  In December 2015, a bounty emerged to establish both reliable communication
and secure transfer of value between the Dogecoin and Ethereum blockchains.
This prized "Dogethereum bridge" would allow parties to "lock" a DOGE coin on
Dogecoin and in exchange receive a newly minted WOW token in Ethereum. Any
subsequent owner of the WOW token could burn it and, in exchange, earn the
right to "unlock" a DOGE on Dogecoin.
  We describe an efficient, trustless, and retrofitting Dogethereum
construction which requires no fork but rather employs economic collateral to
achieve a "lock" operation in Dogecoin. The protocol relies on bulletproofs,
Truebit, and parametrized tokens to efficiently and trustlessly relay events
from the "true" Dogecoin blockchain into Ethereum. The present construction not
only enables cross-platform exchange but also allows Ethereum smart contracts
to trustlessly access Dogecoin. A similar technique adds Ethereum-based smart
contracts to Bitcoin and Bitcoin data to Ethereum smart contracts.
