6452 Quiz Flashcards
What is a ledger?
append-only list of blocks of transactions (TXs)
Ledger structure is….
One list, but operators are in a peer-to-peer network
Distributed systems share ______
ledgers
What are the types of DLT systems?
Permissionless - no auth required
Permissioned - auth required
Public - accessible to the public
Private - accesible to limited people
Which DLT system is easiest to regulate?
Permissioned + Private
What are some examples of permissionless public DLT systems?
Bitcoin, Ethereum, Algorand
What are some examples of Permissioned public DLT systems?
Hedera
Ripple
Avalanche
What are some examples of permissioned private DLT systems
R3 Corda
Quorum
VMware Concord
What is the difference between a replicated and distributed ledgder
Replicated = updated independently by participants
Distributed = updated automatically within minutes, or even instantly such that all users have the same ledger
What are the possible issues that can arise as a result of growing participants?
Inconsistent edgers due to concurrent transactions
Potential for inconsistency with no of ledger copies
Why might waiting for an ack message from all participants in a DL system before updating accounts be problematic?
It will limit concurrency
How reliable is the use of sender’s time to order transactions?
Unreliable as subject to drift and skew and possible change by sender
Why aren’t clocks accurate fro DLT
Drift and skew
What is used in place of time in DLT
global ordering of transactions
What does CAP Theorem say?
Impossible for web service to provide 3 guarantees at the same time:
Consistency, Availability, Partition tolerance
What is partitioning in networks?
Where nodes lose connectivity
In order to achieve reliable consensus, what must a DLT have?
Partition tolearance
Fault tolerance
Misbehaving nodes
What does a Transaction (TX) contain?
Monetary value (Crypto)
Code
Parameters/results of function calls
To, from, Value/data, Sender’s signature
What forms a block’s body?
Collection of ordered TXs
What forms a block’s header
Summary of TXs & hash of previous block
What do nodes agree on?
contents of blocks
order of blocks
who has the right to build a block
What does each node do to ensure high availability and efficient read access?
Each node hosts a replica of the ledger
List some beneficial non-functional properties of blockchains
Integrity
Availability
latency
List some downside non-functional properties of blockchain
confidentiality
Modifiability
Scalability
List the 4 different roles that blockchain can play in an architecture
Storage
Communication
Computational
Asset management and control
can DLT be a standalone system
No, requires UI, IoT integration, Key management, databases etc
By nature of DLT, is it easy to detect TX failures
No, hard to detect errors
What are 3 blockchain adoption paradoxes
Public blockchains are too transparent for many commercial applications
Who pays? Who chooses Policy?
Future of blockchain is ‘off-chain’
Blockchains can store a large volume of data (t/f)
False. Need to store off chain as is very expensive
Data can be read faster, but writing is slow (t/f)
true. recording data is slow as it needs validation
Data on blockchain is secure (t/f)
false
It’s impossible to correct errors in data (t/f)
false
How else might a replicated and distributed ledger be referred to?
Linked list with hash pointers
What does a hash do?
It takes large volume of data and converts into a small, fixed data size
What are some hash algorithms?
MD5, SHA, SHA-3, KECCAK
list some key properties of hash functions
Deterministic = same message results in same hash
Small change to a message -> big difference in hash
Quick to compute
One-way function, cannot invert
What is the Merkle Tree?
Binary tree built using hashes which allow efficient and secure verification of contents of large data structure
What is the pseudo-anonymous feature of an account on a DLT?
the public key i.e. ishfbbasfbsdfhuhadqwd338 represents an account
What is the base currency of a platform called?
Native currency
what generation of cryptocurrency is bitcoin built on?
1st generation
Miners compete to build the next block
What is the averge time between blocks called, and how long is it approximately?
inter-block time, approx 10 mins
how many nodes are approx in the BTC network?
16,896
An account is associated with a _______
Cryptographic key pair
Public key is used to…
create the address of an account
Private key is used to
sign TXs sent from the account
How can the state of the blockchain be described?
Account balances of all users
Result from the genesis block & set of TXs includeed since
All of the UTXOs in the system
What happens, regarding state when a new block is added?
the entire system moves from one discrete state to another
How is it decided who receives the TX fee?
If sum of output < sum of inputs, then fee to miner
What does ‘Linked TXs’ mean?
Outputs of TXs become inputs of new TX
In the transaction format, what is the balance of an address?
It is the sum of values of all of UNSPENT TRANSACTION OUTPUTS associated with the address
What is referred to as a container of TXs?
Blocks
What are blocks identified by?
block hash
What is used to capture ordered list of TXs?
Merkle tress
What is the max block size, and max TX size
block = 4MB, TX = 100k bytes
Explain how mining works
- Recieve a new block
- Aggregation - aggregate subset of remaining valid TXs
- Header construction - Construct merkle tree to summarise all included TXs
- Solve puzzle - find solution to Proof-of-work algorithm (hashcash)
- Propogate - immediately propogate new block to other nodes
Hashcash is a Proof-of-work that is ….
Difficult to compute, easy to validate
If multiple miners find and announce next block at the same time
longest history of blocks is treated as the main chain (also known as Nakamoto consensus)
What are TX fees
Miners collect fees
Higher TX feee -> higher chance of TX getting inc. in a block
As soon as a Bitcoin TX is included in a block, it is safe to assume the TX is final (T/f)
False, as we need to wait for it to go through the mining process to be included in a block
How many merkle trees does Ethereum use?
3.
one for integrity for:
World state
TXs
TX receipts
