What each level actually proves
Four levels, each additive, each stated with what it does not prove. The last column is the one that matters: a defence is only worth the cost it imposes on somebody trying to get round it.
The ladder
| Level | Evidence | It proves | It does not prove | Cost to forge |
|---|---|---|---|---|
| L0 | A claim signed by the subject key. | That this key made this statement, at this time, and cannot deny it later. | Anything at all about the licence. | Nothing. Gas or an upload. |
| L1 | A DNS record on the business domain naming the key, and a claim naming the domain. | That whoever controls that domain controls this key, and the reverse. | That the domain belongs to a licensed professional. | Control of the real domain. |
| L2 | Signed attestations that the claim matched the public register page at a time. | That named parties looked at a public source and recorded what it said. | That the person holding the key is the person on the register. | Appearing on the register, or corrupting a checker. |
| L3 | A file published and signed by the issuing authority. | That the authority asserts this licence and this status at this date. | Tiers A and B still do not bind the licence to a key. Only tier C does. | The authority key. |
Why level 1 does most of the work today
Level 1 is the only layer that is both free and effective against the threat model, because the attack that matters is a lookalike domain. A fraudster can clone a site in minutes and copy a licence number in seconds. What they cannot do is add a DNS record to the domain the client already knows.
It also needs nothing from anybody: a business that owns its domain already has everything required, and the record is one line.
Level 1 fails for a client who does not know the real domain in the first place. Nothing in this protocol helps that client, and saying so is better than implying coverage that is not there.
It also says nothing about licensing. A domain proves a business, not a qualification. That gap is exactly what levels 2 and 3 exist to close.
The gap nobody has closed
Levels 0 to 2 can all be reached by somebody who copied a real licence number, because none of them binds the number to the key. A checker reading a public register page sees that licence 4102938 belongs to Northpier Property. They cannot see whether the key signing this claim belongs to Northpier Property.
Only the issuing authority can close that gap, by recording a key against a licence and publishing it: tier C of RVW-5. Everything else in this lab is an attempt to make the intermediate situation survivable, and to make tier C a small enough ask that an authority says yes.
This is open problem OP-1, and it is the one that decides whether this lab ends up mattering.
How a level is displayed
A consumer shows the level reached and the age of the evidence, in words, with no colour coding that reads as approval. The reference wording, which implementers are free to improve on:
| Situation | Wording |
|---|---|
| Level 3, file one day old | The issuing authority listed this licence as active yesterday. |
| Level 2, two checkers, nine days | The licence was last seen on the public register nine days ago, by two independent checkers. |
| Level 1 only | This key is published on northpier.com.au. No licence evidence. |
| Level 0 only | This claim is signed and dated. Nothing outside it supports it. |
| Expired claim | This claim expired on 9 May 2027 and has not been renewed. |
| Nothing at all | No claim. This address is receiving its first payment here. |
Note that the last row is a warning about absence, and that none of the rows is a verdict. That is rule two, in practice.