Chapter A2 Flashcards

1
Q

Permissionless blockchains are…

A

Public and

Slow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Security issues of the Bitcoin blockchain include…

A

Syblic attack and

51% attack

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a Sybil attack?

A

With Bitcoin, because identities are based on anonymous public
keys, a user can run multiple nodes and have many accounts. The proof of work
mechanism is essential to prevent users from taking advantage of this - their
voice in the system is proportional to their computational power.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a 51% attack?

A

Because the consensus mechanism “longest chain adoption” is
effectively a majority vote, an adversary controlling 51% of the computation power
of the system can subvert the protocol, even allow double-spend. This is
considered an unlikely scenario for a sufficiently widely-adopted protocol like
Bitcoin.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

The ideal properties of cryptographic hash function include the following characteristics:

A
  1. Deterministic: always same output hash for the same input
  2. Fast: quick to obtain the hash value
  3. Secure: hard to find an input that will generate a given ouput hash
  4. Discontinuous: a small change in input should change hash substantially
  5. Low Collision: hard to find two inputs that give the same output hash
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Distributed Ledger Technology is a type of immutable database to record transactions in chronological order (typically, in the form of a blockchain), that is…

A

shared
replicated
synchronized

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

A _____ is a set of steps that are taken by most or all nodes in a blockchain to agree on a proposed state or value.

A

consensus mechanism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

The ______ states that any distributed system cannot have consistency, availability, and partition tolerance simultaneously.

A

CAP theorem

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Proof of Work, Proof of Stake and Proof of Capacity are examples of

A

consensus algorithms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is POW (Proof of Work)?

A

consensus mechanism relies on proof that
adequate computational resources have been spent before proposing a value for
acceptance by the network.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is POS (Proof of Stake)?

A

algorithm works on the idea that a node or user has an
adequate stake in the system; that is, the user has invested enough in the system
so that any malicious attempt by that user would outweigh the benefits of
performing such an attack on the network.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is POC (Proof of Capacity)?

A

scheme uses hard disk space as a resource to mine

the blocks.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Via _____ coins can be moved from one blockchain to another and moved back again.

A

sidechains or

“pegged” sidechains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Any application or database that is shared by the public is a _____

A

shared ledger

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

True/False: The primary challenge of distributed systems is the coordination between nodes and fault tolerance.

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is/are characteristic(s) private blockchains?

A

a. The ledger is shared only among the members of the group

d. Open only to a consortium / group of individuals / organizations

17
Q

Peer-to-peer means…

A

no central controller

no third party for transactions

18
Q

Challenges of blockchain technology include…

A

Scalability

19
Q

What is/are characteristic(s) of public blockchains?

A

a. All users maintain a copy of the ledger
b. Anyone can participate
c. Distributed consensus mechanism

20
Q

True/False: Blockchain’s feature of immutability means that once records are added to the blockchain, they cannot be changed.

A

True

21
Q

Benefits of blockchain technology include…

A

Decentralized trust and cost savings

22
Q

True/False: All blockchains are distributed ledgers, but not all distributed ledgers are a blockchain.

A

True

23
Q

True/False: Part of blockchain’s benefits are cost savings and scalability.

A

False

24
Q

A distributed ledger…

A

stores records contiguously instead of sorting them into blocks