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Blockchain > Blockchain CBBF > Flashcards

Blockchain CBBF Flashcards

1
Q

Who has a copy of the ledger in a blockchain?

A

Everyone has a local copy which can be queried and everyone should get the same answer

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2
Q

Is blockchain impervious to attack?

A

No, it is just a lot more difficult in a blockchain. A 51% consensus is required.

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3
Q

What is Byzantine Fault Tolerance?

A

Defend against failures of system components (with or without symptoms)
…that prevent other components of the system from reaching consensus.
…when consensus is needed for the correct operation of the system.

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4
Q

In the blockchain ……… has a copy of the ledger.

A

Everyone

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5
Q

New transactions are broadcast and …………… by the network.

A

Recorded

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6
Q

If everyone has a copy of the blockchain, when queries, everyone get the …………

A

Same answer

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7
Q

With a decentralised ledger no one has to ………. anyone else.

A

Trust

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8
Q

One of the advantages of a distributed network is many nodes or peers that are connected in a network create no single point of failure or ……….. control.

A

Centralised

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9
Q

The network is designed so that if some peers crash or attack the network maliciously, the network can still operate, this is known as …………..

A

Byzantine Fault Tolerance

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10
Q

What is the difference between a public and private blockchain?

A

Write permissions:

Public - everyone can write
Private - only certain participants can write

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11
Q

What is the difference between an Open vs a Closed blockchain?

A

Read permissions

Open - everyone can read from the blockchain
Closed - only certain participants can read

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12
Q

Who can see data on Ethereum blockchain?

A

Everyone can see everything at any time.

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13
Q

What is the pre-requisite for a permissioned blockchain system?

A

You must know the identity of the users

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14
Q

What kind of blockchain is Hyperledger (public or private)?

A

Private

It comes with native identity managment tools to manage permissions

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15
Q

Can you build a permissioned system on a non permissioned blockchain?

A

Yes. But as the developer, you will need to find a why to track identity and to add permissions based on that identity.

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16
Q

What type of blockchain is Ethereum?

A

Open
public
permissionless

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17
Q

What type of blockchain is Hyperledger?

A

Private
Closed
Permissioned

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18
Q

List some use cases for Hyperledger

A
  • Supply chains
  • Supplier/manufacturer inventory management
  • Managing internal business processes across geographically distributed locations
  • Allowing elected officials to vote on initiatives without being present
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19
Q

Describe a blockchain decision matrix

A

A graph with an axis for closed/open and another for private/public

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20
Q

What can Smart Contracts be used for?

A

Ability to automate processes

Blockchain as workflow (BPM)

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21
Q

Does Group consensus verify the truth of data itself?

A

No, it only verifies that the data was recorded correctly

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22
Q

Which are blockchain characteristics that are least appealing to most businesses?

A

Anonymity

Transparency

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23
Q

Is it ok to build your solution in multiple platforms?

A

Yes and it is often desirable.

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24
Q

Each block contains the hash of ……..

A

The previous block

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25
Q

Only …….. of data can be made on or to the blockchain.

A

Additions

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26
Q

The blockchain provides a snapshot of the current state (true/false)

A

False, it has a record of all previous transactions.

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27
Q

When looking at public vs private Blockchains it is important to look at who can ……… data to the blockchain.

A

Write

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28
Q

Any blockchain solution must be either public or private (true/false)

A

False

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29
Q

When considering a permission-less blockchain it is important to ask: are all participants ……..

A

Equal

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30
Q

Blocks are numbered in ………….. order.

A

Ascending.

0 is the first/oldest

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31
Q

Blocks are only linked to the previous because…..

A

They can’t be linked to the future one as this would require it to be changed. It can’t be changed once committed to the Ledger.

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32
Q

Blocks are created on a …………..

A

Schedule.

Whether they are full or not they will be committed to the chain (providing they are validated) so that blocks are created at a set interval.

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33
Q

Block ……. is the hash of the data in the block

A

ID

digital fingerprint of that block

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34
Q

What data is captured in the header of a block? (7 items)

A 
Version number of the block format
Link to previous block
Merkle root of transactions
Creation Timestamp
Mining difficulty
Nonce
All the transaction data
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35
Q

The number of a block is the …….. of the block.

A

Height

36
Q

Blocks store ………

A

Digital data

37
Q

The block ID is the. ………… of the data on the block, and the. ……… of that block.

A

Hash

Digital fingerprint

38
Q

The connection between blocks means that the Blockchain is much more …….. than a standard database.

A

Tamper-proof

39
Q

Cryptography can be used to address the issue of ……….

A

Privacy

40
Q

What is a cryptographic function?

A

A way of encoding or encrypting data to protect the contents from adversaries.

41
Q

Public key cryptography provides……….. &…………

A

Identity
&
Transaction approval

42
Q

The public key ………….

A

Verifies the digital signature of a given key pair

43
Q

The private key ………

A

Signs/approves any transaction/action that might be made by the holder of the key pair.

44
Q

In blockchain a …………key is used to validate that the transaction has come from the person it claims to have come from.

A

Public

45
Q

What are the 4 terms used in cryptography

A

The secret
The function
The key
The function

46
Q

What is a cryptographic hash function?

A
  • A hash is a one-was function, encrypted information CANNOT be decrypted.
  • Each unique input generates a unique output (deterministic)
47
Q

Why would you want to use a cryptographic hash?

A

So that you can keep privacy.
E.g. instead of using you name, you could use a hashed address as your account number which you could always prove is you.

Passwords can be stored hashed too.

Can use hashes to compare two documents, even if very long.
Hash both copies, of both have the same hash, you know the documents are the same;

48
Q

What technology can you use to check if two very large document contain exactly the same data?

A

Cryptographic Hash

49
Q

Cryptography can be used to address the issue of ……..

A

Privacy

50
Q

…………. is for encoding or encrypting data to protect the contents from adversaries.

A

A cryptographic function

51
Q

Public key cryptography provides ……………. and transaction approval.

A

Identity

52
Q

……….. verify the digital signature of a given key pair.

A

Public keys

53
Q

……………. sign/approved any transactions/action that might be made by the holder of a key pair.

A

Private keys.

54
Q

Hashing is beneficial because it allows us to ……….

A

Instantly compare two or more large volumes of data to ensure they are the same.

55
Q

Transactions take time to ………

A

Confirm

56
Q

Each transaction, once it’s in an accepted block has a ………

A

Height

57
Q

The height of a block is the number of blocks between it and the ………..block.

A

Genesis

58
Q

Each increase in blockchain height is called a ………..

A

Confirmation

59
Q

Data gets ……… secure as it the blocks after are added.

A

More

60
Q

Best to wait for another 5 blocks after yours in confirmation for anything of value, a transaction 5 blocks below the top chain is said to have …… confirmations.

A

6

61
Q

When a transaction is submitted, ……………….. gets sent back straight away, but the actual confirmation (the transaction actually being added to the blockchain) can be minutes later.

A

acknowledgement

62
Q

A fork occurs any time there is an update to the …….. or the ……… on a blockchain

A

Data

Protocol

63
Q

If the upgrade is backward compatible, it is a ……….. fork

A

Soft

64
Q

If the upgrade is not backward compatible, it is a ………. fork

A

Hard

65
Q

In a fork, blocks that are created have a ……….. number.

A

Version

66
Q

Hard forms are much harder and we try to ……….. them.

A

Avoid

67
Q

Upgrades to the protocol can cause problems, but can be managed. (true/false)

A

True

68
Q

If the upgrade is backward compatible, it is a …….. fork.

A

Soft

69
Q

All block data plus the current nonce are run through a ………….

A

Cryptographic hash

70
Q

If the result of a mining calculation matches the current level of ……….., the miner has guessed the right answer.

A

Difficulty

71
Q

The miner with the answer. …….. it with other miners.

A

Shares

72
Q

Miners share the answer with all other miners, miners will confirm the answer is correct by using the ……… with their ……….. ………….. to try and get the correct result.

A

Nonce

Block data

73
Q

When ……. of the miners confirm the nonce is correct, the transaction is added to the blockchain.

A

51%

74
Q

Which is the most commonly used consensus method?

A

Proof of work (POW)

75
Q

When a block is full, or it is time to create a new block what happens? (6 steps)

A

1) All nodes stop accepting new incoming transactions
2) Any transactions that are broadcast to the network are cached on that node
3) Each node competes to guess the puzzle
4) The miner who guesses the nonce value shares the nonce with the rest of the network
5) They try this on their copy of their data, if 51% agree, the block is accepted.
6) The block is added to the chain

76
Q

What are the limits of POW? (3)

A
  • Limits transactions capacity
  • Uses a lot of electricity
  • Concern that it has become centralised as 80% of hash power come from less than a dozen datacenters mostly located in mainland China.
77
Q

Do you need specialised equipment to participate in POS?

A

No

78
Q

How does POS work?

A
  • When a block is full of transactions.
    -All nodes have to take some funds and lock them into a stake.
    (Participation still is optional)
  • Protocol randomly selects a participant
  • The winner hashes and shares with rest of network.
  • Rest of network hashes their version and the two are compared.
    -All nodes vote to agree or disagree
  • If 51% agree, they get a reward.
  • If less than 51% agree, no reward and loose their stake.
79
Q

Which is faster? POW or POS

A

POS

80
Q

Name two other consensus methods. (5)

A

POA - Proof of activity

POB - Proof of burn

POC - Proof of capacity

POET - Proof of elapsed time (based on custom chipset made by Intel)

POA - Proof of authority

81
Q

Consensus …….. are the key to Blockchain

A

Protocols

82
Q

…………is integral to understanding of the blockchain and working with it, but it not something that needs to be discussed with stakeholders when planning solutions.

A

Group consensuS

83
Q

With proof of work, when a block is full, each node competes to guess the …….

A

Nonce

84
Q

With proof of work, when ……. of the miners confirm the nonce is correct, the transaction is added to the blockchain.

A

51%

85
Q

With proof of stake, no computing is ever performed only ………

A

Staking/wagering

86
Q

Proof of stake is the most mature consensus method (true/false)

A

False. POW is.

Blockchain (7 decks)

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