Regarding the Legality of Crypto-Currencies, the Australian Constitution states in Chapter V, Section 115, that the States shall not Coin Money. This means that transacting, in the form of an exchangeable currency, in Australia, other than the Australian Dollar, is deeply Un-Constitutional. Indeed, the Crypto would be parallel to minting your own currency, using your computer, where the particular SSD, Memory or any CPU Utilization, is the functional exchange of value for the currency, separated from the economic value of the Australian Dollar. That the particular Computer Resource utilization, is being measured as an alternative to what the resource being used in Australia is intending to do, it creates a separatist economic policy bias, for such electronic hardware uses, that is then used to value the Crypto within the Australian economy. This differentiation that it creates in separating or a disparity in the fundamental economic transactions within the economy, and its financial value, qualifies it as an alternative Currency to that of the AUD, which is the primary and only vehicle for such economic valuations.
www.aph.gov.au/.../Constitution