Various journalists,[204][211] economists,[212][213] and the central bank of Estonia[214] have voiced concerns that bitcoin is a Ponzi scheme. In 2013, Eric Posner, a law professor at the University of Chicago, stated that "a real Ponzi scheme takes fraud; bitcoin, by contrast, seems more like a collective delusion."[215] A 2014 report by the World Bank concluded that bitcoin was not a deliberate Ponzi scheme.[216]:7 The Swiss Federal Council[217]:21 examined the concerns that bitcoin might be a pyramid scheme; it concluded that, "Since in the case of bitcoin the typical promises of profits are lacking, it cannot be assumed that bitcoin is a pyramid scheme." In July 2017, billionaire Howard Marks referred to bitcoin as a pyramid scheme.[218]
The Bitcoin protocol was designed to encourage the distribution of hashing power among miners rather than its concentration. The reason? Miners wield power not only over which transactions get added to the Bitcoin blockchain but over the evolution of the Bitcoin software itself. When updates are made to the protocol, it is the miners, largely, who enforce these changes. If the miners band together and choose not to deploy an update from Bitcoin’s core developers, they can stall transactions or even cause the currency to split into competing versions.
Bitcoin mining is intentionally designed to be resource-intensive and difficult so that the number of blocks found each day by miners remains steady. Individual blocks must contain a proof of work to be considered valid. This proof of work is verified by other Bitcoin nodes each time they receive a block. Bitcoin uses the hashcash proof-of-work function.
Mining is the process of spending computation power to secure Bitcoin transactions against reversal and introducing new Bitcoins to the system. Technically speaking, mining is the calculation of a hash of the block header, which includes among other things a reference to the previous block, a hash of a set of transactions and a nonce (an arbitrary number used just once for authentication purposes).
Bitcoin Mining is a peer-to-peer computer process used to secure and verify bitcoin transactions—payments from one user to another on a decentralized network. Mining involves adding bitcoin transaction data to Bitcoin's global public ledger of past transactions. Each group of transactions is called a block. Blocks are secured by Bitcoin miners and build on top of each other forming a chain. This ledger of past transactions is called the blockchain. The blockchain serves to confirm transactions to the rest of the network as having taken place. Bitcoin nodes use the blockchain to distinguish legitimate Bitcoin transactions from attempts to re-spend coins that have already been spent elsewhere.
And, inevitably, there was a growing tension with the utilities, which were finally grasping the scale of the miners’ ambitions. In 2014, the public utility district in Chelan County received requests from would-be miners for a total of 220 megawatts—a startling development in a county whose 70,000 residents were then using barely 200 megawatts. Similar patterns were emerging across the river in neighboring Douglas and Grant counties, where power is also cheap.
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
You’ll need a Bitcoin wallet in which to keep your mined Bitcoins. Once you have a wallet, make sure to get your wallet address. It will be a long sequence of letters and numbers. Each wallet has a different way to get the public Bitcoin address, but most wallets are pretty straightforward about it. Notice that you’ll need your PUBLIC Bitcoin address and not your private key (which is like the secret password for your wallet).
Mobile wallets overcome the handicap of desktop wallets, as the latter are fixed in one place. These take the form of paid apps on youOnce you run the app on your smartphone, the wallet can carry out the same functions as a desktop wallet, and help you pay directly from your mobile from anywhere. Thus a mobile wallet facilitates in making payments in physical stores by using "touch-to-pay" via NFC scanning a QR code. Bitcoin Wallet, Hive Android and Mycelium Bitcoin Wallet are few of the mobile wallets. Bitcoin wallets do not generally work on both iOS and Android systems. It's advisable to research your preferred mobile Bitcoin wallet as several malware softwares posing as Bitcoin wallets can be 
Transactions are verified by network nodes through cryptography and recorded in a public distributed ledger called a blockchain. Bitcoin was invented by an unknown person or group of people using the name Satoshi Nakamoto[9] and released as open-source software in 2009.[10] Bitcoins are created as a reward for a process known as mining. They can be exchanged for other currencies,[11] products, and services. Research produced by the University of Cambridge estimates that in 2017, there were 2.9 to 5.8 million unique users using a cryptocurrency wallet, most of them using bitcoin.[12]
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