There has been tremendous interest in blockchain, the technology on which Bitcoin functions. Nakamoto developed the blockchain as an acceptable solution to the game theory puzzle – Byzantine General’s Problem. This lead to a number of firms adopting the technology in different ways to solve real world issues, wherever there was an element of trust involved. Majority of them could be relating to the ability to provide proof of ownership – for documents, software modules/licenses, voting etc.
Cabe destacar el papel de la gente de Blockstream, una de las compañías centradas en la búsqueda de este objetivo (con un extremeño en sus filas, Jorge Timón). Blockstream está trabajando actualmente en el desarrollo de un protocolo que permita crear sidechains. Son los responsables de uno de los papers más conocidos sobre el tema, publicado en Octubre del 2014:
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This approach isn’t fool-proof, but it’s not by mistake that the system looks the way it does today (that’s my history degree talking). Despite best technical efforts, human problems remain within the realm of probability. From “…blame cannot be easily assigned: not even the most sophisticated economists of the era could accurately predict disaster, let alone guard against it. The effects of a public herd mentality at the time of the [insert catastrophe here] are depicted, all too recognizably, as unstoppable.”
The first question to answer is “What is public blockchain?” The very name of this type of networks implies that they are open and permissionless. It means that anyone in the world can join the network, add blocks and view the information stored there. Indeed, public blockchains are totally transparent as any of their members can audit them. For this reason, independent participants can easily agree on transactions without middlemen and the fear of deception.
Decentralized web. The sidechain technology holds premises to expand one of the main values of the blockchains – the decentralization of confidence. There is no need for central structure behind the transactions - the holders of cryptocurrencies are free to use their assets the way they want. The sidechains make their deals even more protected and reliable.
A blockchain is a distributed computing architecture where every node runs in a peer-to-peer topology, where each node executes and records the same transactions. These transactions are grouped into blocks. Each block contains a one-way hash value. Each new block is verified independently by peer nodes and added to the chain when a consensus is reached. These blocks are linked to their predecessor blocks by the unique hash values, forming a chain. In this way, the blockchain’s distributed dataset (a.k.a. distributed ledger) is kept in consensus across all nodes in the network. Individual user interactions (transactions) with the ledger are append-only, immutable, and secured by strong cryptography. Nodes in the network, in particular the public network, that maintain and verify the transactions (a.k.a. mining) are incentivized by mathematically enforced economic incentives coded into the protocol. All mining nodes will eventually have the same dataset throughout.
If you’ve been keeping track of developments in the bitcoin industry, you’d know that the blockchain refers to the public ledger of transactions associated with the cryptocurrency. As the bitcoin ecosystem has grown in size and scale throughout the years, the blockchain has also increased considerably in length and storage size, prompting debates on whether or not to increase its block size limit.
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.
2. Ardor’s Blockchain as a service platform for business: Ardor uses the Proof of Stake consensus mechanism. Ardor calls its sidechains ‘childchains’, and they are tightly integrated into the main chain. Security is enhanced because all transactions are processed and secured by parent chain forgers. Most transactions are pushed down to the childchain level, as the parent mainchain retains minimal features. Global entities such as assets and currencies across chains can be accessed through childchains.
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.
@tetsu – not sure what you mean. My reading of the sidechains paper is that the worst case scenario is that an attacker manages to “reanimate” Bitcoins on the main blockchain that had been sent to the sidechain… but that would be the attacker stealing the coins from the rightful owner on the sidechain. From Bitcoin’s perspective, the coins were always going to be reanimated…. so the risk is entirely borne by the holder(s) on the sidechain. Am I missing something?
Let’s switch gears quickly before we get back to talking about trust mechanisms. We’ll define what a “smart contract” is. The first blockchain that was popularized is obviously the Bitcoin blockchain. But the functionality of Bitcoin is very limited. All it can do is record transaction information. It’s only useful to keep track of the fact that Alice sent Bob 1 Bitcoin.

So if you want to create a more secure Sidechain, we would seriously need to have a look at incentivizing miners in other ways. These could include things such as the Sidechain raising outside funding from investors in order to pay the miners. Staggering mining award so miners have an incentive to keep mining as they will be paid later on rather than at the time or the Sidechain could issue its own mining award on top of the already existing transaction fees and essentially just become an Altcoin.

^ Jump up to: a b c d Bhaskar, Nirupama Devi; Chuen, David Lee Kuo (2015). "3 – Bitcoin Mining Technology". In Cheun, David Lee Kuo. Handbook of Digital Currency: Bitcoin, Innovation, Financial Instruments, and Big Data. Academic Press. pp. 47–51. ISBN 978-0-12-802117-0. Archived from the original on 25 October 2016. Retrieved 2 December 2016 – via ScienceDirect.

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.

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).
Now, making experimental or rapid changes to Bitcoin is very risky and so change happens slowly. So if the one-size-fits-all architecture of Bitcoin doesn’t suit a particular use-case, you have a problem. You either have to use an entirely different cryptocurrency (or build one!). Or you have to use (or build) a centralized service, which brings new risks.
“What is private blockchain?” is a logical question to ask after you found out that there is no such thing as one transcendental blockchain. What makes private networks different from the public is that only a selected group of people can access them. Hence, a random person has no chance to join a private ledger all of a sudden. To do so, a new participant needs an invitation or permission that can be issued by:
A blockchain is a continuously growing list of records called blocks, these blocks are linked and secured using cryptographic algorithms. Each block typically contains a hash (a link to a previous block), a timestamp as well as transaction data. Full nodes validate all the transactions, but are unable to settle the disagreements in regards to the order in which they were received. To prevent double-spending, the entire network needs to reach global consensus on the transaction order. It achieves this by using centralised parties or a decentralised proof of work or proof of stake algorithm (and its derivatives).
Plasma is a proposed framework for incentivized and enforced execution of smart contracts which is scalable to a significant amount of state updates per second (potentially billions) enabling the blockchain to be able to represent a significant amount of decentralized financial applications worldwide. These smart contracts are incentivized to continue operation autonomously via network transaction fees, which is ultimately reliant upon the underlying blockchain (e.g. Ethereum) to enforce transactional state transitions.

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.
Contrary to popular belief, aided by deceptive blockchain marketing, blockchains are not a good solution for storing data. Each piece of information that you store in the blockchain sits in hundreds or more nodes (more than 100,000 in the case of Bitcoin) making it an extremely costly solution. This is why the Iryo Network doesn’t store data on blockchain but instead, uses blockchain to ensure the transparency of transactions. As a disclaimer, competitors also don’t save medical data on the chain itself (even those who use private chains). Instead, only the fingerprint aspect of a medical record file or a hash is stored on the blockchain.

Nikolai Hampton pointed out in Computerworld that "There is also no need for a '51 percent' attack on a private blockchain, as the private blockchain (most likely) already controls 100 percent of all block creation resources. If you could attack or damage the blockchain creation tools on a private corporate server, you could effectively control 100 percent of their network and alter transactions however you wished."[9] This has a set of particularly profound adverse implications during a financial crisis or debt crisis like the financial crisis of 2007–08, where politically powerful actors may make decisions that favor some groups at the expense of others,[51][52] and "the bitcoin blockchain is protected by the massive group mining effort. It's unlikely that any private blockchain will try to protect records using gigawatts of computing power—it's time consuming and expensive."[9] He also said, "Within a private blockchain there is also no 'race'; there's no incentive to use more power or discover blocks faster than competitors. This means that many in-house blockchain solutions will be nothing more than cumbersome databases."[9]
To most people, Bitcoin itself is already deeply esoteric (and many still find it risible.) But to cryptocurrency aficionados, tired old garden-variety Bitcoin is so five minutes ago. Explaining today’s new cryptocurrency hotness to a general audience is an interesting challenge–I have an engineering degree from a top-tier school and I write software for a living, and I still find much of this material pretty impenetrable on first acquaintance–but here goes:
Pegged sidechains employ a two-way peg to transfer assets between chains, and they consist of providing proof of possession in the transferring transactions. The idea is to enable the capability of locking an asset on an original parent chain, which can then be transferred to a sidechain before eventually being redeemed on the original chain. Notably, the original asset on the parent chain is locked in a specific output address and is not destroyed like early implementations of sidechains.
A partir de este momento, se podrán intercambiar y mover estas monedas para hacer uso del potencial de esa sidechain siguiendo las directrices y protocolo que ésta tenga estipulado. Por ejemplo, quizá la velocidad de creación de los bloques es más rápida en esta o quizá los scripts de transacción en esa cadena son turing completos (disponen de un poder de cómputo equivalente a la máquina universal de Turing).
A public blockchain has absolutely no access restrictions. Anyone with an internet connection can send transactions[disambiguation needed] to it as well as become a validator (i.e., participate in the execution of a consensus protocol).[84][self-published source?] Usually, such networks offer economic incentives for those who secure them and utilize some type of a Proof of Stake or Proof of Work algorithm.

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