Guac is an Ethereum single hop payment channel client for the Ethcalate Bi-Directional Payment Channel. This light client is able to send and verify channel opening, updating, and ending transactions. It relies on one or several bounty hunting full nodes which relay transactions onto the blockchain. These bounty hunting nodes are not able to spend any money without the permission of this light client, but they could censor its transactions, in the worst case leading to the loss of some funds stored in the channel. For this reason it is advisable to connect to several bounty hunting nodes.

Guac is structured into 3 modules, guac_core which consists of the implementation of the channel update logic as well as interaction with the blockchain through bounty hunters. guac_actix is an interface over guac_core which sends and receives messages from the external world via HTTP, but receives commands via actix. guac_http makes the command interface HTTP instead to provide wider interoperability.