A permissioned blockchain restricts the actors who can contribute to the consensus of the system state. In a permissioned blockchain, only a restricted set of users have the rights to validate the block transactions. A permissioned blockchain may also restrict access to approved actors who can create smart contracts.
Permissioned blockchains do not have to use the computing power based mining to reach a consensus since all of the actors are known. They end up using consensus algorithms like RAFT or Paxos. There are also other PBFT algorithms that can be used to reach consensus without PoW mining.
# See also
- Plenum
- Permissionless blockchain
- Comparison - medium 