Cryptographic primitives - Test
Before you start:
This test checks whether you actually understand the cryptography building blocks (hashes, encoding, encryption, key pairs) or just remember the words. Several questions deliberately offer plausible-sounding wrong answers, the kind a reader who skimmed the lessons would pick. Read each option carefully before answering.
Which of the following are real cryptographic properties of hash functions like SHA-256? (Select all that apply.)
A blockchain block contains 10,000 transactions, summarized into a single Merkle root. Someone gives you one transaction and a Merkle proof that it belongs in the block. How many hashes does that proof contain?
Which of these can public-key cryptography do that symmetric encryption alone cannot? (Select all that apply.)
A user creates a wallet, sees their first address, sends a test transaction, then deletes the app. A week later they reinstall the app and re-enter the same 12-word seed phrase. What do they see?
Alice signed a message with her private key last week. Today she sends you the same message with what she claims is a brand-new signature of it. Can you tell whether she signed it again today, or just resent last week's signature?
Ten of the twelve words in your seed phrase leak. Is that wallet still safe?