The document provides information to differentiate between Blockchain and Hyperledger: - Blockchain is a decentralized technology that records immutable transaction records in blocks secured by cryptography. It can be public, private, or consortium. Hyperledger is a platform that allows building private blockchains where access is limited.

2. Beginner level

3. 1 Differentiate between Blockchain and Hyperledger.
• Blockchain is a decentralized
technology of immutable records
called blocks, which are secured using
cryptography
• Hyperledger is a platform/
organization that allows people to
build private Blockchain
Blockchain Hyperledger

4. 1 Differentiate between Blockchain and Hyperledger.
• Blockchain is a decentralized
technology of immutable records
called blocks, which are secured using
cryptography
• Blockchain is divided into public,
private and consortium Blockchain
• Hyperledger is a platform/
organization that allows people to
build private Blockchain
• Hyperledger is a private Blockchain
where the access to Blockchain data
is limited to predefined users
Blockchain Hyperledger

5. 1 Differentiate between Blockchain and Hyperledger.
• Blockchain is a decentralized
technology of immutable records
called blocks, which are secured using
cryptography
• Blockchain is divided into public,
private and consortium Blockchain
• It can be used in multiple fields like
(business, governments, healthcare
etc.)
• Hyperledger is a platform/
organization that allows people to
build private Blockchain
• Hyperledger is a private Blockchain
where the access to Blockchain data
is limited to predefined users
• Hyperledger is used in Blockchain for
enterprise based solutions
Blockchain Hyperledger

6. 2
In simple terms, Blockchain technology is a distributed ledger, which stores transaction details in the form of
immutable records (blocks) which are secured using cryptography
How would you explain Blockchain Technology to someone who doesn't know it?

7. 2
Consider an example of a school where Blockchain is similar to a digital report card of a student:
How would you explain Blockchain Technology to someone who doesn't know it?
1 2 3 4
Each block contains students records
which has a label (stating the date
and time) of when the record was
entered
Here, neither the teacher nor the
student will be able to modify the
record of report cards
Also, the teacher owns a private key that allows
him/her to make new records and the student owns a
public key that allows him/her to access the report
card at anytime
This method makes the data both
accessible and secure
X

8. 3 What is Merkel tree?
A Merkle tree is a data structure which is used for verifying a block. It is in a form of a binary trees containing
cryptographic hashes.
Each leaf node is
a hash of a block of
transaction data
Merkel root
Hash AA Hash BB
Hash a Hash b Hash c Hash d
Data
Block 01
Data
Block 02
Data
Block 03
Data
Block 04
0r0234….
0a0234…. 002d34….
ja0234…. da0234…. da0ss4…. ffa0ss4….

9. 3 What is Merkel tree?
A Merkle tree is a data structure which is used for verifying a block. It is in a form of a binary trees containing
cryptographic hashes.
Each non-leaf node is
a hash of its leaf node
Merkel root
Hash AA Hash BB
Hash a Hash b Hash c Hash d
Data
Block 01
Data
Block 02
Data
Block 03
Data
Block 04
0r0234….
0a0234…. 002d34….
ja0234…. da0234…. da0ss4…. ffa0ss4….

10. 3 What is Merkel tree?
A Merkle tree is a data structure which is used for verifying a block. It is in a form of a binary trees containing
cryptographic hashes.
Merkel root
Hash AA Hash BB
Hash a Hash b Hash c Hash d
Data
Block 01
Data
Block 02
Data
Block 03
Data
Block 04
Merkle root or hash root is
the final hash of all the
transaction hashes
0r0234….
0a0234…. 002d34….
ja0234…. da0234…. da0ss4…. ffa0ss4….

11. 4 What do you mean by blocks in the Blockchain technology?
Blockchain is a distributed database of immutable records called blocks, which are secured using cryptography
Transaction
Details
Nonce
Target Hash value
Previous Hash
Block

12. 4 What do you mean by blocks in the Blockchain technology?
Recorded in chronological order
Once the data is
recorded, it cannot be
changed
A block is like a record of transactions. Each time a block is verified, it gets recorded in chronological order

13. 5 How is Blockchain distributed ledger different from a traditional ledger?
Blockchain distributed
ledger
Traditional ledger
Available
Yes
Yes
No
Yes
No
Transparency
Irreversible process
Security
Central authority
Identities can be hidden
Single point of failure
Criteria
Unavailable
No
No
Yes
No
Yes

14. 5 How is Blockchain distributed ledger different from a traditional ledger?
Blockchain distributed
ledger
Traditional ledger
No
Done by the participants
across the network
Shared among all the
participants
Modifying data
Validation
Copy of the ledger
Criteria
Possible
It is done by the central
authority
Not shared among all the
participants

15. 6 How can you identify a block?
Every block consists of four fields
Hash of previous block
Nonce
Hash
Transaction
data
It holds the hash value
of the previous block

16. 6 How can you identify a block?
Every block consists of four fields
Hash of previous block
Nonce
Hash
Transaction
data
Contains details of
several transactions

17. 6 How can you identify a block?
Every block consists of four fields
Hash of previous block
Nonce
Hash
Transaction
data
Contains details of
several transactions
Nonce is a random
value which is used to
vary the value of hash

18. 6 How can you identify a block?
Every block consists of four fields
Hash of previous block
Nonce
Hash
Transaction
data
Contains details of
several transactions
Hash is a alphanumeric
value which is used to
identify a block

19. 6 How can you identify a block?
Every block consists of four fields
Hash of previous block
Nonce
Hash
Transaction
data
Contains details of
several transactions
The hash address is the unique
identification of a block. It is a hex value
of 64 characters that has both letters and
digits. It is obtained by using the SHA -
256 algorithm

20. 6 How can you identify a block?
Every block consists of four fields
Hash of previous block
Nonce
Hash
Transaction
data
Transaction data
Hash (prev. block)
Nonce
Hash value
Hashing
Algorithm
(SHA256)
Header

21. 7 What is cryptography? What is its role in Blockchain?
Blockchain uses cryptography to secure users identities and ensures transactions are done safely with
a hash function
Cryptography:
• Cryptography uses public and private keys to encrypt and decrypt data
• In Blockchain network, public key can be shared with all the Bitcoin users
• A private key is kept secret with the user
Input data Cryptography
Private key
Public key
424242..

22. 7 What is cryptography? What is its role in Blockchain?
Blockchain uses cryptography to secure users identities and ensures transactions are done safely with
a hash function
SHA 256
Secure
Hashing
Algorithm
Stands for the number
of bits it takes up in
memory
SHA 256
Hash function takes an input data and returns an alphanumeric output of 64
characters
Hashing function:

23. 8 What are the different types of Blockchains?
Public
Blockchain
Private
Blockchain
Consortium
Blockchain
Blockchains are of three types:

24. 8 What are the different types of Blockchains?
Public
Blockchain
Private
Blockchain
Consortium
Blockchain
Blockchains are of three types:
Ledgers are visible to all the users on
the internet and any user can verify and
add a block of transactions to the
Blockchain
Examples: Bitcoin and Ethereum

25. Consortium
Blockchain
8 What are the different types of Blockchains?
Blockchains are of three types:
Public
Blockchain
Private
Blockchain
Ledgers are visible to all the users on
the internet but
only specific users in the organization
can verify and add transaction
Example: Blockstack

26. 8 What are the different types of Blockchains?
Public
Blockchain
Private
Blockchain
Consortium
Blockchain
Blockchains are of three types:
Here, the consensus process is
controlled by only specific nodes.
However, ledgers are visible to all the
participants in the Consortium
Blockchain
Example: Ripple

27. 9 What happens when you try to deploy a file with multiple contracts?
• In Blockchain, deploying a file with multiple contracts is not possible
• The compiler only deploys the last contract from the uploaded file and the remaining contracts are neglected
Smart
contract
File

28. 1
0
What is Genesis block?
• Genesis block is the first block in the Blockchain
which is also known as block 0
• In the Blockchain , it is the only block that doesn’t
refer to its previous block
• It defines parameters of the Blockchain such as,
o level of difficulty,
o consensus mechanism etc. to mine blocks
Genesis block

29. 1
0
What is Genesis block?
• Genesis block is the first block in the Blockchain
which is also known as block 0
• In Blockchain , it is the only block that doesn’t
refer to its previous block
• It defines parameters of the Blockchain such as,
o level of difficulty,
o consensus mechanism etc. to mine blocks
Genesis block

30. 1
0
What is Genesis block?
• Genesis block is the first block in the Blockchain
which is also known as block 0
• In Blockchain , it is the only block that doesn’t
refer to its previous block
• It defines parameters of the Blockchain such as,
o level of difficulty,
o consensus mechanism etc. to mine blocks
Consensus mechanism
Level of difficulty

31. Intermediate level

32. • In Blockchain, to generate a digital signature, transaction details are passed through a one-way hash function i.e.,
SHA-256
• Then, the output value is passed through a signature algorithm (like ECDSA) with the user’s private key
• The encrypted hash along with other information (such as the hashing algorithm) is called as the digital signature
11 How is the hash (Block signature) generated ?
Transaction
details
Passed through hash
function
(SHA256)
=+
Digitally signed
document
Signature
algorithm
The output is passed through a
signature algorithm with the
user’s private key

33. List down some of the extensively used cryptographic algorithms?
1 2 3 4 5
RSA
(Rivest-Shamir-Adleman) Triple DES
Blowfish
1
2
SHA - 256
Ethash

34. What is a smart contract and list some of its applications
Some of the applications are:
Shipment of goods
can be easily tracked
using smart contracts
Smart contracts can
protect the ownership
rights
Smart contracts
can identify false
claims and prevent
forgeries
Smart contracts
can be helpful
to facilitate wage
payments
Transportation Protecting copyrighted
content
Insurance Employment
contract
1
3
Smart contracts are self-executing contracts which contains the terms and conditions of an agreement between
the peers

35. Ethereum is a Blockchain based distributed computing platform featuring smart contract functionality that
enables users to create and deploy their decentralized applications
Test network
(like Ropsten, Kovan and
Rinkeby)
Private network
Live network
(main network)
There are three types of network in Ethereum:
What is Ethereum network and how many Ethereum networks are you familiar with?
1
4
What is Ethereum network and how many Ethereum networks are you familiar with?

36. Ethereum is a Blockchain based distributed computing platform featuring smart contract functionality that
enables users to create and deploy their decentralized applications
Test network
(like Ropsten, Kovan and
Rinkeby)
Private network
Live network
(main network)
There are three types of network in Ethereum:
Smart contracts are
deployed on main
network
What is Ethereum network and how many Ethereum networks are you familiar with?
1
4
What is Ethereum network and how many Ethereum networks are you familiar with?

37. Ethereum is a Blockchain based distributed computing platform featuring smart contract functionality that
enables users to create and deploy their decentralized applications
Private network
Live network
(main network)
There are three types of network in Ethereum:
Test networks allow users to run
their smart contracts with no fees
before deploying it on the main
network
Test network
(like Ropsten, Kovan and
Rinkeby)
What is Ethereum network and how many Ethereum networks are you familiar with?
1
4
What is Ethereum network and how many Ethereum networks are you familiar with?

38. Test network
(like Ropsten, Kovan and
Rinkeby)
Ethereum is a Blockchain based distributed computing platform featuring smart contract functionality that
enables users to create and deploy their decentralized applications
Live network
(main network)
There are three types of network in Ethereum:
Private networks are those which
are not connected to the main
network
Private network
What is Ethereum network and how many Ethereum networks are you familiar with?
1
4
What is Ethereum network and how many Ethereum networks are you familiar with?

39. Where do nodes run smart contract code?
Nodes run smart contracts code on Ethereum Virtual Machine (EVM). It is a virtual machine designed to operate
as a runtime environment for Ethereum based smart contracts
Smart
contract
EVM
EVM is operated in a sandboxed environment (isolated from main network). This is a perfect testing environment
1
5
Note: Once a user successfully runs the code on EVM, he/she can deploy the smart contract in the main network

40. What is a Dapp and how is it different from a normal application?
Normal App
• Normal application has a back-end code which
runs on a centralized server
• A Dapp is a decentralized application which
is deployed using smart contract
Dapp
Normal
application
1
6

41. What is a Dapp and how is it different from a normal application?
Normal App
• Normal application has a back-end code which
runs on a centralized server
• It’s a computer software application that is hosted
on a central server
• A Dapp is a decentralized application which
is deployed using smart contract
• A Dapp has its back-end code (smart
contract) which runs on a decentralized
peer-to-peer network
Front-end
Smart
contract
Blockchain
(P2P network)
(Back-end code)
Front-end API Database
(runs on server)
Process:Process:
Dapp
Normal
application
1
6

42. Name some leading open source platforms for developing Blockchain applications.
• Ethereum is one of the popular platforms for building Blockchain based applications
• Eris is used for building enterprise-based solutions
• Also, some of the widely used platforms for building Blockchain are
Hyperledger Multichain OpenchainErisEthereum
1
7

43. What is the very first thing you must specify in a Solidity file?
pragma solidity ^0.4.17;
It is necessary to specify the version number of Solidity at the beginning of a code as it eliminates
incompatibility errors which can arise while compiling with another version
1
8

44. What is the difference between Bitcoin and Ethereum ?
Bitcoin Ethereum
P2P Currency
Proof of work
SHA-256
10 Minutes (approx.)
12.5 BTC
Optional
1 BTC = 6934.34 USD
Concept
Consensus mechanism
Hashing Algorithm
Time taken to mine a block
Reward
Transaction fee
Value (8/21/18)
Criteria
P2P currency and smart contract
Proof of work/ Proof of stake
Ethash
12-15 seconds
3 ETH
Fee is calculated in gas
1 ETH = 278.98 USD
1
9

45. What is nonce and how is it used in mining?20
Determine the
nonceMining
Less than
target value
< targetNonce
Hash value
002AE4..
• In Blockchain, mining is a process to validate transactions by solving a difficult mathematical puzzle called proof of
work
• Proof of work is the process to determine a number (nonce) along with a cryptographic hash algorithm to produce a
hash value lower than a predefined target
• Nonce is a random value which is used to vary the value of hash so that the final hash value meets the hash
conditions

46. Advanced level

47. Name the steps that are involved in the Blockchain project implementation.
Requirement
identification
1
21
 Identifying the problem and goal
 Identifying the most suitable consensus mechanism
 Identifying the most suitable platform
 Implementation and deployment costs

48. Name the steps that are involved in the Blockchain project implementation.
Requirement
identification
1 2
21
In this step, an individual evaluates
all requirements and decides a
suitable blockchain platform to be
implemented
Planning stage

49. Name the steps that are involved in the Blockchain project implementation.
Requirement
identification
Planning stage Development and
implementation of
project
1 2 3
21
 Designing the architecture
 Designing the user interface
 Building the APIs

50. Name the steps that are involved in the Blockchain project implementation.
Requirement
identification
Planning stage Development and
implementation of
project
Controlling and
monitoring the project
1 2 3 4
 Applying proof of concept (POC)
 Identifying and fixing issues
21

51. Explain a real-life use-case where Blockchain is being used.
Distributor Retailer PurchaserSupplier
Raw
materials
Manufacturing
Verify for quality assurance
In supply chain management, smart contracts provide permanent transparency and
validation of transactions shared by multiple supply chain partners
22

52. List and explain the parts of EVM memory.
The memory of an EVM is divided into three types,
Storage Memory Stack
23

53. List and explain the parts of EVM memory.
The memory of an EVM is divided into three types,
• Storage values are stored
permanently on the Blockchain
network
• It is extremely expensive
Storage Memory Stack
23

54. List and explain the parts of EVM memory.
The memory of an EVM is divided into three types,
• Storage values are stored
permanently on the Blockchain
network
• It is extremely expensive
Storage Memory Stack
23
• Memory is a temporary modifiable
storage
• It can be accessed only during
contract execution. Once the
execution is finished, its data is lost

55. 1 List and explain the parts of EVM memory.
The memory of an EVM is divided into three types,
Note: Memory and stack are relatively much cheaper than storage
• Storage values are stored
permanently on the Blockchain
network
• It is extremely expensive
• Memory is a temporary modifiable
storage
• It can be accessed only during
contract execution. Once the
execution is finished, its data is lost
• Stack is a temporary and non-
modifiable storage
• Here, when the execution completes,
the content is lost
Storage Memory Stack
23

56. What happens if the execution of a smart contract costs more than the specified gas?
• Initially, your transaction will be
executed, but if the execution of a
smart contract costs more than the
specified gas, then the miners will
stop validating your contract
• The Blockchain will record the
transaction as failed, also the user
doesn’t get a refund
24
Transaction failed

57. What does the gas usage in a transaction depend on and how is transaction fee calculated?
Gas usage depends upon the amount of storage and set of instructions (codes) used in a smart
contract
Ether = Tx Fees = Gas Limit * Gas Price
The transaction fee is calculated in Ether, which is given as
25

58. What is fork? What are some of the types of forking?
• In simple terms, updating a cryptocurrency protocol or code is called forking
• Fork implies that a Blockchain splits into two branches
• It can happen when the participants of the network cannot come to an agreement with regards to:
o Consensus algorithm
o New rules to validate transactions
Types of forking
Hard forks Soft forks Accidental forks
26

59. Differentiate between proof of work vs proof of stake.
PoS is an alternate to proof
of work by which the
Blockchain aims to achieve
distributed consensus
In Blockchain, PoW is the
process of solving a
complex mathematical
puzzle called mining
Here, the probability of
mining a block is based
upon the amount of
computational work done by
a miner
Miners spend a lot of
computing power (with
hardware) for solving the
cryptographic puzzle
The probability of validating a
block relies upon the amount
of tokens you own. The more
tokens you have, the more
chance you get to validate a
block
It was created as a solution
to minimize the use of
expensive resources spent
in mining
Proof of work -
Proof of stake -
27

60. What is 51% attack?
In Blockchain, 51%
attack refers to a
vulnerability where an
individual or group of people
can control the majority of
the mining power (hash rate)
This would allow the attackers
to prevent new transactions
from being confirmed.
Further, they can double
spend the coins
28
In 51% attack, smaller
cryptocurrencies are being
attacked
1 32

61. What are function modifiers in solidity and mention the most widely used modifiers.29
• In Solidity, function modifiers are used to easily modify behavior of your smart contract functions
• In simple terms, it can build additional features or apply restrictions on the function of smart contracts
• The most extensively used function modifiers in solidity are:
View Pure

62. What are function modifiers in solidity and mention the most widely used modifiers.29
View Pure
• View functions are functions that cannot modify the state of smart
contract
• They are read-only functions
• In Solidity, function modifiers are used to easily modify behavior of your smart contract functions
• In simple terms, it can build additional features or apply restrictions on the function of smart contracts
• The most extensively used function modifiers in solidity are:

63. • In Solidity, function modifiers are used to easily modify behavior of your smart contract functions
• In simple terms, it can build additional features or apply restrictions on the function of smart contracts
• The most extensively used function modifiers in solidity are:
29
View Pure
For example, this function returns address To
simplilearn[msg.sender] without any data being modified
function getsimplilearnName() view
{
return
addressTosimplilearn[msg.sender];
}
What are function modifiers in solidity and mention the most widely used modifiers.

64. What are function modifiers in solidity and mention the most widely used modifiers.29
View Pure
• Pure functions are functions that neither read nor write the state
of smart contract
• They return the same result determined by its input values
• In Solidity, function modifiers are used to easily modify behavior of your smart contract functions
• In simple terms, it can build additional features or apply restrictions on the function of smart contracts
• The most extensively used function modifiers in solidity are:

65. • In Solidity, function modifiers are used to easily modify behavior of your smart contract functions
• In simple terms, it can build additional features or apply restrictions on the function of smart contracts
• The most extensively used function modifiers in solidity are:
What are function modifiers in solidity and mention the most widely used modifiers.29
View Pure
For example, the above function returns the value of the operation
on input variables (num1 and num2)
function Calculate(int num1, int num2) pure
{
return (num1 + num2 * num1) *
(num2 * num1);
}

66. Write a crowd sale smart contract code in solidity programming language30
Function crowdsale(
address ifSuccessfulSendTo,
uint fundingGoalInEthers,
uint durationInMinutes,
uint etherCostOfEachToken,
address addressOfTokenUsedAsReward
)
public
{
beneficiary = ifSuccessfulSendTo;
fundingGoal = fundingGoalInEthers * 1 ether;
deadline = now + durationInMinutes * 1 minutes;
price = etherCostOfEachToken * 1 ether;
tokenReward = token(addressOfTokenUsedAsReward);
}
Crowd sale function

67. Write a crowd sale smart contract code in solidity programming language30
function () payable public
{
require(!crowdsaleClosed);
uint amount = msg.value;
balanceOf[msg.sender] += amount;
amountRaised += amount;
tokenReward.transfer(msg.sender, amount / price);
emit FundTransfer(msg.sender, amount, true);
}
Default function to send
Values

68. Write a crowd sale smart contract code in solidity programming language30
function safeWithdrawal() public afterDeadline
{
if (!fundingGoalReached) {
uint amount = balanceOf[msg.sender];
balanceOf[msg.sender] = 0;
if (amount > 0) {
if (msg.sender.send(amount)) {
emit FundTransfer(msg.sender, amount, false);
} else {
balanceOf[msg.sender] = amount;
}}}
Default function of funds
withdrawal