Cryptocurrency is a form of decentralized digital currency that uses strong cryptography for security and verification.

Proof-of-work cryptocurrencies such as Bitcoin are extremely problematic from the permacomputing point of view. Their market value is closely connected to the amount of energy used for "mining", which is currently a huge amount of wasted energy (IEA estimates ~100 TWh global consumption for 2020; in comparison, all of the world's data centers consumed 200-250 TWh that year). The embodied energy from the production of the vast amounts of computing hardware used exclusively for "mining" is not included in this figure, and the material life cycles of the hardware will of course need to be considered as well.

What about only using renewable surplus energy and otherwise useless hardware for mining, or participating in the PoW-crypto market without participating in mining at all? It can argued that this is problematic as well, since mere participation in the market (even by actively discussing the topic and thus keeping the hype up) may help maintain the value system.

Proof-of-stake is the main alternative to the proof-of-work model. It has not yet been assessed from the permacomputing point of view. (If you have studied this topic, please consider assessing it and expand the page accordingly)

Blockchain is the type of data structure used by cryptocurrencies. They may be useful for some purposes of decentralization, but it is doubtful whether they are an optimal or even good solution for any problem. (If you have studied this topic, please consider expanding the page)