  We propose Ping-Pong Swaps: A secure pure peer-to-peer crosschain swap
mechanism of tokens or cryptocurrencies that does not require escrow nor an
intermediate trusted third party. The only technical requirement is to be able
to open unidirectional payment channels in both blockchain protocols. This
allows anonymous cryptocurrency trading without the need of a centralized
exchange, nor DEX's in DeFi platforms, nor multisignature escrow systems with
penalties. Direct peer-to-peer crosschain swaps can be performed without a
bridge platform. This enables the creation of non-custodial exchanges and also
a global peer-to-peer market of pairs of tokens or cryptocurrencies. Ping-pong
swaps with fiat currency is possible if banks incorporate simple payment
channel functionalities. Some immediate applications are simple and fast
rebalancing of Lightning Network channels, and wrapping tokens in smartchains.
