A private blockchain on the other hand provides only the owner to have the rights on any changes that have to be done. This could be seen as a similar version to the existing infrastructure wherein the owner (a centralized authority) would have the power to change the rules, revert transactions, etc. based on the need. This could be a concept with huge interest from FI’s and large companies. It could find use cases to build proprietary systems and reduce the costs, while at the same time increase their efficiency. Some of the examples could be:
There are many critics of payment channels. Finding the quickest path between unconnected nodes is no trivial exercise. This is a classic “traveling salesman” problem that has been worked on by top computer scientists for decades. Critics argue that it is highly unlikely payment channels like Bitcoin’s Lightning and Ethereum’s Raiden will work as expected in practice due to complexities like the traveling salesman problem. The key for you is just to know that these projects and potential solutions to blockchain scalability issues exist. Many of the smartest minds in the industry are working actively to bring them to life.

It may sound nitpicky, but I think that description leaves something to be desired in terms of presenting the “correct” mental model. First, there is no such thing as “a” bitcoin, as I am sure the author would agree. Speaking of spending or moving bitcoins perpetuates the notion of bitcoins as “things”. It might be preferable to say that you are spending or moving “units of the bitcoin protocol”. There is something similar going on here with dollars. The dollars in your bank account aren’t things either, they are units of demand or claim on a currency. The fact that printed dollars have serial numbers tends to confuse this notion. Treating something as a “thing’ which is not a thing is sometimes referred to as the reification fallacy.
Counterfeiting items is a $1.2 trillion global problem, according to Research and Markets 2018 Global Brand Counterfeiting Report. The rise of online commerce and third-party marketplace sellers have made the crime more prevalent in recent years. Blockchain technology can help consumers verify what they ordered online and what they receive in the mail is what they intended to purchase.
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".
Ethereum is an open-source blockchain platform that allows anyone to build and use decentralized applications running on blockchain technology. Ethereum is a programmable blockchain - it allows users to create their own operations. These operations, coded as Smart Contracts, are deployed and executed by the Ethereum Virtual Machine (EVM) running inside every node.
In private blockchains, only specific, pre-chosen entities have the ability to create new transactions on the chain (this is known as “write permissions”). Thus, a private blockchain is a closed network that offers constituents the benefits of the technology, but is not necessarily decentralized or distributed, even among its members. The extent to which each constituent can view (“read”) and create and validate transactions (“write”) is up to the developers of the chain.
However, even this would have its own separate value and wouldn't necessarily solve any issue especially if a market is deemed to be, well, worthless. The two-way peg isn't perfect however. Especially since SPV can theoretically be tricked into crediting more coins than were originally deposited. If the attack will then transfer those coins back onto the parent it would take coins from another user on the Sidechain to fund the imbalance. And in the process create a permanent dissilience between the two chains. In order to strengthen the security of a Sidechain beyond just SPV, it would require the parent to soft fork and upgrade its core wallet software so that both chains can then validate transfers between them.

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@tradles – thanks for taking the time to explain this. OK – so I get the debate around blockchain bloat and the (grudging) inclusion of OP_RETURN, etc., but what I’m missing is that I can only really see one scenario where embedding any identity data into the blockchain makes sense…. and that’s when I want to *associate* an identity with a transaction I’m performing.
This construction is achieved by composing smart contracts on the main blockchain using fraud proofs whereby state transitions can be enforced on a parent blockchain. We compose blockchains into a tree hierarchy, and treat each as an individual branch blockchain with enforced blockchain history and MapReducable computation committed into merkle proofs. By framing one’s ledger entry into a child blockchain which is enforced by the parent chain, one can enable incredible scale with minimized trust (presuming root blockchain availability and correctness).
Let us call the current Bitcoin System Bitcoin 1.0 and the sidechain Bitcoin 2.0 So one would take one unit of Bitcoin 1.0 and send it to an unspendable address (e.g. 1111111111111111111114bRaS3) they’d also submit cryptographic proof of the transaction signed by the same private key that sent the transaction as a transaction into Bitcoin 2.0. The protocol of Bitcoin 2.0 would entitle the user to receive one unit of Bitcoin 2.0  This is called “One-way Pegging” as the value of one Bitcoin 2.0 is equal to one Bitcoin 1.0.  This system is only one way and creates a wormhole by which Bitcoin 1.0 disappears as there is no way of getting it back.
If you want a deeper look at Proof of Stake check out our detailed POS post. In short, while Proof of Work is an effective mechanism to secure the blockchain and provides a trustless consensus paradigm, it’s extremely energy intensive because of all the computing power required to solve hash problems. Also, while it was meant to be decentralized, it’s actually becoming more centralized as miners consolidate and massive mining setups eat up larger shares of winning blocks.

The creation of sidechains have been a direct result of scalability issues associated with the main blockchain for projects such as Ethereum. Making sidechains increasingly popular way to speed up transactions. Lisk was the first decentralized application (dapp) to implement sidechains. With Lisk, each dapp created exists on its own sidechain without interfering with the mainchain.
To scale Blockchain, sidechain or childchain solutions cannot be undermined. Sidechains are separate Blockchains that are linked to the main Blockchain using a two-way peg. They are an auxiliary network that executes the complementary function of: faster transactions, lower transaction costs and greater scalability in terms of the number of transactions that can be supported in a network at a given time.
So, there is a kind of centralized authority that decides who has a right to contribute to and to audit the network. What is more – it’s possible to restrict viewing information stored on private blockchains. It might seem that in such conditions, a blockchain is no longer the blockchain as it lacks transparency and decentralization. Well, these remarks are fair, but only when the network is estimated from the outside. Within it, the rules remain the same as for public networks: it is still transparent for all the members.
Jump up ^ Kopfstein, Janus (12 December 2013). "The Mission to Decentralize the Internet". The New Yorker. Archived from the original on 31 December 2014. Retrieved 30 December 2014. The network's 'nodes'—users running the bitcoin software on their computers—collectively check the integrity of other nodes to ensure that no one spends the same coins twice. All transactions are published on a shared public ledger, called the 'block chain.'

Let us call the current Bitcoin System Bitcoin 1.0 and the sidechain Bitcoin 2.0 So one would take one unit of Bitcoin 1.0 and send it to an unspendable address (e.g. 1111111111111111111114bRaS3) they’d also submit cryptographic proof of the transaction signed by the same private key that sent the transaction as a transaction into Bitcoin 2.0. The protocol of Bitcoin 2.0 would entitle the user to receive one unit of Bitcoin 2.0  This is called “One-way Pegging” as the value of one Bitcoin 2.0 is equal to one Bitcoin 1.0.  This system is only one way and creates a wormhole by which Bitcoin 1.0 disappears as there is no way of getting it back.
New organizational structures will emerge that will make inside/outside much less clear. These clear boundaries started to erode with the extranets in the 90s, then with the multi-tenant cloud platforms, and lately with the smartphones and the IoT. As we move forward we will see value chains where participants have multiple roles and affiliations. We will be designing token based systems that produce gains for any participants, internal or external.
A side-chain is a secondary blockchain layer designed to facilitate lower-cost and/or higher-speed transactions between two or more parties. One case in which they're often deployed is between parties who make many transactions amongst each other. Committing all of those transactions to the public blockchain would may undesirable for cost or other reasons, so the side-chain's job in this example would be to aggregate the activity into the least transactional activity necessary to reflect the final state of the side-chain's ledger.
“The consortium or company running a private blockchain can easily, if desired, change the rules of a blockchain, revert transactions, modify balances, etc. In some cases, e.g. national land registries, this functionality is necessary; there is no way a system would be allowed to exist where Dread Pirate Roberts can have legal ownership rights over a plainly visible piece of land, and so an attempt to create a government-uncontrollable land registry would in practice quickly devolve into one that is not recognized by the government itself….
A user on the parent chain first has to send their coins to an output address, where the coins become locked so the user is unable to spend them elsewhere. Once the transaction has been completed, a confirmation is communicated across the chains followed by a waiting period for extra security. After the waiting period, the equivalent number of coins is released on the sidechain, allowing the user to access and spend them there. The reverse happens when moving back from a sidechain to the main chain.
Sidechains have been a concept for a relatively long time in the cryptocurrency space. The idea took flight in 2014 when several eminent figures in cryptography and early digital currency innovations published an academic paper introducing Pegged Sidechains. Several of the authors are central figures at Blockstream, who is at the forefront of innovation in sidechains and other Bitcoin developments.
This comparison might make you think that private blockchains are more reasonable to use as they are faster, cheaper, and protect the privacy of their members. However, in certain cases, transparency is more crucial than the speed of transaction approval. So, every company interested in moving their processes to a blockchain evaluates the needs and goals and only then selects a particular type of distributed ledger.
The main point of a side-chain is to allow cryptocurrency networks to scale and interact with one-another. For example alt-coins and Bitcoin run on separate chains, however side chains allow for these separate currencies to be transferred through these two-way 'portal's or interfaces via a fixed conversion amount. Added benefits of side-chains are different asset classes like,stocks, bonds etc being integrated through a converted price onto the main chain, along with additional functionality like smart contracts,unique D-Apps, micro-payments and security updates that can be later incorporated into the primary network from these side-chains.

Perhaps blocks are created faster on that sidechain. Perhaps transaction scripts are “turing complete”. Perhaps you have to pay fees to incent those securing that sidechain. Who knows. The rules can be whatever those running that sidechain want them to be. The only rule that matters is that the sidechain agrees to follow the convention that if you can prove you put some Bitcoins out of reach on the Bitcoin network, the same number will pop into existence on the sidechain.
Jump up ^ Iansiti, Marco; Lakhani, Karim R. (January 2017). "The Truth About Blockchain". Harvard Business Review. Harvard University. Archived from the original on 18 January 2017. Retrieved 17 January 2017. The technology at the heart of bitcoin and other virtual currencies, blockchain is an open, distributed ledger that can record transactions between two parties efficiently and in a verifiable and permanent way.
Instant Payments: Since the creation of Bitcoin there has been a race for faster transaction confirmations. Instant payments allow new use cases, such as retail store payments, and transactions in online games. RSK carefully chosen parameters and new theoretical protocols (such as DECOR+GHOST) allow creating blocks at 10 seconds average interval, with low stale block rate, and no additional centralization incentives.
“Blockchain offers a possible solution to these challenges with its decentralized ledger that can store a history of transactions across a shared database,” Cohen said in the report. “By making the record accessible and verifiable from anywhere in the world, blockchain can enable the authentication of goods and eradicate the criminal element of counterfeit goods in the retail supply chain. By pairing hardware chips with blockchain technology, a product can take on a digital history, going as far back as the raw materials that were used to make the product. This allows retailers and consumers to verify their purchased products are genuine.”
The block time is the average time it takes for the network to generate one extra block in the blockchain.[27] Some blockchains create a new block as frequently as every five seconds.[28] By the time of block completion, the included data becomes verifiable. In cryptocurrency, this is practically when the transaction takes place, so a shorter block time means faster transactions. The block time for Ethereum is set to between 14 and 15 seconds, while for bitcoin it is 10 minutes.[29]
“Given all of this, it may seem like private blockchains are unquestionably a better choice for institutions. However, even in an institutional context, public blockchains still have a lot of value, and, in fact, this value lies to a substantial degree in the philosophical virtues that advocates of public blockchains have been promoting all along, among the chief of which are freedom, neutrality and openness.”