  For the enactment of inter-organizational processes, blockchain can guarantee
the enforcement of process models and the integrity of execution traces.
However, existing solutions come with downsides regarding throughput
scalability, latency, and suboptimal tradeoffs between confidentiality and
transparency. To address these issues, we propose to change the foundation of
blockchain-based process enactment: from on-chain smart contracts to state
channels, an overlay network on top of a blockchain. State channels allow
conducting most transactions off-chain while mostly retaining the core security
properties offered by blockchain. Our proposal, process channels, is a
model-driven approach to enacting processes on state channels, with the aim to
retain the desired blockchain properties while reducing the on-chain footprint
as much as possible. We here focus on the principled approach of state channels
as a platform, to enable manifold future optimizations in various directions,
like latency and confidentiality. We implement our approach prototypical and
evaluate it both qualitatively (w.r.t. assumptions and guarantees) and
quantitatively (w.r.t. correctness and gas cost). In short, while the initial
deployment effort is higher with state channels, it typically pays off after a
few process instances; and as long as the new assumptions hold, so do the
guarantees.
