  In order to provide more security on double-spending, we have implemented a
system allowing for a web-of-trust. In this paper, we explore different
approaches taken against double-spending and implement our own version to avoid
this within TrustChain as part of the ecosystem of EuroToken, the digital
version of the euro. We have used the EVA protocol as a means to transfer data
between users, building on the existing functionality of transferring money
between users. This allows the sender of EuroTokens to leave recommendations of
users based on their previous interactions with other users. This dissemination
of trust through the network allows users to make more trustworthy decisions.
Although this provides an upgrade in terms of usability, the mathematical
details of our implementation can be explored further in other research.
