A credential you hold up to a scanner, not hand to someone

Ana’s laptop is not her only device

She enrolled on a MacBook during a calm week. Six months later she is in a hotel lobby approving an agent from her phone. Nothing about that scenario requires us to copy her keys around like shared files. It requires her devices to prove—through a pairing flow with minimal disclosure and auditable steps—that they belong to the same passport.

That is multi-device sync in human language: your devices coordinate; our infrastructure assists without becoming the key custodian.

The metaphor that matters

Imagine two ways to use a credential.

Handing someone your physical ID means they can read every field the plastic exposes—name, address, height, organ donor status—unless law or etiquette stops them. The verifier gets the bundle.

Holding your ID up to a scanner at a door means the scanner asks a question: is this person allowed into this room right now? The answer can be yes without the scanner learning your home address.

Selective disclosure is that second picture, made cryptographic. SD-JWT gets you claim-level disclosure today. BBS+ gets you unlinkable presentations when two verifiers comparing notes would violate the human’s expectations. The metaphor is not decoration—it tells you what must be true in the math.

Anchoring in the real world

A verifier in Singapore checking a contractor at contract time is not asking “did HUMΛN’s API return 200 last Tuesday?” They are asking for a durable receipt: a DID document (or its hash) anchored at time T on a chain or layer we document honestly—testnet for pipelines, mainnet (or production-equivalent) when third parties need to verify years later without our uptime.

If your identity story stops at “we have a database row,” you have account recovery, not portable verification.

So what?

Builders: treat disclosure as first-class—design for property proofs and presentation unlinkability, not for “we hid some columns in JSON.”

Enterprises: when a vendor says “ZK,” ask which statements are zero-knowledge to whom. Roadmap slides are not verifier paths.

Humans: if you cannot revoke or rotate without a platform employee flipping a switch you cannot audit, you do not hold a passport—you hold their account with your name on it.

Technical companions: ECDH multi-device sync; selective disclosure and L2 anchoring. Cross-cutting: sovereignty spine.