Any services that are centralized can be decentralized using Ethereum. Think about all the intermediary services that exist across hundreds of different industries. From obvious services like loans provided by banks to intermediary services rarely thought about by most people like title registries, voting systems, regulatory compliance and much more.
Ethereum blockchain applications are usually referred to as DApps (decentralized application), since they are based on the decentralized Ethereum Virtual Machine, and its smart contracts. Many uses have been proposed for Ethereum platform, including ones that are impossible or unfeasible. Use case proposals have included finance, the internet-of-things, farm-to-table produce, electricity sourcing and pricing, and sports betting. Ethereum is (as of 2017) the leading blockchain platform for initial coin offering projects, with over 50% market share.
There is ongoing research on how to use formal verification to express and prove non-trivial properties. A Microsoft Research report noted that writing solid smart contracts can be extremely difficult in practice, using The DAO hack to illustrate this problem. The report discussed tools that Microsoft had developed for verifying contracts, and noted that a large-scale analysis of published contracts is likely to uncover widespread vulnerabilities. The report also stated that it is possible to verify the equivalence of a Solidity program and the EVM code.
Physical wallets can also take the form of metal token coins with a private key accessible under a security hologram in a recess struck on the reverse side.:38 The security hologram self-destructs when removed from the token, showing that the private key has been accessed. Originally, these tokens were struck in brass and other base metals, but later used precious metals as bitcoin grew in value and popularity.:80 Coins with stored face value as high as ₿1000 have been struck in gold.:102–104 The British Museum's coin collection includes four specimens from the earliest series:83 of funded bitcoin tokens; one is currently on display in the museum's money gallery. In 2013, a Utahn manufacturer of these tokens was ordered by the Financial Crimes Enforcement Network (FinCEN) to register as a money services business before producing any more funded bitcoin tokens.:80
Third-party internet services called online wallets offer similar functionality but may be easier to use. In this case, credentials to access funds are stored with the online wallet provider rather than on the user's hardware. As a result, the user must have complete trust in the online wallet provider. A malicious provider or a breach in server security may cause entrusted bitcoins to be stolen. An example of such a security breach occurred with Mt. Gox in 2011.
Ethereum was initially described in a white paper by Vitalik Buterin, a programmer involved with Bitcoin Magazine, in late 2013 with a goal of building decentralized applications. Buterin had argued that Bitcoin needed a scripting language for application development. Failing to gain agreement, he proposed development of a new platform with a more general scripting language.:88
Both blockchains have the same features and are identical in every way up to a certain block where the hard-fork was implemented. This means that everything that happened on Ethereum up until the hard-fork is still valid on the Ethereum Classic Blockchain. From the block where the hard fork or change in code was executed onwards, the two blockchains act individually.
In the end, the majority of the Ethereum community voted to perform a hard fork, and retrieve The DAO investors money. But not everyone agreed with this course of action. This resulted in a split where two parallel blockchains now exist. For those members who strongly disagree with any changes to the blockchain even when hacking occurs there is Ethereum classic. For the majority who agreed to rewrite a small part of the blockchain and return the stolen money to their owners, there is Ethereum.
Transactions are defined using a Forth-like scripting language.:ch. 5 Transactions consist of one or more inputs and one or more outputs. When a user sends bitcoins, the user designates each address and the amount of bitcoin being sent to that address in an output. To prevent double spending, each input must refer to a previous unspent output in the blockchain. The use of multiple inputs corresponds to the use of multiple coins in a cash transaction. Since transactions can have multiple outputs, users can send bitcoins to multiple recipients in one transaction. As in a cash transaction, the sum of inputs (coins used to pay) can exceed the intended sum of payments. In such a case, an additional output is used, returning the change back to the payer. Any input satoshis not accounted for in the transaction outputs become the transaction fee.
Ethereum is also being used as a platform to launch other cryptocurrencies. Because of the ERC20 token standard defined by the Ethereum Foundation, other developers can issue their own versions of this token and raise funds with an initial coin offering (ICO). In this fundraising strategy, the issuers of the token set an amount they want to raise, offer it in a crowdsale, and receive Ether in exchange. Billions of dollars have been raised by ICOs on the Ethereum platform in the last two years, and one of the most valuable cryptocurrencies in the world, EOS, is an ERC20 token.