 basics of blockchain myself Rashmi Dixie. Learning outcome at the end of this session students will be able to explain basics of blockchain. So, before that we will spend a couple of minutes on different types of encryption. There are two types of encryption symmetric and asymmetric. Now what happens in symmetric? A private key shared by both user. If Alice wants to send a document to Bob, she will use private key to encrypt that document. At Bob's side, Bob will decrypt the document using the same private key. If intruder able to get that private key, he will get that document. So, that is a problem that private key may be hacked by the intruder. Now in asymmetric encryption, Alice and Bob both generate pair of key. One is their private key and another one is public key. So, as the name indicate private key with themselves and public key is place at public place or known to everyone who are there in the network for the communication. While sending a document, Alice will encrypt that document using Bob's public key as Bob public key is publicly available. So, at Bob's side, Bob will decrypt the document using his own private key. So, private key is known to Bob only. So, other than Bob, no one is able to decrypt the document. So, that is one of the advantage of asymmetric encryption. So, applications of asymmetric encryption SSL SSH PGP that is a pretty good privacy and Bitcoin blockchain which is the one of the recent trend and hot topic of today's or current technology. So, what is blockchain? It is a decentralized computation and information sharing platform two characteristic. Decentralized and information sharing platform that enables multiple authoritative domains. So, many users are working who do not trust each other to cooperate, coordinate and collaborate in a rational decision making process. So, it is a decentralized computation and information sharing platform. So, what is decentralized? Let us look at this slide. There are three types of system or communication, centralized, decentralized and distributed. Now, centralized as the name suggests or the figure, there is a single point of authority just like a client server architecture. Multiple clients connected to single server, server take the decision, all the data is stored on the server. So, advantage it is easy for a deploy? Yes, it is easy for a maintenance? Somewhat yes, but what is the main disadvantage? If this single point failure occur, no replica or no copies of the data is available. So, from centralized move to decentralized. Instead of single point of authority or server here multiple authorities who are able to take the decision. So, decision from centralized move to decentralized. Now, in distributed each node is work as authority means decentralized to the higher extent is distributed. Now, in decentralized each authority maintain a set of data or available copies of a data. So, if failure of a one point or one node occur there will be no problem data is available. In distributed it is a subset of decentralized. Now, in decentralized the decision is taken depending upon the aggregate of node decision. Here, decentralized functionality of decision. Now, move back to the definition of block chain. Now, it is a decentralized computation. Yes, information sharing platform understand. Yes, multiple authority domains who do not trust each other to cooperate, coordinate and collaborate in a rational decision making. So, in block chain it is just like a secure chain where each block store their data may transfer their data in a encrypted mode. When they are sharing or transferring the time stamp is added to that particular record which is stored in a database. So, these are the some characteristic of a block chain open. Anyone can access block chain, distributed or decentralized as we have seen not under the control of single authority. The decision depends on aggregate decision of node. Efficient, fast and scalable new blocks can be added, can be removed, verifiable. Everyone can check the validity of information because each node maintains a copy of transition. Permanent, once a transition is done it is persistent and can't be altered. So, let us see what are the different types of block chain. So, block chain mainly divided into private and public. So, private again divided into two parts completely private and hybrid. We will see one by one public. As the name suggests it is publicly available, fully decentralized that is one of the characteristics. So, no problem everyone can read, write and send transition to that particular block. Participate in a collaborative process. When multiple blocks or multiple nodes are available they participate in a collaborative process for particular decision for a particular completion of works. So, public block chain are publicly available. Anyone can read write there is a no restriction on access. Now, what happens in private? Private as name suggests it is under some organization. One of the organization have authority or restriction for the providing permissions. Writing permissions are centralized and is confined to one organization. These are usually used by organization. Now hybrid it is a mixture of public and private. For some it is act as a private or for other it is act as a public. Concerns process is confined to predefined set of nodes. Some nodes are public, some nodes are private. Public can read and hence carry a partially decentralized character. So, all of you student please pause the video for some time and select appropriate block chain feature. Peer to peer, decentralized, incorruptible and immutable and all of the above. So, let us hope all of you try to answer. So, peer to peer, yes, decentralized, yes, incorruptible and immutable, yes means all of the above. Peer to peer means each node is connected to another node. So, transaction from one node to another node whenever there is a transition timestamp is attached with that particular record and that record is encrypted with hash function. So, if some third party changes that record that hash function changes. So, there is a no monitoring of third party. Decentralized there is a no single authority to take a decision. Decision depends on the aggregate function of nodes decision. And as we have already discussed or discussed before few couple of minutes incorruptible and immutable means record with hash function. So, if record changes hash function changes means encryption changes. So, it is somewhat fixed. So, these are the main features of block chain. So, nowadays what are the different applications of block chain? Cloud storage, yes, cryptocurrency, health care, smart contracts, elections, digital identity management. So, before we will summarize within a couple of minutes. So, block chain in a distributed or decentralized environment. It is a sharing of information sharing done in a very secure way with timestamp hash function. Each block has their own hash function which depends on value of record. So, encryption or sharing of information done without monitoring of third party. So, as we know how it provides a security. So, these are the different applications of block chain. Cloud storage, cryptocurrency, bitcoin, health care, smart contracts, government tender, e-tenders, elections, digital identity management. So, this is one of the thing which provides a high level of security. So, these are the references. Thank you.