Yes you do. If you wish to argue that 'if crypto then useful', and you want to use the proposition 'if crypto then consensus', then you also need to provide som

Yes you do. If you wish to argue that 'if crypto then useful', and you want to use the proposition 'if crypto then consensus', then you also need to provide something to support the proposition 'if consensus then useful'. You can substitude jellybeans on pluto or whatever else you want in the middle, the point is there are two steps necessary to the argument and only one is actually well supported.