ETH
What APIs does it have?
(eth, web3, net, miner these are default), personal, shh, debug, txpool
Proof of Work
- A consensus distribution algorithm that requires an active role in mining data blocks, often consuming resources, such as electricity - The more 'work' you do or the more computational power you provide, the more coins you are rewarded with
Name ways contracts can interact
A contract can invoke, create, and inherit other contracts
What is a blockchain?
A digital ledger that consists of a system fo blocks that are cryptographically encrypted records of various transactions. It is decentralized, so ti can provide security, permanence, transparency, and immutability. Each block contains references to the previous block on the chain.
What is a smart contract?
Computer code that could be compiled from multiple languages (solidity, vyper). They live on the network and enforce rules and perform state changes.
Define byzantine fault tolerance
Consensus algorithm where messages can be sent and confirmed cryptographically
Why would you use a private network?
Data privacy, distributed database, permissions control and testing
How do you determined how much gas is used?
EVM op codes have different fixed amounts
Explain calldata
Similar to a callstack, temporary, non-modifiable, and it stores evm execution data
What is "etherbase"?
The account that receives mining awards
What node does metamask use?
infura.io
Explain memory
temporary storage that is lost once contract execution terminates. you need to use the memory keyword, otherwise it will reference memory
Higher the gas price...
the more likely a transaction is to be mined
What is the average block time in Ethereum?
~14 seconds
Most common vulnerabilities
-Private information and randomness -re-entrancy - gas limit and loops - sending and receiving ether (make sure to use checks effects pattern) -tx.origin (use msg.sender instead)
What is the conversion of Wei To Ether?
10^18 wei = 1 ETH
What do you need to recover Ethereum account?
12 word mneumonic
What is the average block size in ethereum?
2kb (but it depends)
When would you use remix?
For testing and deploying lightweight contracts
Where are transactions recorded?
Public ledger
Can you mine with geth?
Yes, via --mine option
What is web3.js?
a javascript library that provides functions to interact with nodes on the ethereum blockchain
Name kinds of solidity functions
constructor, fallback functions, constant functions, functions that modify state
What is a node?
A computer that is connected to a network that processes transactions
Explain storage in contracts
Each contract manages its own storage variables. It's a key-value datastore. More read and writes === more costly
How is a transaction fee calculated?
Gas price * gas used
What is Geth?
An Ethereum cli client
ERC20 vs ERC721
Both are standards for implementing Ethereum token contracts - 721 each token is unique
Why use truffle?
Build in smart contract compilation, linking, and deployment. Automated testing. Makes it easy to deploy to specific networks.
Where are geth client accounts stored?
In the keystore directory
What does the EVM use to run a smart contract?
It uses a contract's bytecode which is compiled from languages like solidity
What are ways to connect to a geth node?
JSON-RPC
Purpose of BigNumber library?
Javascript doesn't handle big numbers correctly
Name different ETH networks
Live Network (Main), Test Networks (Ropsten, Kovan, Rinkeby) and Private Networks. Could be public, private, or consortium.
What does ecrecover do?
Recovers a public key address from an elliptic curve signature
Define solidity
Statically typed High-level language (types are known at compilation) that compield to bytecode
What do you need to interact with a contract from a dApp?
The contracts ABI and bytecode
