# US 10,484,403 B2 · Avionic equipment with single use signing of a transmitted message and associated avionic system, transmission method and computer program > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,484,403 B2 - Document ID: US10484403B2 - Status: Granted - Kind: B2 - Application number: 15/787,941 - Filed: 2017-10-19 - Published: 2018-05-03 - Granted: 2019-11-19 - Earliest claimed: 2016-10-27 - Assignees: Thales - Applicants: Thales - Inventors: Henri Belfy; Vincent Tainturier; Jean-Arnaud Causse - Web page: https://patentgrep.com/patent/US10484403B2 ## CPC - H04L 12/40019: {Details regarding a bus master} - H04L 9/0643: {Hash functions, e.g. MD5, SHA, HMAC or f9 MAC} - H04L 9/3247: {involving digital signatures} - H04L 63/123: {received data contents, e.g. message integrity} - H04L 63/1416: {Event detection, e.g. attack signature detection} - H04W 12/106: Packet or message integrity - H04L 67/12: specially adapted for proprietary or special-purpose networking environments, e.g. medical networks, sensor networks, networks in vehicles or remote metering networks - H04L 2012/4028: {the transportation system being an aircraft} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract An avionic equipment unit, intended to be on board an aircraft, including a calculating module configured to calculate a signature associated with a data field, the calculated signature depending on the data field, and a transmission module configured to transmit a message to another avionic equipment unit on board the aircraft, the message including the data field and the associated calculated signature, the calculated signature being unique for each data field and for each respective message transmission. ## Claims ### Claim 1 An avionic equipment unit, intended to be on board an aircraft, the avionic equipment unit comprising: a processor for calculating a signature associated with a data field, the calculated signature depending on the data field; and a transmitter configured to transmit a message to another avionic equipment unit on board the aircraft, the message including the data field and the associated signature calculated by said processor, wherein the calculated signature further depends on a preceding signature associated with the data field of a last message transmitted by said transmitter, such that the calculated signature is unique for each data field and for each message transmitted by said transmitter. ### Claim 2 (depends on 1) The avionic equipment unit according to claim 1, wherein, when the signature to be calculated corresponds to a first message to be transmitted, the preceding signature is formed by a hazard. ### Claim 3 (depends on 2) The avionic equipment unit according to claim 2, wherein the hazard is obtained from a pseudo-random algorithm and a physical entropy source. ### Claim 4 (depends on 3) The avionic equipment unit according to claim 3, wherein the hazard depends on a value of the clock of a computer calculating the hazard. ### Claim 5 (depends on 4) The avionic equipment unit according to claim 4, wherein the value of the clock is a time instant of the first execution by the computer of a software application configured to calculate said hazard. ### Claim 6 (depends on 1) The avionic equipment unit according to claim 1, wherein said processor calculates the signature further as a function of a private key, the private key being known by the other avionic equipment unit for which the message is intended. ### Claim 7 (depends on 1) The avionic equipment unit according to claim 1, wherein the avionic equipment unit complies with standard ARINC 664, and said transmitter transmits a message corresponding to a protocol according to standard ARINC 664. ### Claim 8 (depends on 1) An avionic system comprising at least two avionic equipment units connected to one another by a communication link, wherein at least one of said avionic equipment units is according to claim 1, and wherein at least one other of said avionic equipment units comprises: a receiver receiving the transmitted message including the data field and the associated calculated signature; and a verifier verifying consistency between the data field and the associated calculated signature. ### Claim 9 A method for transmitting a message via an avionic equipment unit, intended to be on board an aircraft, the method comprising: calculating a signature associated with a data field, the calculated signature depending on the data field; and transmitting a message to another avionic equipment unit on board the aircraft, the message including the data field and the associated calculated signature, wherein the calculated signature further depends on a preceding signature associated with the data field of a last message transmitted by said transmitting, such that the calculated signature is unique for each data field and for each transmitting of a message. ### Claim 10 (depends on 9) A non-transitory computer-readable medium including a computer program comprising software instructions which, when executed by a computer, implement a method according to claim 9.