What other options are there? To summarize, there are generally three categories of blockchain-like database applications:
- Public blockchains: a public blockchain is a blockchain that anyone in the world can read, anyone in the world can send transactions to and expect to see them included if they are valid, and anyone in the world can participate in the consensus process – the process for determining what blocks get added to the chain and what the current state is. As a substitute for centralized or quasi-centralized trust, public blockchains are secured by cryptoeconomics – the combination of economic incentives and cryptographic verification using mechanisms such as proof of work or proof of stake, following a general principle that the degree to which someone can have an influence in the consensus process is proportional to the quantity of economic resources that they can bring to bear. These blockchains are generally considered to be “fully decentralized”.
- Consortium blockchains: a consortium blockchain is a blockchain where the consensus process is controlled by a pre-selected set of nodes; for example, one might imagine a consortium of 15 financial institutions, each of which operates a node and of which 10 must sign every block in order for the block to be valid. The right to read the blockchain may be public, or restricted to the participants, and there are also hybrid routes such as the root hashes of the blocks being public together with an API that allows members of the public to make a limited number of queries and get back cryptographic proofs of some parts of the blockchain state. These blockchains may be considered “partially decentralized”.
- Fully private blockchains: a fully private blockchain is a blockchain where write permissions are kept centralized to one organization. Read permissions may be public or restricted to an arbitrary extent. Likely applications include database management, auditing, etc internal to a single company, and so public readability may not be necessary in many cases at all, though in other cases public auditability is desired.
by: Vitalik Buterin
Forbes 9 September 2015: Bitcoin’s Shared Ledger Technology: Money’s New Operating System
See also -IB Times UK, by Ian Allison, 8 September 2015:
Read the full article: Permissioned versus un-permissioned Blockchain ledgers?
Blockchain promises back-office revolution
"For now the market remains split between three core system approaches: private blockchains such as R3CEV and DAH, known as permissioned ledgers, which make use of trusted networks; open-ended blockchains such as Ethereum, which stay faithful to bitcoin’s original design but improve on the smartness of the ledger technology; and applications designed to take direct advantage of the prevailing bitcoin network."