128 Fun Facts About Cryptocurrency

Which crypto slang for refusing to sell began as a typo in a 2013 Bitcoin forum post?

HODL was a mistyped 'hold' in a December 2013 Bitcointalk post titled 'I AM HODLING', written mid-crash by a user who said he'd had some whisky; fans later recast it as 'hold on for dear life'.

Bitcoin's white paper appeared in October 2008, weeks after which Wall Street bank went bankrupt?

Lehman Brothers filed for bankruptcy on 15 September 2008; the white paper followed on 31 October, pitching online payments sent directly from one party to another with no financial institution in between.

What is the term for any cryptocurrency other than Bitcoin?

Altcoin is short for 'alternative coin'; because Bitcoin's code is free for anyone to copy, many of them began as copies that reused it with a few settings changed.

Which 2011 cryptocurrency by Charlie Lee is nicknamed the 'silver to Bitcoin's gold'?

Litecoin, released by Charlie Lee in October 2011, copied Bitcoin's code but targets a block every 2.5 minutes, so its payments confirm four times faster.

What is the slang for developers hyping a token, then vanishing with investors' money?

Rug pull is the slang; in 2021 a token cashing in on the TV hit Squid Game soared, then fell to almost nothing as its developers made off with millions of dollars.

The first block of any blockchain, mined for Bitcoin on 3 January 2009, is known as the what block?

The genesis block, Block 0, was mined by Satoshi on 3 January 2009 with that day's Times headline about a second bank bailout embedded in it, a timestamp and a pointed comment in one.

Which key lets whoever holds it spend a wallet's funds?

The private key is the secret that signs transactions, so anyone holding it can spend the wallet's funds; lose it and the coins are stuck for good, because the network accepts no other proof of ownership.

A Bitcoin address that others send coins to is a hashed form of which key?

The public key is usually run through a hash to make the address, so an address can be posted anywhere; coins sent to it stay put until a matching digital signature unlocks them.

Which kind of cryptocurrency is pegged to a national currency such as the US dollar?

Stablecoins usually hold reserves such as dollars and Treasury bills to keep the peg; the algorithmic kind has no such backing, and TerraUSD's collapse in May 2022 wiped out more than $40 billion.

Which US regulator sued Ripple in 2020 and both Coinbase and Binance in 2023 over crypto tokens?

The SEC argued the tokens were investment contracts under the 1946 Howey test, which asks whether buyers put money into a common enterprise expecting profits from others' efforts.

Who received the first bitcoin transaction, ten coins from its creator in January 2009?

Hal Finney, the cypherpunk who built the reusable proof-of-work system RPOW in 2004, downloaded the software the day it was released and received ten bitcoin from its creator on 12 January 2009.

What is the term for a blockchain protocol change that makes old versions incompatible?

A hard fork changes the rules so every node must upgrade or be left on the old chain; a soft fork, by contrast, tightens rules in a way old software still accepts.

What is the primary purpose of a smart contract on a blockchain?

Its purpose is to run agreed terms automatically, as code rather than a legal document; Nick Szabo coined the term in the 1990s, long before there was a blockchain to run one on.

Which country was the first to adopt Bitcoin as legal tender?

El Salvador's Bitcoin Law, pushed by President Nayib Bukele, took effect on 7 September 2021, making bitcoin legal tender alongside the US dollar; acceptance was made voluntary in January 2025 under an IMF loan deal.

What is the roughly four-yearly event that cuts Bitcoin's block reward called?

Halving comes every 210,000 blocks and cuts the reward for adding a block in two; because new supply keeps shrinking this way, the last fraction of a coin is not due until around 2140.

What kind of token certifies ownership of digital art on a blockchain?

A non-fungible token (NFT) is a unique on-chain record that usually points to a file rather than containing it; Beeple's 'Everydays' NFT sold for $69 million at Christie's in March 2021.

Which company revealed in February 2021 that it had bought $1.5 billion of bitcoin?

Tesla disclosed the $1.5 billion purchase and began taking bitcoin for its cars that March, then stopped 49 days later, citing the fossil fuels burned to produce the coins.

Which programmer, aged 19, wrote the white paper that first proposed Ethereum?

Vitalik Buterin wrote it in late 2013 after arguing that Bitcoin needed a fuller programming language and failing to win agreement; he took the name from a list of science-fiction elements.

What is the term for crypto storage that stays connected to the internet, handy but more exposed to hackers?

A hot wallet keeps its keys on a device that is online; in 2018 hackers drained hundreds of millions of dollars of NEM coins that the Japanese exchange Coincheck had left in one.

Which Paris-based company makes the Nano line of hardware wallets?

Ledger's Nano wallets hold a user's keys on a chip that stays offline; a 2020 breach of its marketing database exposed customers' contact details, not their coins.

Which attack did Satoshi's white paper set out to solve without a trusted third party?

Double-spending, using the same coins twice, was the core problem digital cash had to solve; Bitcoin's white paper answers it with a public ledger where the network agrees which conflicting transaction came first.

What is 'DeFi' an abbreviation for in the cryptocurrency world?

DeFi stands for Decentralized Finance: lending and trading run by code with no bank in the middle; the catch is that buggy code can be robbed, and DeFi protocols became hackers' main target in 2021 and 2022.

On Ethereum, transaction fees are priced in a unit named after what?

Ethereum fees are measured in gas, each operation costing a set amount; since the August 2021 London upgrade (EIP-1559) the base portion of every fee is burned rather than paid to validators.

What did Laszlo Hanyecz famously buy for 10,000 bitcoin in May 2010?

Two pizzas from Papa John's, ordered for him by another forum user in exchange for coins then worth about $41; 22 May is now marked as Bitcoin Pizza Day.

What is the maximum supply of Bitcoin that can ever be mined?

Just 21 million can ever exist; the last is expected around 2140, after which miners must live on transaction fees alone.

Handling at most about seven transactions a second is known as Bitcoin's what problem?

Scalability is the capacity to process more transactions as demand grows; Bitcoin's base layer handles roughly 3 to 7 transactions per second, which is why second-layer networks and the 'block size wars' exist.

What is an 'ICO' in the context of cryptocurrency funding?

An Initial Coin Offering sells a new token to fund a project; the 2017 boom raised billions on little more than white papers, and regulators later ruled many tokens were unregistered securities.

Which never-built digital currency did Nick Szabo propose in 1998, a decade before Satoshi's white paper?

Bit Gold, designed by Nick Szabo in 1998 but never built, chained proof-of-work puzzles so closely to Bitcoin's later design that it made Szabo a perennial Satoshi suspect, which he has denied.

What attack did Bitcoin Gold suffer in 2018, letting thieves reverse exchange deposits?

A 51% attack means controlling most of a chain's hashing power, which let the thieves rewrite recent blocks and take back coins they had already paid in, costing exchanges about $18 million.

Which bitcoin-only dark-web marketplace was shut by the FBI in 2013?

Silk Road founder Ross Ulbricht was arrested in San Francisco in October 2013; the FBI seized the site and the US Marshals later auctioned about 30,000 of its bitcoins, and Ulbricht was sentenced to life in 2015.

Which 2011 bitcoin fork lets users register censorship-resistant '.bit' web addresses?

Namecoin stores '.bit' addresses on its own blockchain, outside the ICANN system that governs .com and .net, so there is no registrar who can be ordered to take one down.

In a cryptocurrency network, what is a 'node'?

A node is a computer relaying or validating transactions; anyone can run one, and a full node keeps its own copy of the whole chain and checks every block against the rules instead of trusting anyone else.

How are validators chosen under a proof-of-stake system?

Under proof of stake, validators are chosen in proportion to the coins they lock up as a deposit; misbehaving validators can have that stake 'slashed', doing the job wasted electricity does under proof of work.

Which Tokyo exchange, once the dominant marketplace for bitcoin, collapsed in 2014 with huge losses of coins?

Mt. Gox filed for bankruptcy in February 2014 after reporting about 850,000 bitcoin missing; some 200,000 of them later turned up in an old digital wallet.

What is a 'fork' in a blockchain?

A fork is a split in the chain's history: Bitcoin Cash split from Bitcoin in 2017 over block size, and Ethereum Classic is the chain that refused to reverse the 2016 DAO hack.

Which early digital cash technology from the 1980s was developed by David Chaum?

Ecash used David Chaum's blind signatures, letting a bank sign a coin without seeing it; his company DigiCash ran it through Mark Twain Bank in St. Louis from 1995 before going bankrupt in 1998.

What does the abbreviation 'DLT' stand for?

Distributed Ledger Technology means every participant holds a synchronised copy of the same data with no central administrator; a blockchain is one design of distributed ledger, not the only one.

Which figure is calculated by multiplying a coin's price by the number of coins in circulation?

Market capitalisation is price multiplied by circulating supply, so price alone says little: a token costing a fraction of a cent can outrank one costing thousands if enough units exist.

A token is 'fungible' when what is true of it?

A fungible token is one where any unit can swap for any other, as one dollar bill or one bitcoin is as good as the next; that sameness is what lets a token work as money.

What is 'yield farming' in DeFi?

Shifting coins between pools for returns is yield farming; it took off in June 2020, when the lending service Compound began paying its own COMP token to lenders and borrowers.

Which meme coin did Billy Markus and Jackson Palmer launch as a joke about crypto speculation?

Dogecoin went live in December 2013 with the 'Doge' dog meme as its logo; meant to mock crypto speculation, it instead set off a whole wave of copycat meme coins.

Which 1997 anti-spam scheme by Adam Back supplied the proof-of-work idea that Bitcoin later built on?

Hashcash made a sender's computer solve a small puzzle for every email, a trivial cost for one message but a heavy one for bulk spam; the Bitcoin white paper names it as the model for its own puzzle.

What does a cryptographic hash function do with its input?

A hash function produces a fixed-length fingerprint of any input; change one character and the output changes completely, which is what chains blocks together and makes tampering obvious.

What does 'Web3' describe in the crypto world?

Web3 is a decentralised web built on blockchains, pitched as a way for users rather than big technology companies to own what they make online; an Ethereum co-founder coined the term in 2014.

What name do crypto traders use for government-issued money such as the dollar or euro?

Fiat money's value rests on government decree and public trust rather than a vault of metal; the US cut the dollar's last tie to gold in 1971.

Which US regulator, created in 1974, polices derivatives and has claimed bitcoin as its own turf?

The CFTC, created in 1974 to police futures markets, held in a 2015 case against a bitcoin options site that virtual currencies are commodities, which put them on its patch.

Which kind of token represents an investment stake in an underlying asset, like a share?

A security token represents an investment stake in an underlying asset, so it counts as a security and is sold through a regulated STO rather than the loosely policed ICOs that came first.

What was Ethereum's September 2022 upgrade that dropped proof-of-work called?

The Merge, on 15 September 2022, fused Ethereum's original chain with the Beacon Chain that had run proof of stake in parallel since December 2020; validators replaced miners overnight.

Which quantitative trading firm did Sam Bankman-Fried co-found in 2017, before FTX?

Alameda Research, co-founded by Sam Bankman-Fried in 2017, was about 90 percent owned by him by 2021; its habit of borrowing FTX customer deposits is what brought both companies down in November 2022.

In which country was the FTX exchange headquartered when it collapsed in 2022?

FTX was run from Nassau in The Bahamas from 2021, though it was incorporated in Antigua and Barbuda; Sam Bankman-Fried was arrested at his Bahamian apartment complex in December 2022 and extradited to the US.

Who founded Binance in 2017?

Changpeng Zhao, known as CZ, founded Binance in July 2017 after stints at Bloomberg and OKCoin; he stepped down as CEO in November 2023 after pleading guilty to US anti-money-laundering charges.

About how much did Binance agree to pay US authorities in 2023 over money-laundering failures?

$4.3 billion made it one of the largest corporate penalties in US history; the exchange's founder pleaded guilty the same day, resigned as chief executive and later served four months in a US prison.

Which former Airbnb engineer founded Coinbase in 2012?

Brian Armstrong, an ex-Airbnb engineer, founded Coinbase in 2012 with $150,000 from the Y Combinator start-up programme; former Goldman Sachs trader Fred Ehrsam joined as co-founder after spotting his posts online.

Coinbase went public in April 2021 via a direct listing on which exchange?

Coinbase listed directly on Nasdaq on 14 April 2021 under the ticker COIN and its shares rose about 31% on day one, the same day bitcoin peaked above $64,000 before a sharp slide.

Which dollar-pegged coin was first announced in July 2014 under the name Realcoin?

Tether was announced as Realcoin by Brock Pierce, Reeve Collins and Craig Sellars and renamed that November; in 2019 it overtook bitcoin itself as the most traded cryptocurrency by volume.

Which privacy coin hides the sender among decoy outputs using ring signatures?

Monero, launched in April 2014 from the 2013 CryptoNote white paper by the pseudonymous Nicolas van Saberhagen, hides senders with ring signatures; its RandomX mining algorithm is designed to keep specialised chips out.

Cardano's own cryptocurrency is named after which English mathematician?

Cardano's currency, ada, honours Ada Lovelace, whose 1843 notes on Babbage's Analytical Engine include what is often called the first published computer program; its smallest unit is a lovelace.

Which blockchain was founded in 2018 by Toly Yakovenko and Raj Gokal?

Solana, founded in 2018 by Anatoly 'Toly' Yakovenko and Raj Gokal, launched in March 2020 and rode the 2021 NFT boom as a faster, cheaper rival to Ethereum, though heavy traffic has knocked it offline several times.

Which Ethereum co-founder created Polkadot, the chain that links 'parachains' together?

Gavin Wood's Polkadot raised more than $140 million in an October 2017 token sale; within weeks a flaw in wallet software from Parity, the company he co-founded, froze a large share of it.

Roughly how much ether was drained from The DAO in the June 2016 attack?

The attacker drained about 3.6 million ether, roughly a third of the 11.5 million that investors had committed, worth around $50 million at the time; the fallout split Ethereum into two chains.

What kind of flaw let an attacker drain millions of ether from The DAO in 2016?

A recursive call bug, now called a re-entrancy attack, let the contract be asked for a withdrawal again before it had updated the balance from the last one.

Bitcoin Cash split in November 2018 into BCH and a rival chain called 'Bitcoin' what?

Bitcoin SV, short for 'Satoshi Vision', was the camp led by Craig Wright and billionaire Calvin Ayre that wanted 128 MB blocks; the hash war split Bitcoin Cash on 15 November 2018.

Which 2017 Bitcoin upgrade moved signature data out of the main block to fix transaction malleability?

SegWit, short for Segregated Witness, activated in August 2017 after a long fight over block size; moving the signatures out fixed malleability and let more transactions fit in each block.

Joseph Poon and Thaddeus Dryja's 2015 white paper proposed which off-chain payment layer for Bitcoin?

Lightning Network users open a payment channel, trade off-chain as often as they like and settle on the blockchain only when they close it; it went live in 2018, three years after the paper.

Which November 2021 Bitcoin soft fork added support for Schnorr signatures?

Taproot activated in November 2021 at block 709,632, adding Schnorr signatures that simplify spending by several parties and let unused spending conditions stay private.

Where was Terraform Labs founder Do Kwon arrested in March 2023 with forged travel papers?

Do Kwon was arrested in Montenegro on 23 March 2023 at Podgorica airport, trying to fly to Dubai on falsified Costa Rican documents, ten months after his TerraUSD and LUNA tokens collapsed.

Which crypto lender froze withdrawals in June 2022 and filed for bankruptcy a month later?

Celsius Network's freeze on withdrawals sent crypto prices sharply lower; the lender filed for bankruptcy in July 2022 and did not emerge until January 2024.

Which exchange lost nearly 120,000 bitcoin in a 2016 hack traced to a New York couple?

Bitfinex lost coins worth about $72 million at the time; when Ilya Lichtenstein and Heather Morgan were charged with laundering them in 2022, the portion seized was worth $3.6 billion.

The Ronin sidechain, drained of roughly $620M in 2022, was built for which game?

Axie Infinity's Ronin sidechain lost about $620 million in March 2022, a theft the FBI pinned on North Korea's Lazarus Group; new players had been paying hundreds of dollars for the axolotl-like pets needed to start.

What did the hackers behind the August 2021 Poly Network exploit do with the funds?

Returned nearly all of it: the roughly $610 million came back within about two weeks, and the company took to calling the hackers 'Mr. White Hat' and offered a $500,000 bounty and the post of chief security advisor.

Which company is behind the Bored Ape Yacht Club NFT collection?

Yuga Labs launched the Bored Ape Yacht Club in April 2021, selling each ape as a pass to a members-only club; within a year it had bought the rival CryptoPunks collection and been valued at $4 billion.

Former Siemens engineer Hayden Adams created which decentralised exchange in 2018?

Uniswap launched in November 2018, built by former Siemens mechanical engineer Hayden Adams; in place of an order book it uses pools of tokens supplied by users, so people trade straight from their own wallets.

Chainlink, co-founded by Sergey Nazarov in 2017, is a decentralised network of what?

Chainlink's oracles carry outside data such as prices onto the chain, since a smart contract cannot look beyond its own blockchain; Sergey Nazarov and Steve Ellis created it in 2017 and the network went live in 2019.

Which proof-of-space blockchain did BitTorrent creator Bram Cohen co-found in 2017?

Chia, founded in 2017 by BitTorrent creator Bram Cohen, secures its chain with spare hard-drive space rather than raw computing, an attempt to cut the energy that bitcoin's method burns.

Which Ethereum mixing service was blacklisted by the US Treasury's OFAC in August 2022?

Tornado Cash was sanctioned by OFAC on 8 August 2022; developer Alexey Pertsev was arrested in Amsterdam two days later, and in November 2024 the Fifth Circuit ruled its immutable smart contracts are not property OFAC can sanction.

Which exchange was founded in 2014 by Cameron and Tyler Winklevoss?

Gemini, founded by Cameron and Tyler Winklevoss in 2014, went live in October 2015 with a limited-purpose trust charter from New York's financial regulator; the twins were famous from their Facebook lawsuit.

Which exchange, founded in San Francisco in 2011, is legally named Payward, Inc.?

Kraken was co-founded by Jesse Powell after he spent time in 2011 helping a hacked rival exchange recover; struck by its security problems, he set out to build an alternative with security at its core.

QuadrigaCX's founder died in which country in 2018, taking its wallet passwords with him?

Gerald Cotten, 30, died in Jaipur, India, in December 2018; customers' lawyers asked for his body to be exhumed, and Ontario regulators concluded in 2020 that QuadrigaCX had been a fraud all along.

Ruja Ignatova, the 'Cryptoqueen' who vanished in 2017, ran which fraudulent scheme?

OneCoin, sold by Ruja Ignatova from 2014, never had a real blockchain; she vanished in October 2017 after a secret US warrant was issued, and the FBI added her to its Ten Most Wanted list in 2022.

Facebook's Diem digital currency project was first unveiled under what name?

Facebook unveiled Libra in June 2019; after regulators in the US and Europe objected, backers including PayPal, Visa and Mastercard quit that October, and the renamed Diem was sold off in early 2022.

Under what name did the company behind XRP trade from late 2012 until it became Ripple Labs in 2013?

OpenCoin was its second name: the firm began as NewCoin in September 2012, switched within a month and became Ripple Labs a year later, then spent 2020 to 2025 fighting US regulators over its XRP sales.

Which co-founder of Ripple left to launch the Stellar network in 2014?

Jed McCaleb, who had earlier created the eDonkey file-sharing network, left Ripple in 2013 and launched Stellar in 2014; Stellar settles payments by consensus among groups of accounts rather than by mining.

Which 2012 coin, from a paper by Sunny King, was the first to use proof-of-stake?

Peercoin, launched in August 2012 from Sunny King and Scott Nadal's paper, kept proof-of-work alongside proof-of-stake and used 'coin age', coins held multiplied by time held, to pick who mints the next block.

Bitmain's Antminer rigs are built around which kind of single-purpose chip?

An ASIC is a chip built to do one job, here SHA-256 hashing; Bitmain's first model, the 2013 Antminer S1, managed about 180 gigahashes a second, and its AntPool became one of the largest mining pools.

Which statically typed language is the main one for writing Ethereum smart contracts?

Solidity compiles to bytecode for the Ethereum Virtual Machine and borrows its style from C++, Python and JavaScript; because a deployed contract's code cannot be changed, a bug written in it can prove costly.

What is the smallest unit of ether, in which account balances are stored on-chain?

Wei is the smallest unit of ether, a quintillion (10^18) of them making one ether; fees are usually quoted in gwei, a billion wei, to spare users a long string of zeros.

Which Ethereum token standard, led by William Entriken in 2018, covers unique tokens?

ERC-721, published in 2018 with William Entriken as lead author, gives every token its own ID; CryptoKitties, the cat-breeding game that clogged Ethereum in December 2017, uses it, as do the Bored Apes.

Blockchains summarise a block's transactions in a hash tree named after whom?

The Merkle tree is named after Ralph Merkle, who patented the structure in 1979; it lets a light wallet prove a single payment is in a block without downloading the whole thing.

Ross Ulbricht ran his darknet market under which alias borrowed from The Princess Bride?

Ulbricht's alias Dread Pirate Roberts comes from The Princess Bride, where the name is handed from one pirate to the next; he served over 11 years before a January 2025 presidential pardon.

Where has James Howells's lost bitcoin hard drive lain since 2013?

In a landfill in Newport, Wales: the drive was thrown out by mistake, the council refused to let Howells dig, citing environmental risks, and the High Court dismissed his claim in January 2025.

In which city did the world's first Bitcoin ATM open in October 2013?

Vancouver's machine scanned each user's palm so that nobody could trade more than 3,000 Canadian dollars a day, a cap meant to guard against money laundering.

Which Michael Saylor software firm began buying bitcoin as a treasury asset in 2020?

MicroStrategy, run by Michael Saylor, put its first $250 million into bitcoin in August 2020 and kept buying until it was the largest corporate holder of the coin; it renamed itself Strategy in 2025.

What does Bitcoin retune every 2,016 blocks to keep its ten-minute pace?

Difficulty is recalculated every 2,016 blocks, roughly two weeks: if blocks came too fast it rises, if too slow it falls, so the pace holds however much hardware joins or leaves the network.

How many satoshis make one bitcoin?

100 million satoshis make one bitcoin, so the smallest amount the chain can record is 0.00000001 BTC; the unit is named in homage to Bitcoin's pseudonymous creator.

Which price milestone did bitcoin cross for the first time in December 2024?

$100,000 fell in December 2024, weeks after Donald Trump, who had promised crypto-friendly policies, won the US presidential election.

Whose first-ever tweet sold as an NFT for $2.9M in March 2021?

Jack Dorsey's first tweet, 'just setting up my twttr', went to crypto entrepreneur Sina Estavi; when Estavi tried to resell it a year later, the best offers came to a fraction of one percent of what he had paid.

Which nation's bobsled team reached Sochi 2014 thanks to a Dogecoin community fundraiser?

Jamaica's two-man bobsled team had qualified for Sochi but could not afford to go, so Dogecoin users raised tens of thousands of dollars within days in January 2014; the community later sponsored NASCAR driver Josh Wise.

The 2020 hijack of 130 high-profile Twitter accounts pushed what kind of scam?

The hijackers pushed a bitcoin giveaway scam: accounts including Elon Musk's and Joe Biden's promised to double any coins sent to an address, taking in over a hundred thousand dollars before a Florida teenager was charged.

Which US retailer used a blockchain to cut the time to trace its mangoes from seven days to 2.2 seconds?

A Walmart executive bought a packet of sliced mangoes and asked his team to find the farm they came from; by phone and email it took almost seven days.

Which British newspaper's headline about a bank bailout is embedded in the very first block of Bitcoin's blockchain?

The Times ran the story on 3 January 2009, and the embedded note has been read as both evidence of the date and a jab at the instability of the banking system.

A US maker of which drink saw its shares soar in 2017 simply by putting 'Blockchain' in its company name?

Iced tea was the trade of Long Island Iced Tea Corp. before it became Long Blockchain Corp.; regulators later delisted the shares, noting it never produced any blockchain technology.

Which country housed most of the hardware that creates new bitcoins until its government banned the industry in 2021?

China's ban sent operators abroad, and many moved to coal-powered Kazakhstan, which pushed Bitcoin's carbon footprint up.

Which 2017 game from Canadian studio Dapper Labs grew so popular that it congested the entire Ethereum network?

CryptoKitties let players buy, sell and create virtual cats, and the December 2017 rush pushed Ethereum to a record number of transactions and slowed it down significantly.

Which company used a blockchain in 2018 to track 100 high-value diamonds from the mine to the retailer?

De Beers followed the stones through manufacturing to show they were conflict-free, then launched a tracing platform called Tracr that Russian rival Alrosa also signed up to.

Which UN agency, a Nobel Peace Prize winner in 2020, runs the Building Blocks blockchain for refugee aid?

The World Food Programme network lets several aid groups channel help into one account per recipient, and it has saved millions of dollars in bank fees in Jordan and Bangladesh.

Which Wall Street bank unveiled its own blockchain, Quorum, in 2016 and sold it to ConsenSys four years later?

JPMorgan Chase based Quorum on Ethereum, then sold it to ConsenSys, the Ethereum software company founded by Joseph Lubin.

Which northern European country guards its government networks with KSI, a blockchain technology it designed at home?

Estonia runs KSI across its state networks so that nobody, not even the government itself, can alter the data and get away with it.

Which British university publishes a widely cited index tracking Bitcoin's electricity use in real time?

Cambridge's Centre for Alternative Finance built the index, and its running estimates have fuelled the debate over the environmental cost of cryptocurrencies.

Which shipping giant built the TradeLens blockchain platform with IBM, then announced its closure in 2022?

Maersk said the platform worked but never won the full global industry collaboration it needed, so it had not become commercially viable.

Which 1982 thought experiment about agreeing a plan among traitors names the fault tolerance blockchains rely on?

The Byzantine Generals Problem first cast its plotters as commanders of the Albanian army; the name was changed so that nobody alive could take offence.

Which hashing algorithm, designed by the US National Security Agency, does Bitcoin run twice over each block header?

SHA-256 was first published in 2001, and a new block only counts once the twice-run hash comes out smaller than the network's target number.

What were Stuart Haber and W. Scott Stornetta trying to protect in 1991 when they described a secured chain of blocks?

Document timestamps were the goal: the pair wanted records that nobody could tamper with, and Bitcoin's own blockchain later drew on their research.

Which open-source blockchain project for businesses did the Linux Foundation start in December 2015?

Hyperledger is an umbrella for open-source blockchains and tools rather than a coin, and in 2024 it was folded into a new body called LF Decentralized Trust.

Which term for a number used only once names the value Bitcoin's block makers keep changing to find a valid hash?

Nonce hunting makes block-making something of a lottery: hash outputs cannot be predicted, so the only way to win is to keep trying new values.

The 2017 row that produced Bitcoin Cash was over raising which limit on the network's capacity?

Block size was capped at about one megabyte, and the camp that wanted eight megabytes broke away to create Bitcoin Cash.

Which Ethereum layer-2 systems, in 'optimistic' and 'zero-knowledge' types, execute transactions off the main chain?

Rollups do the computing elsewhere and post the transaction data back to Ethereum, which lets them borrow the main chain's security.

Which blockchain, created by married couple Arthur and Kathleen Breitman, lets holders vote to amend its protocol?

Tezos was pitched as a blockchain that upgrades itself, and its 2017 fundraiser brought in $232 million, one of the biggest sales of its kind.

Which US state piloted a blockchain voting app in 2018 so that deployed members of the military could cast ballots?

West Virginia used the Voatz phone app, which pairs a blockchain with biometrics to check who is voting instead of keeping personal details in a database.

Nick Szabo, who was writing about 'smart contracts' by 1996, pointed to which everyday device as an early example?

A vending machine takes the coins and hands over the goods with no shopkeeper or lawyer involved, which is how Szabo pictured contracts enforced by hardware or software instead of by law.

Ethereum can run any computation, a property described as 'complete' and named after which computing pioneer?

Alan Turing lends his name to Turing-completeness, which Ethereum has and Bitcoin's simpler script language lacks; some contract languages drop it on purpose because it is seen as a security risk.

After The DAO was drained in 2016, the blockchain that refused to reverse the theft lived on under which name?

Ethereum Classic keeps the original, unaltered chain; the far bigger Ethereum is the version that was rewritten to erase the theft.

Which three-letter abbreviation names the software engine that runs smart contract code on every Ethereum node?

EVM stands for Ethereum Virtual Machine: contracts written in human-readable languages are compiled into low-level bytecode before it can execute them.

Which kind of loan, popularised by Aave, must be borrowed and repaid within a single blockchain transaction?

Flash loans need no collateral and can be for any amount, which is why attackers have used them to manipulate cryptocurrency prices.

Which US state became the first to recognise DAOs, groups run by smart contracts, as legal entities in 2021?

Wyoming's law took effect on 1 July 2021, and a group called American CryptoFed DAO became the first business recognised under it.

Which dollar-pegged token did MakerDAO launch in 2017, minted by locking up collateral such as ether in smart contracts?

DAI held close to one dollar through its first year even though ether, then its only collateral, lost more than 80% of its value.

Which smart contract language for Ethereum was designed to read like Python and to put security first?

Vyper aims to be simple on purpose: its stated goals are code that is as human-readable as possible and as difficult as possible to write misleadingly.

Plutus, the smart contract language of the Cardano blockchain, is written in which functional programming language?

Haskell runs through the whole Cardano project, which is itself written in the language; Plutus arrived with the 2021 upgrade that first enabled smart contracts on the chain.

Which smart contract language, first developed for Facebook's abandoned Diem blockchain, was later adopted by Aptos?

Move outlived the project it was written for: former Diem engineers founded Aptos Labs in 2021 and built their new chain around the language.