How it works

Proof of Ownership keeps one ledger per pool of mints and lets the total work behind each ledger decide which one counts. These are the ideas in plain words; the documentation has the exact rules.

1. A series sets the rules

   A series is a published set of rules: how many mints, how many units in each, how mints are grouped into pools, which hash is used, how strong work must be, and which key types and address types are allowed. Its id is the hash of those rules, so they can never change.

2. Mints are grouped into pools

   Each mint is one unit of a series with a fixed supply. Consecutive mints form a pool, and all mints of a pool share one ledger. The first transaction of a mint is its claim, which creates its whole supply.

3. Transactions move portions

   A transaction belongs to one mint. It spends whole portions and creates new ones that add up to the same amount. Owners authorize it with witnesses: the address's rule, such as "2 of these 3 keys", plus the signatures that meet it.

4. Entries bundle transactions

   An entry holds a bundle of a pool's transactions and the hash of the entry before it, forming a chain from the pool's start to its tip.

5. Layers add work

   Work is added separately, as layers: hashes of an entry and a nonce. A layer's credit is 2 to the power of its leading zero bits. (A series may also count an entry's own hash as credit; the default series does not.) Anyone can add layers to any entry, including one already buried under others, and that adds weight to every ledger containing it.

6. The heaviest valid ledger is selected

   A node selects the valid ledger of each pool with the greatest total credit. A rival must out-weigh everything built after the last entry it shares with the selected ledger. A receiver decides how much work it waits for before treating a payment as settled.

Three tiers of rules

Node policy can never make a heavier valid ledger unacceptable. Two nodes with the same information always agree on which ledger is valid.