Ethereum's Transactions, Validation, and Upgrades BDC Practice Questions (Page 3)

Questions 11–15

1. 11foundation · easy

   How is the sender's address recovered from a transaction signature?

   • ABy decrypting the signature with the sender's private key
   • BBy applying ECDSA public key recovery to the signature and hashing the result
   • CBy using the transaction's hash as the address
   • DBy looking up the sender in the transaction's 'from' field
   Reveal Solution Discussion Select an answer first
2. 12foundation · easy

   What is a hard fork in the context of Ethereum upgrades?

   • AA change that is backward-compatible and does not require node upgrades
   • BA change that is automatically applied without consensus
   • CA change to the protocol that is not backward-compatible, requiring all nodes to upgrade
   • DA change that only affects the user interface of wallets
   Reveal Solution Discussion Select an answer first
4. 13application · medium

   A developer is implementing a backend service that needs to verify that a transaction was signed by a specific Ethereum address. They have the raw transaction and the signature components (v, r, s). What is the correct process to recover the sender's address?

   • AUse the v value directly as the address.
   • BDecrypt the signature using the private key to reveal the sender's address.
   • CHash the signature and compare it to the address.
   • DHash the raw transaction, then use the v, r, s values with ECDSA recovery to derive the public key, and then compute the address from the public key.
   Reveal Solution Discussion Select an answer first
5. 14foundation · easy

   Where does a transaction wait before it is selected by a miner?

   • AIn the Ethereum Name Service (ENS)
   • BIn the blockchain's latest block
   • CIn the sender's local wallet only
   • DIn the transaction pool (mempool)
   Reveal Solution Discussion Select an answer first
6. 15application · medium

   A node receives a transaction with a gas limit of 21,000 and a gas price of 50 gwei. The transaction is a simple ETH transfer. Which validation check will cause the transaction to be rejected?

   • AThe gas limit is exactly 21,000, which is the minimum for a simple transfer, so it is valid.
   • BThe signature is valid, so the transaction is accepted.
   • CThe sender's balance is less than the value plus the maximum gas cost.
   • DThe nonce is correct, so the transaction is valid.
   Reveal Solution Discussion Select an answer first