Cachet — Post-quantum authentication for physical goods

The problem

Today's authenticity is a picture of a lock — not the lock.

A QR can be photographed. A hologram can be copied. A paper certificate can be printed by anyone. As soon as a mark can be reproduced, it stops proving anything — and the counterfeit and grey-resale markets know it. What a buyer actually needs isn't a prettier tag. It's a way to make the seller prove, mathematically, that the item is real and theirs to sell.

How it works

One seal. Three moments in an item's life.

Issue

The maker mints a cryptographic identity.

At manufacture, the item gets a unique seal — a post-quantum commitment to the object and its first owner — printed as an ordinary QR. Anyone can copy the picture. No one can forge the seal.

Transfer

Every sale is signed by the owner, recorded once.

Ownership passes hand to hand, each step signed on the seller's own device. The same item can't be sold to two buyers — the ledger accepts the first and refuses the second, provably.

Verify

The buyer scans — and the maths checks itself.

Their phone re-verifies the seal locally and shows: genuine, who owns it, and its certified history. A clone holds the picture, not the key — so when asked to prove ownership, it can't answer.

Why it's different

Built like a security document — not a database lookup.

Most "authentication" is a scan that phones home to a server you have to trust. This is a signed seal a buyer's own device can check — and a ledger that can't quietly rewrite the truth.

Post-quantum

Secure for the item's whole life

Signatures use CRYSTALS-Dilithium (NIST ML-DSA) — built for the decades a watch or a handbag actually lasts, not just today's threats.

Self-custody

We never hold your keys

Keys are born and kept on the owner's device. The platform stores no private key — nothing to breach, nothing to lose, no custody liability.

On-device

Verified by the buyer, not by us

Authenticity is re-checked in the buyer's browser against the printed seal. The server is trusted for nothing — it can't fake a genuine result.

Single-use

Can't be sold twice

Each item carries pre-committed, one-time transfer slots. A second sale of the same item is refused — and, if attempted offline, becomes self-evident.

Clone-resistant

The seller must prove control

A copied QR can't produce the owner's signature. Before you pay, your app challenges the seller — and a counterfeit simply can't respond.

No chain

No blockchain, no token, no gas

No consensus, no coin, no wallet gymnastics. A signed seal and a Certificate-Transparency-style ledger — the discipline that secures the web, applied to things.

Authenticity you can verify.
Ownership no one can fake.