Types of blockchain
Aggiornato il: 17 set 2019
This is the third (and last) of a series revolving around blockchain technology. In the first article we introduced the technology by briefly illustrating its nature and functioning, and in the second we described some of its most relevant applications other than cryptocurrencies. In this article we are going to depict the different types of blockchain that have emerged with such applications.
As described in the previous article, blockchain technology has found numerous applications in fields often different from one another. To tackle the specific necessities associated to those different use cases blockchains have been differentiated according to three main characteristics:
Permissionless or public blockchains are defined as such because they do not require any authorization to access the network, execute transactions, or create new blocks. The two main examples of such type of blockchain are Bitcoin and Ethereum, both networks without access restrictions. In such decentralized blockchains no user has privileges over any other, nor can a user alter the information stored in the chain or change the protocol that determines its functioning. The main issue with this type of blockchain is its lack of scalability: the quantity of nodes does not affect the speed at which transactions are processed, which remains unvaried.
Permissioned blockchains are defined as such because they are subject to a central authority that determines who can access them. In such type of blockchain the central authority defines the roles that each user takes within the network, including the visibility of the data stored in the blocks. As this type of blockchain cannot guarantee immutability there is no necessity to submit a proof-of-work to register new transactions, and it is thus necessary to trust the good faith of the node that records it. The characteristics of a permissioned blockchain make it very appealing to institutions and businesses in need of limiting access and visibility to the network whenever necessary. Moreover, with respect to public blockchains such type of blockchain is faster, more performing, and scalable.
Private blockchains are very similar to permissioned ones but have even more restrictive access and visibility criteria. A private blockchain is not visible to external users, thus sacrificing its decentralization, safety, and immutability in exchange for speed, storage room, and lower costs. As in permissioned blockchains such type of network is controlled by a central authority that has the further ability to modify the protocol that determines the chain’s functioning and freely refuse transactions that do not abide by it. The advantages offered by the further control on the network make so that private blockchains are particularly attractive to private businesses and financial institutions.
[1,2,3] Blockchain Hub (2019). Blockchain Hub. Retrieved on 24/05/2019 from https://blockchainhub.net/blockchains-and-distributed-ledger-technologies-in-general/.