  Cross-correlations in fluctuations of the daily exchange rates within the
basket of the 100 highest-capitalization cryptocurrencies over the period
October 1, 2015, through March 31, 2019, are studied. The corresponding
dynamics predominantly involve one leading eigenvalue of the correlation
matrix, while the others largely coincide with those of Wishart random
matrices. However, the magnitude of the principal eigenvalue, and thus the
degree of collectivity, strongly depends on which cryptocurrency is used as a
base. It is largest when the base is the most peripheral cryptocurrency; when
more significant ones are taken into consideration, its magnitude
systematically decreases, nevertheless preserving a sizable gap with respect to
the random bulk, which in turn indicates that the organization of correlations
becomes more heterogeneous. This finding provides a criterion for recognizing
which currencies or cryptocurrencies play a dominant role in the global
crypto-market. The present study shows that over the period under
consideration, the Bitcoin (BTC) predominates, hallmarking exchange rate
dynamics at least as influential as the US dollar. The BTC started dominating
around the year 2017, while further cryptocurrencies, like the Ethereum (ETH)
and even Ripple (XRP), assumed similar trends. At the same time, the USD, an
original value determinant for the cryptocurrency market, became increasingly
disconnected, its related characteristics eventually approaching those of a
fictitious currency. These results are strong indicators of incipient
independence of the global cryptocurrency market, delineating a self-contained
trade resembling the Forex.
