6452 Quiz

Question 1

What is a ledger?

Answer 1

append-only list of blocks of transactions (TXs)

Question 2

Ledger structure is….

Answer 2

One list, but operators are in a peer-to-peer network

Question 3

Distributed systems share ______

Answer 3

ledgers

Question 4

What are the types of DLT systems?

Answer 4

Permissionless - no auth required
Permissioned - auth required
Public - accessible to the public
Private - accesible to limited people

Question 5

Which DLT system is easiest to regulate?

Answer 5

Permissioned + Private

Question 6

What are some examples of permissionless public DLT systems?

Answer 6

Bitcoin, Ethereum, Algorand

Question 7

What are some examples of Permissioned public DLT systems?

Answer 7

Hedera
Ripple
Avalanche

Question 8

What are some examples of permissioned private DLT systems

Answer 8

R3 Corda
Quorum
VMware Concord

Question 9

What is the difference between a replicated and distributed ledgder

Answer 9

Replicated = updated independently by participants
Distributed = updated automatically within minutes, or even instantly such that all users have the same ledger

Question 10

What are the possible issues that can arise as a result of growing participants?

Answer 10

Inconsistent edgers due to concurrent transactions

Potential for inconsistency with no of ledger copies

Question 11

Why might waiting for an ack message from all participants in a DL system before updating accounts be problematic?

Answer 11

It will limit concurrency

Question 12

How reliable is the use of sender’s time to order transactions?

Answer 12

Unreliable as subject to drift and skew and possible change by sender

Question 13

Why aren’t clocks accurate fro DLT

Answer 13

Drift and skew

Question 14

What is used in place of time in DLT

Answer 14

global ordering of transactions

Question 15

What does CAP Theorem say?

Answer 15

Impossible for web service to provide 3 guarantees at the same time:

Consistency, Availability, Partition tolerance

Question 16

What is partitioning in networks?

Answer 16

Where nodes lose connectivity

Question 17

In order to achieve reliable consensus, what must a DLT have?

Answer 17

Partition tolearance
Fault tolerance
Misbehaving nodes

Question 18

What does a Transaction (TX) contain?

Answer 18

Monetary value (Crypto)
Code
Parameters/results of function calls

To, from, Value/data, Sender’s signature

Question 19

What forms a block’s body?

Answer 19

Collection of ordered TXs

Question 20

What forms a block’s header

Answer 20

Summary of TXs & hash of previous block

Question 21

What do nodes agree on?

Answer 21

contents of blocks
order of blocks
who has the right to build a block

Question 22

What does each node do to ensure high availability and efficient read access?

Answer 22

Each node hosts a replica of the ledger

Question 23

List some beneficial non-functional properties of blockchains

Answer 23

Integrity
Availability
latency

Question 24

List some downside non-functional properties of blockchain

Answer 24

confidentiality
Modifiability
Scalability

Question 25

List the 4 different roles that blockchain can play in an architecture

Answer 25

Storage Communication Computational Asset management and control

Question 26

can DLT be a standalone system

Answer 26

No, requires UI, IoT integration, Key management, databases etc

Question 27

By nature of DLT, is it easy to detect TX failures

Answer 27

No, hard to detect errors

Question 28

What are 3 blockchain adoption paradoxes

Answer 28

Public blockchains are too transparent for many commercial applications Who pays? Who chooses Policy? Future of blockchain is 'off-chain'

Question 29

Blockchains can store a large volume of data (t/f)

Answer 29

False. Need to store off chain as is very expensive

Question 30

Data can be read faster, but writing is slow (t/f)

Answer 30

true. recording data is slow as it needs validation

Question 31

Data on blockchain is secure (t/f)

Answer 31

false

Question 32

It's impossible to correct errors in data (t/f)

Answer 32

false

Question 33

How else might a replicated and distributed ledger be referred to?

Answer 33

Linked list with hash pointers

Question 34

What does a hash do?

Answer 34

It takes large volume of data and converts into a small, fixed data size

Question 35

What are some hash algorithms?

Answer 35

MD5, SHA, SHA-3, KECCAK

Question 36

list some key properties of hash functions

Answer 36

Deterministic = same message results in same hash Small change to a message -> big difference in hash Quick to compute One-way function, cannot invert

Question 37

What is the Merkle Tree?

Answer 37

Binary tree built using hashes which allow efficient and secure verification of contents of large data structure

Question 38

What is the pseudo-anonymous feature of an account on a DLT?

Answer 38

the public key i.e. ishfbbasfbsdfhuhadqwd338 represents an account

Question 39

What is the base currency of a platform called?

Answer 39

Native currency

Question 40

what generation of cryptocurrency is bitcoin built on?

Answer 40

1st generation Miners compete to build the next block

Question 41

What is the averge time between blocks called, and how long is it approximately?

Answer 41

inter-block time, approx 10 mins

Question 42

how many nodes are approx in the BTC network?

Answer 42

16,896

Question 43

An account is associated with a _______

Answer 43

Cryptographic key pair

Question 44

Public key is used to...

Answer 44

create the address of an account

Question 45

Private key is used to

Answer 45

sign TXs sent from the account

Question 46

How can the state of the blockchain be described?

Answer 46

Account balances of all users Result from the genesis block & set of TXs includeed since All of the UTXOs in the system

Question 47

What happens, regarding state when a new block is added?

Answer 47

the entire system moves from one discrete state to another

Question 48

How is it decided who receives the TX fee?

Answer 48

If sum of output < sum of inputs, then fee to miner

Question 49

What does 'Linked TXs' mean?

Answer 49

Outputs of TXs become inputs of new TX

Question 50

In the transaction format, what is the balance of an address?

Answer 50

It is the sum of values of all of UNSPENT TRANSACTION OUTPUTS associated with the address

Question 51

What is referred to as a container of TXs?

Answer 51

Blocks

Question 52

What are blocks identified by?

Answer 52

block hash

Question 53

What is used to capture ordered list of TXs?

Answer 53

Merkle tress

Question 54

What is the max block size, and max TX size

Answer 54

block = 4MB, TX = 100k bytes

Question 55

Explain how mining works

Answer 55

1. Recieve a new block 2. Aggregation - aggregate subset of remaining valid TXs 3. Header construction - Construct merkle tree to summarise all included TXs 4. Solve puzzle - find solution to Proof-of-work algorithm (hashcash) 5. Propogate - immediately propogate new block to other nodes

Question 56

Hashcash is a Proof-of-work that is ....

Answer 56

Difficult to compute, easy to validate

Question 57

If multiple miners find and announce next block at the same time

Answer 57

longest history of blocks is treated as the main chain (also known as Nakamoto consensus)

Question 58

What are TX fees

Answer 58

Miners collect fees Higher TX feee -> higher chance of TX getting inc. in a block

Question 59

As soon as a Bitcoin TX is included in a block, it is safe to assume the TX is final (T/f)

Answer 59

False, as we need to wait for it to go through the mining process to be included in a block

Question 60

How many merkle trees does Ethereum use?

Answer 60

3. one for integrity for: World state TXs TX receipts