On 6 August 2010, a major vulnerability in the bitcoin protocol was spotted. Transactions weren't properly verified before they were included in the transaction log or blockchain, which let users bypass bitcoin's economic restrictions and create an indefinite number of bitcoins. On 15 August, the vulnerability was exploited; over 184 billion bitcoins were generated in a transaction, and sent to two addresses on the network. Within hours, the transaction was spotted and erased from the transaction log after the bug was fixed and the network forked to an updated version of the bitcoin protocol. This was the only major security flaw found and exploited in bitcoin's history.
Computing power is often bundled together or "pooled" to reduce variance in miner income. Individual mining rigs often have to wait for long periods to confirm a block of transactions and receive payment. In a pool, all participating miners get paid every time a participating server solves a block. This payment depends on the amount of work an individual miner contributed to help find that block.
The concept of a virtual currency is still novel and, compared to traditional investments, Bitcoin doesn't have much of a longterm track record or history of credibility to back it. With their increasing use, bitcoins are becoming less experimental every day, of course; still, after eight years, they (like all digital currencies) remain in a development phase, still evolving. "It is pretty much the highest-risk, highest-return investment that you can possibly make,” says Barry Silbert, CEO of Digital Currency Group, which builds and invests in Bitcoin and blockchain companies.
Bitcoin is a cryptocurrency, a digital asset designed to work as a medium of exchange that uses cryptography to control its creation and management, rather than relying on central authorities. The presumed pseudonymous Satoshi Nakamoto integrated many existing ideas from the cypherpunk community when creating bitcoin. Over the course of bitcoin's history, it has undergone rapid growth to become a significant currency both on and offline – from the mid 2010s, some businesses began accepting bitcoin in addition to traditional currencies.
The bitcoin blockchain is a public ledger that records bitcoin transactions. It is implemented as a chain of blocks, each block containing a hash of the previous block up to the genesis block[a] of the chain. A network of communicating nodes running bitcoin software maintains the blockchain.:215–219 Transactions of the form payer X sends Y bitcoins to payee Z are broadcast to this network using readily available software applications.