In this paper, Camenisch et al. describe how to design an ecash system with Coins that can be spent more than once (n times) without having to come online.
Imagine an (n x 32) satoshi coin. To make a payment, you peel off 1 x 32 sats and keep (n-1 x 32) sats in your wallet. You can do this offline.
Double spending is not prevented but disincentivized: Users who spend a coin more than n times lose their privacy and the mint operator can identify and punish them. This is typically how offline ecash systems are designed, they break your privacy if you misbehave.
Very interesting and well-written paper.
