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.
Beam Mimblewimble is a scalable, fungible, and confidential cryptocurrency based on the Mimblewimble implementation. WHY BEAM? Core features include complete control over your privacy, All transactions are private by default, No addresses or other private information are stored on the blockchain, Superior scalability due to compact blockchain size, Opt-in Auditability, Support online and offline transactions, atomic swap, hardware wallets integration. Governance model No premine, No ICO. Backed by Treasury Establishing a non-profit foundation to govern the protocol after Mainnet launch How does it work? Wallets’ owners create new transaction using secure channel either online or offline Both wallets participate in signing the transaction using Schnorr protocol Wallet sends transaction to node Each transaction contains a list of Inputs and Outputs represented by Pedersen Commitments, as well as explicit fees and kernels. Each transaction also contains non-interactive zero knowledge range proof to verify that the output transaction value is positive Transaction is verified by the node Each transaction is verified with respect to the recent blockchain state which is stored as a Merkle Tree. The root hash of the tree is recorded in block header along with a proof of work. In addition, each node periodically creates compacted history to allow ‘fast sync’ of new and existing nodes. Transaction is added to the mining pool A block is mined every minute and is sent back to the node for verification and distribution. Mined blocks containing the new transactions are sent to the known peers A valid block that is extending the longest chain is accepted as a new Tip and propagated further until full consensus is reached. Fast sync When a new node connects to the network for the first time it can request compacted history containing only system state and blockchain headers. There is no need to retrieve the entire transaction history.