Blockstream has also released an “Alpha” sidechain with all of those features up and running except the last, coupled to the Bitcoin testnet. (Used for testing Bitcoin software without putting real value at risk.) In the absence of the Bitcoin protocol change that will cryptographically secure the programmatic transfer of value between Bitcoin and sidechains, they’re cooperating with several external organizations to perform and validate those transfers. If and when that protocol change happens, though, pegged sidechains will be as permissionless, and as decentralized, as Bitcoin itself.
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.
RSK is the first open-source smart contract platform with a 2-way peg to Bitcoin that also rewards the Bitcoin miners via merge-mining, allowing them to actively participate in the Smart Contract revolution. RSK goal is to add value and functionality to the Bitcoin ecosystem by enabling smart-contracts, near instant payments and higher-scalability.

Congratulations! You’ve just educated yourself on the most common advanced topics in blockchain that you’ll hear about. By understanding these concepts, you have a firmer grasp on the fundamental tradeoffs and latest research on the blockchain than most industry “experts”! Better yet, next time you hear your colleagues around the water cooler talking about state channels, the Lightning Network and Byzantine fault tolerance, not only will you know what they’re talking about but you might be able to teach them a thing or two!
Unlike the other two-way peg mechanisms discussed in this article, SPV sidechains do not give direct control of real bitcoins on the main chain to a custodian; however, the ability for a majority of miners to produce and build upon fraudulent SPV proofs gives them indirect control over the funds, including the ability to send to themselves. Having said that, there are ways to mitigate this issue.

Necessity is the answer to that question, well for the short term anyway. Currently public & private blockchains still have a lot of challenging technological problems that need to be sorted out, with privacy and scalability being foremost. Gallactic’s blockchain can certainly help with scalability due to its multi-chain architecture that allows for massive scaling to rival and in most cases surpass other blockchains in the market with transactions at 300 per second on mainchain with the ability to scale up to hundreds of thousands per second when the multi-chain model is configured for speed.
Further, despite sidechains being independent of each other, they are responsible for their individual security and need the requisite mining power to remain secure. Bitcoin’s blockchain has sufficient PoW mining power to remain secure even from the most coordinated of attacks, but many more nascent sidechains lack the necessary network effects and mining power to guarantee security to users.
My take is that the Bitcoin architecture is a solution to the problem of how to maintain consensus about a ledger when the participants are unknown and many of them are adversarial (I know this is loose language… computer scientists working in the consensus space are more precise but I think this captures the essence…. i.e. we’re explicitly in a world where there is no “leader” and no identities for those providing the consensus services).
The term “sidechains” was first described in the paper “Enabling Blockchain Innovations with Pegged Sidechains”, circa 2014 by Adam Back et al. The paper describes “two-way pegged sidechains”, a mechanism where by proving that you had “locked” some coins that were previously in your posession, you were allowed to move some other coins within a sidechain.
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, eg. 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. Of course, one can argue that one can do this on a public blockchain by giving the government a backdoor key to a contract; the counter-argument to that is that such an approach is essentially a Rube Goldbergian alternative to the more efficient route of having a private blockchain, although there is in turn a partial counter-argument to that that I will describe later.
As an engineer and an entrepreneur, I truly believe blockchain technology is going to revolutionize the world. One of the biggest hurdles we need to tackle in the blockchain industry is scalability. Ethereum can only handle 15 transactions per second. I previously wrote about why that will prevent blockchain from going mainstream and how DAG could potentially be a winner.

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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.
Blockstream recently released a whitepaper on “strong federations,” which is essentially their vision of a federated two-way peg system. Liquid is a sidechain created by Blockstream that uses the strong federations model. The sidechain is used to transfer bitcoins between centralized bitcoin institutions, such as exchanges, at a faster pace than the public Bitcoin blockchain.
The cheapest and most simple option is doing calculations on your local network (off-chain) and integrating with main blockchain by sending the results. It has flaws; you cannot live full advantage of blockchain as we do in bitcoin, because you will still have existing constraints of your current system. Despite all this, it is still a valid option; perhaps you won't need all the features of blockchain technology. Perhaps it is just enough to use blockchain only for your pain points. Factom can be considered under that kind of option. They used bitcoin wisely in their design. They hold the actual mass data in their network and utilize stability of bitcoin in their solution. This project is so successful that at coindesk magazine, it is saying that Factom can be used for the land titles in Honduras. http://www.coindesk.com/debate-f...
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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.'
In September 2015, the first peer-reviewed academic journal dedicated to cryptocurrency and blockchain technology research, Ledger, was announced. The inaugural issue was published in December 2016.[91] The journal covers aspects of mathematics, computer science, engineering, law, economics and philosophy that relate to cryptocurrencies such as bitcoin.[92][93]
People believe that permissioned means that only a select group of people can access the data and that’s the security feature. But it’s not. Since there is no real user data on the blockchain, (you) as a member of the public, can’t verify the actual content of it. This means that data resides in a location where corruption can stay undetected and data can be easily modified. So why does it even exist? Mainly because of the phenomena known as “hype surfing”; essentially reusing old technology and strapping a blockchain sticker on it gets IBM salesmen a foot in the door to institutions who can’t evaluate the technology accurately in the first place. Unfortunately, even some teams doing public token offerings started to sell this deeply flawed approach to the public.
For example, let’s say we have side chain 1 (SC1) and side chain 2 (SC2). A transaction occurs on SC1. A node in SC1 broadcasts the transaction to nodes in the main chain to record this transaction. The same node of SC1 calls a function from SC2 with a proof. The function in the nodes of SC2 verifies the proof on the main chain. The function gets executed.

Jump up ^ Shah, Rakesh (1 March 2018). "How Can The Banking Sector Leverage Blockchain Technology?". PostBox Communications. PostBox Communications Blog. Archived from the original on 17 March 2018. Banks preferably have a notable interest in utilizing Blockchain Technology because it is a great source to avoid fraudulent transactions. Blockchain is considered hassle free, because of the extra level of security it offers.
Sidechain is a blockchain that runs parallel to the main blockchain. It extends the functionality of interplorable blockchain networks. Interpolable blockchain networks signifies the ability to share data between different computer systems on different machines. It means that data can be sent and received between interconnected networks eliminating the possibility of negative impact to the networks. Sidechain enables this to be done in a decentralised manner to transfer and synchronise tokens between two chains.
Sometimes separate blocks can be produced concurrently, creating a temporary fork. In addition to a secure hash-based history, any blockchain has a specified algorithm for scoring different versions of the history so that one with a higher value can be selected over others. Blocks not selected for inclusion in the chain are called orphan blocks.[22] Peers supporting the database have different versions of the history from time to time. They keep only the highest-scoring version of the database known to them. Whenever a peer receives a higher-scoring version (usually the old version with a single new block added) they extend or overwrite their own database and retransmit the improvement to their peers. There is never an absolute guarantee that any particular entry will remain in the best version of the history forever. Because blockchains are typically built to add the score of new blocks onto old blocks and because there are incentives to work only on extending with new blocks rather than overwriting old blocks, the probability of an entry becoming superseded goes down exponentially[23] as more blocks are built on top of it, eventually becoming very low.[1][24]:ch. 08[25] For example, in a blockchain using the proof-of-work system, the chain with the most cumulative proof-of-work is always considered the valid one by the network. There are a number of methods that can be used to demonstrate a sufficient level of computation. Within a blockchain the computation is carried out redundantly rather than in the traditional segregated and parallel manner.[26]
Mastercoin and Counterparty are embedded consensus protocols (or meta-protocols) that use the blockchain to store their transactional data. Bitcoin devs, except Peter Todd who was hired by both teams to help them find a proper solution, are very unhappy, to say mildly, about storing the data on the blockchain. Heated discussions on this topic go on for hundreds of pages on bitcointalk and Mastercoin github issue. Mining pools like Eligius started censoring Mastercoin transactions (not sure if they are continuing with this practice right now, but the operators of this pool are adamant that data do not belong to the blockchain).
Private blockchains, or as I like to call them, shared databases, have a place in improving efficiency for financial institution for back-office settlement processes. They should not be seen as controversial, or part of some dialectic struggle between punks and police. To the extent that the identifying shroud of AML/KYC can be placed into public blockchain metadata (possible in Omni Layer transactions over the Bitcoin blockchain) there may even be interoperability between these two sides of the train tracks. Right now, due to state-granted monopolies to issue credit, most of the world's liquidity is still in banks. However, we believe that in the long-term, public blockchains, especially those based on work, will come to take a more significant part in the ‘System D’ informal economy, which is where most of the global economic growth will originate.” 
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