Blockchain and Cryptocurrency Cheat Sheet

The core ideas of Blockchain and Cryptocurrency distilled into a single, scannable reference — perfect for review or quick lookup.

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Quick Reference

Blockchain

A decentralized, distributed digital ledger that records transactions across many computers in a way that makes the registered transactions virtually impossible to alter retroactively. Each block contains a cryptographic hash of the previous block, creating an immutable chain of records.

Consensus Mechanism

A protocol used by blockchain networks to achieve agreement among distributed nodes on the current state of the ledger. Different mechanisms balance security, decentralization, and scalability in various ways, determining who gets to add the next block.

Smart Contract

Self-executing programs stored on a blockchain that automatically enforce and execute the terms of an agreement when predetermined conditions are met. They eliminate the need for intermediaries and run exactly as programmed without possibility of censorship or downtime.

Decentralized Finance (DeFi)

A financial ecosystem built on blockchain technology that recreates and improves upon traditional financial services such as lending, borrowing, trading, and insurance without centralized intermediaries like banks. DeFi protocols operate through smart contracts and are accessible to anyone with an internet connection.

Cryptographic Hashing

A mathematical function that converts input data of any size into a fixed-length string of characters, which acts as a unique digital fingerprint. In blockchain, hashing ensures data integrity because even a tiny change to the input produces a completely different hash output.

Mining and Staking

Two primary methods for validating transactions and creating new blocks on a blockchain. Mining (Proof of Work) requires computational power to solve complex puzzles, while staking (Proof of Stake) requires validators to lock up cryptocurrency as collateral to participate in block validation.

Public and Private Keys

A pair of cryptographic keys used to secure cryptocurrency transactions. The public key serves as an address that others can use to send funds, while the private key is a secret code that proves ownership and authorizes transactions. Losing a private key means permanently losing access to associated funds.

Tokenization

The process of converting rights to a real-world or digital asset into a digital token on a blockchain. Tokens can represent ownership of physical assets, access rights, voting power, or utility within a specific platform, enabling fractional ownership and easier transferability.

Layer 2 Scaling Solutions

Protocols built on top of an existing blockchain (Layer 1) designed to increase transaction throughput and reduce fees without compromising the security of the underlying network. They process transactions off the main chain and periodically settle the results back to it.

Non-Fungible Token (NFT)

A unique digital token on a blockchain that represents ownership of a specific item such as digital art, music, collectibles, or virtual real estate. Unlike cryptocurrencies, NFTs are not interchangeable because each one has distinct properties and metadata that make it one-of-a-kind.

Key Terms at a Glance

Blockchain:A decentralized, distributed digital ledger technology that records transactions in a chain of cryptographically linked blocks, providing transparency, immutability, and security without requiring a central authority.

Cryptocurrency:A digital or virtual currency that uses cryptographic techniques to secure transactions, control the creation of new units, and operate independently of a central bank on a blockchain network.

Bitcoin:The first and most widely recognized cryptocurrency, created in 2009 by the pseudonymous Satoshi Nakamoto. It uses Proof of Work consensus and has a fixed supply cap of 21 million coins.

Ethereum:A blockchain platform that extends beyond simple currency transactions by supporting programmable smart contracts and decentralized applications (dApps), using Ether (ETH) as its native cryptocurrency.

Smart Contract:A self-executing program stored on a blockchain that automatically enforces and executes contractual terms when predefined conditions are met, eliminating the need for trusted intermediaries.

Consensus Mechanism:A protocol by which all participants in a blockchain network agree on the current valid state of the distributed ledger, ensuring that all copies of the database are synchronized and accurate.

Proof of Work (PoW):A consensus mechanism requiring miners to expend computational energy solving cryptographic puzzles to validate transactions and create new blocks, rewarding the first successful miner.

Proof of Stake (PoS):A consensus mechanism where validators are selected to create new blocks proportional to the amount of cryptocurrency they have staked as collateral, providing an energy-efficient alternative to Proof of Work.

Mining:The process of using computational power to validate transactions and add new blocks to a Proof of Work blockchain. Miners are rewarded with newly created cryptocurrency and transaction fees.

Wallet:Software or hardware that stores the private keys needed to access and manage cryptocurrency holdings. Wallets can be hot (internet-connected) or cold (offline) and come in many forms including mobile apps, browser extensions, and physical devices.

Private Key:A secret cryptographic key that proves ownership of a blockchain address and is required to authorize transactions. It must be kept confidential, as anyone with access to it can control the associated funds.

DeFi (Decentralized Finance):An ecosystem of financial applications built on blockchain networks that provide services like lending, borrowing, trading, and insurance without traditional intermediaries such as banks or brokerages.

NFT (Non-Fungible Token):A unique digital token on a blockchain that represents verifiable ownership of a specific digital or physical asset, distinguishing it from fungible tokens which are interchangeable and identical.

Gas:A unit of measurement for the computational work required to execute transactions and smart contract operations on the Ethereum network. Users pay gas fees in ETH to compensate validators.

Stablecoin:A cryptocurrency designed to maintain a stable value relative to a reference asset, typically a fiat currency like the US dollar. Mechanisms include fiat reserves (USDC), crypto collateral (DAI), or algorithmic supply management.

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