How could the frontend sign submissions

[fretchen]

We currently only enable the backend to sign the files. How could we enable the frontend to sign ?

• It is a bit different as no one is his right mind wants to set up an additional key if they already have a token.
• But how do we store the token ? Currently is stored in clear on the qlued server. Should this change somehow ?
• It would seem that the most common way is to simply show the token once and then store an encrypted version...