  Payment systems are a critical component of everyday life in our society.
While in many situations payments are still slow, opaque, siloed, expensive or
even fail, users expect them to be fast, transparent, cheap, reliable and
global. Recent technologies such as distributed ledgers create opportunities
for near-real-time, cheaper and more transparent payments. However, in order to
achieve a global payment system, payments should be possible not only within
one ledger, but also across different ledgers and geographies. In this paper we
propose Secure Payments with Overlay Networks (SPON), a service that enables
global payments across multiple ledgers by combining the transaction exchange
provided by the Interledger protocol with an intrusion-tolerant overlay of
relay nodes to achieve (1) improved payment latency, (2) fault tolerance to
benign failures such as node failures and network partitions, and (3)
resilience to BGP hijacking attacks. We discuss the design goals and present an
implementation based on the Interledger protocol and Spines overlay network. We
analyze the resilience of SPON and demonstrate through experimental evaluation
that it is able to improve payment latency, recover from path outages,
withstand network partition attacks, and disseminate payments fairly across
multiple ledgers. We also show how SPON can be deployed to make the
communication between different ledgers resilient to BGP hijacking attacks.
