✅ You Understand Merkle Trees & Data Verification

Master Merkle roots, proofs, and why light clients are possible

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🎯 Key Takeaways

You've mastered Merkle trees! Let's review the core concepts and test your knowledge.

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Binary hash tree where each leaf is a transaction hash and each parent is the hash of its children. Root represents all data.

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Verification requires O(log n) hashes. For 1 million transactions, only 20 hashes needed instead of 1 million!

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Any data tampering changes all parent hashes up to root. Cryptographically impossible to forge with collision-resistant hash functions.

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SPV wallets use Merkle proofs to verify payments with ~100 MB storage vs ~550 GB for full nodes. Mobile blockchain access!

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Bitcoin uses Merkle trees in every block - The block header stores only the 32-byte root, allowing SPV wallets to verify transactions efficiently.

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Ethereum uses three Merkle trees per block - Transactions, receipts, and state, enabling more sophisticated light client capabilities.

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Proof size grows logarithmically - Doubling transactions only adds one hash to proof. Scales beautifully!

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Bottom-up construction is O(n) - Hash all leaves, then combine pairs recursively. Simple and parallelizable.

Answer all questions to complete this module. Each question explains the correct answer after submission.

What is the primary benefit of Merkle trees in blockchain?

For a block with 1,000 transactions, how many hashes are needed for a Merkle proof?

What happens if you try to forge a Merkle proof?

How do SPV wallets verify payments?

What is the time complexity of building a Merkle tree?