Clear DefinitionsLight Node
1 min read
Pronunciation
[lahyt nohd]
Analogy
If a full node is like having an entire encyclopedia set at home for reference, a light node is like having just the table of contents and calling the library when you need specific information. You save a lot of shelf space, but depend on the library's accuracy and availability.
Definition
A network participant that only downloads block headers rather than the entire blockchain, relying on full nodes to provide relevant transaction data when needed. Light nodes enable blockchain interactions with reduced resource requirements compared to full nodes.
Key Points Intro
Light nodes make blockchain technology accessible on resource-constrained devices like mobile phones.
Key Points
Downloads only block headers, not full transaction data.
Verifies proof-of-work or other consensus mechanisms in headers.
Uses Simplified Payment Verification (SPV) to confirm specific transactions.
Requires significantly less storage, bandwidth, and processing power.
Example
Mobile wallet apps typically operate as light nodes, storing only a few MB of critical blockchain data and requesting specific transaction details from connected full nodes when needed to verify payments.
Technical Deep Dive
Light nodes use a technique called Simplified Payment Verification (SPV), described in the original Bitcoin whitepaper. By downloading only block headers (which contain the Merkle root of all transactions), a light node can request a cryptographic proof (Merkle path) from a full node that a particular transaction is included in a block without downloading all transactions. This allows verification that a transaction was accepted by the network without needing the full blockchain.
Security Warning
Light nodes must trust the full nodes they connect to for accurate transaction data. Using multiple connection points and/or trusted node operators reduces the risk of receiving manipulated information.
Caveat
While more efficient, light nodes trade some security for convenience. They can verify that transactions exist within blocks but cannot independently verify all consensus rules, making them potentially vulnerable to certain types of network attacks.
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