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Fixed Typographical Error in guide/english/blockchain/index.md (#35542) 

* Update index.md

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Rajiv Ranjan Singh 2019-03-19 09:05:56 +05:30 committed by Manish Giri
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@ -41,7 +41,7 @@ Well, now let’s move on in understanding on the construction of the blocks in
A blockchain consists of blocks in which the current block refers to the earlier block using a hash.
For example, the latest block present in a Blockchain would refer / call to the previous block using the previous block’s hash number and would also declare its current hash using a cryptographic hashing algorithm.
For example, the latest block present in a Blockchain would refer/call to the previous block using the previous block’s hash number and would also declare its current hash using a cryptographic hashing algorithm.
When the next node is going to be created, it creates it’s newest hash number using a cryptographic hashing algorithm and indicates the previous hash number in the block itself.
@ -52,7 +52,7 @@ I know some of you coders might assume this is a `linked list`, but hang on 
>
> --Bettina Warburg<sup>1</sup>
Blockchains are often associated with Bitcoin and other cryptocurrencies, but they are not the same thing. Bitcoin was the first to implement the concept of a blockchain. The structure of a blockchain, an ever growing list of records, can be applied to many other fields such as digital identity, supply chain, and even [democracy](https://www.democracy.earth/).
Blockchains are often associated with Bitcoin and other cryptocurrencies, but they are not the same thing. Bitcoin was the first to implement the concept of a blockchain. The structure of a blockchain, an ever-growing list of records, can be applied to many other fields such as digital identity, supply chain, and even [democracy](https://www.democracy.earth/).
A blockchain is built out of a combination of two different “hash-based data structures” (Narayanan, Bonneau, Felten, Miller, & Goldfeder, 2016, p. 64), a hash chain of blocks and a Merkle tree. “In short, the blockchain is a network and a database; it has rules and built-in security; and it maintains internal integrity and its own history” (Depository Trust and Clearing Corporation, 2016, p. 7). In the chain, each block has a pointer to the previous block as well as a pointer to its Merkle tree of transactions. A Merkle tree, sometimes called a hash tree, is a type of tree where each node that has at least one child is marked with a hash of its own children.
@ -87,20 +87,20 @@ Blockchains can be broadly classified into two categories -
2. Permissioned blockchain - these are typically owned by a single party, or by a consortium of organizations. The participants in the network, along with their roles in the network, are pre-determined. These kinds of blockchains are implemented by enterprises who are looking to improve efficiencies across business processes that span multiple parties. Examples of permissioned blockchain platforms would be Ripple, Corda, Quorum and Hyperledger. [Hyperledger](https://www.hyperledger.org) is an open source project run by [The Linux Foundation](https://www.linuxfoundation.org/projects/), and is a set of frameworks and tools which can be used to build permissioned blockchain networks. Of the frameworks available, Hyperledge Fabric has gained a level of maturity required for production level blockchains.
## Bitcoin
The main problem Bitcoin faced was how to achieve distributed consensus while remaining a decentralized system. Distributed consensus is essentially the idea that all the nodes that make up the network must reach a collective agreement without the use of a centralized control. In the Bitcoin blockchain, the nodes must agree on exactly which transactions present on the network are valid. This is difficult in many ways, one of which is the potential for `n` number of nodes to be malicious and not want to follow the consensus of the other nodes. Bitcoin has the benefit of being able to incentivize its nodes to “follow the rules” through rewards and transaction fees because it is a currency system.
The main problem Bitcoin faced was how to achieve distributed consensus while remaining a decentralized system. A distributed consensus is essentially the idea that all the nodes that make up the network must reach a collective agreement without the use of centralized control. In the Bitcoin blockchain, the nodes must agree on exactly which transactions present on the network are valid. This is difficult in many ways, one of which is the potential for `n` number of nodes to be malicious and not want to follow the consensus of the other nodes. Bitcoin has the benefit of being able to incentivize its nodes to “follow the rules” through rewards and transaction fees because it is a currency system.
## Byzantine Fault Tolerance
Imagine the scenario where there is an empire and there are three generals with their respective armies at different positions. All of them must attack in order to win the fight or they can choose to retreat. Their only means of communications are through pigeon posts. But there is a problem, the generals can't trust each other or ensure that the message has not been corrupted along the way. How do they solve this problem? Blockchain essentially does so by listening to information broadcasted by other people, reaching to a consensus of which information is deemed true. As such, this model asssumes that the amount of "traitors" do not exceed more than 1/3 of the entire network.
Imagine the scenario where there is an empire and there are three generals with their respective armies at different positions. All of them must attack in order to win the fight or they can choose to retreat. Their only means of communications are through pigeon posts. But there is a problem, the generals can't trust each other or ensure that the message has not been corrupted along the way. How do they solve this problem? Blockchain essentially does so by listening to information broadcasted by other people, reaching to a consensus of which information is deemed true. As such, this model assumes that the amount of "traitors" do not exceed more than 1/3 of the entire network.
## Modern Use Cases of Blockchain
- Asset Tokenization : Using blockchain technology, previously illiquid assets can now be converted into its tokenized form and cheaply and efficiently fractionalized, traded and settled on chain (rather than go through the lengthy process of clearing and settlement process through third parties like clearing houses)
- Supply Chain Management : Blockchains allow multiple parties to access a database to act as the single source of truth. Recorded transactions are immutable, are append only and provide a time stamped audit trail.
- Digital Identity : A self sovereign ID can be used to verify identity without needing an individual to produce numerous documents and paperwork each time they need their identity verified. This could be done with a single key that can be matched against an immutable ledger. The digital ID can also collect other online information about a user’s identity like social security information, medical records and social media credentials and have that stored securely on the blockchain.
- Asset Tokenization : Using blockchain technology, previously illiquid assets can now be converted into its tokenized form and cheaply and efficiently fractionalized, traded and settled on the chain (rather than go through the lengthy process of clearing and settlement process through third parties like clearinghouses)
- Supply Chain Management : Blockchains allow multiple parties to access a database to act as a single source of truth. Recorded transactions are immutable, are append-only and provide a time-stamped audit trail.
- Digital Identity : A self-sovereign ID can be used to verify identity without needing an individual to produce numerous documents and paperwork each time they need their identity verified. This could be done with a single key that can be matched against an immutable ledger. The digital ID can also collect other online information about a user’s identity like social security information, medical records and social media credentials and have that stored securely on the blockchain.
- Energy Market : Blockchain technology can enable the smart metering of electricity generated through an individual’s solar panels to be recorded, traded and settled on a ledger.
- Healthcare : Using blockchain technology to record patient information on a distributed ledger can allow different stakeholders conditional access to a single source of truth where each interaction with a patient’s health data can be recorded on a ledger as a transaction with a time stamped audit trail.
- Healthcare : Using blockchain technology to record patient information on a distributed ledger can allow different stakeholders conditional access to a single source of truth where each interaction with a patient’s health data can be recorded on a ledger as a transaction with a time-stamped audit trail.
## Issues
Whilst blockchain technology is undoubtedly elegant, there are several problems that its presence brings, the main one being use my malicious third parties. Due to the extremely secure nature of blockchain, its technologies are often used by criminals to carry out transactions, which are impossible for governments to track.
Whilst blockchain technology is undoubtedly elegant, there are several problems that its presence brings, the main one being used by malicious third parties. Due to the extremely secure nature of blockchain, its technologies are often used by criminals to carry out transactions, which are impossible for governments to track.
An unavoidable issue with the security of the system itself is the so-called "51% attack" whereby if more than half of the nodes on the network are issuing false ledgers, the "lie" becomes truth. This means that the global network has to constantly be monitored to make sure that nobody can gain this kind of influence.