WO 2018/057322
`
`PCT/USZOl7/050817
`
`WHAT IS CLAIMED IS:
`
`1.
`
`An apparatus, comprising:
`
`a first circuit having a first clock configured to maintain a local time value for a node
`
`coupled to a network, wherein the first circuit is configured to:
`
`send a first message to a second circuit, wherein the first message includes a first
`
`nonce, wherein the second circuit has a second clock that maintains a reference time value for the
`
`network,
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`receive a second message from the second circuit, wherein the second message
`
`includes a second nonce and is associated with a timestamp identifying the reference time value;
`
`compare the first nonce to the second nonce to determine whether the timestamp
`
`is valid, and
`
`in response to determining that the timestamp is valid, use the timestamp to
`
`synchronize the first clock with the second clock.
`
`2.
`
`The apparatus of claim 1, wherein the first circuit is configured to send the first message
`
`during an exchange with the second circuit to determine a propagation delay between the first
`
`circuit and the second circuit.
`
`3.
`
`The apparatus of claim 2, wherein the first circuit is configured to:
`
`use the timestamp to synchronize the first clock with the second clock by determining an
`
`offset between the first clock and the second clock based on the propagation delay and the
`
`ti mestamp.
`
`4.
`
`The apparatus of claim 3, wherein the first circuit is configured to:
`
`calculate an expected offset between the first and second clocks such that the expected
`
`offset is calculated based on timing information determined from the exchange, and
`
`validate the determined offset by comparing the determined offset with the expected
`
`offset.
`
`5.
`
`The apparatus of claim 1, wherein the first circuit is configured to receive, from the
`
`second circuit, a follow-up message to the second message, wherein the timestamp is included in
`
`the follow-up message and indicates the reference time value when the second message is sent
`
`from the second circuit.
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`PCT/USZOl7/050817
`
`WHAT IS CLAIMED IS:
`
`1.
`
`An apparatus, comprising:
`
`a first circuit having a first clock configured to maintain a local time value for a node
`
`coupled to a network, wherein the first circuit is configured to:
`
`send a first message to a second circuit, wherein the first message includes a first
`
`nonce, wherein the second circuit has a second clock that maintains a reference time value for the
`
`network,
`
`receive a second message from the second circuit, wherein the second message
`
`includes a second nonce and is associated with a timestamp identifying the reference time value;
`
`compare the first nonce to the second nonce to determine whether the timestamp
`
`is valid, and
`
`in response to determining that the timestamp is valid, use the timestamp to
`
`synchronize the first clock with the second clock.
`
`2.
`
`The apparatus of claim 1, wherein the first circuit is configured to send the first message
`
`during an exchange with the second circuit to determine a propagation delay between the first
`
`circuit and the second circuit.
`
`3.
`
`The apparatus of claim 2, wherein the first circuit is configured to:
`
`use the timestamp to synchronize the first clock with the second clock by determining an
`
`offset between the first clock and the second clock based on the propagation delay and the
`
`ti mestamp.
`
`4.
`
`The apparatus of claim 3, wherein the first circuit is configured to:
`
`calculate an expected offset between the first and second clocks such that the expected
`
`offset is calculated based on timing information determined from the exchange, and
`
`validate the determined offset by comparing the determined offset with the expected
`
`offset.
`
`5.
`
`The apparatus of claim 1, wherein the first circuit is configured to receive, from the
`
`second circuit, a follow-up message to the second message, wherein the timestamp is included in
`
`the follow-up message and indicates the reference time value when the second message is sent
`
`from the second circuit.
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`WO 2018/057322
`
`PCT/USZOl7/050817
`
`6.
`
`The apparatus of claim 1, wherein the second message includes a cryptographic
`
`checksum for the second message; and
`
`wherein the first circuit includes a cryptographic circuit configured to verify the
`
`cryptographic checksum using a key stored in the cryptographic circuit to determine whether the
`
`timestamp is valid.
`
`7.
`
`The apparatus of claim 1, further comprising:
`
`the node, wherein the first circuit is coupled to the node and configured to provide, to the
`
`node, timing information based on synchronization of the first clock with the second clock.
`
`8.
`
`An apparatus, comprising:
`
`a first clock circuit configured to maintain a first time value associated with a network;
`
`a synchronization circuit configured to:
`
`determine a propagation delay over the network for receiving synchronization
`
`information associated with a second clock circuit that maintains a second time value, wherein
`
`determining the propagation delay includes the synchronization circuit sending a first message
`
`over the network and receiving a second message over the network;
`
`determine an expected offset between the first time value and the second time
`
`value based on departure and arrival times of the first message and departure and arrival times of
`
`the second message;
`
`receive synchronization information specifying a timestamp of the second time
`
`value, and
`
`determine whether the timestamp is valid by comparing the expected offset to an
`
`offset calculated based on the timestamp.
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`9.
`
`The apparatus of claim 8, wherein determining the expected offset includes:
`
`calculating a first average between the arrival time of the first message and the departure
`
`time of the second messages,
`
`calculating a second average between the departure time of the first message and the
`
`arrival time of the second message; and
`
`determining a difference between the first average and the second average, wherein the
`
`expected offset is the difference.
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`WO 2018/057322
`
`PCT/USZOl7/050817
`
`10.
`
`The apparatus of claim 9; wherein the synchronization circuit is configured to:
`
`store the departure time of the first message and the arrival time of the second message;
`
`receive the arrival time of the first message within the second message; and
`
`receive a third message that includes the departure time of the second message.
`
`11.
`
`The apparatus of claim 8; wherein the received synchronization information includes a
`
`third message that specifies the timestamp and an integrity check value of the third message; and
`
`wherein the synchronization circuit is configured to use the integrity check value to
`
`validate the third message.
`
`12.
`
`The apparatus of claim 11, wherein the received synchronization information includes a
`
`fourth message that includes a nonce; and
`
`wherein the synchronization circuit is configured to validate the received synchronization
`
`information by comparing the nonce with a nonce sent in the first message.
`
`13.
`
`The apparatus of claim 12; wherein the nonce in the second message is included in a field
`
`appended to the end of the second message with an integrity check value field.
`
`14.
`
`The apparatus of claim 8; further comprising:
`
`an electronic control unit (ECU) configured to communicate network traffic on the
`
`network based on the first time value and the calculated offset.
`
`15.
`
`An apparatus; comprising:
`
`an electronic control unit (ECU) configured to control operation of a vehicle; wherein the
`
`ECU is configured to communicate traffic over a network in accordance with a master clock for
`
`the network; and
`
`a secure circuit configured to:
`
`receive a synchronization message specifying a time value associated with the
`
`master clock and an integrity check value for the synchronization message;
`
`determine whether the synchronization message is valid based on the integrity
`
`check value; and
`
`in response to determining that the synchronization message is valid; provide time
`
`information associated with the time value to the ECU.
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`WO 2018/057322
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`PCT/USZOl7/050817
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`16.
`
`The apparatus of claim 15; wherein the secure circuit is configured to:
`
`determine a propagation delay between the secure circuit and a sender of the
`
`synchronization message by sending a first message asking for a response and receiving a second
`
`message including the response; wherein the first message and the second messages include
`
`integrity check values; and
`
`wherein the time information is determined based on the propagation delay and the time
`
`value of the master clock.
`
`17.
`
`The apparatus of claim 16; wherein the integrity check values are appended to ends of the
`
`first and second messages.
`
`18.
`
`The apparatus of claim 16; wherein the first message includes a first nonce; and
`
`wherein the secure circuit is configured to:
`
`perform a comparison of the first nonce with a second nonce received in a
`
`message associated with the time value; and
`
`determine whether the synchronization message is valid based on the comparison.
`
`19.
`
`The apparatus of claim 16; wherein the secure circuit is configured to:
`
`calculate an offset based on a departure time of the first message and an arrival
`
`time of the second message; and
`
`determine whether the synchronization message is valid based on a comparison
`
`between the offset and an offset calculated based on the time value.
`
`20.
`
`The apparatus of claim 15; further comprising:
`
`a network node including the master clock; wherein the network node is configured to
`
`calculate the integrity check value using a key that is unique to the secure circuit.
`
`21.
`
`An apparatus; comprising:
`
`a first circuit having a first clock; wherein the first circuit is configured to determine a
`
`validity of a timestamp of a second clock used to synchronize the first clock with the second
`
`clock by:
`
`sending a first message to a second circuit having the second clock; wherein the
`
`first message includes a first nonce;
`
`receiving a second message from the second circuit; wherein the second message
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`WO 2018/057322
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`PCT/USZOl7/050817
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`includes a second nonce and is associated with the timestamp;
`
`receiving a third message from the second circuit, wherein the third message
`
`includes information indicative of the first nonce and the second nonce, and
`
`based on the first nonce, the second nonce, and the information, determining
`
`whether the timestamp is valid.
`
`22.
`
`The apparatus of claim 21, wherein the second message includes the timestamp.
`
`23.
`
`The apparatus of claim 21, wherein the third message includes the timestamp, and
`
`wherein the timestamp is a value of the second clock when the second message is sent by the
`
`second circuit.
`
`24.
`
`The apparatus of claim 21, wherein the information included in the third message
`
`includes the first nonce and the second nonce; and
`
`wherein the determining includes comparing 1) the first nonce in the first message with
`
`the first nonce in the information and 2) the second nonce in the second message with the second
`
`nonce in the information.
`
`25.
`
`The apparatus of claim 21, wherein the information included in the third message
`
`includes a checksum generated based on the first nonce and a checksum generated based on the
`
`second nonce, and
`
`wherein the determining includes:
`
`comparing the checksum generated based on the first nonce with a checksum
`
`generated based on the first nonce in the first message; and
`
`comparing the checksum generated based on the second nonce with a checksum
`
`generated based on the second nonce in the second message.
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