The bitcoin network is a peer-to-peer payment network that operates on a cryptographic protocol. Users send and receive bitcoins, the units of currency, by broadcasting digitally signed messages to the network using bitcoin cryptocurrency wallet software. Transactions are recorded into a distributed, replicated public database known as the blockchain, with consensus achieved by a proof-of-work system called mining. Satoshi Nakamoto, the designer of bitcoin claimed that design and coding of bitcoin began in 2007. The project was released in 2009 as open source software. The network requires the minimal structure to share transactions. An ad hoc decentralized network of volunteers is sufficient. Messages are broadcast on a best effort basis, and nodes can leave and rejoin the network at will. Upon reconnection, a node downloads and verifies new blocks from other nodes to complete its local copy of the blockchain. A bitcoin is defined by a sequence of digitally signed transactions that began with the bitcoin's creation, as a block reward. The owner of a bitcoin transfers it by digitally signing it over to the next owner using a bitcoin transaction, much like endorsing a traditional bank check. A payee can examine each previous transaction to verify the chain of ownership. Unlike traditional check endorsements, bitcoin transactions are irreversible, which eliminates the risk of chargeback fraud. Although it is possible to handle bitcoins individually, it would be unwieldy to require a separate transaction for every bitcoin in a transaction. Transactions are therefore allowed to contain multiple inputs and outputs, allowing bitcoins to be split and combined. Common transactions will have either a single input from a larger previous transaction or multiple inputs combining smaller amounts, and one or two outputs: one for the payment, and one returning the change, if any, to the sender. Any difference between the total input and output amounts of a transaction goes to miners as a transaction fee. In 2013, Mark Gimein estimated electricity consumption to be about 40.9 megawatts (982 megawatt-hours a day). In 2014, Hass McCook estimated 80.7 megawatts (80,666 kW). As of 2015, The Economist estimated that even if all miners used modern facilities, the combined electricity consumption would be 166.7 megawatts (1.46 terawatt-hours per year). To lower the costs, bitcoin miners have set up in places like Iceland where geothermal energy is cheap and cooling Arctic air is free. Chinese bitcoin miners are known to use hydroelectric power in Tibet to reduce electricity costs. Various potential attacks on the bitcoin network and its use as a payment system, real or theoretical, have been considered. The bitcoin protocol includes several features that protect it against some of those attacks, such as unauthorized spending, double spending, forging bitcoins, and tampering with the blockchain. Other attacks, such as theft of private keys, require due care by users.
The Stellar network is an open source, distributed, and community owned network used to facilitate cross-asset transfers of value. Stellar aims to help facilitate cross-asset transfer of value at a fraction of a penny while aiming to be an open financial system that gives people of all income levels access to low-cost financial services. Stellar can handle exchanges between fiat-based currencies and between cryptocurrencies. Stellar.org, the organization that supports Stellar, is centralized like XRP and meant to handle cross platform transactions and micro transactions like XRP. However, unlike Ripple, Stellar.org is non-profit and their platform itself is open source and decentralized. Stellar was founded by Jed McCaleb in 2014. Jed McCaleb is also the founder of Mt. Gox and co-founder of Ripple, launched the network system Stellar with former lawyer Joyce Kim. Stellar is also a payment technology that aims to connect financial institutions and drastically reduce the cost and time required for cross-border transfers. In fact, both payment networks used the same protocol initially. Distributed Exchange Through the use of its intermediary currency Lumens (XLM), a user can send any currency that they own to anyone else in a different currency. For instance, if Joe wanted to send USD to Mary using her EUR, an offer is submitted to the distributed exchange selling USD for EUR. This submitted offer forms is known as an order book. The network will use the order book to find the best exchange rate for the transaction in-order to minimize the fee paid by a user. This multi-currency transaction is possible because of 'Anchors'. Anchors are trusted entities that hold people’s deposits and can issue credit. In essence, Anchors serves as the bridge between different currencies and the Stellar network. Lumens (XLM) Lumens are the native asset (digital currency) that exist on the Stellar network that helps to facilitate multi-currency transactions and prevent spams. For multi-currency transactions, XLM is the digital intermediary that allows for such a transaction to occur at a low cost. In-order to prevent DoS attacks (aka spams) that would inevitably occur on the Stellar network, a small fee of 0.00001 XLM is associated with every transaction that occurs on the network. This fee is small enough so it does not significantly affect the cost of transaction, but large enough so it dissuades bad actors from spamming the network. The collected fee is then redistributed and added to an inflation pool. This inflation pool releases Lumens at a rate of 1% each year.