Tamper-respondent assembly with nonlinearity monitoring

• US 10,242,543 B2
• Filed: 11/22/2017
• Issued: 03/26/2019
• Est. Priority Date: 06/28/2016
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Busby, James A., Isaacs, Phillip Duane
• Primary Examiner(s): Nguyen, Tai T
• Application Number:
  US15/820,620
• Publication Number:
  US 20180108229A1
• Time in Patent Office: 489 Days
• Field of Search: 3405451, 3405456, 340 101, 340 106, 340505, 340506, 340508, 340509
• CPC Class Codes: G01N 27/041 of a solid body
• CPC Class Codes: G01N 27/205 in insulating materials
• CPC Class Codes: G08B 13/128 the housing being an electronic circuit unit, e.g. memory or CPU chip protecting computer components in secure or tamper resistant housings G06F21/86; protecting computer input devices, e.g. keyboards G06F21/83
• CPC Class Codes: H05K 1/0275 Security details, e.g. tampering prevention or detection
• CPC Class Codes: H05K 1/0296 Conductive pattern lay-out details not covered by sub groups H05K1/02 - H05K1/0295 H05K1/11 takes precedence; lay-out adapted to mounted component configuration H05K1/18
• CPC Class Codes: H05K 1/182 associated with components mounted in the printed circuit board, e.g. insert mounted components [IMC]
• CPC Class Codes: H05K 2201/09263 Meander
• CPC Class Codes: H05K 2201/10151 Sensor
• CPC Class Codes: H05K 3/4697 having cavities, e.g. for mounting components H05K3/4691 takes precedence

Abstract

Tamper-respondent assemblies and methods of fabrication are provided which include at least one tamper-respondent sensor and a detector. The at least one tamper-respondent sensor includes conductive lines which form, at least in part, at least one tamper-detect network of the tamper-respondent sensor(s). The detector monitors the tamper-respondent sensor(s) by applying an electrical signal to the conductive lines of the at least one tamper-respondent sensor to monitor over time for a non-linear conductivity change indicative of a tamper event at the tamper-respondent sensor(s). For instance, the detector may monitor a second harmonic of the electrical signal applied to the conductive lines for the non-linear conductivity change indicative of the tamper event, such as an attempted shunt of one or more conductive lines of the tamper-respondent sensor(s).

Claims

1. A tamper-respondent assembly comprising:

at least one tamper-respondent sensor including conductive lines forming, at least in part, at least one tamper-detect network of the at least one tamper-respondent sensor; and

a detector to monitor the at least one tamper-respondent sensor, the detector applying an electrical signal to the conductive lines of the at least one tamper-respondent sensor to monitor over time a harmonic of the electrical signal applied to the conductive lines for a non-linear conductivity change, the electrical signal being a composite alternating current and direct current signal, and the harmonic, which is an integer multiple of a fundamental frequency, resulting from the applying of the composite alternating current and direct current signal to the conductive lines of the at least one tamper-respondent sensor, where the non-linear conductivity change in the harmonic is indicative of a tamper event at the at least one tamper-respondent sensor.

2. The tamper-respondent assembly of claim 1, wherein the detector monitors a second harmonic of the electrical signal applied to the conductive lines for the non-linear conductivity change indicative of the tamper event at the at least one tamper-respondent sensor.

3. The tamper-respondent assembly of claim 2, wherein the electrical signal has both known DC characteristics and known AC characteristics.

4. The tamper-respondent assembly of claim 1, wherein the tamper event comprises a shunt of one or more conductive lines of the conductive lines of the at least one tamper-respondent sensor, the non-linear conductivity change resulting from the shunt contacting the one or more conductive lines.

5. The tamper-respondent assembly of claim 1, wherein the at least one tamper-respondent sensor comprises at least one flexible layer, and the conductive lines are disposed on the at least one flexible layer to form, at least in part, the at least one tamper-detect network.

6. The tamper-respondent assembly of claim 1, further comprising:

a circuit board; and

the at least one tamper-respondent sensor comprises an embedded tamper-respondent sensor embedded within the circuit board, the conductive lines being conductive lines embedded within the circuit board.

7. The tamper-respondent assembly of claim 1, wherein the detector periodically applies the electrical signal to the conductive lines.

8. The tamper-respondent assembly of claim 1, wherein the conductive lines of the at least one tamper-respondent sensor each have a line width W₁≤

200 μ

m.

9. The tamper-respondent assembly of claim 1, wherein the conductive lines of the at least one tamper-respondent sensor comprise copper or a copper alloy.

10. A tamper-respondent assembly comprising:

at least one electronic component;

an enclosure surrounding, at least in part, the at least one electronic component;

a tamper-respondent sensor associated with the enclosure and facilitating forming a secure volume about the at least one electronic component, the tamper-respondent sensor comprising conductive lines forming, at least in part, a tamper-detect network of the tamper-respondent sensor; and

a detector to monitor the tamper-respondent sensor, the detector applying an electrical signal to the conductive lines of the tamper-respondent sensor to monitor over time a harmonic of the electrical signal applied to the conductive lines for a non-linear conductivity change, the electrical signal being a composite alternating current and direct current signal, and the harmonic, which is an integer multiple of a fundamental frequency, resulting from the applying of the composite alternating current and direct current signal to the conductive lines of the at least one tamper-respondent sensor, the non-linear conductivity change in the harmonic being indicative of a tamper event at the tamper-respondent sensor.

11. The tamper-respondent assembly of claim 10, wherein the detector monitors a second harmonic of the electrical signal applied to the conductive lines for the non-linear conductive change indicative of the tamper event at the at least one tamper-respondent sensor.

12. The tamper-respondent assembly of claim 10, wherein the tamper event comprises a shunt of one or more conductive lines of the conductive lines of the tamper-respondent sensor, and the non-linear conductivity change results from the shunt contacting the one or more conductive lines.

13. The tamper-respondent assembly of claim 10, wherein the tamper-respondent sensor comprises at least one flexible layer, and the conductive lines are disposed on the at least one flexible layer to form, at least in part, the at least one tamper-detect network.

14. The tamper-respondent assembly of claim 13, wherein the tamper-respondent sensor is mounted to an inner surface of the enclosure.

15. The tamper-respondent assembly of claim 14, further comprising:

a circuit board; and

an embedded tamper-respondent sensor embedded within the circuit board, wherein the tamper-respondent sensor and the embedded tamper-respondent sensor together facilitate defining the secure volume about the at least one electronic component.

16. The tamper-respondent assembly of claim 10, wherein the conductive lines of the tamper-respondent sensor comprise copper or a copper alloy, and the conductive lines each have a line width W₁≤

200 μ

ms.

17. A fabrication method comprising:

fabricating a tamper-respondent assembly, the fabricating comprising;

providing at least one tamper-respondent sensor comprising conductive lines forming, at least in part, at least one tamper-detect network of the at least one tamper-respondent sensor; and

providing a detector to monitor the at least one tamper-respondent sensor, the detector applying an electrical signal to the conductive lines of the at least one tamper-respondent sensor to monitor over time a harmonic of the electrical signal applied to the conductive lines for a non-linear conductivity change, the electrical signal being a composite alternating current and direct current signal, and the harmonic, which is an integer multiple of a fundamental frequency, resulting from the applying of the composite alternating current and direct current signal to the conductive lines of the at least one tamper-respondent sensor, where the non-linear conductivity change in the harmonic is indicative of a tamper event at the at least one tamper-respondent sensor.

18. The fabrication method of claim 17, wherein the detector monitors a second harmonic of the electrical signal applied to the conductive lines for the non-linear conductivity change indicative of the tamper event at the at least one tamper-respondent sensor.

19. The fabrication method of claim 17, wherein the applying by the detector comprises periodically applying the electrical signal to the conductive lines, and wherein the electrical signal has both known DC characteristics and known AC characteristics.

20. The fabrication method of claim 17, further comprising:

providing an enclosure surrounding, at least in part, at least one electronic component;

associating the at least one tamper-respondent sensor with the enclosure to facilitate forming a secure volume about the at least one electronic component;

providing a circuit board; and

mounting the enclosure with the tamper-respondent sensor to the circuit board to facilitate defining the secure volume about the at least one electronic component.