# US 11,445,373 B1 · Validation of position, navigation, time signals > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,445,373 B1 - Document ID: US11445373B1 - Status: Granted - Kind: B1 - Application number: 16/531,334 - Filed: 2019-08-05 - Granted: 2022-09-13 - Earliest claimed: 2019-08-05 - Assignees: Satelles, Inc. - Applicants: Satelles, Inc. - Inventors: Michael L. O'Connor; David G. Lawrence; Gregory Gutt - Web page: https://patentgrep.com/patent/US11445373B1 ## CPC - H04W 12/108: Source integrity - G01S 19/03: Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers - G01S 19/215: {issues related to spoofing} - H04L 9/0872: {using geo-location information, e.g. location data, time, relative position or proximity to other entities} - H04L 9/3242: {involving keyed hash functions, e.g. message authentication codes [MACs], CBC-MAC or HMAC} - H04L 9/3247: {involving digital signatures} - H04W 12/06: Authentication - H04W 12/122: Counter-measures against attacks; Protection against rogue devices - H04W 12/63: Location-dependent; Proximity-dependent - G01S 19/20: Integrity monitoring, fault detection or fault isolation of space segment - H04L 9/50: {using hash chains, e.g. blockchains or hash trees} - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract For validation of position, navigation, time (PNT) signals, a hash included in messages with PNT data is used to validate the source of the message without backhaul. Different tags from a hash chain are included in different messages. The receiver is pre-loaded with the root or later trusted hash tag of the chain as created. The hash of any received message may be hashed by the receiver. The result of the hashing will match the pre-loaded or trusted hash tag if the transmitter of the message is a valid source. The PNT data may be validated using a digital signature formed from the PNT data for one or more messages and the hash tag wherein a hash tag of the chain in a subsequently received message is used as the key. The digital signature may be formed from data across multiple messages. ## Claims ### Claim 1 A method for validation of position, navigation, time signals from a transmitter, the method comprising: receiving, at a radio frequency receiver, a first sequence of messages; extracting first data from the messages, wherein extracting the first data comprises extracting a first hash chain tag and a first digital signature; receiving by the radio frequency receiver a subsequent message including a second hash chain tag extracting second data from the messages, the second data being position, navigation, or time data spread across multiple of the messages of the first sequence; validating an origin of the messages as an expected origin based on the first data; and validating authenticity of the second data based on the first data, wherein validating the authenticity comprises creating a second digital signature from the first hash chain tag and the second data with the second hash chain tag received in the subsequent message and comparing the second digital signature to the first digital signature. ### Claim 2 (depends on 1) The method of claim 1 wherein receiving comprises receiving the first sequence as signals from a low earth satellite, and wherein validating the origin comprises validating the origin as the low earth orbit satellite. ### Claim 3 (depends on 2) The method of claim 2 wherein receiving the first sequence as signals from a low earth satellite comprises receiving bursts as the signals from the low earth satellite. ### Claim 4 (depends on 1) The method of claim 1 wherein validating the origin comprises hashing the first hash chain tag and comparing results of the hashing to a trusted hash chain tag. ### Claim 5 (depends on 4) The method of claim 4 wherein the trusted hash chain tag is received from the transmitter while the receiver is in a known and trusted environment. ### Claim 6 (depends on 4) The method of claim 4 wherein the trusted hash chain tag is a hash chain root. ### Claim 7 (depends on 6) The method of claim 6 wherein comparing comprises comparing the results to the hash chain root, the hash chain root stored at the radio frequency receiver, the comparing being without a call to remote server. ### Claim 8 (depends on 7) The method of claim 7 wherein comparing comprises comparing to the hash chain root as trusted data based on security of installation at the radio frequency receiver. ### Claim 9 (depends on 7) The method of claim 7 further comprising: resetting the hash chain root periodically or asynchronously. ### Claim 10 (depends on 6) The method of claim 6 wherein extracting comprise extracting the first hash chain tag where the first hash chain tag has a sequence number, and wherein hashing comprises hashing the first hash chain tag a number of times based on the sequence number. ### Claim 11 (depends on 1) The method of claim 1 wherein validating the origin comprises validating based on a Timed Efficient Stream Loss-tolerant Algorithm. ### Claim 12 (depends on 1) The method of claim 1 further comprising verifying a global navigation satellite system position or time based on the second data after validating the origin and the authenticity. ### Claim 13 A method for validation of position, navigation, time signals from a transmitter, the method comprising: receiving, at a radio frequency receiver, a first sequence of messages; extracting first data from the messages; extracting second data from the messages, the second data being position, navigation, or time data spread across multiple of the messages of the first sequence; validating an origin of the messages as an expected origin based on the first data; and validating authenticity of the second data based on the first data; calculating a time estimate from the signal and the second data, comparing the time estimate to a clock estimate from a different source, and identifying a long-delay replay attack from the comparison. ### Claim 14 A system for validation of a source and content of a message, the system comprising: a memory storing a sequence of messages; a radio frequency transmitter configured to transmit the messages with first data usable for determination of time or geolocation of a receiver, a subset of the messages having second data usable to validate a source as the radio frequency transmitter and usable to authenticate content of the first data, wherein the second data comprises a first hash chain tag and a first digital signature, the first digital signature formed from the first hash chain tag and the first data of the messages using a second hash chain tag as a key, the second hash chain tag from a subsequent message of the radio frequency transmitter. ### Claim 15 (depends on 14) The system of claim 14 wherein the radio frequency transmitter comprises a low earth orbit satellite transmitter configured to transmit the messages as bursts. ### Claim 16 (depends on 14) The system of claim 14 wherein the first hash chain tag is from a sequence of hash chain tags to be transmitted in reverse order. ### Claim 17 (depends on 16) The system of claim 16 wherein the first hash chain tag has a sequence number such that hashing the first hash chain tag a number of times corresponding to the sequence number results in a hash chain root. ### Claim 18 (depends on 14) The system of claim 14 wherein the second data comprises information based on a Timed Efficient Stream Loss-tolerant Algorithm. ### Claim 19 A method for validation of position, navigation, time signals from a transmitter of a low earth orbit satellite, the method comprising: receiving, at a radio frequency receiver, a message; extracting first data from the message; extracting second data from the message, the second data being position, navigation, or time data, wherein extracting the first data comprises extracting a first hash chain tag and a first digital signature, the first digital signature as received in the message believed to have been formed from the first hash chain tag and the second data of the message using a second hash chain tag as a key; receiving by the radio frequency receiver a subsequent message including the second hash chain tag; validating an origin of the message as the transmitter of the low earth orbit satellite, the validating being based on the first data; and validating an authenticity of the second data, validating the authenticity comprising creating a second digital signature from the first hash chain tag and the second data with the second hash chain tag received in the subsequent message and comparing the second digital signature to the first digital signature. ### Claim 20 (depends on 19) The method of claim 19 wherein validating the origin comprises hashing the first hash chain tag and comparing results of the hashing to a trusted hash chain tag. ### Claim 21 (depends on 20) The method of claim 20 wherein extracting comprise extracting the first hash chain tag where the first hash chain tag has a sequence number, and wherein hashing comprises hashing the first hash chain tag a number of times based on the sequence number. ### Claim 22 (depends on 20) The method of claim 20 wherein the trusted hash chain tag is received from the transmitter while the receiver is in a known and trusted environment. ### Claim 23 (depends on 20) The method of claim 20 wherein the trusted hash chain tag is a hash chain root. ### Claim 24 (depends on 20) The method of claim 20 wherein comparing comprises comparing the results to the hash chain root, the hash chain root stored at the radio frequency receiver, the comparing being without a call to a remote server. ### Claim 25 (depends on 24) The method of claim 24 wherein comparing comprises comparing to the hash chain root as trusted data based on security of installation at the radio frequency receiver. ### Claim 26 (depends on 24) The method of claim 24 further comprising: resetting the hash chain root periodically or asynchronously. ### Claim 27 (depends on 19) The method of claim 19 wherein validating the origin comprises validating based on a Timed Efficient Stream Loss-tolerant Algorithm. ### Claim 28 (depends on 19) The method of claim 19 further comprising verifying a global navigation satellite system position or time based on the second data after validating the origin. ### Claim 29 (depends on 19) The method of claim 19 wherein receiving the message and the second message comprises receiving the message and the subsequent message as bursts from the low earth orbit satellite. ### Claim 30 A system for validation of a source of a message, the system comprising: a memory storing a trusted hash chain tag of a hash chain; a radio frequency receiver configured to receive a first message from a low earth orbit satellite, the first message including a first hash chain tag of the hash chain, the first hash chain tag being an earlier tag than the trusted hash chain tag in the hash chain, and first position, navigation, or timing data for measurement of time or geolocation; and a processor configured to hash in sequence from the first hash chain tag received in the first message and compare a result of the hash in the sequence to the trusted hash chain tag; wherein the first message, in the one burst, includes a first digital signature formed from the first hash chain tag and the first position, navigation, or timing data prior to transmission based on a first key, the first key being a second hash chain tag, wherein the radio frequency receiver is configured to receive the second hash chain tag in a second message received subsequent to the first message, and wherein the processor is configured to generate a second digital signature from the first hash chain tag and the first position, navigation, or timing data as received by the radio frequency receiver in the first message using the second hash chain tag as received by the radio frequency receiver in the second message as a second key, the processor configured to authenticate the first position, navigation, or timing data based on comparison of the first and second digital signatures. ### Claim 31 (depends on 30) The method of claim 30 wherein the trusted hash chain tag is a hash chain root. ### Claim 32 (depends on 30) The system of claim 30 wherein the radio frequency receiver is configured to receive third and fourth messages with third and fourth position, navigation, or timing data, the third and fourth messages received prior to the second message, wherein the first digital signature is formed from the first hash chain tag and the first, third, and fourth position, navigation, or timing data, and wherein the second digital signature is formed from the first hash chain tag and the first, third, and fourth position, navigation, or timing data as received in the first, third, and fourth messages. ### Claim 33 (depends on 30) The system of claim 30, wherein the radio frequency receiver is configured to receive a first message from a low earth orbit satellite as a burst. ### Claim 34 A system for validation of a source of a message, the system comprising: a memory storing a trusted hash chain tag of a hash chain; a radio frequency receiver configured to receive a first message from a low earth orbit satellite, the first message including a first hash chain tag of the hash chain, the first hash chain tag being an earlier tag than the trusted hash chain tag in the hash chain, and first position, navigation, or timing data for measurement of time or geolocation; and a processor configured to hash in sequence from the first hash chain tag received in the first message and compare a result of the hash in the sequence to the trusted hash chain tag, wherein the processor is configured to estimate the time estimate from the first position, navigation, or timing data, compare the time to a clock estimate, and identify a long-delay replay attack from the comparison.