Block Chain & Crypto-Currencies (CY-702 (B)) - Important Questions

Describe the architecture of Ethereum and explain the role, responsibilities and operational model of the Ethereum Virtual Machine (EVM). Include how transactions are processed, the distinction between externally owned accounts and contract accounts, and how the EVM ensures determinism across nodes.

Explain the EVM execution model in detail. Discuss the EVM stack, memory, storage, program counter, and how gas is consumed during execution. Illustrate how an instruction modifies the EVM state during a transaction.

Define gas in Ethereum and show how transaction cost is calculated. If a transaction uses $gas\_used$ units and the gas price is $gas\_price$ (in wei), give the formula for the total transaction cost and explain each term.

Describe the compilation pipeline from Solidity source code to EVM bytecode. Explain the difference between Solidity source, intermediate representation (IR) if any, contract ABI, and the final EVM bytecode deployed on-chain.

Explain how the EVM implements contract storage. Describe the storage slot layout for fixed-size variables and explain how mappings and dynamic arrays are located using the storage hashing scheme. Use the storage slot hashing expression for a mapping key to illustrate your answer.

List and explain the function of the major EVM opcode categories (stack, memory, storage, environment, arithmetic, control flow, and system). For any two opcodes, give their typical gas cost implications.

Discuss common smart contract vulnerabilities that arise from EVM semantics (for example, re-entrancy, gas-limit related issues, and unchecked external calls). For each vulnerability describe its root cause at the EVM level and list standard mitigation patterns.

Compare the EVM with proposed alternatives or upgrades (for example eWASM or notable EIPs affecting execution like EIP-1559 and EVM-related EIPs). Explain the key technical differences and expected impact on execution, gas accounting or determinism.