Practice Test GeeksCBE - Certified Blockchain Expert Practice Test
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Foundational Concepts Flashcards

7 cards from real CBE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. What is the maximum total supply of bitcoin?

    Answer: 21 million

    Bitcoin's protocol caps the total supply at 21 million coins.

  2. How often does Bitcoin's block subsidy halve?

    Answer: Every 210,000 blocks

    The block reward halves every 210,000 blocks, about every four years.

  3. In September 2022, Ethereum moved from Proof-of-Work to Proof-of-Stake. What is this event called?

    Answer: The Merge

    The Merge joined Ethereum's execution layer with the Beacon Chain and switched it to Proof-of-Stake.

  4. What does a 51% attack let an attacker do?

    Answer: Reorganize recent blocks and double-spend their own coins

    Majority hash power lets an attacker rewrite recent history to double-spend, but not forge signatures or break supply rules.

  5. Which hash function does Ethereum mainly use?

    Answer: Keccak-256

    Ethereum uses Keccak-256, a variant of the SHA-3 family, for addresses and hashing.

  6. What does a mnemonic seed phrase (BIP-39) represent?

    Answer: A human-readable backup that can regenerate a wallet's private keys

    The 12- or 24-word seed phrase encodes the master seed from which all of the wallet's keys are derived.

  7. Which feature of blockchain makes it hard to alter past records without detection?

    Answer: Each block includes the previous block's hash, so changing one block breaks every later link

    Hash-linking means tampering with any block invalidates every block after it.