cryptocurrency

The first cryptocurrency was Bitcoin, created by an anonymous computer programmer or group of programmers known as Satoshi Nakamoto in 2009. Satoshi Nakamoto was concerned that traditional currencies were too reliant on the trustworthiness of banks or governments to work properly.

Bitcoin relies on public key cryptography, in which users have a public key that is available for everyone to see and a private key known only to their computers. In a Bitcoin transaction users receiving Bitcoins send their public keys to users transferring the Bitcoins. Users transferring the coins sign with their private keys, and the transaction is then transmitted over the Bitcoin network. So that no Bitcoin can be spent more than once at the same time, the time and amount of each transaction is recorded in a ledger file that exists at each node of the network. The identities of the users remain relatively anonymous, but everyone can see that certain Bitcoins were transferred.

Transactions are put together in groups called blocks. The blocks are organized in a chronological sequence called the blockchain. Blocks are added to the chain using a mathematical process that makes it extremely difficult for an individual user to hijack the blockchain. The blockchain technology that underpins Bitcoin has attracted considerable attention, even from skeptics of Bitcoin, as a basis for allowing trustworthy recordkeeping and commerce without a central authority. Blockchain technology is also critical to NFTs (non-fungible tokens), which are often paid for with cryptocurrency.

New Bitcoins are created by users running the Bitcoin client on their computers. The client “mines” Bitcoins by running a program that solves a difficult mathematical problem in a file called a “block” received by all users on the Bitcoin network. The difficulty of the problem is adjusted so that, no matter how many people are mining Bitcoins, the problem is solved, on average, six times an hour. When a user solves the problem in a block, that user receives a certain number of Bitcoins. The elaborate procedure for mining Bitcoins ensures that their supply is restricted and grows at a steadily decreasing rate. About every four years the number of Bitcoins in a block, which began at 50, is halved, and the number of maximum allowable Bitcoins is slightly less than 21 million. As of 2024 there were more than 19.8 million Bitcoins, and it is estimated that the maximum number will be reached in 2140.

The method by which Bitcoin adds new blocks to the blockchain through the computational power exerted by its users is called “proof of work,” which is used by the majority of cryptocurrencies. Another method of adding valid blocks to the blockchain is “proof of stake,” in which the ability to validate a block is based on a user’s already existing stake in the cryptocurrency. Proof of stake has the advantage over proof of work of being much less energy-intensive. Indeed, Ethereum, the second largest cryptocurrency after Bitcoin, plans to change from proof of work to proof of stake.

As of 2024 the market capitalization of cryptocurrencies was about $3 trillion. Bitcoin and Ethereum make up the majority of that sum, with market capitalizations of about $1.8 trillion and $396 billion, respectively. Although there are hundreds of cryptocurrencies, the top 20 coins make up much of the market.

Such large amounts of money in cryptocurrencies have attracted the attention of thieves. An early, spectacular theft occurred in February 2014, when Mt. Gox, the world’s third largest Bitcoin exchange, declared bankruptcy because of the theft of about 650,000 Bitcoins, then valued at about $380 million. The largest cryptocurrency hack happened from late 2021 to early 2022, when $614 million in Ethereum and USDC (a “stablecoin” pegged to the U.S. dollar) was stolen from the Ronin Network, an exchange that allowed players of the online game Axie Infinity to convert tokens earned in the game into cryptocurrency. The Federal Bureau of Investigation identified the Lazarus Group of North Korean hackers as being behind the Ronin Network theft.

Cryptocurrencies have proved controversial. Some economists have pointed out that cryptocurrencies do not fulfill the traditional functions of money and so should be regarded as merely speculative schemes. In this view, cryptocurrencies are not mediums of exchange, because they are not typically used to buy or sell goods and services; they are not a store of value, since their values can fluctuate wildly over time; and they are not a unit of account, since very few goods and services are denominated in them. Cryptocurrency experts have responded that the technology is still not mature or widespread enough to replace traditional money.

Proof-of-work coins, especially Bitcoins, have been criticized for their energy usage. The profitability of Bitcoin has driven the construction of many large operations with thousands of computers that are specially optimized integrated circuits for mining,. This has led to Bitcoin consuming 0.5 percent of the world’s electricity. Defenders of Bitcoin have stated that the currency could accelerate the world’s transition to renewable energy by providing a profitable use for wind and solar power during off-peak hours.

As of 2024 only two countries, El Salvador and the Central African Republic, accept a cryptocurrency, Bitcoin, as legal tender. Several countries, most notably China, have banned cryptocurrency altogether, citing the high energy use of mining networks and cryptocurrency’s use in fraud and money laundering. About 40 other countries have banned certain aspects of cryptocurrency trading, such as cryptocurrency exchanges, and have forbidden banks from dealing in them.

In late 2022 Sam Bankman-Fried, the founder and former chief executive officer of FTX Trading Ltd., a cryptocurrency exchange, was arrested and charged criminally and civilly with conspiracy, securities fraud, and money laundering. He was convicted by a jury on multiple counts of fraud and conspiracy in October 2023. Massive numbers of customers of FTX and Alameda Research LLC, also founded by Bankman-Fried, lost at least $10 billion.