The words block and chain were used separately in Satoshi Nakamoto's original paper, but were eventually popularized as a single word, blockchain, by 2016. The term blockchain 2.0 refers to new applications of the distributed blockchain database, first emerging in 2014.[13] The Economist described one implementation of this second-generation programmable blockchain as coming with "a programming language that allows users to write more sophisticated smart contracts, thus creating invoices that pay themselves when a shipment arrives or share certificates which automatically send their owners dividends if profits reach a certain level."[1]
Bitcoin’s block interval is ten minutes so it takes about five ten minutes on average for a new transaction to find its way into a block, even if it pays a high fee. This is too slow for some people so they have experimented with alternative cryptocurrencies, based on the Bitcoin code-base, which employ quicker block intervals   [UPDATED 2014-10-27 to correct my embarrassing misunderstanding of mathematics…]

As we’ve talked about, writing to the blockchain is slow and expensive. This is because every node in the entire network needs to verify and slurp in the whole blockchain and all the data it contains. Executing a large smart contract on a blockchain can be prohibitively expensive, and doing things like storing images on blockchains is economically infeasible.


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.
!function(n,t){function r(e,n){return Object.prototype.hasOwnProperty.call(e,n)}function i(e){return void 0===e}if(n){var o={},s=n.TraceKit,a=[].slice,l="?";o.noConflict=function(){return n.TraceKit=s,o},o.wrap=function(e){function n(){try{return e.apply(this,arguments)}catch(e){throw o.report(e),e}}return n},o.report=function(){function e(e){l(),h.push(e)}function t(e){for(var n=h.length-1;n>=0;--n)h[n]===e&&h.splice(n,1)}function i(e,n){var t=null;if(!n||o.collectWindowErrors){for(var i in h)if(r(h,i))try{h[i].apply(null,[e].concat(a.call(arguments,2)))}catch(e){t=e}if(t)throw t}}function s(e,n,t,r,s){var a=null;if(w)o.computeStackTrace.augmentStackTraceWithInitialElement(w,n,t,e),u();else if(s)a=o.computeStackTrace(s),i(a,!0);else{var l={url:n,line:t,column:r};l.func=o.computeStackTrace.guessFunctionName(l.url,l.line),l.context=o.computeStackTrace.gatherContext(l.url,l.line),a={mode:"onerror",message:e,stack:[l]},i(a,!0)}return!!f&&f.apply(this,arguments)}function l(){!0!==d&&(f=n.onerror,n.onerror=s,d=!0)}function u(){var e=w,n=p;p=null,w=null,m=null,i.apply(null,[e,!1].concat(n))}function c(e){if(w){if(m===e)return;u()}var t=o.computeStackTrace(e);throw w=t,m=e,p=a.call(arguments,1),n.setTimeout(function(){m===e&&u()},t.incomplete?2e3:0),e}var f,d,h=[],p=null,m=null,w=null;return c.subscribe=e,c.unsubscribe=t,c}(),o.computeStackTrace=function(){function e(e){if(!o.remoteFetching)return"";try{var t=function(){try{return new n.XMLHttpRequest}catch(e){return new n.ActiveXObject("Microsoft.XMLHTTP")}},r=t();return r.open("GET",e,!1),r.send(""),r.responseText}catch(e){return""}}function t(t){if("string"!=typeof t)return[];if(!r(j,t)){var i="",o="";try{o=n.document.domain}catch(e){}var s=/(.*)\:\/\/([^:\/]+)([:\d]*)\/{0,1}([\s\S]*)/.exec(t);s&&s[2]===o&&(i=e(t)),j[t]=i?i.split("\n"):[]}return j[t]}function s(e,n){var r,o=/function ([^(]*)\(([^)]*)\)/,s=/['"]?([0-9A-Za-z$_]+)['"]?\s*[:=]\s*(function|eval|new Function)/,a="",u=10,c=t(e);if(!c.length)return l;for(var f=0;f0?s:null}function u(e){return e.replace(/[\-\[\]{}()*+?.,\\\^$|#]/g,"\\$&")}function c(e){return u(e).replace("<","(?:<|<)").replace(">","(?:>|>)").replace("&","(?:&|&)").replace('"','(?:"|")').replace(/\s+/g,"\\s+")}function f(e,n){for(var r,i,o=0,s=n.length;or&&(i=s.exec(o[r]))?i.index:null}function h(e){if(!i(n&&n.document)){for(var t,r,o,s,a=[n.location.href],l=n.document.getElementsByTagName("script"),d=""+e,h=/^function(?:\s+([\w$]+))?\s*\(([\w\s,]*)\)\s*\{\s*(\S[\s\S]*\S)\s*\}\s*$/,p=/^function on([\w$]+)\s*\(event\)\s*\{\s*(\S[\s\S]*\S)\s*\}\s*$/,m=0;m]+)>|([^\)]+))\((.*)\))? in (.*):\s*$/i,o=n.split("\n"),l=[],u=0;u=0&&(g.line=v+x.substring(0,j).split("\n").length)}}}else if(o=d.exec(i[y])){var _=n.location.href.replace(/#.*$/,""),T=new RegExp(c(i[y+1])),E=f(T,[_]);g={url:_,func:"",args:[],line:E?E.line:o[1],column:null}}if(g){g.func||(g.func=s(g.url,g.line));var k=a(g.url,g.line),A=k?k[Math.floor(k.length/2)]:null;k&&A.replace(/^\s*/,"")===i[y+1].replace(/^\s*/,"")?g.context=k:g.context=[i[y+1]],h.push(g)}}return h.length?{mode:"multiline",name:e.name,message:i[0],stack:h}:null}function y(e,n,t,r){var i={url:n,line:t};if(i.url&&i.line){e.incomplete=!1,i.func||(i.func=s(i.url,i.line)),i.context||(i.context=a(i.url,i.line));var o=/ '([^']+)' /.exec(r);if(o&&(i.column=d(o[1],i.url,i.line)),e.stack.length>0&&e.stack[0].url===i.url){if(e.stack[0].line===i.line)return!1;if(!e.stack[0].line&&e.stack[0].func===i.func)return e.stack[0].line=i.line,e.stack[0].context=i.context,!1}return e.stack.unshift(i),e.partial=!0,!0}return e.incomplete=!0,!1}function g(e,n){for(var t,r,i,a=/function\s+([_$a-zA-Z\xA0-\uFFFF][_$a-zA-Z0-9\xA0-\uFFFF]*)?\s*\(/i,u=[],c={},f=!1,p=g.caller;p&&!f;p=p.caller)if(p!==v&&p!==o.report){if(r={url:null,func:l,args:[],line:null,column:null},p.name?r.func=p.name:(t=a.exec(p.toString()))&&(r.func=t[1]),"undefined"==typeof r.func)try{r.func=t.input.substring(0,t.input.indexOf("{"))}catch(e){}if(i=h(p)){r.url=i.url,r.line=i.line,r.func===l&&(r.func=s(r.url,r.line));var m=/ '([^']+)' /.exec(e.message||e.description);m&&(r.column=d(m[1],i.url,i.line))}c[""+p]?f=!0:c[""+p]=!0,u.push(r)}n&&u.splice(0,n);var w={mode:"callers",name:e.name,message:e.message,stack:u};return y(w,e.sourceURL||e.fileName,e.line||e.lineNumber,e.message||e.description),w}function v(e,n){var t=null;n=null==n?0:+n;try{if(t=m(e))return t}catch(e){if(x)throw e}try{if(t=p(e))return t}catch(e){if(x)throw e}try{if(t=w(e))return t}catch(e){if(x)throw e}try{if(t=g(e,n+1))return t}catch(e){if(x)throw e}return{mode:"failed"}}function b(e){e=1+(null==e?0:+e);try{throw new Error}catch(n){return v(n,e+1)}}var x=!1,j={};return v.augmentStackTraceWithInitialElement=y,v.guessFunctionName=s,v.gatherContext=a,v.ofCaller=b,v.getSource=t,v}(),o.extendToAsynchronousCallbacks=function(){var e=function(e){var t=n[e];n[e]=function(){var e=a.call(arguments),n=e[0];return"function"==typeof n&&(e[0]=o.wrap(n)),t.apply?t.apply(this,e):t(e[0],e[1])}};e("setTimeout"),e("setInterval")},o.remoteFetching||(o.remoteFetching=!0),o.collectWindowErrors||(o.collectWindowErrors=!0),(!o.linesOfContext||o.linesOfContext<1)&&(o.linesOfContext=11),void 0!==e&&e.exports&&n.module!==e?e.exports=o:"function"==typeof define&&define.amd?define("TraceKit",[],o):n.TraceKit=o}}("undefined"!=typeof window?window:global)},"./webpack-loaders/expose-loader/index.js?require!./shared/require-global.js":function(e,n,t){(function(n){e.exports=n.require=t("./shared/require-global.js")}).call(n,t("../../../lib/node_modules/webpack/buildin/global.js"))}});
Things get a bit more interesting when you replace the single custodian with a federation of notaries by way of a multisignature address. In this model, a federation of entities must sign-off on movements to and from the sidechain, so more parties must be compromised for a failure situation to unfold where the bitcoins frozen on the main chain are stolen.
Peer-to-peer blockchain networks lack centralized points of vulnerability that computer crackers can exploit; likewise, it has no central point of failure. Blockchain security methods include the use of public-key cryptography.[4]:5 A public key (a long, random-looking string of numbers) is an address on the blockchain. Value tokens sent across the network are recorded as belonging to that address. A private key is like a password that gives its owner access to their digital assets or the means to otherwise interact with the various capabilities that blockchains now support. Data stored on the blockchain is generally considered incorruptible.[1]
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).
Imagine over several hours, the camps produced a chain of messages that each required intensive Proof of Work. This means that the majority of the camps had to agree on this chain of messages and each camp can confidently trust the final outcome. It’s important to note here that Proof of Work does not care about the message itself, only that the nodes agreed to the final message. This majority network consensus keeps it secure and provides a solution to the Byzantine Generals Problem, leading to Byzantine Fault Tolerance.
Sidechains as an idea have existed and had been floating around for quite some time now, the bases is to extend the decentralization of trust into other sectors and to other digital assets. However, while this all sounds great it's a perfect example of good in theory but not so much in practice. Nevertheless, this hasn't stopped people from trying with groups such as Blockstream exploring the idea and our friends over at Rootstock co-creating a Sidechain which is allowing Litecoin and Bitcoin to execute smart contracts and all without changing the core software of the original currency.
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.

Aelf uses a consensus algorithm called DPoS (Delegated Proof of Stake) that takes the best of both cooperative and competitive consensus algorithms. DPoS uses votes from stakeholders to achieve consensus. The competitive part is larger stakeholders having an influence on their delegate of choice. The delegates that have the most votes will take their turn to produce a block cooperatively in a sequence. DPoS makes transactions permanent. A rollback isn’t possible so a confirmation can be fast. DPoS is also scalable because anyone can participate in the consensus. Additionally, DPoS is environmentally friendly because electricity isn’t wasted like in Proof of Work.

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.


Sidechains offer a way for new, more radical settings and technologies to be implemented without affecting the main chain. This ensures that the main chain is as secure as possible whilst providing the freedom to explore options which would never be considered for use on the main chain. Sidechains should be quite powerful as they provide cases like anonymity, transparency, confirmation times and turing complete options like rootstock all whilst utilizing bitcoins rather than relying on the hashing power (security) of some far less secure alt coin. That being said… there is quite some controvery regarding blockstream’s funding of most of the core development team and their inflexiblity regarding the max blocksize. This inflexibility has directly contributed to the success of ethereum and it remains to be seen whether the dream of bitcoin maximalism will survive long enough for sidechains with all of the promised functionality to be rolled out. I am skeptical.
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.
Applicature is a blockchain development agency focused on strategic consulting and implementation of Blockchain projects. We provide A-Z ICO launching services: ICO Marketing, technical strategy, concept, white paper, token mechanics, Blockchain architecture, suite of ICO Smart Contracts, ICO Investor Cabinets and a wide range of custom Blockchain solutions: Blockchain Proof of Concepts, forks of different Blockchains with their maintenance, wall ... Read more
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.
We use node 2 to receive a payment of 200 via the smart contract function, receivePayment(). Note that the receivePayment() function can accept a second parameter for the account address that is used to create this transaction. (Note that you can also set web3.eth.defaultAccount = "<…account address…>", after which you can just call receivePayment(200) with one parameter.)

The ShipChain platform unifies shipment tracking on the Ethereum blockchain, using a sidechain to track individual encrypted geographic waypoints across each smart contract. With this system, the meaning of each cryptographic waypoint is only accessible for interpretation by the parties involved in the shipment itself. This gives shippers more visibility across their supply chain, and allows carriers to communicate with ease. 

Ardor is a blockchain platform predicated on childchains (sidechains) that use proof of stake (PoS) consensus. It uses the primary chain as a security chain and the childchains for processing transactions to increase scalability. Their design is specifically focused on speed and efficiency through PoS consensus and removing blockchain bloat through pruning.
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.
Governance: Every enterprise needs to design standards, processes, methods, and tools to develop and operate a private blockchain. To achieve this they will need tools and frameworks such as IDE, testing framework, security auditing tool etc. For long-term successful operation, they also need to develop high-quality documentation. This requires proactive governance. Read more about the importance of the “Fundamental challenges with public blockchains” here.
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).
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.

A consortium blockchain is part public, part private. This split works at the level of the consensus process: on a consortium chain, a pre-selected group of nodes control the consensus process, but other nodes may be allowed to participate in creating new transactions and/or reviewing it. The specific configuration of each consortium chain (i.e., which nodes have the power to authorize transactions via the consensus process, which can review the history of the chain, which can create new transactions, and more) is the decision of each individual consortium.


Function Transactions executed between the locks and unlocks of the main chain tokens don't bloat the main chain. As the technology of a side chain is connected to its main chain, it can be used to build on the developments of the main chain and introduce new features to the market. Child chains serve as the transactional chains of the parent-child architecture, as the parent chain retains minimal features.
¡Por supuesto! para todo ello existen muchas propuestas con soluciones muy interesantes, pero hacer cambios experimentales sobre el código de Bitcoin es arriesgado y, que la mayoría de nodos se adapten, lleva tiempo. Bitcoin es grande y esto hace que la toma de decisiones sea lenta al reflexionarse los cambios de manera muy profunda. Esta toma de decisiones lenta e incapacidad del protocolo de ampliar con modulos las capacidades de Bitcoin es el principal motivo por el que empezaron a salir otras criptomendas centradas en nichos y casos de usos concretos. Era más sencillo clonarse el código abierto de Bitcoin y adaptartlo que esperar a que en Bitcoin se decidiese aceptar su funcionalidad. Este es, principalmente, el motivo por el cual hay cientos de criptomonedas y se necesita un wallet por cada una de ellas, siendo un absoluto caos a veces, ya que todas están desconectadas entre ellas.

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:
Sidechains interactuando con blockchain. Blockstream explica en su paper como, a las sidechains, se les añade una nueva pieza llamada two-way peg. Two-way peg es “el conector” entre ambas cadenas y se encarga de hacer la “magia” para que los bitcoins “salten” a la otra cadena. Juntando ambas cosas obtenemos las pegged sidechain: cadenas laterales conectadas en todo momento. En la imagen puedes observar como, incluso, las sidechain pueden interactuar entre ellas. ¿Llegaremos a un escenario de blockchains interactuando con aspecto fractal?
Write permissions are kept centralized to one organization. Read permissions may be public or restricted to an arbitrary extent. Example applications include database management, auditing, etc. which are internal to a single company, and so public readability may in many cases not be necessary at all. In other cases public audit ability is desired. Private blockchains are a way of taking advantage of blockchain technology by setting up groups and participants who can verify transactions internally. This puts you at the risk of security breaches just like in a centralized system, as opposed to public blockchain secured by game theoretic incentive mechanisms. However, private blockchains have their use case, especially when it comes to scalability and state compliance of data privacy rules and other regulatory issues. They have certain security advantages, and other security disadvantages (as stated before).
The consensus mechanism involves ascertaining transaction validity and uniqueness. Smart contracts address the validity portion. To ensure uniqueness, the protocol program in Corda checks whether any other transaction has used any of the input states of this transaction. If no other transaction has used any of the input states, that this transaction is unique.

The two-way peg is the mechanism for transferring assets between sidechains and is set at a fixed or predefined rate. Bitcoin’s Dynamic Membership Multi-Party Signature (DMMS) plays a vital role in the functionality of the two-way peg. The DMMS is one of Bitcoin’s lesser known but incredibly important components. It is a group digital signature — composed of the block headers in Bitcoin — that has no fixed size due to the computationally powered PoW nature of its blockchain. The Pegged Sidechain paper further describes it as:

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.

Sidechains solve a lot of problems, but at what cost? The introduction of sidechains makes things even more complex and much harder to understand for those who are not actively involved in the blockchain space. This also divides assets, no more “one chain, one asset” adage, which further complicates things. And on a network level there are multiple independent unsynchronised blockchains interacting with each other.
Blockchain Council is an authoritative group of subject experts and enthusiasts who are evangelizing the Blockchain Research and Development, Use Cases and Products and Knowledge for the better world. Blockchain council creates an environment and raise awareness among businesses, enterprises, developers, and society by educating them in the Blockchain space. We are a private de-facto organization working individually and proliferating Blockchain technology globally.    
Recordemos, como hemos mencionado anteriormente, que actualmente son cientos los proyectos y monedas alternativas que trabajan con su propia cadena de bloques, totalmente desconectadas de la de Bitcoin. Todas con su cotización volatil. El problema de estas monedas es que ninguna de ellas dispone del efecto red ni de la seguridad que sí tiene Bitcoin. De hecho muchas, pese a haber implementado propuestas interesantes, se quedan en nada, con miles de horas y esfuerzo “tirado a la basura”. Incluso algunas de ellas han replicado el codigo de Bitcoin, pero también los fallos que en ese momento pudiera tener y mientras que en Bitcoin si se han solucionado, en esa Altcoin no.
Bitcoin’s block interval is ten minutes so it takes about five ten minutes on average for a new transaction to find its way into a block, even if it pays a high fee. This is too slow for some people so they have experimented with alternative cryptocurrencies, based on the Bitcoin code-base, which employ quicker block intervals   [UPDATED 2014-10-27 to correct my embarrassing misunderstanding of mathematics…]
Blockstream believes that to be secure, blockchain systems must be built with open source technology. Towards that goal, we've created the Elements Project, a community of people extending and improving the Bitcoin codebase. As open source, protocol-level technology, developers can use Elements to extend the functionality of Bitcoin and explore new applications of the blockchain. Join the expanding group of individual and corporate developers using Elements to build robust, advanced, and innovative blockchains.
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.

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]

Setting up an environment to test and research blockchain requires an ecosystem with multiple systems to be able to develop research and test. The big players in the cloud industry like Amazon(AWS), Microsoft(Azure), IBM(BlueMix) have seen the potential benefits of offering blockchain services in the cloud and started providing some level of BaaS to their customers. Users will benefit from not having to face the problem of configuring and setting up a working blockchain. Hardware investments won’t be needed as well. Microsoft has partnered with ConsenSys to offer Ethereum Blockchain as a Service (EBaaS) on Microsoft Azure. IBM(BueMix) has partnered with Hyperledger to offer BaaS to its customers. Amazon announced they would be offering the service in collaboration with the Digital Currency Group. Developers will have a single-click cloud-based blockchain developer environment, that will allow for rapid development of smart contracts.
Consider a proof-of-existence application, where you want to authenticate your document in the Ethereum (for example) network, but you do not need your document to be online. So, you will store the hash generated from your document in the blockchain, but the document itself will be in your local machine, out of any blockchain-related structured, being off-chain.
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.
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.[36][37][38][39][40] 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.[41] 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.[42]: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.[36][38] 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."[9][43]
Imagine over several hours, the camps produced a chain of messages that each required intensive Proof of Work. This means that the majority of the camps had to agree on this chain of messages and each camp can confidently trust the final outcome. It’s important to note here that Proof of Work does not care about the message itself, only that the nodes agreed to the final message. This majority network consensus keeps it secure and provides a solution to the Byzantine Generals Problem, leading to Byzantine Fault Tolerance.

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.” 
×