SECURE CLOCK SYNCHRONIZATION

• US 20120163521A1
• Filed: 12/30/2011
• Published: 06/28/2012
• Est. Priority Date: 06/09/2010
• Status: Active Grant

• Current Assignee: Hitachi Energy Limited (Hitachi, Ltd.)
• Original Assignee: ABB Research Ltd. (ABB Ltd.)
• Inventors: KIRRMANN, Hubert, TOURNIER, Jean-Charles
• Granted Patent: US 9,363,273 B2
• Time in Patent Office: Days
• US Class Current: 375/356
• CPC Class Codes: G04G 7/00 Synchronisation radio-controlled time-pieces G04R
• CPC Class Codes: H04J 3/0664 unidirectional timestamps
• CPC Class Codes: H04J 3/067 Details of the timestamp structure
• CPC Class Codes: H04L 63/123 received data contents, e.g. message integrity
• CPC Class Codes: H04L 7/0008 Synchronisation information channels, e.g. clock distribution lines
• CPC Class Codes: H04L 9/3242 involving keyed hash functions, e.g. message authentication codes [MACs], CBC-MAC or HMAC
• CPC Class Codes: Y04S 40/20 Information technology specific aspects, e.g. CAD, simulation, modelling, system security

Abstract

The present disclosure provides a secure one-step IEEE 1588 clock using either a symmetric or asymmetric protection scheme. Clocks of mission-critical or highly-available devices in industrial automation systems connected to a communication network are synchronized by sending, by a master clock, a synchronization message, e.g., a single message of the one-step-clock type according to IEEE 1588, including a time stamp, and by receiving and evaluating, by a slave clock, the synchronization message. A synchronization component or module of the master clock prepares, or composes, prior to a projected send time, a synchronization message including a time stamp of the projected send time, and secures the synchronization message in advance of the projected send time. Securing the synchronization message occurs by suitable cryptographic means allowing for authentication of the time stamp at a receiving slave clock. At the projected send time, the secured synchronization message is transmitted.

Claims

1. A method of synchronizing clocks connected to a communication network, comprising:

sending, by a master clock, a synchronization message including a time stamp; and

receiving the synchronization message by a slave clock,

wherein the sending of the synchronization message comprises;

preparing, prior to a projected send time t_send, a synchronization message including a time stamp of the projected send time t_send,

securing the synchronization message; and

sending, at the projected send time t_send, the secured synchronization message.

2. The method according to claim 1, comprising:

storing, in a wait component, the secured synchronization message prior to sending at the projected send time t_send.

3. The method according to claim 1, comprising:

disabling, for a blocking interval Δ

_block prior to the projected send time t_send, sending of non-synchronization messages with a length exceeding a length of the blocking interval Δ

_block.

4. The method according to claim 1, comprising:

starting preparation of the secured synchronization message at a time t_prep preceding the projected send time t_send by Δ

t,

wherein Δ

t is a preparation delay based on a processing capacity of processing hardware generating the synchronization message.

5. The method according to claim 1, wherein:

the communication network has a ring topology;

the master clock comprises a master clock device with a first communication port and a second communication port respectively connected to a first neighboring node and a second neighboring node of the communication network; and

the method comprises, by the master clock device;

generating a duplicate synchronization message of the secured synchronization message; and

transmitting, essentially simultaneously via the first port and the second port, respectively, the synchronization message and the duplicate synchronization message to the first neighboring node and the second neighboring node.

6. The method according claim 5, wherein the slave clock is comprised in an Intelligent Electronic Devices (IED) of a Process Control or Substation Automation (SA) system.

9. The method according to claim 2, wherein:

the communication network has a ring topology;

the master clock comprises a master clock device with a first communication port and a second communication port respectively connected to a first neighboring node and a second neighboring node of the communication network; and

the method comprises, by the master clock device;

generating a duplicate synchronization message of the secured synchronization message; and

transmitting, essentially simultaneously via the first port and the second port, respectively, the synchronization message and the duplicate synchronization message to the first neighboring node and the second neighboring node.

10. The method according claim 9, wherein the slave clock is comprised in an Intelligent Electronic Devices (IED) of a Process Control or Substation Automation (SA) system.

11. The method according to claim 3, wherein:

the communication network has a ring topology;

the master clock comprises a master clock device with a first communication port and a second communication port respectively connected to a first neighboring node and a second neighboring node of the communication network; and

the method comprises, by the master clock device;

generating a duplicate synchronization message of the secured synchronization message; and

transmitting, essentially simultaneously via the first port and the second port, respectively, the synchronization message and the duplicate synchronization message to the first neighboring node and the second neighboring node.

12. The method according claim 11, wherein the slave clock is comprised in an Intelligent Electronic Devices (IED) of a Process Control or Substation Automation (SA) system.

13. The method according to claim 4, wherein:

the communication network has a ring topology;

the master clock comprises a master clock device with a first communication port and a second communication port respectively connected to a first neighboring node and a second neighboring node of the communication network; and

the method comprises, by the master clock device;

generating a duplicate synchronization message of the secured synchronization message; and

transmitting, essentially simultaneously via the first port and the second port, respectively, the synchronization message and the duplicate synchronization message to the first neighboring node and the second neighboring node.

14. The method according claim 13, wherein the slave clock is comprised in an Intelligent Electronic Devices (IED) of a Process Control or Substation Automation (SA) system.

7. A master clock device for synchronizing slave clocks connected to a communication network, the device being configured to prepare and send synchronization messages including a time stamp, wherein the device comprises:

a synchronization component configured for preparing a synchronization message including a time stamp of a projected send time t_send and for securing the synchronization message; and

a wait component configured for temporarily storing the secured synchronization message until the projected send time t_send.

8. The master clock device according to claim 7, comprising:

a transmission port TX with a Low Priority Queue LPQ,

wherein during a blocking interval Δ

_block prior to the projected send time t_send, sending of non-synchronization messages from the LPQ with a length exceeding the length of the blocking interval Δ

_block is disabled.

15. A non-transitory computer-readable recording medium having a program recorded thereon that causes a processor of a master clock device to execute operations of synchronizing clocks connected to a communication network, the operations comprising:

sending a synchronization message including a time stamp to be received by a slave clock,

wherein the sending of the synchronization message comprises;

preparing, prior to a projected send time t_send, a synchronization message including a time stamp of the projected send time t_send, securing the synchronization message; and

sending, at the projected send time t_send, the secured synchronization message.

16. The non-transitory computer-readable recording medium according to claim 15, wherein the program causes the processor to execute operations comprising:

storing, in a wait component, the secured synchronization message prior to sending at the projected send time t_send.

17. The non-transitory computer-readable recording medium according to claim 15, wherein the program causes the processor to execute operations comprising:

disabling, for a blocking interval Δ

_block prior to the projected send time t_send, sending of non-synchronization messages with a length exceeding a length of the blocking interval Δ

_block.

18. The non-transitory computer-readable recording medium according to claim 15, wherein the program causes the processor to execute operations comprising:

starting preparation of the secured synchronization message at a time t_prep preceding the projected send time t_send by Δ

t,

wherein Δ

t is a preparation delay based on a processing capacity of processing hardware generating the synchronization message.

19. The non-transitory computer-readable recording medium according to claim 15, wherein:

the communication network has a ring topology;

the master clock comprises a master clock device with a first communication port and a second communication port respectively connected to a first neighboring node and a second neighboring node of the communication network; and

the program causes the processor to execute operations comprising;

generating a duplicate synchronization message of the secured synchronization message; and

transmitting, essentially simultaneously via the first port and the second port, respectively, the synchronization message and the duplicate synchronization message to the first neighboring node and the second neighboring node.

20. The non-transitory computer-readable recording medium according claim 19, wherein the slave clock is comprised in an Intelligent Electronic Devices (IED) of a Process Control or Substation Automation (SA) system.