A method for preparing usage data for a relay implemented in a computer network is disclosed. In one aspect, the network comprises at least one source device, one destination device, and at least one relay constituting a circuit to set up a communication between the source device and the destination device. The source device first of all retrieves the identifiers of the relays constituting the circuit and sends a proof of use (PoU) frame addressed to the destination device, each relay of the circuit adding to the PoU frame, at the time of passage, a signature made from a challenge and a key proper to the relay. The source device retrieves at least the signatures of each relay, and verifies the signatures received by using the public keys of the relays, the authentication of the signatures triggering the following steps: preparing, from the data received, an ordered list of identifiers of the relays used to set up the communication, sending transaction frames addressed to each relay identified in the list to generate proofs of use comprising at least the signatures contained in the PoU frame, the transaction frames being designed to trigger the sending by each relay of a proof of use recorded in a shared memory.