Episode 03 showed how value is stored and spent privately. Funds live as sealed notes: the asset, the amount, and the owner stay hidden, while a proof confirms every transaction is valid without revealing any of them.

But a payment is more than its contents. It has a destination. Before value can reach you, the sender needs somewhere to send it, and that destination is the next leak.

Today continues:

How We Built The Best Privacy Protocol On The Market

Signature Series, Episode 04: Under-the-Hood: Stealth Addresses

A reused address is an identity.

On a public chain, your receiving address is a public record of who pays you. If every payment lands at the same address, anyone watching can group them: this counterparty pays this recipient, every week, since this date. Hiding the amounts does not hide the relationship.

For an institution taking payments from many counterparties through the same infrastructure, a fixed receiving address rebuilds the exact counterparty graph the note model was built to hide. 

Most privacy solutions stop at the contents of a transaction and leave the receiving address unchanged, treating it as a fixed fact of the system, like an account number. We choose a different design.

An address that survives from one payment to the next is an identity, and an identity accumulates history. That’s why we decided to make it so a receiving address works exactly once, then never again. 

Every time you copy your address, your wallet generates a brand-new one. Copy it twice, and you get two different addresses. Each address receives a single payment, and nothing on-chain connects it to any of your other addresses. We call each one a stealth address.

There is nothing for you to manage: no list of addresses to track, no rotation to remember, no way to accidentally reuse one. 

How do stealth addresses work?

Two keys, two jobs.

Every Hinkal account runs on two keys.

The spending key moves funds. Nothing moves without it. Your wallet derives it from a signature you produce with the wallet you already use, computed the same way every time, so the same wallet always recovers the same account and the key never leaves your device.

The viewing key detects and reads incoming payments. It cannot move a single token. It is derived from the spending key, so it belongs to the same account, but it can be shared on its own. You can hand it to an auditor and they see what arrived. 

Every address your wallet generates is built from the viewing key. That split, seeing separated from spending, is what later lets privacy and compliance coexist.

Only you can find your own payments.

Because there is no permanent address to look up, your wallet scans instead. As new sealed records appear on-chain, it tests each one with your viewing key and recognizes the payments addressed to you, one check per record. All of that runs on your own device. There is no directory, no lookup service, and no intermediary that first has to be told who you are.

Stealth addresses run on Baby Jubjub because it is efficient inside a zero-knowledge circuit. Its core operation is fast to compute and infeasible to reverse.

Generating a fresh address from your account keys and new randomness takes milliseconds. Your viewing key confirms in one check which payments are yours.

The address is then committed with the same hash function the proof system already uses, so it sits inside the circuit at almost no added cost. The cryptography is standard, audited, and already running at scale. 

One design, three layers.

The stealth address is sealed into the note beside the asset and the amount, so it inherits the same confidentiality the note already carries. The proof from Episode 02 then confirms that every payment belongs to an address its recipient actually controls, without revealing the address, the key, or which note was spent.

Remove any layer and the privacy turns partial. The note alone hides the amount but leaks the recipient. The address alone cannot be verified. The proof alone has nothing to attest to. We built them as one design because only together do they deliver the guarantee.

Received as privately as it is held.

A counterparty can now pay the same person / company every week, and no observer can group those payments, link them to the recipient, or read the relationship from public data. On-chain settlement has always turned a receiving address into a permanent identity. With stealth addresses, every payment lands somewhere new.

Now you might ask: if every destination is used once and every amount is sealed, how does any of it stay auditable and compliant?

The answer is already built into this layer. The viewing key that finds your payments is the same key that can open them, selectively and on your terms, to a regulator who needs to see them. That is where we go next.

Next in the series: Episode 05, Under-the-hood: Compliance and Selective Disclosure.

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