Since in proof-of-stake (PoS) there is no mining process, according to functionality of permissioned and permissionless blockchains, which type is PoS more adapted for?
In the other words, is a PoS-based public permissionless blockchain as secure a PoW-based public permissionless blockchain ? Or Do we need to restrict the permission for the transactions validation to a limited permitted and known validators (i.e. private permissioned blockchain) ?
The term "permissioneless or public blockchain" is referred to as a blockchain platform in which a user does not have any permission for using (sending transaction) or participating in validating transactions process. For example, Bitcoin and Ethereum are public permissionless blockchain, such that they are open to everybody for both sending transaction and participating in validation of transactions (i.e. PoW process).
On the other hands, "permissioned blockchain" allows the network to appoint a group of participants in the network who are given the authority to provide the validation of blocks and transactions, meaning that there is an an access control layer to allow certain actions to be performed only by certain identifiable participants. Since access to this type of blockchains is not open to everybody, unlike Bitcoin or Ethereum, they are usually called also private blockchains. For example, Ripple and Hyperledger Fabric are permissioned blockchain.
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