[proposal] Don't require users to be always online

[szpasztor]

Decred's PoS Voting Service Provider (VSP) voting uses a mechanism that lets users vote even if their node if offline. The way it works is there are multiple addresses attached to each ticket:

• the commitment address (after revocation/voting the funds go here)
• the voting address (controls on-chain voting)
• the change address
  When voting via VSP (as opposed to solo-voting, ie. running an always-online node), there's a 1-of-2 multisig used for the voting address, so either the user or the VSP can vote on the given ticket.

See the IsSStx function in dcrd for more details and the PoS docs for a description on how tickets work. There's also a good informal review on IsSStx by Matheus Degiovani here.

What if a similar mechanism could be used in MixEth so that users don't need to be always online without giving anyone access to their funds?