51% Attack

A 51% Attack happens when the majority of the cryptocurrency network’s hash rate or validation authority is controlled by a single person or entity.

Also known as a majority attack, malicious actors could use a 51% attack to cause disruption on the network, potentially overriding the consensus mechanism of the network.

Smaller networks are more susceptible to 51% attacks, as they have fewer participants, making it easier for a single person to gain control over more computing power compared to all other network participants.

51% attacks, while possible, are considered extremely unlikely, especially for larger networks like Bitcoin and Ethereum , because of the high cost of obtaining that much hash power.

Bitcoin SV, Bitcoin Gold and Ethereum Classic (ETC) all suffered 51% attacks.

Related Terms

Bitcoin (BTC)

Bitcoin (BTC) is most well known as a digital decentralized cryptocurrency, without a central bank or single administrator, that can be sent from user to user on the peer-to-peer Bitcoin network without the need for intermediaries, such as payment gateways or banks or routing services. Think of bitcoin as Internet money, that you can send and receive directly, to and from anyone, and you can use it to pay for stuff.

Ethereum (ETH)

Ethereum is a decentralized blockchain platform that makes digital money, global payments, and applications possible using open-source software and smart contract functionality. The big difference between the two is that Ethereum is programmable, meaning you can build and use decentralized apps on the network. That means the Ethereum blockchain can be programmed to do virtually anything.

Immutability

A core feature of blockchains that makes their ledgers, the data record of transactions, unchangeable and unalterable. Immutability drives the trustworthiness and integrity of blockchain data as chain transactions and rulesets are protected from fraud, hacking and other wrongdoing.

Distributed Ledger Technology

A database that is used to record transactions across a network of devices, usually computers or servers. “Distributed” refers to how the nodes (or computers or servers) of the network are designed architecturally, and where they are located geographically. “Ledger” in this context, and traditionally, simply refers to a centralized database that is used to store financial records, such as a company’s financials, liabilities, revenues, owner’s equity, and other financial information. Now, combine the two ideas and you have a ledger that is distributed across many devices, instead of one device, in many different locations, possibly around the world. Even if one of those locations disappears, or a computer or server goes down, the ledger is still intact, still secure, and the data stored within the ledger can still be processed, validated, and authenticated to.

Blockchain

Blockchain networks are at the heart of cryptocurrencies. A blockchain is a database, or digital ledger, made up of a series of interconnected blocks containing transaction data created on the network over some period of time. Each block in a blockchain also contains a unique identifier unlike any other block in the chain called a hash. Think of the hash as a fingerprint identifying that block for all other blocks. Distributed ledger technology (DLT) is another name frequently used in relation to blockchains.