Blockchain Technology Cheat Sheet 2026

The 30 highest-yield Blockchain Technology facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. What is the primary purpose of a DAO (Decentralized Autonomous Organization) smart contract? → To encode governance rules so token holders can vote on proposals without central control
2. Why are private keys never transmitted during a transaction? → Signatures prove ownership without revealing the key
3. In Proof of Work, what does the 'difficulty' parameter primarily control? → The expected time to find a valid block
4. What is 'block propagation' and why does its speed matter in blockchain networks? → The time it takes for a newly mined block to reach all nodes, affecting orphan block rates
5. Which consensus algorithm is specifically designed to tolerate up to one-third of nodes acting maliciously? → Practical Byzantine Fault Tolerance (PBFT)
6. What is the benefit of encrypting peer-to-peer connections between nodes? → Prevents eavesdropping and traffic tampering
7. How are transactions ordered within a block's Merkle tree construction? → In a defined, deterministic order so the root is reproducible
8. In a federated (consortium) blockchain, which entity typically acts as the validator? → A pre-selected set of member organization nodes
9. In ERC-20, what is the well-known race-condition risk associated with the approve() function? → A spender can front-run a changed approval and spend both the old and new amounts
10. Why is Blockchain a trusted approach? → All of the above
11. Which attack involves sending tiny amounts of cryptocurrency to many addresses to break the privacy of wallet owners through later transaction analysis? → Dusting attack
12. What is a key defense against DDoS attacks targeting public-facing nodes? → Use of upstream DDoS mitigation and traffic scrubbing
13. How does a blockchain network achieve fault tolerance against Byzantine failures? → Through consensus mechanisms that require agreement among a majority of nodes
14. Describe cold storage. → A private key that isn't linked to the internet
15. Why are time-weighted average price (TWAP) oracles more resistant to flash loan attacks? → They average prices over time, resisting single-block manipulation
16. A proxy upgrade pattern introduces which key security concern? → A compromised admin can swap in malicious implementation logic
17. Which design principle helps prevent reentrancy vulnerabilities? → Checks-Effects-Interactions pattern
18. In DeFi, what is an 'AMM' (Automated Market Maker)? → A protocol that prices assets using liquidity pool formulas instead of order books
19. What does 'stake grinding' attempt to exploit? → Manipulating the randomness used to select the next block proposer
20. What is 'chain reorganization' (reorg) in a blockchain? → Replacing blocks with a different competing branch
21. How does each block in a blockchain link to the previous one? → By storing the previous block's hash in its header
22. Which of the following biockchains has an architectural design that is channel-focused? → Hyperledger
23. What does deterministic execution guarantee in smart contract architecture? → Every node computes the same result
24. On a public Blockchain, who can read the records? → Everyone on the Blockchain
25. What does 'on-chain' governance mean in the context of blockchain network types? → Protocol changes are voted on and executed directly via blockchain transactions
26. What is the primary purpose of a 'finality gadget' like Casper FFG? → To provide checkpoints that make blocks irreversible
27. What does 'liveness' guarantee in a consensus protocol? → The system continues to make progress and process new transactions
28. What is the purpose of transaction fees in a blockchain network? → To incentivize miners/validators to include transactions in blocks and prevent spam
29. What is a 'flash loan' in DeFi? → An uncollateralized loan that must be borrowed and repaid within the same transaction
30. What is the key difference between Proof of Work used on a public blockchain and Proof of Authority used on a private blockchain? → PoA relies on trusted validators while PoW relies on computational competition