The integrity chain stays intact.

Comparison uses constant-time evaluation to prevent timing attacks. That's a technical detail most users will never think about, but it means even sophisticated attempts to reverse-engineer the signature by measuring response times won't work.

Cloud verification

When sessions sync to the cloud, the server verifies every signature. A tampered session gets flagged immediately. It won't corrupt your log or anyone else's. The bad data gets caught at the door.

Invisible by design

You'll never see a signature hash or a verification badge. There's no "verified" checkmark cluttering the UI. The system runs in the background, silently. The only time it surfaces is if something's wrong — and for honest users, nothing ever is.

Why this matters

Driving logs exist for safety. A teen who claims 50 hours but only drove 20 isn't ready for the road. Paper logs rely on the honor system. Moda doesn't. Every hour in your log is backed by a cryptographic signature that proves the data wasn't fabricated or modified after the fact.

That's not about catching cheaters. It's about making the log mean something.