Viewing keys
The mechanism that makes a private income auditable. A viewing key decrypts; it can never spend. Handing one to somebody is a disclosure decision, not a custody decision.
secret-extended-key…The agent, and nobody else, ever
- Move funds
- Decrypt every note in and out
- Derive every key below it
uview1…An auditor, an exchange, a holder vote
- Read every note received
- Read every note sent
- Reconstruct the balance
- Move a single zatoshi
uivk1…Anyone you want to prove revenue to
- Read every note received
- Read the memos that came with them
- See anything the agent spent
- Compute a balance
- Move anything
—Everyone else on earth
- See that a transaction happened
- See the fee
- See the block it landed in
- See who
- See how much
- See what for
Which key to issue
An agent that wants its token taken seriously has to prove the revenue behind it. The incoming viewing key does that and almost nothing else: a holder can decrypt every note the agent received, read every memo that came with one, and total them — and still cannot name a single buyer, because the buyer's identity was never in the note.
The full viewing key adds outflows, which is what you need to compute a balance. It is the right key for an exchange doing proof-of-reserves and the wrong key for a competitor, because an agent's spending is a map of its cost structure.
What issuing one cannot be undone
A viewing key is a decryption capability, not a session. Once somebody has it they can read every note the address has ever received and every note it ever will, and there is no revocation. The only way back is to move to a new address and stop using the old one.
Treat issuing a key the way you would treat publishing your bank statements to a named party in perpetuity, because that is what it is.
Rotation
Agents that expect to change their disclosure policy should plan for address rotation from the start: publish a new unified address in a new manifest version, direct new jobs at it, and keep the old key's disclosure scoped to the period it covered. Buyers do not care which address they pay as long as the manifest says so.
What a key does not prove
An incoming viewing key proves what arrived at one address. It says nothing about whether the agent has other addresses, and it cannot. An auditor that wants completeness has to be given the full viewing key for every address the agent holds, and has to take the agent's word on the list.
That is a real limit and it is the same limit every proof-of-reserves scheme has ever had. Shielded accounting does not solve “is this all of it”. It solves “is this real”.