Pow Ethereum



ethereum капитализация программа ethereum Ledger Live has an intuitive and convenient user interfaceсети bitcoin эпоха ethereum clicks bitcoin cryptocurrency trade Whenever you hear the word 'hacker' spoken aloud, it’s not usually in a positive light; no self-respecting business wants anything to do with hackers (well, except for ethical hackers, but that’s a different story for a different time). However, it’s precisely the hacker mentality that helps make good Blockchain developers. That’s because hackers tend to think outside the box when faced with problems and obstacles, rather than engage in conventional thinking.bitcoin куплю to bitcoin логотип bitcoin bitcoin flip reddit cryptocurrency

etf bitcoin

ethereum ферма usdt tether bitcoin nyse

курса ethereum

captcha bitcoin

wmz bitcoin bitcoin основатель логотип bitcoin

прогнозы bitcoin

in bitcoin bitcoin развитие equihash bitcoin bitcoin ticker смысл bitcoin ninjatrader bitcoin bitcoin конвертер картинки bitcoin tether 2 ethereum доходность lavkalavka bitcoin bitcoin etherium bitcoin car tether валюта

app bitcoin

korbit bitcoin collector bitcoin прогноз bitcoin polkadot stingray mac bitcoin bitcoin вложить monero калькулятор

cryptocurrency nem

bitcoin сборщик ethereum addresses bitcoin bounty bitcoin форекс ethereum контракт ethereum клиент сложность bitcoin bitcoin pay vk bitcoin Insight:bitcoin frog валюта bitcoin bitcoin tails hashrate bitcoin ethereum siacoin bitcoin genesis проекта ethereum

bitcoin лого

майнинга bitcoin bitcoin symbol сложность bitcoin bitcoin nodes видео bitcoin

виталик ethereum

играть bitcoin I’ve also tried to group the different devices in terms of the applications that they’re best suited for. I’ll be giving you my recommendations for Bitcoin mining rigs for:txid bitcoin bitcoin окупаемость

accept bitcoin

decred cryptocurrency bitcoin кошельки widget bitcoin

дешевеет bitcoin

bitcoin accepted bitcoin казино bitcoin государство bitcoin tor blocks bitcoin

bitcoin sign

bitcoin clouding easy bitcoin bitcoin транзакция The other main property of Bitcoin that no other coin has is decentralization. By decentralized, I mean that Bitcoin does not have a single point of failure or choke point. Every other coin has a founder or a company that created their coin and they have the most influence over the coin. A hard fork (a backwards incompatible change) that’s forced on the user, for example, is an indication that the coin is pretty centralized.If you have decided to do some *****U mining (just for the fun of it, since as we've seen above you are not going to make any profit), you could download Pooler's *****uminer. GPU mining is considerably harder to set up, and not much more efficient than *****U mining when compared to ASICs. Therefore, unless you're a historian doing research on the early days of Litecoin, GPU mining is almost certainly a bad idea.1. What is cryptocurrency?bitcoin people bitcoin rotator вывод monero monero ico получить bitcoin blocks bitcoin bitcoin center будущее bitcoin tether android

bitcoin ico

ethereum пул

ethereum news

qiwi bitcoin продам bitcoin ethereum metropolis эмиссия ethereum хешрейт ethereum topfan bitcoin китай bitcoin byzantium ethereum bitcoin statistic pool bitcoin

bitcoin multibit

bitcoin google pos bitcoin bitcoin заработка fast bitcoin пример bitcoin bitcoin iq bitcoin machine bitcoin alert bitcoin официальный

mining bitcoin

ethereum биткоин bitcoin fan bitcoin коллектор mainer bitcoin bitcoin прогноз protocol bitcoin bag bitcoin ethereum com запуск bitcoin

boom bitcoin

mindgate bitcoin

обзор bitcoin abi ethereum bitcoin отзывы tether clockworkmod

bitcoin клиент

bitcoin vip bitcoin abc epay bitcoin

ethereum биржа

ethereum ios

bitcoin xt

ethereum кошелек bitcoin fun bitcoin pools bitcoin расчет bitcoin 2 будущее ethereum ethereum обмен bitcoin adress

bitcoin telegram

bitcoin теханализ bitcoin rub up bitcoin подтверждение bitcoin monero краны planet bitcoin bitcoin knots ethereum форум биржи ethereum Time is taken to mine a block22 bitcoin bitcoin инвестирование Once the latest transaction in a coin is buried under enough blocks, the spent transactions beforeLow electricity consumption - Electricity is the biggest cost of mining.настройка ethereum nanopool ethereum вирус bitcoin криптовалют ethereum

electrum bitcoin

bitcoin x рубли bitcoin видеокарта bitcoin unconfirmed bitcoin matteo monero bitcoin смесители What is a cryptocurrency: the Ethereum platform.bitcoin кэш шифрование bitcoin icons bitcoin bitcoin daily bitcoin программирование mt5 bitcoin кликер bitcoin bitcoin сервера краны monero ethereum parity bitcoin сша ethereum supernova mine monero datadir bitcoin bitcoin информация x2 bitcoin 1000 bitcoin ethereum node

пример bitcoin

tx bitcoin

ann ethereum

charts bitcoin биржи monero bitcoin earning bitcoin click кошель bitcoin monero обмен bitcoin accelerator alpha bitcoin

bitcoin airbit

The advent of the Internet of Things (IoT) has unleashed a plethora of smart machines that transfer data over the Internet without any human interaction needed. Likewise, technology is even used for public services such as rubbish collection, transportation, and traffic management. So, in the world of IoT, you can make Smart Contracts and allow smart objects to perform the listed tasks, which in turn negates the need for human involvement.future bitcoin bitcoin аналоги topfan bitcoin ethereum twitter love bitcoin bitcoin дешевеет bitcoin security майнер bitcoin ads bitcoin bot bitcoin ethereum прогнозы bitcoin python blake bitcoin dog bitcoin bitcoin bear bitcoin ebay

boom bitcoin

cms bitcoin ethereum siacoin nanopool ethereum bitcoin fees ethereum contracts bitcoin vector

bitcoin обзор

lazy bitcoin bitcoin автоматически tether пополнение panda bitcoin ethereum install

bitcoin лучшие

bitcoin core

location bitcoin bitcoin пожертвование bitcoin drip auto bitcoin ethereum asics bitcoin форум bitcoin перевод accepts bitcoin bitcoin сложность tether bootstrap moneybox bitcoin bitcoin de php bitcoin bitcoin телефон bitcoin xl

location bitcoin

bitcoin stealer bitcoin etherium bitcoin вывести

decred cryptocurrency

ethereum news bitcoin ico sec bitcoin blocks bitcoin bitcoin блокчейн algorithm bitcoin ethereum node ethereum алгоритм api bitcoin bitcoin сервера tx bitcoin ethereum markets bitcoin rt ethereum бутерин bitcoin sign cryptocurrency charts адрес bitcoin stock bitcoin

bitcoin clicks

монеты bitcoin grayscale bitcoin

теханализ bitcoin

bitcoin пицца

прогноз bitcoin

bitcoin symbol ethereum wallet monero алгоритм tether usd cubits bitcoin txid ethereum bitcoin лохотрон ethereum рост сервер bitcoin bitcoin google microsoft bitcoin bitcoin проект

iphone tether

bitcoin farm

bitcoin mail криптовалюта monero blogspot bitcoin обвал bitcoin monero pro bitcoin сегодня ethereum телеграмм bitcoin wordpress bitcoin заработка bitcoin 2018 stealer bitcoin bitcoin расчет cryptocurrency trading bitcoin tx майн bitcoin bitcoin pools monero продать сбор bitcoin

bitcoin компьютер

bitcoin wmz

википедия ethereum

tracker bitcoin

status bitcoin cryptocurrency ethereum go bitcoin bitcoin прогноз ethereum russia bitcoin monkey bitcoin автоматически кредит bitcoin приват24 bitcoin 777 bitcoin panda bitcoin lootool bitcoin bitcoin mac

lite bitcoin

goldmine bitcoin график monero ethereum node bitcoin youtube

bitcoin терминалы

bitcoin torrent

monero miner

анализ bitcoin rush bitcoin

bitcoin farm

bitcoin location bitcoin сигналы protocol bitcoin прогноз bitcoin обновление ethereum обмен tether bitcoin иконка bitcoin all bitcoin asic index bitcoin ethereum complexity 2 bitcoin bitcoin qr ethereum токен bitcoin luxury ethereum info bitcoin ru динамика ethereum bitcoin github bitcoin protocol bitcoin взлом bitcoin япония портал bitcoin bitcoin journal polkadot cadaver fenix bitcoin заработок ethereum protocol bitcoin ethereum russia bitcoin mac addnode bitcoin ethereum картинки monero minergate майнер ethereum mempool bitcoin bitcoin onecoin greenaddress bitcoin bitcoin ios auction bitcoin goldmine bitcoin faucet ethereum mist ethereum bitcoin лотерея ethereum stats 3. A decentralized data feed. For financial contracts for difference, it may actually be possible to decentralize the data feed via a protocol called SchellingCoin. SchellingCoin basically works as follows: N parties all put into the system the value of a given datum (eg. the ETH/USD price), the values are sorted, and everyone between the 25th and 75th percentile gets one token as a reward. Everyone has the incentive to provide the answer that everyone else will provide, and the only value that a large number of players can realistically agree on is the obvious default: the truth. This creates a decentralized protocol that can theoretically provide any number of values, including the ETH/USD price, the temperature in Berlin or even the result of a particular hard computation.bitcoin баланс bitcoin 1000 bitcoin future mixer bitcoin

korbit bitcoin

enterprise ethereum bitcoin atm ethereum node bitcoin utopia стоимость monero

bitcoin клиент

bitcoin matrix monero js вирус bitcoin

wikipedia ethereum

captcha bitcoin bitcoin calc bitcoin обменник large institutional investors, but it remains niche relative to incumbent monetary assetsmonero калькулятор sberbank bitcoin shot bitcoin lootool bitcoin bitcoin asics mmm bitcoin nicehash monero moon bitcoin bitcoin халява bitcoin cny bitcoin проблемы bitcoin 4 avto bitcoin ethereum chart bitcoin динамика отдам bitcoin field bitcoin bitcoin суть mining bitcoin bitcoin download

buy ethereum

ethereum ротаторы bitfenix bitcoin bitcoin 10

get bitcoin

bitcoin автоматически monero poloniex статистика ethereum pool bitcoin birds bitcoin ставки bitcoin bitcoin cny faucet bitcoin bitcoin значок game bitcoin coingecko ethereum

мониторинг bitcoin

bitcoin сбор bitcoin goldman bitcoin code bitcoin fire bitcoin ocean

bitcoin x2

1070 ethereum pool bitcoin prune bitcoin кликер bitcoin майнить bitcoin avatrade bitcoin bitcoin reddit bitcoin nvidia брокеры bitcoin

wild bitcoin

bestchange bitcoin bitcoin 123 скачать ethereum monero калькулятор daily bitcoin moto bitcoin dash cryptocurrency 20 bitcoin bitcoin переводчик ethereum wikipedia продам ethereum bitcoin серфинг

bitcoin etf

bitcoin review

boxbit bitcoin

новости bitcoin bitcoin blog bitcoin plugin bitcoin лопнет To ensure their reputation wasn’t tarnished, they incorporated blockchain into their supply chain. Each event and detail within each step of the supply chain was logged. Now, in the scenario where a product was deemed bad and returned, Walmart would be able to determine where the issue with the product originated from in the supply chain. bitcoin scanner ethereum кошелька

weekly bitcoin

market bitcoin

tether bootstrap bitcoin apk bitcoin nyse rush bitcoin заработать monero

ethereum gold

ethereum habrahabr bitcoin reindex bitcoin отследить

bitcoin 999

bitcoin будущее elysium bitcoin bitcoin cnbc mine ethereum bitcoin список

bitcoin passphrase

bitcoin mastercard

eos cryptocurrency

опционы bitcoin dark bitcoin казино ethereum cranes bitcoin ethereum faucet bitcoin орг zcash bitcoin bitcoin картинки gek monero

bitcoin puzzle

bitcoin count monero xmr bitcoin орг bitcoin pdf monero криптовалюта

billionaire bitcoin

баланс bitcoin

etherium bitcoin

куплю ethereum

сети bitcoin ethereum coins 0 bitcoin эпоха ethereum bitcoin что fenix bitcoin bitcoin удвоить bitcoin создатель poloniex ethereum bitcoin explorer bitcoin arbitrage rise cryptocurrency lurkmore bitcoin 60 bitcoin ethereum complexity bitcoin скрипт bitcoin stellar

аналоги bitcoin

bitcoin скачать bitcoin автосборщик bitcoin bear bitcoin ledger курс ethereum опционы bitcoin

q bitcoin

bitcoin marketplace bitcoin список make bitcoin What kinds of digital property might be transferred in this way? Think about digital signatures, digital contracts, digital keys (to physical locks, or to online lockers), digital ownership of physical assets such as cars and houses, digital stocks and bonds … and digital money.

bitcoin trading

love bitcoin bitcoin symbol

cryptocurrency calendar

bitcoin maker валюта bitcoin компания bitcoin bitcoin вклады tether coinmarketcap bitcoin monkey sec bitcoin bitcoin hype network bitcoin balance bitcoin bitcoin trojan bitcoin 20 bitcoin обои bitcoin weekend bitcoin ukraine bitcoin legal bitcoin оплата ethereum краны bitcoin 20 fast bitcoin bitcoin обменники forecast bitcoin продам ethereum check bitcoin bcn bitcoin solidity ethereum bitcoin кредит monero ann second bitcoin ethereum dag mine bitcoin joker bitcoin bitcoin neteller bitcoin зебра bitcoin переводчик bitcoin список bcc bitcoin bitcoin описание escrow bitcoin bitcoin utopia

san bitcoin

ethereum обозначение download bitcoin валюты bitcoin bitcoin koshelek

cryptocurrency dash

bitcoin tube bitcoin pools сборщик bitcoin raspberry bitcoin bitcoin json nova bitcoin bitcoin okpay

bitcoin автосборщик

payable ethereum ethereum cryptocurrency bitcoin сервисы bitcoin цена pool bitcoin

лучшие bitcoin

кошелька ethereum пицца bitcoin ethereum прогноз bitcoin reindex

bitcoin weekly

bitcoin ethereum bitcoin change ethereum os takara bitcoin удвоитель bitcoin терминалы bitcoin расчет bitcoin bitcoin cap accept bitcoin платформе ethereum ethereum news bitcoin prosto bitcoin airbit clame bitcoin котировки ethereum bitcoin payza bitcoin china фарм bitcoin boxbit bitcoin bitcoin 2 биржа bitcoin видеокарты bitcoin

Click here for cryptocurrency Links

Cryptocurrency bubble
From Wikipedia, the free encyclopedia
Jump to navigationJump to search
Ambox current red Americas.svg
Parts of this article (those related to documentation) need to be updated. Please update this article to reflect recent events or newly available information. (January 2021)
Predictions of a collapse of a speculative bubble in cryptocurrencies have been made by numerous experts in economics and financial markets.

Bitcoin and other cryptocurrencies have been identified as speculative bubbles by several laureates of the Nobel Memorial Prize in Economic Sciences, central bankers, and investors.

In 2018, there was a large sell-off of cryptocurrencies. From January to February 2018, the price of bitcoin fell 65 percent. By September 2018, the MVIS CryptoCompare Digital Assets 10 Index had lost 80 percent of its value, making the decline of the cryptocurrency market, in percentage terms, larger than the bursting of the Dot-com bubble in 2002. In November 2018, the total market capitalization for bitcoin fell below $100 billion for the first time since October 2017, and the Bitcoin price fell below $4,000, representing an 80 percent decline from its peak the previous January. From March 8–12, 2020, the Bitcoin price fell by 30 percent from $8,901 to $6,206 (with it down 22 percent on March 12 alone). By October 2020, Bitcoin was worth approximately $13,200.

In November of 2020, Bitcoin again surpassed its previous all time high of over $19,000. After another surge on 3 January 2021 with $34,792.47, bitcoin crashed by 17 percent the next day. Bitcoin traded above $40,000 for the first time on 8 January 2021.


Contents
1 Bitcoin
2 Altcoins
3 Initial coin offerings
4 2017 boom and 2018 crash
4.1 Timeline of the crash
5 Early 2021 Bitcoin boom
6 See also
7 References
8 Further reading
Bitcoin
Further information: Economics of bitcoin

Bitcoin price fluctuations in 2011, 2013 and 2017
Bitcoin has been characterized as a speculative bubble by eight winners of the Nobel Memorial Prize in Economic Sciences: Paul Krugman, Robert J. Shiller, Joseph Stiglitz, Richard Thaler, James Heckman, Thomas Sargent, Angus Deaton, and Oliver Hart; and by central bank officials including Alan Greenspan, Agustín Carstens, Vítor Constâncio, and Nout Wellink.

The investors Warren Buffett and George Soros have respectively characterized it as a "mirage" and a "bubble"; while the business executives Jack Ma and Jamie Dimon have called it a "bubble" and a "fraud", respectively. J.P. Morgan Chase CEO Jamie Dimon said later he regrets calling bitcoin a fraud.

Altcoins
Since the release of bitcoin, over 6,000 altcoins (alternative variants of bitcoin, or other cryptocurrencies) have been created.

A January 2018 article by CBS cautioned about a cryptocurrency bubble and fraud, citing the case of BitConnect, a British company, which received a cease-and-desist order from the Texas State Securities Board. BitConnect had promised very high monthly returns but hadn't registered with state securities regulators or given their office address.

Initial coin offerings
Wired noted in 2017 that the bubble in initial coin offerings (ICOs) was about to burst. Some investors bought ICOs in hopes of participating in the financial gains similar to those enjoyed by early bitcoin or Ethereum speculators.

Binance has been one of the biggest winners in this boom as it surged to become the largest cryptocurrency trading platform by volume. It lists dozens of digital tokens on its exchange.

In June 2018 Ella Zhang of Binance Labs, a division of the cryptocurrency exchange Binance, stated that she was hoping to see the bubble in ICOs collapse. She promised to help "fight scams and shit coins".

2017 boom and 2018 crash
The 2018 cryptocurrency crash (also known as the Bitcoin crash and the Great crypto crash) is the sell-off of most cryptocurrencies from January 2018. After an unprecedented boom in 2017, the price of bitcoin fell by about 65 percent during the month from 6 January to 6 February 2018. Subsequently, nearly all other cryptocurrencies also peaked from December 2017 through January 2018, and then followed bitcoin. By September 2018, cryptocurrencies collapsed 80% from their peak in January 2018, making the 2018 cryptocurrency crash worse than the Dot-com bubble's 78% collapse. By 26 November, bitcoin also fell by over 80% from its peak, having lost almost one-third of its value in the previous week.

Timeline of the crash
December 17, 2017: bitcoin's price briefly reaches its all time high of $19,783.06.
December 22, 2017, bitcoin fell below $11,000, a fall of 45% from its peak.
January 12, 2018, Amidst rumors that South Korea could be preparing to ban trading in cryptocurrency, the price of bitcoin depreciated by 12 percent.
January 26, 2018, Coincheck, Japan's largest cryptocurrency OTC market, was hacked. 530 million US dollars of the NEM were stolen by the hacker, and the loss was the largest ever by an incident of theft, which caused Coincheck to indefinitely suspend trading.
From 26 January to 6 February, the price of bitcoin halved, and reached 6,000 US dollars.[citation needed] Additional negative news for the cryptocurrency market continued in the first quarter of 2018.[citation needed] The price remained low though the level slightly recovered in the first quarter of 2018.[citation needed]
March 7, 2018, Compromised Binance API keys were used to execute irregular trades.
Late March 2018, Facebook, Google, and Twitter banned advertisements for initial coin offerings (ICO) and token sales.
November 15, 2018, bitcoin's market capitalization fell below $100 billion for the first time since October 2017 and the price of bitcoin fell to $5,500.
Early 2021 Bitcoin boom
In early 2021, bitcoin price witnessed another boom, soaring more than 700% since March 2020 and surged above the $40,000 mark for the first time on 7 January. On 11 January, the UK Financial Conduct Authority warned investors against lending or investments in cryptoassets, that they should be prepared "to lose all their money"



bitcoin видео ethereum russia prune bitcoin bitcoin poloniex If an asset’s primary (if not sole) utility is the exchange for other goods and services and if it does not have a claim on the income stream of a productive asset (such as a stock or bond), it must compete as a form of money and will only store value if it possesses credible monetary properties. With each 'feature' change, those that attempt to copy bitcoin signal a failure to understand the properties that make bitcoin valuable or viable as money. When bitcoin’s software code was released, it wasn’t money. To this day, bitcoin’s software code is not money. You can copy the code tomorrow or create your own variant with a new feature and no one that has adopted bitcoin as money will treat it as such. Bitcoin has become money over time only as the bitcoin network developed emergent properties that did not exist at inception and which are next to impossible to replicate now that bitcoin exists. android tether clicker bitcoin

android tether

bitcoin покер

service bitcoin

explorer ethereum bitcoin проблемы bitcoin 15

ethereum биржа

collector bitcoin bitcoin google bitcoin black ethereum core ico bitcoin bitcoin cudaminer ethereum gold bitcoin attack check bitcoin bitcoin оборудование

ethereum dark

ethereum gas bitcoin регистрация bitcoin rub

казино bitcoin

abc bitcoin bitcoin land bitcoin онлайн alliance bitcoin стратегия bitcoin bitcoin страна monero обменник фьючерсы bitcoin Bitcoin’s incentive system allows the best of both worlds. Like an open allocation project, it can harness a large group of contributors without deadlock and balkanization. Contributors get the benefit of working on a meaningful project, without incurring unwanted technical debt.bitcoin сервер bitcoin crash testnet ethereum bitcoin ru bitcoin habrahabr bitcoin genesis agario bitcoin bitcoin fpga home bitcoin терминал bitcoin bitcoin вложить qr bitcoin bitcoin casino erc20 ethereum конвертер ethereum bitcoin gadget обвал ethereum bitcoin it bitcoin vizit adc bitcoin transactions bitcoin A blockchain carries no transaction cost.bitcoin майнить bitcoin etf bitcoin инвестиции расчет bitcoin ethereum github bitcoin цена алгоритм bitcoin trade cryptocurrency As electronic and digital payments take over from physical cash, the central banks will look to replace physical cash with its electronic equivalent, i.e., CBDC. Doing this will increase the proceeds from creating money, aka, seigniorage, earned by the bank.bitcoin основы

monero форк

exchanges bitcoin withdraw bitcoin

youtube bitcoin

ethereum создатель ethereum blockchain poloniex bitcoin ethereum акции chaindata ethereum

ethereum пул

map bitcoin bitcoin algorithm калькулятор ethereum ethereum контракт bitcoin сервисы bitcoin перспектива remix ethereum tor bitcoin bitcoin purse dogecoin bitcoin alien bitcoin bitcoin pro bitcoin doubler bitcoin обменники форекс bitcoin tether bootstrap ethereum bonus api bitcoin bitcoin stealer ethereum ico ethereum cgminer пулы monero simple bitcoin bitcoin course bitcoin ads sgminer monero

bitcoin wallet

bitcoin xl bitcoin up bitcoin mining bitcoin заработка okpay bitcoin аналитика bitcoin bitcoin оборудование новый bitcoin Proof of work and digital cash: A catch-22. You may know that proof of work did not succeed in its original application as an anti-spam measure. One possible reason is the dramatic difference in the puzzle-solving speed of different devices. That means spammers will be able to make a small investment in custom hardware to increase their spam rate by orders of magnitude. In economics, the natural response to an asymmetry in the cost of production is trade—that is, a market for proof-of-work solutions. But this presents a catch-22, because that would require a working digital currency. Indeed, the lack of such a currency is a major part of the motivation for proof of work in the first place. One crude solution to this problem is to declare puzzle solutions to be cash, as hashcash tries to do.To this day, no one knows who Satoshi Nakamoto really is. Even a man named Dorian Nakamoto was erroneously named as Bitcoin’s creator by a Newsweek reporter in 2014.

bistler bitcoin

bitcoin masters blender bitcoin ethereum wikipedia ethereum github app bitcoin

bitcoin sportsbook

bitcoin принцип bitcoin atm акции bitcoin capitalization bitcoin sberbank bitcoin erc20 ethereum

bitcoin motherboard

british bitcoin eth ethereum

скачать bitcoin

обмен bitcoin keys bitcoin bitcoin описание nodes bitcoin запросы bitcoin bitcoin antminer обсуждение bitcoin bitcoin blockstream взлом bitcoin etoro bitcoin биржи bitcoin биржи bitcoin bitcoin продам

кран ethereum

bitcoin in bitcoin maps приложение tether банкомат bitcoin bitcoin chains bitcoin терминал монета ethereum программа bitcoin bitcoin farm ethereum кошелек обсуждение bitcoin machine bitcoin криптовалюту monero multiplier bitcoin