  The Ripple credit network has emerged as a payment backbone with key
advantages for financial institutions and the remittance industry. Its
path-based IOweYou (IOU) settlements across different (crypto)currencies
conceptually distinguishes the Ripple blockchain from cryptocurrencies, and
makes it highly suitable to an orthogonal yet vast set of applications in the
remittance world for cross-border transactions and beyond.
  This work studies the structure and evolution of the Ripple network since its
inception, and investigates its vulnerability to devilry attacks that affect
the credit of linnet users' wallets. We find that about 13M USD are at risk in
the current Ripple network due to inappropriate configuration of the rippling
flag on credit links, facilitating undesired redistribution of credit across
those links. Although the Ripple network has grown around a few highly
connected hub (gateway) wallets that constitute the network's core and provide
high liquidity to users, such a credit link distribution results in a user base
of around 112,000 wallets that can be financially isolated by as few as 10
highly connected gateway wallets. Indeed, today about 4.9M USD cannot be
withdrawn by their owners from the Ripple network due to PayRoutes, a gateway
tagged as faulty by the Ripple community. Finally, we observe that stale
exchange offers pose a real problem, and exchanges (market makers) have not
always been vigilant about periodically updating their exchange offers
according to current real-world exchange rates. For example, stale offers were
used by 84 Ripple wallets to gain more than 4.5M USD from mid-July to
mid-August 2017. Our findings should prompt the Ripple community to improve the
health of the network by educating its users on increasing their connectivity,
and by appropriately maintaining the credit limits, rippling flags, and
exchange offers on their credit links.
