Blockchain is a distributed digital ledger technology that records transactions across multiple computers in a way that makes the data tamper-resistant and transparent. At its core, blockchain combines cryptography, consensus mechanisms, and peer-to-peer networks to create trustless systems where participants can transact without intermediaries. Understanding blockchain fundamentals—from how blocks link through cryptographic hashes to how networks reach consensus—is essential for anyone working with cryptocurrencies, smart contracts, or decentralized applications. The key insight: blockchain achieves security not through central authority but through mathematical proofs and network-wide verification.
What This Cheat Sheet Covers
This topic spans 12 focused tables and 90 indexed concepts. Below is a complete table-by-table outline of this topic, spanning foundational concepts through advanced details.
Table 1: Core Components
The fundamental building blocks every blockchain shares — understanding how blocks, hashes, and transactions fit together gives you the mental model needed to reason about anything built on top.
| Component | Example | Description |
|---|---|---|
Header: prev_hash, merkle_root, timestamp, nonceBody: [tx1, tx2, tx3...] | Container for transaction data consisting of a header (metadata) and body (transactions), linked via hashes to form the chain. | |
from: addr1, to: addr2,amount: 0.5 BTC, signature: ... | Record of value transfer including sender, recipient, amount, and digital signature for authentication. | |
SHA-256("hello") =2cf24dba... (64 hex chars) | • Cryptographic fingerprint of data — one-way function producing fixed-size output • any input change produces a completely different hash | |
Every node stores full copy of blockchain | • Decentralized database replicated across all network nodes with no single point of control • all participants maintain identical records |