Blockchain for Business. Группа авторов

working of the Blockchain. In this section of this chapter the basic architecture of the blockchain will be discussed, but moving ahead towards the architecture one should discuss few of the important terms which will be majorly used in the security and privacy aspects of the blockchain.

      1 Immutable—Making the ledge secures with the digital signature or hash function.

      2 POW—Proof of work, which is a protocol which has the main goal to deterring the cyber attacks.

      3 Hash—It is unique value being assigned by the set of rules/algorithms/functions or the combination of all to make the ledger unique and separated from other blocks.

      4 Digital Signature—It is another means of securing measure of the ledge, so that the data must be verified and treated as authentic.

      5 Mining—Mining in general an activity to collect the useful out of whole.

      These are the major terms which we may encounter in this chapter commonly. You will get to know more about these terms in the coming sections of this chapter, but before that the different types of blockchain architectures will be discussed below.

      Logically, a blockchain is a chain of blocks which contain specific information (database), but in a secure and genuine way that is grouped together in a network (peer-to-peer) as shown in Figure 1.2. In other words, blockchain is a combination of computers linked to each other instead of a central server, meaning that the whole network is decentralized (Figure 1.3) [3].

      Understanding it with the help of a relevant example like work on the Google docs and wait for others to make the necessary changes if required the same scenario is in the decentralized architecture of the blockchain. Blockchain allows and permit us to make the relevant docs shared rather copied [2, 3]. This distributed piece of information (ledger) provides the trust factor and the security of data.

      Figure 1.2 The diagrammatic representation of the types of blockchain architecture [3].

      Figure 1.3 Figure states the types of blockchains in trend.

      Whereas the exact different case is there in the centralized architecture, the information or ledger which was shared is now kept private and shared with the authentic and with those who have required and necessary authority to access the data, which means now the data/ledger is kept private and not shared globally.

      Now what left the distributed architecture, in this type a local copy of the ledger is given to all the parties/entities, so that the major alterations are done by the high officials or the major party whereas the information of the ledger is being distributed within the complete locality.

Table 1.1 will make the concept more clear and transparent to understand.

      Table 1.1 A novel comparison among public, consortium, private blockchain.

Property	Public blockchain	Consortium blockchain	Private blockchain
Consensus determination	All miners	Selected set of nodes	Within one organization
Read permission	Public	Public or restricted	Public or restricted
Immutability level	Almost impossible to tamper	Could be tampered	Could be tampered
Efficiency (use of resources)	Low	High	High
Centralization	No	Partial	Yes
Consensus process	Permission less	Needs permission	Needs permission

      1.1.1 Public Blockchain Architecture

      A public blockchain architecture states that the data or the ledger and access to the system is available to anyone who is willing to participate for instance Bitcoin, Ethereum, and Litecoin blockchain systems are public and can be accessed by anyone globally [2, 3].

      1.1.2 Private Blockchain Architecture

      An opposite situation to the public blockchain architecture, the private system is highly controlled and managed only by users from a specific organization or institution or the company or authorized users who have an invitation for participation.

      1.1.3 Consortium Blockchain Architecture

      This blockchain structure can consist of a few organizations [3]. In a consortium, procedures are set up and controlled by the preliminary assigned users. It a system that is ‘semi-private’ and has a group which controls it, but works across different organizations. In simple terms it can be said as a distributed blockchain architecture.

      The following table provides a detailed comparison among these three blockchain systems [3]:

1.2 The Privacy Challenges of Blockchain

      In the previous section, the basic introductory part of blockchain is discussed. In this part the requirement of privacy including different tools and techniques are going to be discussed.

      As shown in Figure 1.4 in this section, a blockchain is a highly secure mechanism or technology which allows the user to make secure and safe transactions [1, 3]. It is a statement said by many engineers, scientist and researchers but how......?

      To know about this said statement in detail, one should back track a blockchain and need to collect the required information about how this technique is too strong and safe for transactions. Here we also need to know if this technology is too tremendous then why was it being garbaged in 1991 and then again re-launched in 2004 [1].

      The working paradigm of a blockchain:

      Let’s have a closer and a deeper look at Figure 1.4 that illustrates what a block is in a blockchain.

      Each block in a blockchain consists of:

       certain data

       the hash of the block

       the hash from the previous block (HOPB).

      The data stored in each block completely depends on the type of blockchain. For instance, in the Bitcoin blockchain structure, the block maintains data about the receiver, sender, and the amount of coins.

A hash is a unique set of alphanumeric codes which is auto generated by the algorithms and the functions of the blockchain (in general terms it can be treated as the fingerprint, long record consisting of some digits and letters). Each block hash is generated