Based on the descriptions in this link, I don't think crypto neatly fits into any of these categories. It's not quite fiduciary money because there is no issue

Based on the descriptions in this link, I don't think crypto neatly fits into any of these categories. It's not quite fiduciary money because there is no issuer that gives any promises of convertibility. Perhaps you could argue there is some implied promise of convertibility due to the prominence of fiat<->crypto exchanges? It seems closest to commodity money, because it's value depends on asset scarcity, but it's not a real commodity with utility in and of itself. Then again, it's not clear that gold was actually valuable to people before they started using it as money. It's possible that use as jewelry emerged after use as money to peacock and show off wealth, and industrial use is a relatively modern invention. Crypto is a novel invention of self-securing abstract scarcity. It's a scarce number in a database. Its scarcity is assured by the properties of the network, rather than trust in an issuing authority. It just doesn't fit perfectly in any of our pre-existing categories.