Step back from the details for moment and consider what’s been described.  We now have a way to move coins from Bitcoin onto another platform (a sidechain) and move them back again.   That’s pretty much what we do when we move them to a wallet platform or an exchange.  The difference is that the “platform” they’ve been moved to is also a blockchain… so it has the possibility of decentralised security, visibility and to gain from other innovation in this space.

Sidechains are an essential innovation in the blockchain field with some interesting long-term implications and effects on the broader interoperability and scalability of blockchain networks. They are effectively extensions of existing blockchains that increase their functionality and allow for validation of data from other blockchains and for assets to be seamlessly transferred between them.

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.
The differences between these types of blockchains are based on the levels of trust existing among the members of the network and the resulting level of security. Indeed, the higher the level of trust between the members of the network, the lighter the consensus mechanism (which aims to add the blocks to the blockchain securely). As we will see, there is no trust between the members of a public blockchain since it is open to everyone and inversely the confidence is much stronger on the private blockchain since members are pre-selected. In networks based on a blockchain, the level of trust among the members therefore directly impacts the structure and mechanisms of the network.
Thus Tradle set out to build a meta-protocol that saves the data in the overlay network, and only puts minimal referencing data on the blockchain. There is a general grumpy consensus among bitcoin core devs and mining pool operators on allowing one small data chunk, a hash, per transaction. Many devs say it is not possible to secure this second overlay network. I agree, unless we use the blockchain to help with the task. We have a partial solution working, and are preparing a new design to improve it (partial, as it can not yet handle all known attacks). We are actively sharing the designs at various meetups (and on the github) and are inviting devs to find attack vectors and propose solutions. Tradle’s protocol not only relieves the pressure on bitcoin’s blockchain but is also able to handle larger transaction sizes than Counterparty and Mastercoin, so it can be used for complex identity, supply chain management and many other applications. It is also capable of handling attachment files, needed in the healthcare and financial industries.
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.
Start mining on node 1 by using the function miner.start(1), where 1 refers to the number of threads. Note that the miner.start(n) function will always return "null." Unless you have many CPU cores, keep the thread number low to avoid high CPU usage. Note that mining without any pending transaction can still earn your default account incentive (ETH). It creates empty blocks, thus strengthening the integrity of the blockchain tree.
An important distinction to be made about sidechains that needs to be understood is that sidechains themselves help to fuel innovation through experimentation. Rather than providing scalability directly, they allow for trivial experimentation on sidechains with various scalability mechanisms. Using sidechains, one can avoid the problems of initial distribution, market volatility, and barriers to entry when experimenting with altcoins due to the inherent derivation of their scarcity and supply from Bitcoin. That being said, each sidechain is independent and flexible to tool around with various features.
You cannot be a crypto investor or entrepreneur without having a real understanding of the differences between these types of blockchains as well as their implications. Even if they are based on similar principles, their operation is, in fact, different to all levels. So the tokens issued by these blockchains will not be assessed in the same manner.
In simple terms, public blockchains can receive and send transactions from anybody in the world. They can also be audited by anybody, and every node has as much transmission power as any other. Before a transaction is considered valid, it must be authorized by each of its constituent nodes via the chain’s consensus process. As long as each node abides by the specific stipulations of the protocol, their transactions can be validated, and thus add to the chain
Permissioned blockchains use an access control layer to govern who has access to the network.[46] In contrast to public blockchain networks, validators on private blockchain networks are vetted by the network owner. They do not rely on anonymous nodes to validate transactions nor do they benefit from the network effect.[47][better source needed] Permissioned blockchains can also go by the name of 'consortium' or 'hybrid' blockchains.[48]
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The second option will be to use sidechains. Blockstream first announced side chain in 2014 and published its whitepaper ( I believe in the future, bitcoin will have its desired flexibility with its sidechains. The idea of the sidechain is you can innovate and design your solution freely in the sidechains. These sidechains are independent, if they are failed or hacked, they won't damage other chains. So damage will be limited within that chain, for that reason you can be less conservative. Otherwise you would be more risk averse, if you had 42.5 billion dollar market cap like Bitcoin.
It is different with a private blockchain (or closed) since the members of the network are selected before being able to download the protocol and therefore use the proposed service by the network. The mining capabilities and the system of consensus as a whole are centralized within the hands of the same entity. A network based on a private blockchain is therefore not decentralized in itself.
Hasta la fecha (Agosto del 2016), las sidechains sobre Bitcoin no son más que algo teórico. Una implementación de este tipo requeriría de un cambio en el código Bitcoin (hay miembros de la comunidad Bitcoin con gran prestigio, como es el caso de Peter Todd, que argumentan que una sidechain, tal y como la describe Blockstream en su paper, no podrían llevarse a la práctica en Bitcoin sin hacer un gran cambio, hard fork, en Bitcoin). En el mismo paper de blockstream se reconoce que una implementación de este tipo, la cual su teoría es simple pero su implementación compleja, se enfrenta a problemas que no está del todo claro que puedan solventarse (y no todos son de tipo técnico).
Using Rootstock as an example, in order to transfer assets from one chain to the other a user on the parent first has to send their coins to a special output address where they will consequently become locked and un-spendable. Once the transaction is completed, SPV then confirms it across the chains and after waiting out a contest period, which is just a secondary method to help prevent double spending, the equivalent amount will be credited and spendable on the Sidechain and vice versa.

Sidechains allow cryptocurrencies to interact with one another. They add flexibility and allow developers to experiment with Beta releases of Altcoins or software updates before pushing them on to the main chain. Traditional banking functions like issuing and tracking ownership of shares can be tested on sidechains before moving them onto main chains. If the security mechanisms for sidechains can be bolstered, sidechain technology holds promise for massive blockchain scalability.

The idea emerged that the Bitcoin blockchain could be in fact used for any kind of value transaction or any kind of agreement such as P2P insurance, P2P energy trading, P2P ride sharing, etc. Colored Coins and Mastercoin tried to solve that problem based on the Bitcoin Blockchain Protocol. The Ethereum project decided to create their own blockchain, with very different properties than Bitcoin, decoupling the smart contract layer from the core blockchain protocol, offering a radical new way to create online markets and programmable transactions known as Smart Contracts.
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.
A typical use case for a private blockchain is intra-business: when a company decides to implement blockchain as a business solution, they may opt for a chain to which only company members have access. This is useful if there’s no need for anybody outside of the company to become part of the chain, because private blockchains are more efficient than public and consortium chains. Also, because they are smaller and contained, it is easier for a consensus process or other technical stipulation to be altered on a blockchain. So, for example, if the developers or proprietors want to change the cryptographic method which runs its consensus process, it is much easier to do this on a private blockchain than a public or consortium chain.

Looking for a top private blockchain open source? Here is a list of private blockchain development companies with client reviews and ratings. Private blockchain network on contrary to public and permission blockchain can be run and utilized by one organization only. Additionally, private blockchain platform organizes distinctive components of the technology in order to serve different applications. By prioritizing productivity over the secrecy, permanence, and transparency, private blockchain open source adheres to the qualities normally connected with the technology. The scope of uses for private blockchain might be narrow yet its power to enhance processes are no less important. GoodFirms has thus created a list of top private blockchain companies below:

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.