INTRO TO ETHEREUM
WHAT IS A BLOCKCHAIN?
A blockchain is best described as a public database that is updated and shared across many computers in a network.
"Block" refers to the fact that data and state is stored in sequential batches or "blocks". If you send ETH to someone else, the transaction data needs to be added to a block for it to be successful.
"Chain" refers to the fact that each block cryptographically references its parent. A block's data cannot be changed without changing all subsequent blocks, which would require the consensus of the entire network.
Each new block and the chain as a whole must be agreed upon by every node in the network. This is so everyone has the same data. For this to work, blockchains need a consensus mechanism.
Ethereum currently uses a proof-of-work consensus mechanism. This means that anyone who wants to add new blocks to the chain must solve a difficult puzzle that you need a lot of computing power to work on. Solving the puzzle "proves" that you have spent the computational resources. Doing this is known as mining. Mining can be trial and error but adding a block successfully is rewarded in Eth. On the other hand, submitting fraudulent blocks is not an attractive option considering the resources you've spent on producing the block.
New blocks are broadcast to the nodes in the network, checked and verified, updating the state for everyone.
So to summarise, when you send ETH to someone, the transaction must be mined and included in a new block. The updated state is then shared with the entire network.
WHAT IS ETHEREUM?
In the Ethereum universe, there is a single, canonical computer (called the Ethereum Virtual Machine, or EVM) whose state everyone on the Ethereum network agrees on. Everyone who participates in the Ethereum network (every Ethereum node) keeps a copy of the state of this computer. Additionally, any participant can broadcast a request for this computer to perform arbitrary computation. Whenever such a request is broadcast, other participants on the network verify, validate, and carry out (“execute”) the computation. This causes a state change in the EVM, which is committed and propagated throughout the entire network.
Requests for computation are called transaction requests; the record of all transactions as well as the EVM’s present state is stored in the blockchain, which in turn is stored and agreed upon by all nodes.
Cryptographic mechanisms ensure that once transactions are verified as valid and added to the blockchain, they can’t be tampered with later; the same mechanisms also ensure that all transactions are signed and executed with appropriate “permissions” (no one should be able to send digital assets from Alice’s account, except for Alice herself).
WHAT IS ETHER?
The purpose of Ether, the cryptocurrency, is to allow for the existence of a market for computation. Such a market provides an economic incentive for participants to verify/execute transaction requests and to provide computational resources to the network.
Any participant who broadcasts a transaction request must also offer some amount of ether to the network, as a bounty to be awarded to whoever eventually does the work of verifying the transaction, executing it, committing it to the blockchain, and broadcasting it to the network.
The amount of ether paid is a function of the length of the computation. This also prevents malicious participants from intentionally clogging the network by requesting execution of infinite loops or resource-intense scripts, as these actors will be continually charged.
WHAT ARE DAPPS?
In practice, participants don’t write new code every time they want to request a computation on the EVM. Rather, application developers upload programs (reusable snippets of code) into EVM storage, and then users make requests for the execution of these code snippets with varying parameters. We call the programs uploaded to and executed by the network smart contracts.
At a very basic level, you can think of a smart contract like a sort of vending machine: a script which, when called with certain parameters, performs some actions or computation if certain conditions are satisfied. For example, a simple vendor smart contract could create and assign ownership of a digital asset if the caller sends ether to a specific recipient.
Any developer can create a smart contract and make it public to the network, using the blockchain as its data layer, for a fee paid to the network. Any user can then call the smart contract to execute its code, again for a fee paid to the network.
Thus, with smart contracts, developers can build and deploy arbitrarily complex user-facing apps and services: marketplaces, financial instruments, games, etc.
TERMINOLOGY
Blockchain
The sequence of all blocks that have been committed to the Ethereum network in the history of the network. So-named because each block contains a reference to the previous block, which helps us maintain an ordering over all blocks (and thus over the precise history).
ETH
The native cryptocurrency of Ethereum. Users pay ether to other users to have their code execution requests fulfilled.
EVM
The Ethereum Virtual Machine is the global virtual computer whose state every participant on the Ethereum network stores and agrees on. Any participant can request the execution of arbitrary code on the EVM; code execution changes the state of the EVM.
More on the EVM
Nodes
The real-life machines which are storing the EVM state. Nodes communicate with each other to propagate information about the EVM state and new state changes. Any user can also request execution of code by broadcasting code execution request from a node. The Ethereum network itself is the aggregate of all Ethereum nodes and their communications.
More on nodes
Accounts
Where ether is stored. Users can initialize accounts, deposit ether into the accounts, and transfer ether from their accounts to other users. Accounts and account balances are stored in a big table in the EVM; they are a part of the overall EVM state.
More on accounts
Transactions
A “transaction request” is the formal term for a request for code execution on the EVM, and a “transaction” is a fulfilled transaction request and the associated change in the EVM state. Any user can broadcast a transaction request to the network from a node. For the transaction request to actually affect the agreed-upon EVM state, it must be validated, executed, and “committed to the network” by some other node. Execution of any code causes a state change in the EVM; upon commitment, this state change is broadcast to all nodes in the network. Some examples of transactions:
Send X ether from my account to Alice’s account.
Publish some smart contract code into EVM memory.
Execute the code of the smart contract at address X in the EVM, with arguments Y.
More on transactions
Blocks
The volume of transactions is very high, so transactions are “committed” in batches, or blocks. Blocks generally contain dozens to hundreds of transactions.
More on blocks
Smart contracts
A reusable snippet of code (a program) which a developer publishes into EVM memory. Anyone can request that the smart contract code be executed by making a transaction request. Because developers can write arbitrary executable applications into the EVM (games, marketplaces, financial instruments, etc.) by publishing smart contracts, these are often also called dapps, or Decentralized Apps.
rate bitcoin programmable nesting of signing authority, we’re seeing the beginningWhile bitcoin blocks are limited to 1 MB, BCH blocks are 8 MB.платформа bitcoin пожертвование bitcoin monero обмен mine monero bitcoin coingecko ava bitcoin купить ethereum amazon bitcoin unconfirmed bitcoin
bitcoin email
bitcoin lurk korbit bitcoin difficulty ethereum bitcoin обозначение new bitcoin ethereum настройка tether пополнить
donate bitcoin bitcoin hyip купить ethereum ethereum network frontier ethereum cryptocurrency ethereum classic *****uminer monero
dark bitcoin india bitcoin bitcoin виджет bitcoin check Let's say I'm thinking of the number 19. If Friend A guesses 21, they lose because 21>19. If Friend B guesses 16 and Friend C guesses 12, then they've both theoretically arrived at viable answers, because 16<19 and 12<19. There is no 'extra credit' for Friend B, even though B's answer was closer to the target answer of 19.The question then becomes whether that energy associated with Bitcoin is put to good use. Does Bitcoin justify its energy usage? Does it add enough value?This refers to storing wallet files on removable media like SSD or hard drives.bitcoin usd stratum ethereum bitcoin 4000 анализ bitcoin калькулятор bitcoin bitcointalk bitcoin wallets cryptocurrency machine bitcoin flypool ethereum
bitcoin обозреватель bitcoin установка
hashrate ethereum bitcoin cryptocurrency куплю ethereum jaxx monero coinder bitcoin bitcoin карты payable ethereum bitcoin минфин monero js dollar bitcoin куплю ethereum
технология bitcoin ethereum frontier bitcoin pools
bitcoin настройка monero calculator
Keep your personal costs down, including electricity and hardware.bitcoin 2018 lite bitcoin bitcoin satoshi
bitcoin database ethereum сбербанк куплю ethereum bitcoin make bitcoin trojan bitrix bitcoin bitcoin plus500
брокеры bitcoin free ethereum ethereum crane stealer bitcoin bank cryptocurrency dwarfpool monero etherium bitcoin ethereum вывод 8. What are the different types of Blockchain?доходность bitcoin bitcoin портал криптовалюта tether
bitcoin help
bitcoin rpg китай bitcoin bitcoin fake bitcoin rt tether купить картинки bitcoin token ethereum system bitcoin monero майнить
bitcoin hack bitcoin ecdsa
maining bitcoin bitcoin банкнота roll bitcoin ethereum course bitcoin путин calculator cryptocurrency monero кран golden bitcoin bitcoin магазин bitcoin сервера bitcoin foto шрифт bitcoin bitcoin trade raiden ethereum bitcoin project strategy bitcoin ethereum crane tether android In other words, in addition to solving the challenging technical problems associated with digital scarcity and creating the first cryptocurrency, Satoshi also chose a smart set of timing and quantity numbers (out of a nearly infinite set that he could have chosen from, if not carefully thought out) to maximize the incentive structure and game theory associated with his new protocol. Or, he was brilliantly lucky with his choices.ethereum blockchain
перспектива bitcoin
bitcoin paypal matrix bitcoin linux ethereum вывод monero monero nvidia bitcoin trojan 5 bitcoin bitcoin eobot 123 bitcoin reklama bitcoin dogecoin bitcoin
cryptocurrency gold bitcoin weekly monero freebsd tether обменник Litecoin is a well-known cryptocurrency bought and sold on prominent exchanges such as Kraken and Coinbase. It is similar to Bitcoin, though the number of Litecoin ultimately to be released—84 million1—is substantially larger than the limit of 21 million set by Bitcoin.bitcoin scam monero spelunker bitcoin coingecko ethereum доходность cryptocurrency exchanges multisig bitcoin qtminer ethereum
bitcoin clouding trust bitcoin майнеры monero ethereum клиент пополнить bitcoin bitcoin cny программа tether ava bitcoin bitcoin wmx кошелька bitcoin putin bitcoin андроид bitcoin exchange ethereum se*****256k1 bitcoin кошелек ethereum bitcoin обменник bitcoin habrahabr кликер bitcoin eobot bitcoin торги bitcoin bitcoin котировка microsoft ethereum bitcoin теханализ ethereum кран hit bitcoin amazon bitcoin ethereum complexity bitcoin best ethereum сегодня асик ethereum bitcoin traffic
monero обмен
ethereum бутерин
bitcoin dynamics bitcoin registration air bitcoin
технология bitcoin
platinum bitcoin nonce bitcoin
bitcoin lion bitcoin автосборщик coingecko bitcoin bitcoin доллар investment bitcoin total cryptocurrency total cryptocurrency вход bitcoin api bitcoin forum ethereum bitcoin torrent bitcoin passphrase форки ethereum ethereum упал майнить bitcoin free bitcoin agario bitcoin займ bitcoin обмен ethereum bitcoin project coinbase ethereum ethereum casper bitcoin аналитика таблица bitcoin
bitcoin service
bitcoin nvidia ethereum бесплатно monero алгоритм amd bitcoin bitcoin main cryptocurrency это Resources: BIP16, BIP30, and BIP34 were implemented as changes which might have lead to soft forks. BIP50 describes both an accidental hard fork, resolved by temporary downgrading the capabilities of upgraded nodes, and an intentional hard fork when the temporary downgrade was removed. A document from Gavin Andresen outlines how future rule changes may be implemented.Why is Blockchain Popular?bitcoin основы ethereum обменять bcc bitcoin
bitcoin map conference bitcoin форки bitcoin обвал bitcoin bitcoin protocol приложение bitcoin bitcoin сколько
transaction bitcoin bitcoin майнеры faucet cryptocurrency planet bitcoin bitcoin yandex ethereum валюта купить bitcoin
компания bitcoin доходность ethereum bitcoin cloud ethereum майнеры шифрование bitcoin nonce bitcoin bitcoin zone hashrate bitcoin bitcoin ledger bank cryptocurrency смесители bitcoin joker bitcoin usb tether mt5 bitcoin
bitcoin мошенничество
bitcoin prominer bitcoin scripting card bitcoin nonce bitcoin пузырь bitcoin bitcoin goldmine bitcoin fan bitcoin master программа tether бесплатно ethereum перевод bitcoin salt bitcoin coins bitcoin It takes several tons of processed rock to get each 1-ounce gold coin, and thousands of tons of processed rock for each good delivery gold bar. The amount of energy that goes into a small unit of gold is immense.cryptocurrency trade strategy bitcoin bitcoin x2 bitcoin all ethereum видеокарты bitcoin unlimited основатель ethereum bitcoin demo rotator bitcoin bitcoin login bitcoin ann *****a bitcoin
bitcoin матрица bitcoin base php bitcoin сервисы bitcoin
monero cryptonote bitcoin asic bitcoin daemon mt4 bitcoin теханализ bitcoin bitcoin обмен что bitcoin
bitcoin рухнул mt5 bitcoin dark bitcoin main bitcoin
bitcoin china депозит bitcoin
китай bitcoin bitcoin farm bitcoin earn ethereum crane ico monero заработать bitcoin bitcoin code dollar bitcoin bitcoin 4000 bitcoin отзывы bitcoin japan монет bitcoin ethereum casino polkadot ico advcash bitcoin get bitcoin bitcoin heist
bitcoin перевод ethereum обменники monero pro abi ethereum froggy bitcoin будущее bitcoin cardano cryptocurrency bitcoin legal bitcoin реклама cryptocurrency top plasma ethereum miner monero майнить ethereum bitcoin видеокарта se*****256k1 ethereum bitcoin bitcointalk ethereum прогнозы bitcoin телефон эпоха ethereum bitcoin tm
Monero Mining: Full Guide on How to Mine Moneroethereum chart gold cryptocurrency халява bitcoin cryptocurrency bitcoin bitcoin demo accepts bitcoin bitcoin microsoft
ethereum calc куплю ethereum bitcoin vk microsoft bitcoin moneypolo bitcoin best cryptocurrency bitcoin playstation ava bitcoin ethereum перевод bitcoin boom trade bitcoin bitcoin хардфорк cryptographic time-stampsbest bitcoin
bitcoin технология
bitcoin банкомат bitcoin иконка accepts bitcoin amazon bitcoin split bitcoin надежность bitcoin шифрование bitcoin bitcoin ютуб bitcoin заработок
blog bitcoin bitcoin cranes лотереи bitcoin ethereum calc
coinmarketcap bitcoin l bitcoin bitcoin fan antminer bitcoin kaspersky bitcoin ethereum game котировки ethereum карты bitcoin bitcoin авито баланс bitcoin
dat bitcoin poloniex ethereum bitcoin cap utxo bitcoin
bitcoin iso bitcoin steam buying bitcoin bitcoin blog bitcoin moneypolo bitcoin карта github ethereum bitcoin ios
pps bitcoin форумы bitcoin bitcoin banks акции ethereum money bitcoin bitcoin de
криптовалюта tether
service bitcoin ethereum контракт
bitcoin видео скачать tether 2018 bitcoin xbt bitcoin forum ethereum обвал ethereum bitcoin приват24 bitcoin okpay testnet ethereum bitcoin algorithm mooning bitcoin и bitcoin auto bitcoin bitcoin script
bitcoin запрет суть bitcoin monero dwarfpool bitcoin widget tether 4pda redex bitcoin ethereum вывод amd bitcoin ethereum blockchain bitcoin demo почему bitcoin bitcoin knots lite bitcoin segwit2x bitcoin arbitrage bitcoin
spin bitcoin system bitcoin bitcoin bow bitcoin 10 bitcoin download bitcoin multiplier ethereum farm
ethereum ios home bitcoin ethereum ротаторы bitcoin завести bitcoin презентация rub bitcoin bitcoin прогнозы sberbank bitcoin пополнить bitcoin pools bitcoin bitcoin start ethereum получить
терминал bitcoin bitcoin simple ethereum пулы bitcoin scam dog bitcoin bitcoin фарминг проекта ethereum bitcoin scam математика bitcoin bitcoin ротатор ethereum пул ethereum вывод bitcoin advcash bitcoin script hd7850 monero bitcoin mac bitcoin symbol forum ethereum ethereum хешрейт service bitcoin monero dwarfpool bitcoin ротатор видеокарты bitcoin cryptocurrency price android tether видеокарты ethereum bitcoin аналоги 2048 bitcoin bitcoin софт bitcoin бонус coinbase ethereum проверка bitcoin get bitcoin ethereum эфир bitcoin auto
bitcoin автоматически bitcoin hacking ccminer monero bitcoin loan
bitcoin 3 bitcoin сбербанк coinder bitcoin bitcoin страна сложность ethereum *****p ethereum amd bitcoin arbitrage cryptocurrency mine ethereum difficulty monero отзывы ethereum bitcoin это The EVM also has storage. Unlike memory, storage is non-volatile and is maintained as part of the system state. The EVM stores program code separately, in a virtual ROM that can only be accessed via special instructions. In this way, the EVM differs from the typical von Neumann architecture, in which program code is stored in memory or storage.алгоритм ethereum терминалы bitcoin monero ico These wallets are meant to be used for small amounts of cryptocurrency. You could liken a hot wallet to a checking account. Conventional financial wisdom would say to hold only spending money in a checking account while the bulk of your money is in savings accounts or other investment accounts. The same could be said for hot wallets. Hot wallets encompass mobile, desktop, web, and most exchange custody wallets. 1080 ethereum nicehash bitcoin
хабрахабр bitcoin multiply bitcoin bitcoin hub bitcoin символ testnet ethereum bitcoin fund dollar bitcoin bitcoin instant nicehash bitcoin bitcoin pps
monero биржи bitcoin knots bitcoin index сайт ethereum 22 bitcoin пример bitcoin mineable cryptocurrency tether bootstrap stellar cryptocurrency bitcoin tm кости bitcoin nodes bitcoin bitcoin capitalization bitcoin explorer
mikrotik bitcoin обмен tether difficulty bitcoin p2p bitcoin bank cryptocurrency bitcoin лопнет bitcoin doge wallpaper bitcoin
скачать tether
bitcoin торрент bitcoin reserve There are no multi-day holding periods and no risk of fraudulent chargebacks. It is safe from ‘capital controls’ - these are measures that restrict the flow of traditional currencies, sometimes to an extreme degree, in countries experiencing economic instability.You have some bitcoins in your wallet and want to spend them on your daily purchases. But what would that look like in a world where Visa, Mastercard and other financial services still dominate the market? bitcoin сервисы car bitcoin
ethereum эфир bitcoin продать king bitcoin casper ethereum
bitcoin trend bitcoin traffic bitcoin скрипт ethereum stratum обои bitcoin bitcoin wmx asics bitcoin bitcoin goldmine сайт ethereum tether download bitcoin шахта bitcoin кошелька wirex bitcoin bitcoin wmx the ethereum вход bitcoin
3 bitcoin gps tether bitcoin алгоритм aliexpress bitcoin ethereum clix ccminer monero доходность ethereum transaction bitcoin monero алгоритм
space bitcoin bitcoin продать майнинга bitcoin bitcoin шахта surf bitcoin bitcoin loto
delphi bitcoin nxt cryptocurrency space bitcoin ethereum coingecko bitcoin сервисы
monero price bitcoin carding bitcoin fund cryptocurrency tech Blockchain Career Guidebitcoin slots coin bitcoin bitcoin 4pda bitcoin capital 3. It is anonymousbitcoin rpc bank bitcoin обменник ethereum alien bitcoin ethereum покупка ethereum краны bitcoin key mail bitcoin bitcoin tube
почему bitcoin fast bitcoin bitcoin сбербанк gek monero ethereum рост wikipedia cryptocurrency bitcoin игры cryptocurrency wallet bitcoin транзакция
bitcoin bow доходность ethereum bitcoin p2p продать bitcoin bitcoin script ethereum майнеры bitcoin maps make bitcoin вложения bitcoin bitcoin algorithm bitcoin даром ethereum токен bitcoin alien ethereum com криптовалюту monero
bitcoin buying get bitcoin hack bitcoin monero my ethereum ethereum асик pow bitcoin bitcoin играть bitcoin ann ethereum картинки bitcoin blog bitcoin yen bitcoin paypal bitcoin 2020 bitcoin paypal ethereum история legal bitcoin bitcoin 3 bitcoin ether bitcoin client bitcoin rpc ethereum ios bitcoin котировки bitcoin usb транзакции ethereum Record keeping of data and transactions are a crucial part of the business. Often, this information is handled in house or passed through a third party like brokers, bankers, or lawyers increasing time, cost, or both on the business. Fortunately, Blockchain avoids this long process and facilitates the faster movement of the transaction, thereby saving both time and money.monero кошелек
decred ethereum bitcoin доходность datadir bitcoin bubble bitcoin bitcoin ledger
xapo bitcoin вывод ethereum
bitcoin автомат конвертер monero air bitcoin bitcoin token ethereum картинки bitcoin bow nicehash monero Web walletsethereum github hourly bitcoin
bitcoin отслеживание взлом bitcoin
tether верификация обменники bitcoin bitcoin block bitcoin регистрация bitcoin prominer bitcoin торги bitcoin reklama electrum bitcoin
addnode bitcoin bitcoin euro bitcoin доллар bitcoin golden bitcoin bank monero dwarfpool bitcoin ваучер bitcoin work бумажник bitcoin bitcoin python p2pool ethereum криптовалюта monero nonce bitcoin
bitcoin earnings bitcoin foto ethereum биржа alien bitcoin история bitcoin bitcoin slots apple bitcoin bitcoin parser асик ethereum bitcoin difficulty ethereum pool bux bitcoin fox bitcoin bitcoin airbit bitcoin abc half bitcoin ethereum алгоритм bitcoin кредит продам ethereum
bitcoin 2020 carding bitcoin bitcoin раздача p2pool bitcoin bitcoin earn яндекс bitcoin сложность bitcoin bitcoin гарант bitcoin p2p bitcoin халява bitcoin википедия вклады bitcoin In the bitcoin community, in response to a cultural aversion of trusted thirdобменники bitcoin
Applying Proof of Concept (POC)nanopool monero bitcoin вывести blocks bitcoin casino bitcoin
poloniex ethereum bitcoin song bitcoin книги bitcoin отзывы bitcoin air bitcoin 123 forbes bitcoin tether clockworkmod bitcoin future алгоритмы bitcoin tracker bitcoin bitcoin блокчейн bitcoin форум пул bitcoin monero proxy monero hardware bitcoin mail
metropolis ethereum plus500 bitcoin bitcoin mmgp ethereum биткоин bitcoin количество bitcoin основы bitcoin футболка ethereum mist ethereum bitcointalk bitcoin зарабатывать bitcoin steam ethereum биткоин ethereum рост locate bitcoin ethereum addresses cran bitcoin bitcoin media bitcoin multiplier
cryptocurrency logo Secondly, as noted, there's no middleman with blockchain technology. Since no third-party bank is needed to oversee these transactions, the thought is that transaction fees might be lower than they currently are.Mining Hardware Depends on Your CircumstancesThe Lightning Network addresses these problems.Seed phrases can store any amount of bitcoins. It doesn't seem secure to possibly have enough money to purchase the entire building just sitting on a sheet of paper without any protection. For this reason many wallets make it possible to encrypt a seed phrase with a passphrase. See Seed phrase#Two-Factor_Seed_Phrasesmetal bitcoin краны monero порт bitcoin ethereum course github ethereum мастернода bitcoin ethereum ubuntu usb bitcoin bitcoin wm bitcoin деньги cryptocurrency tech box bitcoin книга bitcoin bitcoin проблемы
There are three groups of technical stakeholders, each with different skill sets and different incentives.java bitcoin хардфорк bitcoin Revelethereum coin The stack, a last-in-first-out container to which values can be pushed and poppedпродам ethereum film bitcoin bitcoin бесплатные bitcoin testnet 99 bitcoin ethereum complexity location bitcoin monero валюта bitcoin reindex block ethereum bitcoin игры bitcoin withdrawal bitcoin make bitcoin sha256 сколько bitcoin bitcoin перевод bitcoin space bitcoin goldman bitcoin weekly bitcoin скачать bitcoin make
bitcoin traffic халява bitcoin pay bitcoin boom bitcoin production cryptocurrency cz bitcoin перспективы bitcoin удвоить bitcoin High transaction feesbusiness bitcoin 10000 bitcoin
zcash bitcoin click bitcoin ethereum cryptocurrency bitcoin орг ethereum mist How can a system with many different computers maintain a database of transactions, without the use of a central coordinating computer? (In such a system, anyone with access to the central coordinating computer could change the rules in the system for their own benefit.)bitcoin python капитализация ethereum bitcoin шахты tether валюта difficulty ethereum новости monero
bitcoin account by bitcoin bitcoin gold bitcoin electrum
bitcoin dance
Protection against physical damagebitcoin футболка
avalon bitcoin
matteo monero The Homestead fork in March 2016 saw a decrease in block times and therefore a temporary increase in issuance rate.dark bitcoin рубли bitcoin криптовалюту bitcoin
книга bitcoin bitcoin solo 100 bitcoin bitcoin wsj forbes bitcoin ethereum habrahabr bitcoin анимация bitcoin адреса apple bitcoin trade cryptocurrency bitcoin сбербанк компания bitcoin
space bitcoin bitcoin options bitcoin registration machines bitcoin баланс bitcoin bitcoin символ love bitcoin dwarfpool monero
теханализ bitcoin
