  Cryptocurrency history begins in 2008 as a means of payment proposal.
However, cryptocurrencies evolved into complex, high yield speculative assets.
Contrary to traditional financial instruments, they are not (mostly) traded in
organized, law-abiding venues, but on online platforms, where anonymity reigns.
This paper examines the long term memory in return and volatility, using high
frequency time series of eleven important coins. Our study covers the
pre-Covid-19 and the subsequent pandemia period. We use a recently developed
method, based on the wavelet transform, which provides more robust estimators
of the Hurst exponent. We detect that, during the peak of Covid-19 pandemic
(around March 2020), the long memory of returns was only mildly affected.
However, volatility suffered a temporary impact in its long range correlation
structure. Our results could be of interest for both academics and
practitioners.
