class 1.txt

Immutable --> Once data is inserted into the ledger, it cant be modified


normal --> insert username, age, department into employee table (Create, Read, Update, Delete)
blockchain --> we can only insert data. update and delete is not possble.


Consensus --> Establishment of agreement among multiple nodes in the system


crypto exchange --> similar to normal exchnages, we trade digital coins (eth, sol, pol)

IOTA  --> Framework for IOT use case implementation (device - device communication secured on the ledger)

public vs private blockchains:
-------------------------------

public  --> involves crypto, high txn fees, data is visible to everyone 

private --> hyperledger (elimintaes crypto tokens, high tx fee) 

(bank of 6 in a single network) ---> private blockchain ---> decentalized


Banks want to form a Credit history of account holders (Credit Ledger) ---> 

Use case: Credit ledger

Problem statement: Banks takes long turn around time to sanction loans and also depend on third party aganecies for cibil score (3-5 business days)

Solution approach: 

Banks will coordinate among them self to ditribute each others data on the status of active loans/inactive/high credit users

write a smart contract by building these logics

customer id, crdit score indicator, eligible


Smart contract:
---------------- 

variables/identifiers to be shared/stored on the ledger

private data collections (current loan amount, no of emi due)

public 

var 

 ( username
   customer id 
   credit indicator
   eligible status )

methods

 queryCreditdata()
 eligiCriteria()
 Loanstatus()


tranactions between two different blockchain networks ----> Interoperability 

public blockchains ---> Oracles and Bridges


private blockchains ---> solution (bridges that enable data transfer b/w multiple networks)



network 1 ----- 6 banks

Intermediate network (even the bridges are to be truly distributed) --- ??

network 2 ----- 4 Insurance firms (claim verification)


Node is nothing but a server/machine/system --> which validtaes and records the data

HYperledger Cactus ---> Interoperability issues



Node ---- Machine

Ledger --- File system in the machine

Block --- part of this file system in the machine

multiple blocks will form the ledger



https://lms.simplilearn.com/



Money transfer b/w Banks:
--------------------------


1. Bank1 -- sender bank

2. Bank2 -- receiver bank


Banks employ a regulator/intermediatary which establishes the trust among them


bank1 --> 1000 CR


Intermediatary ----> which have some funds as collateral stored for all banks (bank have to deploy a minimum guarantee fee of 5000 CR)

(1000 cr, bank1, bank2)
 
 (5000 cr)


bank2 --> 1000 CR (bankruptcy)


Data structure of a block:
--------------------------

type Block 

{

 Header
  var current hash string
  var previous hash string
  var timestamp timestamp
  var block number int

 Body
  transactions [] string

 chain *Block

}


Sequence of such blocks linked by previous hash forms blockchain

Linked List of blocks appended to each other by Hashes


Public Blockchain:

 Bitcoin ---> used as only crypto token, no entreprises can build appications on top of bitcoin(lacks the feature of smart contracts)
 Ethereum --> which is an alternative for bitcoin, which also supports the business logic to embed into the network(smart contract) and they can create, control and manage the entire asset lifcycles
              (users have to pay txn fee in form of crypto token (ETH))

Private Blockchain:

 HYperledger ---> Linux and IBM initiative
             (eliminates the need for crypto tokens, txn fee)
             (code is open source, smart contract)  

 R3 Corda

 IOTA

 Multichain



Merkle Hash:

Block can either have 1 transaction or multiple transactions

 blocks are created ----> either for specific period or specific size
                          (100 txn) or 1 MB size (25 txn)

block1 ---> 100

block2 ---> 50

block3 ----> 75



Banks 5
-------------

Bank1 ---> [b1 b2 b3 b4 b5]

Bank2 ---> [b1 b2 b3 b4 b5] ---> goes down

smart contract will produce same result for a transaction for all the nodes in the network

100 tnx ----> 50 txn ----> 5-10 min ---> staled network

txn size (or) no of txn (or) time period 



block1 ---> 10 txn {t1 t2 t3 t4 ---- t10}
       ---> creates a merkle hash/root hash ---> ABC12345678910

any node in the network wishes to validate if a block is created correctly

input -- {t1 t2 t3 t4 ---- t10}

 CreateBlock(input) (output)

  {
    createhash = logic ({t1 t2 t3 t4 ---- t10})
    storehash  = ABC12345678910
  }


user1 ----> user2 (balance transfer of 100 USD)

node has a smart contract ---> validates balance of user1 (>100 usd)
 t1--> b1 ---> Chain

Enterprise use cases:
----------------------

 Onboarding process will happen. Banks will give out their certifictaes, ip adrress, port, dns names
 banks which are part of this onboarding process will only accept the traffic

network {

 cert, ip, port, dns 

 }



Token is a digital asset created and managed on the blockchain by emebding functions in a smart contract


Babks wish to create a digital token (CBDC)


type Token struct {

 Token name   string
 Token supply int
 owner        string
 expiry date  date
 walletid     string
 bankname     string
}


type Itoken Interface {

 create()
 transfer()
 checkbalance()
 burn()

}

 ERC20 ---> Fungible Tokens (digital currency)
  
 CBDC ---> INR

(token serialnumber 123  = token serialnumber 456)

 

ERC721 ---> Non Fungible tokens (digital assets)

 token for land registry

type Land struct {

 Land token id
 Land cordinates 
 Locality
 Area
 sqft
 price
 purchased date
 owner
 Status
}



type Iland interface {

 create()
 transfer()
 checkownership()

}


 land1 ---> serail number 111 ---> 3 CR
 land2 ---> serial number 222 ---> 5 CR


Database:
------------

1 usera - balance - 100 USD

txn (usera, 100)

Update operation is performed on the existing data record in the database

1 useraa - balance - 150 USD



Blockchain:
-------------

1 usera - balance - 100 USD

txn (usera, 100) -- credit txn
                 -- debit txn (50)

insert operation is performed on the existing data record in the database


1 usera - balance - 100 USD cr
1 usera - balance - 100 USD cr
1 usera - balance -  50 USD db



Token is an object
Transaction is an action on tht object (credit, debit, getbalance)



ledger -----> log files/encrypted ---> hashes


token:

 land id 123
 cord  24 26
 ownnership user A ---> old record


usera--->userb

land id 123
 cord   24 26
 ownsehrip user b ---> new entry record


smartcontract ----> getallhistiry(123)
            ---->it gives 2 reords as output
             userA --- old
             userB --- new

blocks ---> txn details --->

Use Case discussion:
-------------------------

Big Bazar and Reliance merger

a. convert credit card reward points to Big bazar coupons
b. users were also purchasing coupons from retail stores
c. other ways


all of these coupons were invalidated/went in vain

on an avg 100 users ----> 2000 INR ---> 2 Lacs on coupons which went wasted

Reliance ----> reward scheme went in vain

blockchian based reward base system:
-------------------------------------

 query the token id from ledger and validated it status


Reward based systems
Online aucion systems
NFT market places