Patent ID: 8671278

Claim:
A method for authenticating a transmission between a first circuit and a second circuit transiting through at least one third circuit, the method comprising: transmitting data from the first circuit to the at least one third circuit, and from the at least one third circuit to the second circuit; calculating a first signature of the data by the first circuit using a first key shared between the first circuit and the at least one third circuit; independently of receiving the first signature by the at least one third circuit, calculating at least one second signature of the data by the at least one third circuit using a second key different from the first key, wherein the second key being shared between the at least one third circuit and the second circuit; transmitting a first portion of the first signature by the first circuit to the at least one third circuit; transmitting a first portion of the at least one second signature by the at least one third circuit to the second circuit; and in response to the first circuit calculating and transmitting the first portion of the first signature to the at least one third circuit and the at least one third circuit transmitting the first portion of the at least one second signature to the second circuit, authenticating the first portion of the first signature by the at least one third circuit; when the authentication of the first portion of the first signature by the at least one third circuit succeeds, transmitting, by the at least one third circuit, a second portion of the at least one second signature to the second circuit; and when the authentication of the first portion of the first signature by the at least one third circuit fails, transmitting, by the at least one third circuit, a modified second portion of the at least one second signature to the slave second circuit.