Open blockchains are more user-friendly than some traditional ownership records, which, while open to the public, still require physical access to view. Because all early blockchains were permissionless, controversy has arisen over the blockchain definition. An issue in this ongoing debate is whether a private system with verifiers tasked and authorized (permissioned) by a central authority should be considered a blockchain. Proponents of permissioned or private chains argue that the term "blockchain" may be applied to any data structure that batches data into time-stamped blocks. These blockchains serve as a distributed version of multiversion concurrency control (MVCC) in databases. Just as MVCC prevents two transactions from concurrently modifying a single object in a database, blockchains prevent two transactions from spending the same single output in a blockchain.:30–31 Opponents say that permissioned systems resemble traditional corporate databases, not supporting decentralized data verification, and that such systems are not hardened against operator tampering and revision. Nikolai Hampton of Computerworld said that "many in-house blockchain solutions will be nothing more than cumbersome databases," and "without a clear security model, proprietary blockchains should be eyed with suspicion."
What is the difference between a public blockchain and a private blockchain? Does it matter? Which is better? Gallactic believes that currently there are pros and cons between both Private and Public Blockchains, but time and “convergence”, a term that is gaining prominence in the Blockchain Industry, is clearly showing that the lines between these categories, once clear, are starting to fade.
These kinds of blockchains are forks of the original implementations but deployed in a permissioned manner. Mainly hyped because the companies behind these chains want to onboard corporations in order to generate buzz around their their chain. It’s tolerable for proof of concepts or if they plan to move to public as soon as possible; otherwise they are just using the wrong set of tools for the job.
There is a whole other issue of identity theft that needs to be addressed. Just a short note here as this is a big subject: If the private key to identity object is stolen, the true owner of the identity needs to have a way to change the key. One approach to that would be to use the private key of the bitcoin transaction that created the first version of the identity object. Another way could be to prove the ownership of other public keys on the identity object, like the one used for encryption (PGP key management suggests a separate key for each purpose, signing, encryption, etc.). Other non-automatic ways could include a trusted third-party, social proof, etc.
This list is not exhaustive. There are plenty of public blockchains, and they are actively adopted by such industries as FinTech, gaming, logistics, and beyond. However, it not always makes sense to move certain processes and businesses to the public network as the latter are characterized by comparatively low speed of transactions execution and high costs. Indeed, every transaction requires a consensus of the entire network. Unfortunately, it takes time and resources.
Sidechain transactions using a two-way peg effectively only allow for intra-chain transactions. A transfer from Bitcoin (parent chain) to Ethereum (sidechain) would allow a user to use the functionality of Ethereum (i.e., fully expressive smart contracts), but the underlying original asset would remain precisely that, Bitcoin. So, a Bitcoin on an Ethereum sidechain technically remains a Bitcoin.
The “three-part” transaction structure is very general but it only allows you to transfer ownership of Bitcoins. Some people would like to transmit richer forms of information across these sorts of systems. For example, a decentralized exchange needs a way for participants to place orders. Projects such as Mastercoin, Counterparty, NXT and others either build layers on top of Bitcoin or use entirely different codebases to achieve their goals.
This type of permissioned blockchain model offers the ability to leverage more than 30 years of technical literature to realize significant benefits. Digital identity in particular, is fundamental for most industry use cases, be it handling supply chain challenges, disrupting the financial industry, or facilitating security-rich patient/provider data exchanges in healthcare. Only the entities participating in a particular transaction will have knowledge and access to it — other entities will have no access to it. Permissioned blockchains also permit a couple of orders of magnitude greater scalability in terms of transactional throughput.