IP Law Daily, PATENT—Fed. Cir.: PTAB’s partial invalidity of IBM’s single sign-on patent affirmed, (Dec 10, 2025)

By Saurabh Kashyap, B.A., M.A., LL.B., LL.M.

PTAB correctly found some claims obvious while others failed to be anticipated or rendered obvious by the cited prior art.

In a precedential disposition, the U.S. Court of Appeals for the Federal Circuit affirmed a mixed ruling of the Patent Trial and Appeal Board (PTAB) that invalidated several claims of International Business Machines Corporation’s (IBM) single sign-on (SSO) patent as obvious while upholding others as patentable. The court concluded that claims 1–4, 12–16, and 18–19 of U.S. Patent No. 7,631,346 (’346 patent) were unpatentable over prior art, but sustained the Board’s decision that claims 5–11, 17, and 20 were not shown unpatentable (International Business Machines Corp. v. Zillow Group, Inc., No. 24-1170, 24-1274 (Fed. Cir. Dec. 9, 2025)).

Background. IBM, the appellant, is a multinational technology corporation engaged in cloud computing, artificial intelligence, and digital infrastructure services. The cross-appellants, Zillow Group, Inc. and Zillow, Inc. (together, Zillow), operate a prominent U.S.-based real estate technology platform offering services for buying, renting, and selling property online. Rakuten Rewards, the original petitioner in the IPR proceedings, challenged the validity of the ’346 patent, with Zillow joining after the IPR was instituted.

IBM’s ’346 patent, titled “Method for managing user authentication within a distributed data processing system,” relates to federated identity systems that support SSO across different domains. The invention allows a user authenticated by the first system (e.g., a social media platform) to access protected resources on the second system (e.g., a healthcare provider) without creating a new account.

Rakuten initiated inter partes review, asserting that Sunada, a Japanese patent application describing a network authentication server, either anticipated or rendered obvious the claims of the ’346 patent. It relied on Sunada alone and in combination with (i) OASIS, a set of technical specifications developed by the Organization for the Advancement of Structured Information Standards, which define the Security Assertion Markup Language (SAML) used for exchanging authentication and authorization data across domains; and (ii) Dutcher, another referenced prior art.

The PTAB adopted IBM’s construction of key terms, including “protected resources” and “identifier associated with the user,” yet found claims 1–4, 12–16, and 18–19 unpatentable on obviousness grounds. It rejected the anticipation ground, which Rakuten had effectively withdrawn, and upheld claims 5–11, 17, and 20, finding that the prior art did not disclose or suggest certain limitations required by those claims.

Petition scope on “protected resources.” IBM argued that the PTAB erred by relying on a theory not presented in Rakuten’s petition, namely that Sunada implied the use of URLs necessary to satisfy the “protected resources” limitation. The Federal Circuit disagreed, holding that the Board’s conclusion was consistent with the petition’s anticipation theory. The court found that Sunada’s reference to “web applications” would be understood by a skilled artisan to imply access via conventional URLs or URIs. This inference, though not explicit in Sunada, was supported by expert testimony and fell within permissible anticipatory analysis. Citing Sage Prods., LLC v. Stewart, 133 F.4th 1376 (Fed. Cir. 2025) and Acoustic Tech., Inc. v. Itron Networked Sols., Inc., 949 F.3d 1366 (Fed. Cir. 2020), the court confirmed that anticipation may include what is implicitly taught when viewed through the lens of a skilled artisan.

Identifier finding. IBM also challenged the Board’s finding that Sunada disclosed the transmission of “an identifier associated with the user” from the first system to the second system. While IBM acknowledged that Sunada generated a unique User ID, it claimed there was no evidence that the second system received it. The Federal Circuit rejected this argument, citing Sunada’s disclosure of transmitting “information regarding the user” to the second system. The Board had reasonably interpreted this phrase to include the User ID. The court emphasized that in the context of network authentication, such an inference was supported by substantial evidence and aligned with precedent, including Quake v. Lo, 928 F.3d 1365, 1373 (Fed. Cir. 2019).

Zillow’s cross-appeal. Zillow argued that the PTAB erred in upholding claim 5 while invalidating claim 14, which contains similar limitations. Both claims involve requesting additional user attributes during account creation, but they differ in where the request is sent. Claim 5 requires the request to be sent from the second system to the first system (e.g., the initial authenticating platform), whereas claim 14 specifies that the request is sent to the fourth system (the user’s device).

The Federal Circuit agreed with the Board’s distinction. In Sunada, when the second system lacks sufficient data to create a user account, it prompts the user directly—i.e., the fourth system—for additional input. This disclosure aligns with claim 14, not claim 5. The court found no suggestion in Sunada, OASIS, or Dutcher of a mechanism by which the second system could contact the first system in such a situation. As a result, it affirmed the Board’s determination that the combination of prior art did not render claim 5 unpatentable.

Procedural challenges. The court addressed a procedural challenge regarding the timeliness of Zillow’s cross-appeal, which was filed beyond the 63-day window and more than 14 days after IBM’s notice of appeal. The USPTO Director granted Zillow a retroactive extension for excusable neglect. The Federal Circuit found the extension proper and noted IBM did not oppose it either before the agency or on appeal.

Thus, the Federal Circuit’s ruling affirmed the PTAB’s findings in full, preserving a portion of IBM’s ’346 patent while invalidating other claims based on obviousness.

The Case is Nos. 24-1170, 24-1274.

Judge: Chen, R.

Attorneys: Karim Zeddam Oussayef (Desmarais LLP) for International Business Machines Corp. Shawn Daniel Blackburn (Susman Godfrey LLP) for Zillow Group, Inc. and Zillow, Inc.

Companies: International Business Machines Corp.; Zillow Group, Inc.; Zillow, Inc.

Cases: Patent TechnologyInternet FedCirNews USPTO