Smart Contract Audit Hopr ChainSecurity

Hopr – Payment Channels

Security Audit

Download Audit Report

HOPR is building a privacy-focused network featuring a built-in incentive model. The reviewed HoprChannels contract allows nodes to create a payment channel between each other and authorize transfer of HOPR token between them. These transfers are done via a ticket system, where each ticket has a certain predefined probability to win. Winning causes a transfer of tokens between the channel participants. On a code level the channels are unidirectional, meaning channel “A to B” is not equal to “B to A”.

To keep the whole process fair, the winning probability depends on variables that are unknown in advance. For each ticket emitted by A for the “A to B” channel, B has a commitment that is unknown to A. Meanwhile, B does not know this proof of relay in advance and has to transfer the message further to the network to know it. This process makes HOPR’s proof-of-relay incentive mechanism cheat-proof and ensures relay node operators actually do their work to get paid.

Each of these unidirectional channels has “channelEpoch”, “ticketEpoch”, and “ticketIndex” as associated variables, which the ticket emitter is assumed to take in account during the generation.

About Hopr – Payment Channels

“The HOPR protocol is a layer-0 privacy foundation for anyone to build on, providing network-level and metadata privacy for every kind of data exchange. A mixnet protects the identity of both sender and recipient by routing data via multiple intermediate relay hops that mix traffic. Payments are handled via probabilistic micropayments, HOPR’s custom layer-2 scaling solution. Relay mix nodes are rewarded for their work in HOPR tokens. HOPR’s proof-of-relay mechanism protects the network from dishonest behaviour, providing everyone with economic incentives to run a global privacy network sustainably and at scale without compromising privacy.”

For more information, visit

The entire HOPR team is once again grateful for the highly professional audit by ChainSecurity. Our payment channel and proof-of-relay mechanism is an intricate design that was rapidly understood and evaluated by their auditors, who then delivered an excellent review to help the HOPR community keeping funds in the HOPR payment channels SAFU.
Dr Sebastian Bürgel, HOPR Founder