Under stand the Cryptocurrency and Indices an overview...

Decentralized cryptocurrency is produced by the entire cryptocurrency system collectively, at a rate which is defined when the system is created and which is publicly known. In centralized banking and economic systems such as the Federal Reserve System, corporate boards or governments control the supply of currency by printing units of fiat money or demanding additions to digital banking ledgers. In case of decentralized cryptocurrency, companies or governments cannot produce new units, and have not so far provided backing for other firms, banks or corporate entities which hold asset value measured in it. The underlying technical system upon which decentralized cryptocurrencies are based was created by the group or individual known as Satoshi Nakamoto.
As of September 2017, over a thousand cryptocurrency specifications exist; most are similar to and derived from the first fully implemented decentralized cryptocurrency, bitcoin. Within cryptocurrency systems the safety, integrity and balance of ledgers is maintained by a community of mutually distrustful parties referred to as miners: members of the general public using their computers to help validate and timestamp transactions adding them to the ledger in accordance with a particular timestamping scheme. Miners have a financial incentive to maintain the security of a cryptocurrency ledger.

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Most cryptocurrencies are designed to gradually decrease production of currency, placing an ultimate cap on the total amount of currency that will ever be in circulation, mimicking precious metals. Compared with ordinary currencies held by financial institutions or kept as cash on hand, cryptocurrencies can be more difficult for seizureby law enforcement. This difficulty is derived from leveraging cryptographic technologies. A primary example of this new challenge for law enforcement comes from the Silk Road case, where Ulbricht's bitcoin stash "was held separately and ... encrypted." Cryptocurrencies such as bitcoin are pseudonymous, though additions such as Zerocoinhave been suggested, which would allow for true anonymity.
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In order to follow the development of the market of cryptocurrencies, indices keep track of notable cryptocurrencies and their cumulative market value.
Cryptocurrency Indexes CRYX
CRYX is a company launched in 2017 offering three ranges of Cryptocurrency Indexes, each having different calculation methods (i.e. Cap-Weighted, Equal-Weighted, and Exponential flattening - FLEX) with a fixed number of cryptocurrencies (i.e. CRYX5, CRYX10, CRYX25, CRYX50, and CRYX100). The Cap-Weighted Index range will be tracking the cryptocurrency market based on each individual market capitalization. The Equal-Weighted Index range is purposely erasing the market capitalization factor from each asset in order to achieve a simple goal – all the assets weights are equal. Finally, the FLEX Index range takes into consideration the market capitalization and the ranking of every cryptocurrency, but it also reduces their standard deviation in order to give more weights to cryptocurrencies. CRYX is also said to have one of the biggest cryptocurrency databases with data dating back until April 28, 2013.
Crypto index CRIX
The cryptocurrency index CRIX is a conceptual measurement jointly developed by statisticians at Humboldt University of Berlin, Singapore Management Universityand the enterprise CoinGecko and was launched in 2016.The index represents cryptocurrency market characteristics dating back until July 31, 2014. Its algorithm takes into account that the cryptocurrency market is frequently changing, with the continuous creation of new cryptocurrencies and infrequent trading of some of the existing ones.Therefore, the number of index members is adjusted quarterly according to their relevance on the cryptocurrency market as a whole.It is the first dynamic index reflecting changes on the cryptocurrency market.

Source: Wikipedia