I will tell you the opinion about secure from a master of economics, Friedrich August von Hayek.You can learn what Secure currency could be holded.
There are four main uses as currency. The first is for buying service, the second is for holding future reserves, the third is for contractual delayed payments, and the fourth is for The accounting unit .
In the first type, the quantity of goods that the currency can buy determines the need of this currency; in the second, the public's demand for it comes from the stability of its price, especially its potential for appreciation. (There seems to be some contradiction for the stable currency, but it can increase the number of stable coins held by the public according to the proportion of the stable currency to achieve the purpose of increasing value); In the third , the borrower and the Payer like the depreciation or appreciation currency . From the long-term market, there will be no one-sided phenomenon, which will be more offset by the loss of income; in the fourth,the key to economic calculations and to the currency of production and trading is the stability of accounting values.
In summary, the public nees a wide range of trading objects, stable prices, appreciation of value, and stable accounting value currency.And it is also necessary to prevent the government from hindering and controlling the decentralization、security、and privacy .