Asymmetric Cryptography and Key Algorithms BDC Practice Questions (Page 7)

Questions 31–35

1. 31application · medium

   A blockchain startup is creating a digital identity system where users control their own keys. The system must allow users to recover access if they lose their private key, but without creating a single point of failure or requiring a trusted third party. Which approach best meets these requirements?

   • ASplit the private key into multiple shares using Shamir's Secret Sharing and distribute them to several independent custodians.
   • BStore a backup of the private key on the startup's central server.
   • CGenerate a new key pair and ask the user to re-register their identity.
   • DUse a password-derived symmetric key to encrypt the private key and store it on the user's device.
   Reveal Solution Discussion Select an answer first
2. 32application · medium

   A developer is building a blockchain-based supply chain system where each shipment is tracked by a unique ID. Each participant (manufacturer, shipper, retailer) has a key pair. When a shipment changes hands, the new custodian must prove they received it from the previous custodian. Which cryptographic operation should be used to create this proof?

   • AThe new custodian hashes the shipment ID and sends the hash to the previous custodian.
   • BThe new custodian encrypts the shipment ID with their private key and sends it to the previous custodian.
   • CThe previous custodian shares their private key with the new custodian.
   • DThe previous custodian signs a transaction that transfers custody to the new custodian's public key.
   Reveal Solution Discussion Select an answer first
4. 33foundation · easy

   Which of the following best describes the purpose of the public key in an asymmetric key pair?

   • AIt is kept secret by the owner and used to sign transactions.
   • BIt is used to generate the private key when needed.
   • CIt is shared openly and used to encrypt data or verify signatures.
   • DIt is used to decrypt data that was encrypted with the private key.
   Reveal Solution Discussion Select an answer first
5. 34application · medium

   A developer is designing a key management system for a blockchain wallet. The system must allow users to sign transactions from multiple devices (phone, laptop, tablet) without ever exposing the private key to the cloud. Which approach best satisfies this requirement?

   • AStore the private key on a central server and have devices request signatures via API.
   • BUse a hardware wallet that holds the private key and signs transactions via USB or Bluetooth, with the devices only sending unsigned transactions.
   • CGenerate a new key pair on each device and merge the public keys into a single wallet address.
   • DStore the same private key on each device, encrypted with a user-chosen password.
   Reveal Solution Discussion Select an answer first
6. 35application · medium

   A company is deploying a private blockchain for supply-chain tracking. Each participant node needs a key pair to sign blocks and verify peers. The security team requires that private keys never leave the hardware they are generated on, and that the key generation algorithm be resistant to future quantum attacks. Which approach best satisfies these requirements?

   • AGenerate RSA-4096 key pairs on a central server and distribute them to nodes over TLS.
   • BGenerate ECC P-256 key pairs on each node's HSM and store the private keys in the HSM.
   • CGenerate lattice-based key pairs on each node's HSM and store the private keys in the HSM.
   • DGenerate RSA-2048 key pairs on each node's hardware security module (HSM) and store the private keys in the HSM.
   Reveal Solution Discussion Select an answer first