Asymmetric Cryptography and Key Algorithms BDC Practice Questions (Page 1)

Questions 1–5

1. 1application · medium

   A blockchain developer is building a mobile wallet that lets users sign transactions offline. The wallet generates a key pair on the device, stores the private key in the device's secure enclave, and derives the public address from the public key. When a user signs a transaction, the wallet sends the raw transaction and the signature to a public node for broadcast. Which property of asymmetric cryptography ensures that any node can verify the transaction came from the user without having access to the user's private key?

   • AThe node compares the signature to a hash of the user's private key stored in the transaction header.
   • BThe signature is verified using the user's public key, which is derived from the private key but cannot be used to derive the private key.
   • CThe node uses the user's public address as a symmetric key to decrypt the signature and check the transaction hash.
   • DThe transaction is encrypted with the user's private key, so only the node with the matching public key can decrypt and verify it.
   Reveal Solution Discussion Select an answer first
2. 2application · medium

   A developer is implementing a voting system on a blockchain. Each voter has a key pair, and votes are recorded as transactions. The system must allow any observer to confirm that a vote was cast by a registered voter without revealing the voter's private key or allowing the voter to deny having cast the vote. Which mechanism achieves this?

   • AThe voter uses a symmetric key shared with the blockchain to encrypt the vote, and observers use the same key to decrypt.
   • BThe voter signs the vote with their private key, and observers verify the signature using the voter's public key.
   • CThe voter encrypts the vote with their private key, and observers decrypt it with the voter's public key.
   • DThe voter includes their private key in the transaction, and observers compare it to the registered public key.
   Reveal Solution Discussion Select an answer first
4. 3application · medium

   A developer is designing a lightweight blockchain client for IoT devices with limited CPU and memory. The client only needs to sign transactions and verify signatures. Which asymmetric algorithm is most appropriate?

   • AECC (Elliptic Curve Cryptography)
   • BRSA with 2048-bit keys
   • CAES
   • DDiffie-Hellman
   Reveal Solution Discussion Select an answer first
5. 4foundation · easy

   In a blockchain transaction, what does the sender's digital signature prove?

   • AThat the sender has enough funds in their account.
   • BThat the recipient's address is valid.
   • CThat the transaction will be included in the next block.
   • DThat the sender is authorized to spend the funds and that the transaction data has not been altered.
   Reveal Solution Discussion Select an answer first
6. 5expert · hard

   A user's blockchain wallet private key is suspected to be compromised. The user has already transferred most funds to a new wallet, but some tokens remain in the old wallet. What should the user do first?

   • AChange the private key of the old wallet.
   • BNotify the blockchain network to freeze the old wallet.
   • CImmediately move the remaining tokens to the new wallet.
   • DWait to see if the attacker moves the tokens.
   Reveal Solution Discussion Select an answer first