In cryptocurrency networks, mining is a validation of transactions. For this effort, successful miners obtain new cryptocurrency as a reward. The reward decreases transaction fees by creating a complementary incentive to contribute to the processing power of the network. The rate of generating hashes, which validate any transaction, has been increased by the use of specialized machines such as FPGAs and ASICs running complex hashing algorithms like SHA-256 and Scrypt.[30] This arms race for cheaper-yet-efficient machines has been on since the day the first cryptocurrency, bitcoin, was introduced in 2009.[30] With more people venturing into the world of virtual currency, generating hashes for this validation has become far more complex over the years, with miners having to invest large sums of money on employing multiple high performance ASICs. Thus the value of the currency obtained for finding a hash often does not justify the amount of money spent on setting up the machines, the cooling facilities to overcome the enormous amount of heat they produce, and the electricity required to run them.[30][31] 


A lot of concerns have been raised regarding cryptocurrencies’ decentralized nature and their ability to be used almost completely anonymously. The authorities all over the world are worried about the cryptocurrencies’ appeal to the traders of illegal goods and services. Moreover, they are worried about their use in money laundering and tax evasion schemes.

Markets are dirty. But this doesn‘t change the fact that cryptocurrencies are here to stay – and here to change the world. This is already happening. People all over the world buy Bitcoin to protect themselves against the devaluation of their national currency. Mostly in Asia, a vivid market for Bitcoin remittance has emerged, and the Bitcoin using darknets of cybercrime are flourishing. More and more companies discover the power of Smart Contracts or token on Ethereum, the first real-world application of blockchain technologies emerge.


比特币与莱特币都采用了区块链技术,且都有51%攻击的问题。它们采用区块链技术,所有历史记录按照时间先后顺序,打包成一个个单独的区块,再把这些单独的区块链接在一起形成一个总账本 [5]  。这些区块内除了包含交易记录外,还包含新发行的莱特币和交易的手续费,这两笔钱支付给挖矿的矿工作为酬劳。无论谁挖到该区块,那么该区块内含有的新发行的莱特币和交易的手续费这两笔钱都归挖到者,以鼓励矿工积极参与结算。区块链技术容易产生51%攻击的问题:无论任何组织甚至个人,只要掌控某一种基于区块链原理的虚拟货币的全部运算能力的51%,这个人或组织就能够任意操纵该虚拟货币的所有交易。如果区块链只认运算能力最大者,谁的运算能力最大,谁就能抢到下一个区块,如果某个个人或组织掌控了全部运算能力的51%,那就意味着没人比他运算能力更强,故而他就可以随意操纵。所以,对于基于区块链原理的虚拟货币,参与挖矿的越多就越健壮,运算能力越分散就越健壮;挖坑者越少越脆弱,运算能力越集中就越脆弱,矿池越集中也就越脆弱 [1]  。


Many people believe that cryptocurrencies are the hottest investment opportunity currently available. Indeed, there are many stories of people becoming millionaires through their Bitcoin investments. Bitcoin is the most recognizable digital currency to date, and just last year one BTC was valued at $800. In November 2017, the price of one Bitcoin exceeded $7,000.