Private blockchains
Private blockchains (or permissioned blockchains) are different from public blockchains, which are available to any node that wishes to download the network. Critics of public blockchains say because everyone can download a blockchain and access the history of transactions, there is not much privacy.[9] In private blockchains, nodes must be granted access to participate, view transactions, and deploy consensus protocols. Because transactions listed on a private blockchain are private, they ensure an extra layer of privacy.Because private blockchains have restricted access and nodes must be specifically selected to view and participate in a network, some[who?] argue that private blockchains grant more privacy to users.[9] While private blockchains are considered the most realistic way to adopt blockchain technology into business to maintain a high level of privacy, there are disadvantages.[8] For example, private blockchains delegate specific actors to verify blocks and transactions.[11] Although some[who?] argue that this provides efficiency and security, concerns that in nature, private blockchains are not truly decentralized because the verification of transactions and control are put back into the hands of a central entity, have arisen.[11]
Hybrid blockchains
Hybrid blockchains allow more flexibility to determine which data remain private and which data can be shared publicly.[12] A hybrid approach is compliant with GDPR and allows entities to store data on clouds of their choices to be in compliance with local laws to protect peoples privacy. A hybrid blockchain contains characteristics of private and public blockchains. Not every hybrid blockchain contains the same characteristics. Bitcoin and Ethereum do not share the same characteristics, although they are both public blockchains.
