PTAB

IPR2021-00495

TCL Industries Holdings Co Ltd v. Koninklijke Philips NV

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Secure Device Authentication and Proximity Verification
  • Brief Description: The ’977 patent discloses a multi-step authentication procedure between two devices. The procedure requires a first device to authenticate a second device, securely share a common secret with it, and then use that secret in a challenge-response protocol to verify that the second device is within a predetermined physical distance by measuring signal round-trip time.

3. Grounds for Unpatentability

Ground 1: Claims 11-12 and 14-17 are obvious over Maillard, Davis, and Lundkvist

  • Prior Art Relied Upon: Maillard (European Patent Application EP 1045585), Davis (PCT Application WO 97/39553), and Lundkvist (PCT Application WO 02/35036).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that the prior art teaches all steps of the claimed method in the same sequence. Maillard was asserted to disclose a system for preventing illegal copying of digital data by first authenticating a second device (e.g., a TV) via certificate exchange and then securely sharing a common secret (a "session key") with it for encrypting subsequent data transfers. Davis and Lundkvist were asserted to teach augmenting such security systems with a challenge-response protocol to ensure physical proximity. This protocol involves a first device sending a challenge signal to a second device and requiring a valid response within a predetermined time, corresponding to a maximum physical distance. The combination allegedly discloses all limitations of independent claim 11, including device authentication, sharing a secret, and using that secret in a subsequent challenge-response exchange to measure distance before transferring protected content.
    • Motivation to Combine: Petitioner contended that a person of ordinary skill in the art (POSITA) would combine these references to enhance security. A POSITA would recognize that Maillard's authentication-only system is vulnerable if an authenticated device is not physically present. Davis explicitly addresses this vulnerability by teaching a proximity check based on signal timing. Davis further teaches that its disclosed challenge-response protocols are merely examples and that other protocols could be used, leading a POSITA directly to alternatives like the one described in Lundkvist, which details a similar challenge-response and distance measurement protocol for vehicle access.
    • Expectation of Success: A POSITA would have a high expectation of success because the references address related problems in the same technical field (secure access) with complementary solutions. Combining Maillard's robust device validation with the proximity verification of Davis and Lundkvist was presented as a predictable and logical improvement to overall system security.

Ground 2: Claim 18 is obvious over Maillard, Davis, Lundkvist, and Schneier

  • Prior Art Relied Upon: Maillard, Davis, Lundkvist, and Schneier (Applied Cryptography, Second Edition, 1996).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground builds on the combination in Ground 1 to address dependent claim 18, which specifies that modifying a signal during the challenge-response protocol is done via a XOR operation. Petitioner argued that Schneier, a foundational textbook on cryptography, explicitly teaches that a simple and fast form of symmetric encryption involves XORing the plaintext with a secret key. This directly teaches the XOR modification limitation.
    • Motivation to Combine: A POSITA implementing the symmetric encryption suggested by Lundkvist for the challenge-response signals would seek a computationally efficient method to ensure the timing measurements are accurate and rapid. Petitioner asserted that Schneier provides the well-known XOR operation as an ideal candidate, as it is significantly faster than other algorithms like DES and requires fewer resources, a rationale consistent with the ’977 patent’s own disclosure.

Ground 3: Claims 19 and 20 are obvious over Maillard, Davis, Lundkvist, and HAC

  • Prior Art Relied Upon: Maillard, Davis, Lundkvist, and HAC (Handbook of Applied Cryptography, 1997).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground builds on the combination in Ground 1 to address dependent claims 19 and 20, which recite transmitting the secret using a "key transport protocol." Petitioner argued that HAC, another foundational textbook, defines a "key transport protocol" as any technique where one party creates a secret value and securely transfers it to another. This definition was alleged to precisely describe the process taught in Maillard, where a security module (first device) generates a random session key and securely transmits it to the second device.
    • Motivation to Combine: Petitioner argued that this ground involves applying a standard industry definition from a well-known treatise (HAC) to the process already established by the primary references. A POSITA would immediately recognize that Maillard's method for securely sharing its session key is a textbook example of a key transport protocol as defined by HAC, making the limitation obvious.

4. Arguments Regarding Discretionary Denial

  • Petitioner argued that discretionary denial under §325(d) would be inappropriate because the core prior art combinations and arguments are new. It was contended that Maillard, Schneier, and HAC were never considered during prosecution. While Davis and Lundkvist were of record, their substantive teachings regarding challenge-response timing for proximity verification were never discussed or applied by the Examiner. Therefore, Petitioner asserted that the presented combination represents a new and distinct invalidity challenge that warrants consideration.

5. Relief Requested

  • Petitioner requests the institution of an inter partes review and cancellation of claims 11-12 and 14-20 of the ’977 patent as unpatentable.