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Web3 Glossary

51% attack or majority attack

an attack on a blockchain made possible when a single person or group gains control of over 50% of a blockchain's hashing power, enabling them to block new transactions from being confirmed as well as change the ordering of new transactions. It also allows the malicious agents to essentially rewrite parts of the blockchain and reverse their own transactions, leading to an issue known as double spending. (CoinDesk)

abi

In computer software, an application binary interface (ABI) is an interface between two binary program modules. Often, one of these modules is a library or operating system facility, and the other is a program that is being run by a user.

airdrop

a distribution of a cryptocurrency token or an asset like an NFT, usually for free, to numerous wallet addresses. Airdrops are primarily implemented as a way of gaining attention and new followers, resulting in a larger user-base and a wider disbursement of coins. (Wikipedia)

apes

typically referring to the popular Bored Apes Yacht Club NFT project, "apes" has also become a slang term to refer to NFTs in general (regardless of what they depict)

audit

a process in which an individual or company checks a blockchain-based project for flaws in its code, as well as tries to determine the legitimacy of the project based on other factors (identity of its creators, etc.)

blockchain

a blockchain is a type of distributed database that is often decentralized across many different servers. Entries can be added to a blockchain, but typically can't be changed or erased without enormous difficulty and disruption to the network. There are many different blockchains; some of the best known include Bitcoin and Ethereum. (Wikipedia)

bridge

a blockchain bridge is a method of allowing different blockchains to interoperate, allowing users to use tokens in a currency tied to one blockchain to operate on another.

bug bounty

typically referred to funds distributed to ethical hackers in exchange for them privately disclosing software bugs to the company, crypto projects have taken to using the term "bug bounty" to also refer to ransom that is offered to hackers who have successfully stolen money, in exchange for them returning the funds and usually with promises that the affected platform won't seek prosecution

burning

the process in which users remove tokens from circulation. This can apply to various assets including cryptocurrencies, where it is done to reduce the number of coins in circulation, or to NFTs, where it makes the NFT impossible to ever trade again. The process of burning involves sending the token to a wallet address that is unable to send tokens, permanently locking it there. (Investopedia)

coin

a specific cryptocurrency (e.g. Bitcoin, Ethereum, Dogecoin)

cold wallet

a cryptocurrency wallet that is not Internet-connected, in contrast to a "hot wallet"

DAO / decentralized autonomous organization

an organization represented by rules encoded as a computer program that is transparent, controlled by the organization members and not influenced by a central government (Wikipedia)

dApp / decentralized app

a computer application that runs on a decentralized computing system (Wikipedia)

DeFi / decentralized finance

a blockchain-based form of finance that does not rely on central financial intermediaries such as brokerages, exchanges, or banks to offer traditional financial instruments, and instead utilizes smart contracts on blockchains. Types of DeFi platforms include crypto exchanges, loan platforms, investment and savings accounts, and insurance providers. (Wikipedia)

double-spending

a potential flaw in a digital cash scheme in which the same single digital token can be spent more than once (Wikipedia)

doxxing

discovering the identity of pseudonymous cryptocurrency traders, often those running a project. The term "self-doxing" is the process of disclosing one's own identity (often in hopes of lending legitimacy to a project). Projects where the developers' identities are known are often described as "fully-doxed". In the crypto space, the term is not typically used with the negative meaning that it has elsewhere.

Dutch auction

an auction which begins with a high asking price which lowers over a set time period until a buyer accepts the price, or a reserve price is hit (Wikipedia)

DYOR (do your own research)

a common phrase in the crypto communities. Proponents would say that it is used to tell people they should verify everything themselves and not take advice from those who may not have their best interests in mind. Critics would point out that it's often used to dodge answering tricky questions, or imply someone doesn't know what they're talking about.

fiat

government-issued legal tender---what most of us know as "money"

flash loan

unsecured loans that don't require collateral from the borrower. Funds are borrowed, used, and returned all within one transaction, and they are typically used to provide leverage in arbitrage opportunities. They have also become a common entry point for hackers to exploit flaws in various DeFi protocols. (Radix)

floor price

the lowest price at which any NFT in a collection can be bought

fork

creating a new version of a blockchain or project based on an existing one. This is sometimes done when starting an entirely new project that is similar to one that already exists, to take advantage of the work that's already been done. It is also the term used when a blockchain needs to make a change to functionality, either to add new features or to fix security bugs---in this case, nodes must change over to the new version, or the chain will split into two separate chains with the same history, but different data going forward. (Wikipedia)

freezing

a process in which a given exchange prevents an asset (such as an NFT) from being traded, usually because it has been identified as stolen. This also sometimes refers to the process of preventing an entire wallet from transacting on a platform. There is effectively no way for third parties to completely prevent a person from trading a specific asset, but when major exchanges freeze trading for an asset or wallet it makes it substantially harder for that asset to be sold or traded.

FUD (fear/uncertainty/doubt)

a strategy to influence perception by disseminating negative and dubious or false information and a manifestation of the appeal to fear. Crypto projects often use the term more broadly to describe anything remotely negative about a project. (Wikipedia)

gas

gas fees are the transaction fees required to perform any transaction on the Ethereum blockchain: minting, buying an NFT, etc. (Wikipedia)

gm

an abbreviation for "good morning" that has become signature crypto slang (NFT ska)

governance token

tokens that represent a person's stake in the governance of a project, usually granting them voting powers

hardware wallet

a type of cold wallet (non-Internet-connected wallet) where cryptocurrency is stored on a physical device much like a flash drive (but often with additional features)

hashrate

the total combined computational power that is being used to mine and process transactions on a proof-of-work blockchain (CoinDesk)

hot wallet

a cryptocurrency wallet that is connected to the Internet, which allows the currency to be quickly accessed for trading and spending

ICO / initial coin offering

a crypto industry equivalent to an initial public offering (IPO). In an ICO, a quantity of cryptocurrency is sold to speculators or investors in exchange for legal tender or other (generally established and more stable) cryptocurrencies such as Bitcoin or Ether. The tokens are promoted as future functional units of currency if or when the ICO's funding goal is met and the project successfully launches. (Wikipedia)

KYC / know your customer / know your client

procedures to verify the identity of a customer or client in a business relationship. Within the cryptocurrency space, this typically means verifying the real-life identity of a person behind a cryptocurrency wallet, or the identities of people running a project. (Wikipedia)

liquidity pool

funds locked in a smart contract, which facilitate trading and lending in a given exchange

memecoin / shitcoin

cryptocurrency that originated from an Internet meme or has some other humorous characteristic. Examples include Dogecoin, Shiba Inu, and other dog-themed coins. (Wikipedia)

metaverse

a network of 3D virtual worlds focused on social connection. Some metaverses envision using cryptocurrencies, NFTs, and other blockchain-based technologies both to make exchanges within a given metaverse, and potentially transfer assets between metaverses. (The Conversation)

mining

cryptocurrency mining is the process of validating blockchain transactions, and obtaining new cryptocurrency as a reward (Wikipedia)

mining pool

the pooling of resources by miners, who share their processing power over a network, to split the reward equally, according to the amount of work they contributed to the probability of finding a block (Wikipedia)

minting

the process of creating new tokens on a blockchain. This often refers to users creating NFTs, but also refers to the addition of other tokens, such as increasing the quantity of a cryptocurrency in circulation

NFT / non-fungible token

a non-interchangeable unit of data stored on a blockchain that can be sold and traded. Types of NFT data units may be associated with digital files such as photos, videos, and audio. (Wikipedia)

ngmi / not going [to] make it

slang to suggest that a person or group will not be successful in crypto due to a bad decision or poor judgment (NTFska)

orange pill

a reference to the Matrix's red and blue pills, "taking the orange pill" is a metaphor for seeing the "truth" that Bitcoin (represented by an orange ₿) is the way of the future

phishing

a type of social engineering where an attacker sends a fraudulent message designed to appear to be from a legitimate source, such as a trusted company like a bank. Phishing is intended trick a victim into actions including revealing sensitive information, authorizing transactions, or installing malicious software (Wikipedia)

play-to-earn / P2E

a game mechanic in which players are rewarded with cryptocurrency tokens or other blockchain-based items (Protocol)

privacycoin

cryptocurrencies that preserve anonymity by obscuring the flow of money across their networks, making it difficult to work out who sent what to whom (CoinDesk)

private key

a generated passphrase that grants access to assets including cryptocurrencies and NFTs. A compromised private key allows an attacker to steal all assets belonging to the person or group with that private key.

proof of stake

a class of consensus mechanisms for blockchains that work by selecting validators in proportion to their quantity of holdings in the associated cryptocurrency. Examples of proof-of-stake blockchains include Avalanche, Cardano, Polkadot, Solana, and Tezos. (Wikipedia)

proof of work

a class of consensus mechanisms for blockchains in which one party (the prover) proves to others (the verifiers) that a certain amount of a specific computational effort has been expended. Examples of proof-of-work blockchains include Bitcoin, Ethereum, and Monero.

pumping (and dumping)

pumping (and then dumping) involves artificially inflating the price of a token or project with false or misleading information, allowing those behind it or who got in early to then "dump" the coin---that is, cash out before the price tanks

right-clicker

a pejorative term for people who are skeptical of or otherwise don't "get" NFTs. It refers to the fairly common point by NFT skeptics, that someone seeking to obtain the artwork purchased by an NFT holder could simply right-click and save the file to their computer.

rug pull

when a development team suddenly abandons a project and takes all the money

seed phrase

a secret series of words that function as a password to a cryptocurrency wallet, giving access to the currency or other assets associated with that wallet

smart contract

a computer program or a transaction protocol which is intended to automatically execute, control or document legally relevant events and actions according to the terms of a contract or an agreement

stablecoin

cryptocurrencies where the price is designed to be pegged to a cryptocurrency, fiat money, or to exchange-traded commodities

staking

a strategy to earn rewards on cryptocurrency or other assets by locking up the assets in a way that supports the blockchain network

Sybil attack

an attack or exploitation of a computer system in which a person creates many pseudonymous identities to gain disproportionate control or influence in the system

token swap, token migration, or token fork

a process in which a project migrates from using one token to using a new one. There are several reasons a project might do this, including to restore a snapshot of a project from before when a hack occurred, to try to restore users' original holdings and to drop the value of the stolen tokens to 0.

tumbler or mixer

a cryptocurrency tumbler (or cryptocurrency mixing service) is a service offered to mix potentially identifiable or "tainted" cryptocurrency funds with others, so as to obscure the trail back to the fund's original source (Wikipedia)

wallet

a place where the keys to access one's cryptocurrency and other holdings (such as NFTs) are stored. These are sometimes physical devices similar to flash drives, or they can also be software-based.

wash trading

the process of selling an NFT between two wallets secretly owned by the same person (or by two people working together). This is often done to artificially inflate the price of an NFT by making it appear to be in demand but is also sometimes done to obtain rewards for transactions offered by some platforms.

web3 / web 3.0

an idea for a new iteration of the World Wide Web based on the blockchain, which incorporates concepts including decentralization and token-based economics (Wikipedia)

whale

a person who has invested a large amount into cryptocurrencies or other blockchain-based assets. The term is also used to refer to a person who holds a large proportion of assets within a given project.

wrapped token

a wrapped token (often denoted with a lowercase "w" before the token abbreviation, like wETH for wrapped Ethereum) is a token that is pegged to the value of the original currency, and able to be used on other blockchains.

yield farming

lending or staking cryptocurrency in exchange for interest and other rewards

Etherscan Glossary

Account

An object containing an address, balance, nonce and optional storage and code. An account can be a contract account or an EOA (externally owned account).

Address

Most generally, this represents an EOA or contract that can receive (destination address) or send (source address) transactions on the blockchain. More specifically, it is the right-most 160 bits of a Keccak hash of an ECDSA public key.

Arbitrage

Making buy and sell transactions of the same asset at the same time and profiting from a difference in prices. Typically done across different markets, it is also possible to do by manipulating transaction ordering within the same block.

Assert

In Solidity, assert(false) compiles to 0xfe, an invalid opcode, which uses up all remaining gas and reverts all changes. When an assert() statement fails, something very wrong and unexpected should be happening, and you will need to fix your code. You should use assert to avoid conditions which should never, ever occur.

Back running

The act of monitoring the transaction pool for a particular type of transaction (such as an oracle updating token price), then submitting a new transaction to take advantage of the previous one immediately afterwards (such as executing a liquidation of an on-chain loan after the oracle price update).

Block

A block is a collection of required information (a block header) about the comprised transactions, and a set of other block headers known as ommers. It is added to the Ethereum network by miners.

Blockchain

In Ethereum, a sequence of blocks validated by the proof-of-work system, each linking to its predecessor all the way to the genesis block. This varies from the Bitcoin protocol in that it does not have a block size limit; it instead uses varying gas limits.

Bytecode

Abstract instruction set designed for efficient execution by a software interpreter or a virtual machine. Unlike human readable source code, bytecode is expressed in numeric format.

Byzantium fork

Byzantium is the first of two hard forks for the Metropolis development stage. It included EIP-649: Metropolis Difficulty Bomb Delay and Block Reward Reduction, where the Ice Age (see below) was delayed by 1 year, and the block reward was reduced from 5 to 3 ether.

Compiling

Converting code written in a high-level programming language (e.g. Solidity) into a lower level language (e.g. EVM bytecode).

Consensus

When numerous nodes, usually most nodes on the network, all have the same blocks in their locally validated best block chain. Not to be confused with "consensus rules".

Consensus rules

The block validation rules that full nodes follow to stay in consensus with other nodes. Not to be confused with "consensus".

Constantinople

The second part of the Metropolis stage, planned for mid-2018. Expected to include a switch to hybrid Proof-of-Work/Proof-of-Stake consensus algorithm, among other changes.

Contract account

An account containing code that executes whenever it receives a transaction from another account (EOA or contract).

Contract creation transaction

A special transaction, with the "zero address" as the recipient, that is used to register a contract and record it on the Ethereum blockchain (see "zero address").

DAO

Decentralized Autonomous Organization. Companies and other organizations which operate without hierarchical management. Also may refer to a contract named "The DAO" launched on 30th April 2016, which was then hacked in June 2016 and ultimately motivated a hard fork (codenamed DAO) at block #1,192,000 which reversed the hacked DAO contract, and caused Ethereum and Ethereum Classic to split into two competing systems.

DApp

Decentralized Application. At a minimum, it is a smart contract and a web user-interface. More broadly, a DApp is a web application that is built on top of open, decentralized, peer-to-peer infrastructure services. In addition, many DApps include decentralized storage and/or message protocol and platform.

Deed

Non-fungible token (NFT) standard introduced by the ERC721 proposal. Unlike ERC20 tokens, deeds prove ownership and are not interchangeable, though they are not recognized as legal documents in any jurisdiction, at least not currently (see also "NFT").

DEFI

Short for Decentralized Finance referring to financial smart contracts, protocols, and decentralized applications built on Ethereum.

DEX

Decentralized Exchange

Difficulty

A network-wide setting that controls how much computation is required to produce a proof of work.

Digital signature

A digital signing algorithm is a process by which a user can produce a short string of data called a "signature" of a document using a private key such that anyone with the corresponding public key, the signature, and the document can verify that (1) the document was "signed" by the owner of that particular private key, and (2) the document was not changed after it was signed.

ECDSA

Elliptic Curve Digital Signature Algorithm, or ECDSA, is a cryptographic algorithm used by Ethereum to ensure that funds can only be spent by their owners.

EIP

Ethereum Improvement Proposals describe proposed standards for the Ethereum platform. An EIP is a design document providing information to the Ethereum community, describing a new feature or its processes or environment. For more information, see https://github.com/ethereum/EIPs (see also "ERC").

Entropy

In the context of cryptography, lack of predictability, or level of randomness. When generating secret information, such as private keys, algorithms usually rely on a source of high entropy to ensure the output is unpredictable.

ENS

Ethereum Name Service. For more information, see https://github.com/ethereum/ens/ .

EOA

Externally Owned Account. Accounts created by or for human users of the Ethereum network.

ERC

Ethereum Request for Comments, a label given to some EIPs which attempt to define a specific standard of Ethereum usage.

Ethash

A Proof-of-Work algorithm for Ethereum 1.0. For more information, see https://github.com/ethereum/wiki/wiki/Ethash .

Ethereum 2.0 (Eth2)

Ethereum 2.0 (Eth2) is the next phase of Ethereum shifting from a Proof of Work to Proof of Stake consensus algorithm. Eth2 will improve issues from scalability, security, and usability for the network. Phase 0 is the first phase for Eth2.

Ether

Ether is the native cryptocurrency used by the Ethereum ecosystem, which covers gas costs when executing Smart Contracts. Its symbol is Ξ, the Greek uppercase Xi character.

Event

An event allows the use of EVM logging facilities. DApps can listen for events and use them to trigger JavaScript callbacks in the user interface. For more information, see http://solidity.readthedocs.io/en/develop/contracts.html#events .

EVM

Ethereum Virtual Machine, a stack-based virtual machine which executes bytecode. In Ethereum, the execution model specifies how the system state is altered given a series of bytecode instructions and a small tuple of environmental data. This is specified through a formal model of a virtual state machine.

EVM assembly language

A human-readable form of EVM bytecode.

Fallback function

A default function called in the absence of data or a declared function name.

Faucet

A service that dispenses funds in the form of free test ether that can be used on a testnet.

Finney

A denomination of ether. 10 ** 15 finney = 1 ether.

Flash loan

A loan that is borrowed and repaid in the same transaction. Flash loans allow users to borrow tokens without any collateral and use them for DeFi activities such as arbitrage and liquidation.

Fork

This term assumes two main meanings: a change in protocol causing the creation of an alternative chain, or a temporal divergence in two potential block paths during mining.

Frontier

The initial test development stage of Ethereum, which lasted from July 2015 to March 2016.

Front running

The act of monitoring the transaction pool for a particular type of transaction (such as purchasing an Ethereum domain name), then submitting the same transaction with a higher gas fee to ensure it goes through instead of the targeted transaction.

Futures

Derivative financial contracts which require transacting parties to transact at a predetermined future date and price. Upon expiration of the contract, both buyer and seller must exchange the underlying asset at the set price regardless of its market price.

Ganache

Personal Ethereum blockchain which you can use to run tests, execute commands, and inspect state while controlling how the chain operates.

Gas

A virtual fuel used in Ethereum to execute smart contracts. The Ethereum Virtual Machine uses an accounting mechanism to measure the consumption of gas and limit the consumption of computing resources (see "Turing complete").

Gas limit

The maximum amount of gas a transaction or block may consume.

Genesis block

The first block in a blockchain, used to initialize a particular network and its cryptocurrency.

Geth

Go Ethereum. One of the most prominent implementations of the Ethereum protocol, written in Go.

Hard fork

A hard fork, also known as a Hard-Forking Change, is a permanent divergence in the blockchain; one commonly occurs when non-upgraded nodes can't validate blocks created by upgraded nodes that follow newer consensus rules. Not to be confused with fork, soft fork, software fork or Git fork.

Hash

fixed-length fingerprint of variable-size input, produced by a hash function.

HD wallet

A wallet using the Hierarchical Deterministic (HD Protocol) key creation and transfer protocol (BIP32).

HD wallet seed

An HD wallet seed, or seed, is a value used to generate the master private key and master chain code for an HD wallet. The wallet seed can be represented by mnemonic words, making it easier for humans to copy, backup and restore private keys.

Homestead

The second development stage of Ethereum, launched in March 2016 at block #1,150,000.

Ice Age

A hard fork of Ethereum at block #200,000 to introduce an exponential difficulty increase (aka Difficulty Bomb), motivating a transition to Proof-of-Stake.

IDE

Short for Integrated Development Environment, an integrated user interface that typically combines a code editor, compiler, runtime, and debugger.

Immutable Deployed Code Problem

Once a contract's (or library's) code is deployed it becomes immutable. Standard software development practices rely on being able to fix possible bugs and add new features, so this represents a challenge for smart contract development.

Internal transaction (also "message")

A transaction sent from a contract account to another contract account or an EOA.

IPFS

The Inter Planetary File System is a protocol, a network and an open-source project designed to create a content-addressable, peer-to-peer method of storing and sharing hypermedia in a distributed file system.

Istanbul

The eight-development stage of Ethereum, launched at block #9,069,000

Keccak256

Cryptographic hash function used in Ethereum. Keccak256 was standardized as SHA-3.

Keystore File

A JSON-encoded file that contains a single (randomly generated) private key, encrypted by a passphrase for extra security.

Layer 2 (L2)

Layer 2 refers to several approaches to handle transactions off the main Ethereum chain. These allow for higher scalability of the network and reduced transaction fees. Some examples include Optimistic and Zero-Knowledge (ZK) Rollups, Validium, Plasma and State Channels.

Library

A library in Ethereum is a special type of contract that has no payable functions, no fallback function, and no data storage. Therefore, it cannot receive or hold ether, or store data. A library serves as previously deployed code that other contracts can call for read-only computation.

Lightweight client

A lightweight client is an Ethereum client that does not store a local copy of the blockchain, or validate blocks and transactions. It offers the functions of a wallet and can create and broadcast transactions.

Liquidation

In Defi, it refers to the process of selling assets off from an under-collateralized loan.

Merkle Patricia Tree

A data structure used in Ethereum to efficiently store key-value pairs.

Message

An internal transaction that is never serialized and only sent within the EVM.

Message Call

The act of passing a message from one Account to another. If the destination account is associated with EVM Code, then the VM will be started with the state of said Object and the Message acted upon.

Metropolis

Metropolis is the third development stage of Ethereum, launched in October 2017.

MEV

Short for Maximal Extractable Value (previously Miner Extractable Value), it refers to the value that a miner or validator are able to obtain from reordering transactions within the blocks they produce, on top of the block reward and transaction fees they normally benefit from. Transactions leading to MEV include arbitrage and liquidations.

Metadata

Creation date, Expiration date and the Registration date for an ENS NFT contract. See https://github.com/ensdomains/ens-metadata-service

Miner

A network node that finds valid proof of work for new blocks, by repeated hashing.

Mist

The first Ethereum-enabled browser, built by the Ethereum Foundation. It contains a browser based wallet that was the first implementation of the ERC20 token standard (Fabian Vogelsteller, author of ERC20, was also the main developer of Mist). Mist was also the first wallet to introduce the camelCase checksum (EIP-55). Mist runs a full node, and offers a full DApp browser with support for Swarm-based storage and ENS addresses.

Network

Referring to the Ethereum network, a peer-to-peer network that propagates transactions and blocks to every Ethereum node (network participant).

NFT

A non-fungible token (also known as a "deed"). This is a token standard introduced by the ERC721 proposal. NFTs can be tracked and traded, but each token is unique and distinct; they are not interchangeable like ERC20 tokens. NFTs can represent ownership of digital or physical assets.

Node

A software client that participates in the network.

Nonce

In cryptography, a value that can only be used once. There are two types of nonce used in Ethereum. (1) An account nonce: A transaction counter in each account, which is used to prevent replay attacks. (2) Proof of work nonce: The random value in a block that was used to satisfy the proof of work. -- See video below.

Private key

The secret number that allows Ethereum users to prove ownership of an account or contracts, by producing a digital signature (see public key, address, ECDSA).

Private transaction

A transaction that bypassed the Ethereum transaction pool and was sent directly to miners.

Proof-of-Stake (PoS)

Proof-of-Stake is a method by which a cryptocurrency blockchain protocol aims to achieve distributed consensus. Proof-of-Stake asks users to prove ownership of a certain amount of cryptocurrency (their "stake" in the network) in order to be able to participate in the validation of transactions.

Proof-of-Work (PoW)

A piece of data (the proof) that requires significant computation to find. In Ethereum, miners must find a numeric solution to the Ethash algorithm that meets a network-wide difficulty target.

Public key

A number, derived via a one-way function from a private key, which can be shared publicly and used by anyone to verify a digital signature made with the corresponding private key.

Receipt

Data returned by an Ethereum client to represent the result of a particular transaction, including a hash of the transaction, its block number, the amount of gas used and, in case of deployment of a Smart Contract, the address of the Contract.

Re-entrancy attack

An attack that consists of an Attacker contract calling a Victim contract function in such a way that during execution the Victim calls the Attacker contract again, recursively. This can result, for example, in the theft of funds by skipping parts of the Victim contract that update balances or count withdrawal amounts.

Reward

An amount of ether included in each new block as a reward by the network to the miner who found the Proof-of-Work solution.

Sandwich attack

The act of monitoring the transaction pool for a sufficiently valuable transaction (such as a large trade on a decentralized exchange), then submitting two transactions 'sandwiching' the target transaction. The first one immediately before the target pushes price in one direction, while the second one immediately after the target does the opposite. The attacker profits from the arbitrage between their two transactions.

Satoshi Nakamoto

The name used by the person or people who designed Bitcoin, created its original reference implementation, and were the first to solve the double-spend problem for digital currency. Their real identity remains unknown.

SHA

The Secure Hash Algorithm (SHA) is a family of cryptographic hash functions published by the National Institute of Standards and Technology (NIST).

Serenity

The fourth and final development stage of Ethereum. Serenity does not yet have a planned release date.

Smart contract

A program which executes on the Ethereum computing infrastructure.

Solidity

A procedural (imperative) programming language with syntax that is similar to JavaScript, C++ or Java. The most popular and most frequently used language for Ethereum smart contracts. Created by Gavin Wood (co-author of this book).

Solidity inline assembly

EVM assembly language in a Solidity program. Solidity's support for inline assembly makes it easier to write certain operations.

Spurious Dragon

A hard fork of the Ethereum blockchain, which occurred at block #2,675,000 to address more denial of service attack vectors, and another state clearing; see "Tangerine Whistle". Also, a replay attack protection mechanism.

Stablecoin

Tokens that are pegged to the price of a separate stable asset, most commonly with the US Dollar. Different approaches exist including centralized reserves and algorithmic collateral.

Swarm

A decentralized (P2P) storage network, used along with Web3 and Whisper to build DApps.

Szabo

A denomination of ether. 10^12 szabo = 1 ether.

Tangerine Whistle

A hard fork of the Ethereum blockchain, which occurred at block #2,463,000 to change the gas calculation for certain I/O-intensive operations and to clear the accumulated state from a denial of service attack, which exploited the low gas cost of those operations.

Testnet

Short for "test network", a network used to simulate the behavior of the main Ethereum network.

TradFi

Short for Traditional Finance, referring to the mainstream non-blockchain finance industry.

Transaction

Data committed to the Ethereum Blockchain signed by an originating account, targeting a specific address. The transaction contains metadata such as the gas limit for the transaction.

Transaction Pool

Also known as Mempool, the transaction pool refers to the collection of pending transactions that have been created by users and are pending confirmation by miners.

Truffle

One of the most commonly used Ethereum Development Frameworks.

Turing complete

A system of data-manipulation rules (such as a computer's instruction set, a programming language, or a cellular automaton) is said to be "Turing complete" or "computationally universal" if it can be used to simulate any Turing machine. The concept is named after English mathematician and computer scientist Alan Turing.

Vitalik Buterin

Vitalik Buterin is a Russian--Canadian programmer and writer primarily known as the co-founder of Ethereum and as the co-founder of Bitcoin Magazine.

Vyper

A high-level programming language, similar to Serpent, with Python-like syntax. Intended to get closer to a pure-functional language. Created by Vitalik Buterin.

Wallet

Software that holds private keys. Used to access and control Ethereum accounts and interact with Smart Contracts. Keys need not be stored in a wallet, and can instead be retrieved from an offline storage (e.g. a memory card or paper) for improved security. Despite the name, wallets never store the actual coins or tokens.

Web3

The third version of the web. First proposed by Gavin Wood, Web3 represents a new vision and focus for web applications: from centrally owned and managed applications to applications built on decentralized protocols.

Wei

The smallest denomination of ether. 10^18 wei = 1 ether.

Whisper

A decentralized (P2P) messaging service. It is used along with Web3 and Swarm to build DApps.

Zero address

A special Ethereum address, composed entirely of zeros, that is specified as the destination address of a contract creation transaction.