Proof of Reflection
Proof of Reflection is a consensus technique: a chain counts the work of other chains that record its history, designed so that attacking it means attacking them too.
It starts with : one chain records and checks another’s .image - to record and check another chain’s block headers. The whitepaper calls the record a projection.block header - A block’s summary: it commits to every transaction in the block and links to the block before it. The whitepaper builds it in five steps, from imaging to mutual .reflection - When a chain counts the work of another chain that records its headers, it is reflected in that chain.
From imaging to mutual reflection
Step 1 of 5: Chain R images Chain L.
Dashed: headers recorded. Solid: work counted. Outlined: an attacker’s blocks. Tallies: the blocks each fork rule counts.
Step 1: Chain R images Chain L.
R records and checks L’s block headers as L produces them.
Step 2: Chain L images Chain R.
L does the same with R’s headers. Each chain now holds a record of the other.
Step 3: L proves its history is recorded in R.
Using its record of R, L shows that R holds L’s own history: a proof of reflection. On its own, this adds no security.
Step 4: One-way reflection: L counts R’s work.
When L picks between competing histories, it now counts R’s work as well as its own. It is designed so that rewriting L means out-working L and R.
Step 5: Mutual reflection: R does the same.
R proves its history is recorded in L and counts L’s work. Each chain is designed to be harder to attack than it is alone.
Imaging foreign chains
Amaroo images Bitcoin, Ethereum and other foreign chains one way: it records and checks their headers, with no committee in the middle, and nothing changes on the foreign chain. Imaging is not reflection: a foreign chain neither lends Amaroo security nor gains any.
From that record, Amaroo can check a : that a payment happened on the foreign chain and is buried there at its , which is set for each chain. The same record allows a : the balance at addresses a holder names.proof of payment - A proof, checked against a foreign chain’s imaged headers, that a payment happened on that chain and is buried at its confirmation depth.confirmation depth - The number of blocks that must bury a payment on its chain before Amaroo acts on a proof of it, set for each chain.proof of reserve - A proof, checked the same way, of the balance at addresses a holder names on that chain.
Fig. 2
- Bitcoin’s headers flow one way into Amaroo. Once a payment is buried to the depth set for that chain, Amaroo can prove it.
Terms
- image
- To record and check another chain’s block headers. The whitepaper calls the record a projection.
- block header
- A block’s summary: it commits to every transaction in the block and links to the block before it.
- fork rule
- How a chain picks between competing histories, by comparing the work behind each.
- reflection
- When a chain counts the work of another chain that records its headers, it is reflected in that chain.
- confirmation depth
- The number of blocks that must bury a payment on its chain before Amaroo acts on a proof of it, set for each chain.
- proof of payment
- A proof, checked against a foreign chain’s imaged headers, that a payment happened on that chain and is buried at its confirmation depth.
- proof of reserve
- A proof, checked the same way, of the balance at addresses a holder names on that chain.
Definition
Proof of Reflection
The consensus technique whereby a blockchain becomes more difficult to attack by including work done by reflecting blockchains in its fork rule.
Whitepaper v1.1, section 2.2.4, p. 15. Proof of Reflection is designed so that counting that work makes a chain harder to attack (section 2.2).
US patent 12,706,764, granted for secure consensus between cooperating chains, covers Proof of Reflection and Ultra Terminum.