Ethereum and Smart Contracts

Question 1

Ethereum 1.0

Answer 1

Different network propagation layer than Bitcoin
Different mean to deal with uncle blocks
Smart Contracts

Question 2

Ethereum Network propagation

Answer 2

Upon recieving a new block the node verifies it before propagating it further
For n neighbours:
root of n neighbours get the block directly
n - root of n neighbours get the hash of the block

Question 3

Eth uncle rewards

Answer 3

Uncle blocks are not part of the main chain but receive fraction of the reward for fairness purpose

Question 4

Smart contract reentrancy

Answer 4

Can be used to reenter calling contract for it to receive funds for example. However if reentrancy is happening unexpectly it can be exploited
Is ethereum specific problem

Question 5

Cross function reentrancy

Answer 5

Function A calls contract which then fallsback to calling contract and calls function B

Question 6

Delegated reentrancy

Answer 6

Victim contract function is called and uses library contract which then allows to call the attacker contract again

Question 7

create based reentrancy

Answer 7

malfunctioning function calls function a which creates a new contract that then calls the mal function again

Question 8

Update smart contract

Answer 8

Create proxy contract which uses delegatecall to call the buisness logic.
If the contract is supposed to be updated change the address of the buisness logic contract
EVMPatch