Blockchain CBBF Flashcards
Who has a copy of the ledger in a blockchain?
Everyone has a local copy which can be queried and everyone should get the same answer
Is blockchain impervious to attack?
No, it is just a lot more difficult in a blockchain. A 51% consensus is required.
What is Byzantine Fault Tolerance?
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.
In the blockchain ……… has a copy of the ledger.
Everyone
New transactions are broadcast and …………… by the network.
Recorded
If everyone has a copy of the blockchain, when queries, everyone get the …………
Same answer
With a decentralised ledger no one has to ………. anyone else.
Trust
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.
Centralised
The network is designed so that if some peers crash or attack the network maliciously, the network can still operate, this is known as …………..
Byzantine Fault Tolerance
What is the difference between a public and private blockchain?
Write permissions:
Public - everyone can write
Private - only certain participants can write
What is the difference between an Open vs a Closed blockchain?
Read permissions
Open - everyone can read from the blockchain
Closed - only certain participants can read
Who can see data on Ethereum blockchain?
Everyone can see everything at any time.
What is the pre-requisite for a permissioned blockchain system?
You must know the identity of the users
What kind of blockchain is Hyperledger (public or private)?
Private
It comes with native identity managment tools to manage permissions
Can you build a permissioned system on a non permissioned blockchain?
Yes. But as the developer, you will need to find a why to track identity and to add permissions based on that identity.
What type of blockchain is Ethereum?
Open
public
permissionless
What type of blockchain is Hyperledger?
Private
Closed
Permissioned
List some use cases for Hyperledger
- Supply chains
- Supplier/manufacturer inventory management
- Managing internal business processes across geographically distributed locations
- Allowing elected officials to vote on initiatives without being present
Describe a blockchain decision matrix
A graph with an axis for closed/open and another for private/public
What can Smart Contracts be used for?
Ability to automate processes
Blockchain as workflow (BPM)
Does Group consensus verify the truth of data itself?
No, it only verifies that the data was recorded correctly
Which are blockchain characteristics that are least appealing to most businesses?
Anonymity
Transparency
Is it ok to build your solution in multiple platforms?
Yes and it is often desirable.
Each block contains the hash of ……..
The previous block
Only …….. of data can be made on or to the blockchain.
Additions
The blockchain provides a snapshot of the current state (true/false)
False, it has a record of all previous transactions.
When looking at public vs private Blockchains it is important to look at who can ……… data to the blockchain.
Write
Any blockchain solution must be either public or private (true/false)
False
When considering a permission-less blockchain it is important to ask: are all participants ……..
Equal
Blocks are numbered in ………….. order.
Ascending.
0 is the first/oldest
Blocks are only linked to the previous because…..
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.
Blocks are created on 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.
Block ……. is the hash of the data in the block
ID
digital fingerprint of that block
What data is captured in the header of a block? (7 items)
Version number of the block format Link to previous block Merkle root of transactions Creation Timestamp Mining difficulty Nonce All the transaction data
The number of a block is the …….. of the block.
Height
Blocks store ………
Digital data
The block ID is the. ………… of the data on the block, and the. ……… of that block.
Hash
Digital fingerprint
The connection between blocks means that the Blockchain is much more …….. than a standard database.
Tamper-proof
Cryptography can be used to address the issue of ……….
Privacy
What is a cryptographic function?
A way of encoding or encrypting data to protect the contents from adversaries.
Public key cryptography provides……….. &…………
Identity
&
Transaction approval
The public key ………….
Verifies the digital signature of a given key pair
The private key ………
Signs/approves any transaction/action that might be made by the holder of the key pair.
In blockchain a …………key is used to validate that the transaction has come from the person it claims to have come from.
Public
What are the 4 terms used in cryptography
The secret
The function
The key
The function
What is a cryptographic hash function?
- A hash is a one-was function, encrypted information CANNOT be decrypted.
- Each unique input generates a unique output (deterministic)
Why would you want to use a cryptographic hash?
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;
What technology can you use to check if two very large document contain exactly the same data?
Cryptographic Hash
Cryptography can be used to address the issue of ……..
Privacy
…………. is for encoding or encrypting data to protect the contents from adversaries.
A cryptographic function
Public key cryptography provides ……………. and transaction approval.
Identity
……….. verify the digital signature of a given key pair.
Public keys
……………. sign/approved any transactions/action that might be made by the holder of a key pair.
Private keys.
Hashing is beneficial because it allows us to ……….
Instantly compare two or more large volumes of data to ensure they are the same.
Transactions take time to ………
Confirm
Each transaction, once it’s in an accepted block has a ………
Height
The height of a block is the number of blocks between it and the ………..block.
Genesis
Each increase in blockchain height is called a ………..
Confirmation
Data gets ……… secure as it the blocks after are added.
More
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.
6
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.
acknowledgement
A fork occurs any time there is an update to the …….. or the ……… on a blockchain
Data
Protocol
If the upgrade is backward compatible, it is a ……….. fork
Soft
If the upgrade is not backward compatible, it is a ………. fork
Hard
In a fork, blocks that are created have a ……….. number.
Version
Hard forms are much harder and we try to ……….. them.
Avoid
Upgrades to the protocol can cause problems, but can be managed. (true/false)
True
If the upgrade is backward compatible, it is a …….. fork.
Soft
All block data plus the current nonce are run through a ………….
Cryptographic hash
If the result of a mining calculation matches the current level of ……….., the miner has guessed the right answer.
Difficulty
The miner with the answer. …….. it with other miners.
Shares
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.
Nonce
Block data
When ……. of the miners confirm the nonce is correct, the transaction is added to the blockchain.
51%
Which is the most commonly used consensus method?
Proof of work (POW)
When a block is full, or it is time to create a new block what happens? (6 steps)
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
What are the limits of POW? (3)
- 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.
Do you need specialised equipment to participate in POS?
No
How does POS work?
- 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.
Which is faster? POW or POS
POS
Name two other consensus methods. (5)
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
Consensus …….. are the key to Blockchain
Protocols
…………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.
Group consensuS
With proof of work, when a block is full, each node competes to guess the …….
Nonce
With proof of work, when ……. of the miners confirm the nonce is correct, the transaction is added to the blockchain.
51%
With proof of stake, no computing is ever performed only ………
Staking/wagering
Proof of stake is the most mature consensus method (true/false)
False. POW is.
