Unpermissioned ledgers

Unpermissioned ledgers such as Bitcoin have no single owner - they cannot be owned. The purpose of an unpermissioned ledger is to allow anyone to contribute data to the ledger and for everyone in possession of the ledger to have identical copies of it. This creates censorship resistance, which means that no actor can prevent a transaction from being added to the ledger. Participants maintain the integrity of the ledger by reaching a consensus about its state.

Permissioned ledgers

Permissioned ledgers are ledgers where actors must have permission to access it. Permissioned ledgers may have one or many owners. When a new record is added, the ledger’s integrity is checked by a limited consensus process. This is carried out by trusted actors - government departments or banks, for example - which makes maintaining a shared record much simpler that the consensus process used by unpermissioned ledgers. Permissioned blockchains provide highly-verifiable data sets because the consensus process creates a digital signature, which can be seen by all parties. A permissioned ledger is usually faster than an unpermissioned ledger.