PTAB

IPR2025-00495

Samsung Electronics Co Ltd v. Four Batons Wireless LLC

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petition

1. Case Identification

2. Patent Overview

  • Title: Channel Binding for Network Authentication
  • Brief Description: The ’671 patent discloses a channel binding method for authenticating a mobile device (supplicant) to a wireless access network. The method cryptographically binds access network parameters to a key during a key derivation procedure, which avoids the need to carry those parameters within the authentication methods themselves.

3. Grounds for Unpatentability

Ground 1: Obviousness over Sood - Claims 1-4, 7, 8, 12, 14, and 16 are obvious over Sood.

  • Prior Art Relied Upon: Sood (Patent 7,787,627).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Sood taught every limitation of the challenged claims. Sood’s hierarchical key derivation process, which generates a Pairwise Transient Key (PTK) for secure communication, was presented as the claimed “channel binding method.” Petitioner mapped Sood’s disclosure of binding lower-level MAC-layer identifiers (like BSSID) to the PTK as meeting the “parameter binding” limitation. Sood’s method of advertising network parameters (e.g., R0KH-ID, R1KH-ID) via beacons was argued to satisfy the limitation of binding parameters “without needing to carry” them in authentication methods. Further, Petitioner asserted that Sood’s derivation of a key (PMK-R1) from a master key (MSK or PMK-R0) using a Key Derivation Function (KDF) and a concatenated string of parameters (the “key binding blob”) meets the remaining limitations of independent claim 1.

Ground 2: Obviousness over Sood and Aboba - Claims 5 and 18 are obvious over Sood in view of Aboba.

  • Prior Art Relied Upon: Sood (Patent 7,787,627) and Aboba (an Extensible Authentication Protocol (EAP) Internet-Draft).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground addressed limitations not explicitly found in Sood. For claim 5, which requires the channel binding master key to be at least 64 octets long, Petitioner argued that while Sood discloses a Master Secret Key (MSK), it does not specify a length. Aboba, a foundational EAP framework document, taught that an analogous MSK must be at least 64 octets to be secure. For claim 18, which recites a key derivation function as CBK =kdf+(CBMK, KBB), Petitioner argued kdf+ implies a variable-length output function. While Sood’s KDF is fixed-length, Aboba taught a variable-length PRF function suitable for deriving keys of different lengths.
    • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) implementing Sood’s key management system would consult well-known standards like Aboba to determine appropriate, secure parameters, such as the MSK length. A POSITA would also be motivated to incorporate Aboba’s flexible, variable-length KDF to improve Sood’s system.
    • Expectation of Success: A POSITA would have a reasonable expectation of success because the combination involved applying a known technique (using a standard key length or variable-length KDF from Aboba) to a known system (Sood) to achieve the predictable results of improved security and greater flexibility.

Ground 3: Obviousness over Sood and Lee - Claims 6, 10, 11, 13, 15, 17, and 19 are obvious over Sood in view of Lee.

  • Prior Art Relied Upon: Sood (Patent 7,787,627) and Lee (Application # 2004/0242228).

  • Core Argument for this Ground:

    • Prior Art Mapping: This ground addressed claims requiring a server to generate and transmit keys, as well as claims related to hierarchical key generation. Petitioner argued that Sood’s system could be modified by Lee’s teachings. Lee explicitly disclosed a server that proactively generates and distributes keys to neighboring access points to facilitate fast roaming and reduce the memory burden on the access points themselves. Lee also taught a hierarchical key structure where the key for a new access point is derived from the key of the previously visited one, which directly addresses the “hierarchical channel binding” limitations.
    • Motivation to Combine: A POSITA would combine Lee’s server-centric key generation with Sood’s system to gain the clear benefits of centralized management and improved efficiency for access points, as described in Lee. The motivation to add Lee’s hierarchical key derivation was to improve the security of Sood’s system by binding keys to the subscriber’s path through the network, thus preventing reuse of old keys by an attacker.
    • Expectation of Success: The combination was expected to succeed because Sood already included an authentication server, and implementing Lee's central key derivation functionality on that server would be a straightforward and well-understood enhancement for a POSITA.

  • Additional Grounds: Petitioner asserted an additional obviousness challenge against claims 1-8 and 10-19 based on the combination of Sood, Aboba, and Lee, relying on similar arguments and motivations presented in the grounds above.

4. Key Claim Construction Positions

  • Petitioner argued for a specific construction of the phrase “deriving a…channel binding key from a channel binding master key bound to a key binding blob using a key derivation function” (claims 1 and 6).
  • Petitioner contended this phrase requires the “key binding blob” (KBB) to be cryptographically bound to the resulting “channel binding key” (CBK), not the initial “channel binding master key” (CBMK). This construction was based on the patent’s own lexicography for “Channel Binding Key” and was argued to be necessary to give meaning to dependent claims, such as claim 18, which defines the derivation function in a way that shows the KBB as an input to generate the CBK (CBK =kdf+(CBMK, KBB)).

5. Arguments Regarding Discretionary Denial

  • Petitioner argued that discretionary denial under Fintiv would be inappropriate. The parallel district court litigation is in a very early stage, with the trial date (February 2026) set for several months after the projected Final Written Decision (FWD) date (July 2026). Petitioner asserted that investment in the litigation has been minimal and no substantive court orders have been issued. Furthermore, Petitioner argued there is incomplete overlap between the proceedings, as the IPR challenges a broader set of claims (1-8, 10-19) than those asserted in the district court case.

6. Relief Requested

  • Petitioner requests institution of inter partes review and cancellation of claims 1-8 and 10-19 of the ’671 patent as unpatentable.