To heighten financial privacy, a new bitcoin address can be generated for each transaction.[113] For example, hierarchical deterministic wallets generate pseudorandom "rolling addresses" for every transaction from a single seed, while only requiring a single passphrase to be remembered to recover all corresponding private keys.[114] Researchers at Stanford and Concordia universities have also shown that bitcoin exchanges and other entities can prove assets, liabilities, and solvency without revealing their addresses using zero-knowledge proofs.[115] "Bulletproofs," a version of Confidential Transactions proposed by Greg Maxwell, have been tested by Professor Dan Boneh of Stanford.[116] Other solutions such Merkelized Abstract Syntax Trees (MAST), pay-to-script-hash (P2SH) with MERKLE-BRANCH-VERIFY, and "Tail Call Execution Semantics", have also been proposed to support private smart contracts.
Bitcoins can be accepted as a means of payment for products sold or services provided. If you have a brick and mortar store, just display a sign saying “Bitcoin Accepted Here” and many of your customers may well take you up on it; the transactions can be handled with the requisite hardware terminal or wallet address through QR codes and touch screen apps. An online business can easily accept bitcoins by just adding this payment option to the others it offers, like credit cards, PayPal, etc. Online payments will require a Bitcoin merchant tool (an external processor like Coinbase or BitPay). 
“These companies are using extraordinary amounts of electricity – typically thousands of times more electricity than an average residential customer would use,” a spokesperson for the New York State Department of Public Service told Wired. “The sheer amount of electricity being used is leading to higher costs for customers in small communities because of a limited supply of low-cost hydropower.”
During the last several years an incredible amount of Bitcoin mining power (hashrate) has come online making it harder for individuals to have enough hashrate to single-handedly solve a block and earn the payout reward. To compensate for this pool mining was introduced. Pooled mining is a mining approach where groups of individual miners contribute to the generation of a block, and then split the block reward according the contributed processing power.
Bitcoin's origin story sounds like something out of science fiction: It was launched in 2008 on the heels of a white paper published by the mysterious Satoshi Nakamoto, whose real identity – and country of origin – are unknown. Nakamoto conceived of Bitcoin as a currency that was 1) encrypted; 2) decentralized, i.e. it was ungoverned and did not belong to any nation; and 3) a digital "distributed ledger," such that everyone can verify online the legitimacy of transactions.
How hard are the puzzles involved in mining? Well, that depends on how much effort is being put into mining across the network. The difficulty of the mining can be adjusted, and is adjusted by the protocol every 2016 blocks, or roughly every 2 weeks. The difficulty adjusts itself with the aim of keeping the rate of block discovery constant. Thus if more computational power is employed in mining, then the difficulty will adjust upwards to make mining harder.  And if computational power is taken off of the network, the opposite happens. The difficulty adjusts downward to make mining easier.
The trick, though, was finding a location where you could put all that cheap power to work. You needed an existing building, because in those days, when bitcoin was trading for just a few dollars, no one could afford to build something new. You needed space for a few hundred high-speed computer servers, and also for the heavy-duty cooling system to keep them from melting down as they churned out the trillions of calculations necessary to mine bitcoin. Above all, you needed a location that could handle a lot of electricity—a quarter of a megawatt, maybe, or even a half a megawatt, enough to light up a couple hundred homes.
Several deep web black markets have been shut by authorities. In October 2013 Silk Road was shut down by U.S. law enforcement[35][36][37] leading to a short-term decrease in the value of bitcoin.[38] In 2015, the founder of the site was sentenced to life in prison.[39] Alternative sites were soon available, and in early 2014 the Australian Broadcasting Corporation reported that the closure of Silk Road had little impact on the number of Australians selling drugs online, which had actually increased.[40] In early 2014, Dutch authorities closed Utopia, an online illegal goods market, and seized 900 bitcoins.[41] In late 2014, a joint police operation saw European and American authorities seize bitcoins and close 400 deep web sites including the illicit goods market Silk Road 2.0.[42] Law enforcement activity has resulted in several convictions. In December 2014, Charlie Shrem was sentenced to two years in prison for indirectly helping to send $1 million to the Silk Road drugs site,[43] and in February 2015, its founder, Ross Ulbricht, was convicted on drugs charges and faces a life sentence.[44]
Electricity cost: How many dollars are you paying per kilowatt? You’ll need to find out your electricity rate in order to calculate profitability. This can usually be found on your monthly electricity bill. The reason this is important is that miners consume electricity, whether for powering up the miner or for cooling it down (these machines can get really hot).
In parts of the basin, utility crews now actively hunt unpermitted miners, in a manner not unlike the way police look for indoor cannabis farms. The biggest giveaway, Stoll says, is a sustained jump in power use. But crews have learned to look, and listen, for other telltales, such as “fans that are exhausting out of the garage or a bedroom.” In any given week, the utility flushes out two to five suspected miners, Stoll says. Some come clean. They pay for permits and the often-substantial wiring upgrades, or they quit. But others quietly move their servers to another residential location and plug back in. “It’s a bit of a cat-and-mouse game,” Stoll admits.

Legal Gray Area. Major governments have largely remained on the sidelines, and this has created both a sense of potential and apprehension for Bitcoin proponents and critics respectively. Bitcoin isn’t backed by a regulatory agency and a government would technically be ceding power by supporting a decentralized currency. This has been largely officially unaddressed. Bitcoin’s price, however, tends to be very sensitive to any news concerning the US government’s opinion of cryptocurrencies. For example, when the SEC denied the approval of bitcoin-based exchange-traded-products—essentially bitcoin-backed assets on the stock market—in 2017, Bitcoin’s price dropped 18%. Yet while the price and adoption of Bitcoin would be affected by government action, governments are unable to criminalize Bitcoin. In fact, governments such as the United States and China have invested in it at some capacity.

You can buy bitcoins at online exchanges similar to a paypal account. Companies like Coinbase allow you to buy bitcoin with a credit card along with wire transfers, checks and ACH. You can also use professional exchanges like Coinbase Pro that allow for institutional investors and experienced traders to trade in high volumes in a variety of cryptocurrencies with minimal fees.

In the blockchain, bitcoins are registered to bitcoin addresses. Creating a bitcoin address requires nothing more than picking a random valid private key and computing the corresponding bitcoin address. This computation can be done in a split second. But the reverse, computing the private key of a given bitcoin address, is mathematically unfeasible. Users can tell others or make public a bitcoin address without compromising its corresponding private key. Moreover, the number of valid private keys is so vast that it is extremely unlikely someone will compute a key-pair that is already in use and has funds. The vast number of valid private keys makes it unfeasible that brute force could be used to compromise a private key. To be able to spend their bitcoins, the owner must know the corresponding private key and digitally sign the transaction. The network verifies the signature using the public key.[3]:ch. 5