DCT

5:18-cv-05619

PersonalWeb Tech LLC v. Twitch Interactive Inc

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 5:18-cv-05619, N.D. Cal., 10/04/2018
  • Venue Allegations: Plaintiff alleges venue is proper because Defendant has a regular and established place of business in the Northern District of California and has committed acts of infringement within the district.
  • Core Dispute: Plaintiff alleges that Defendant’s twitch.tv website and its associated content delivery infrastructure infringe four patents related to using content-based identifiers to manage, locate, and control access to data in distributed computer networks.
  • Technical Context: The technology concerns methods for uniquely identifying data based on its content (e.g., via cryptographic hashing) rather than its name or location, a foundational concept for modern content delivery networks (CDNs) and cloud storage.
  • Key Procedural History: The complaint states that the patents-in-suit have been successfully enforced against third parties, resulting in settlements and non-exclusive licenses. It also notes that the patents have expired and that the infringement allegations are directed to the time period before expiration.

Case Timeline

Date Event
1995-04-11 Earliest Priority Date for all Patents-in-Suit
2005-08-09 U.S. Patent No. 6,928,442 Issued
2010-09-21 U.S. Patent No. 7,802,310 Issued
2011-05-17 U.S. Patent No. 7,945,544 Issued
2012-01-17 U.S. Patent No. 8,099,420 Issued
2018-10-04 Complaint Filed

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 6,928,442 - "Enforcement and Policing of Licensed Content Using Content-Based Identifiers," Issued August 9, 2005

The Invention Explained

  • Problem Addressed: The patent's background describes the inefficiency of conventional data processing systems that identify data items by name and location. In large, distributed networks, this context-dependent naming can lead to data duplication, difficulty in locating files, and an inability to verify that a retrieved file is the correct one (Compl. ¶¶12-13; ’442 Patent, col. 1:49-2:28).
  • The Patented Solution: The invention proposes a system using a "substantially unique" content-based identifier, called a "True Name," for each data item. This True Name is generated by applying a cryptographic hash function (such as MD5 or SHA) to the data's content, making the identifier dependent only on the data itself, not its name or location ('442 Patent, Abstract; col. 5:7-11). The system uses these True Names to manage, locate, and police access to data across a network of computers (Compl. ¶¶14-17).
  • Technical Importance: This content-based addressing method provides a reliable way to identify and de-duplicate data, which can reduce bandwidth and storage requirements while also creating a mechanism to verify data integrity and control access in distributed systems (Compl. ¶11; '442 Patent, col. 3:7-4:43).

Key Claims at a Glance

  • The complaint asserts at least independent claim 10 and dependent claim 11 (Compl. ¶55).
  • Independent Claim 10 recites a method with the following essential elements:
    • In a system of distributed files across multiple computers, obtaining a name for a data file that is based on a function of the file's contents.
    • Using that name to determine if a copy of the data file is present on at least one of the computers.
    • Determining if the present copy of the data file is an "unauthorized copy or an unlicensed copy."

U.S. Patent No. 7,802,310 - "Controlling Access to Data in a Data Processing System," Issued September 21, 2010

The Invention Explained

  • Problem Addressed: The patent addresses the same problem as its parent '442 patent: the challenges of managing data in distributed networks using traditional, context-dependent identifiers (’310 Patent, col. 1:50-2:29).
  • The Patented Solution: The invention provides a method and system for controlling the distribution of content. A "first computer" (e.g., an origin or cache server) receives a request from a "second computer" (e.g., a browser or downstream cache) that includes a content-dependent name for a data item. The first computer then compares this name against a set of values to determine if access is authorized, permitting or denying the content accordingly ('310 Patent, Abstract).
  • Technical Importance: This system allows for efficient and secure access control in a distributed network by leveraging content-based names to verify whether a requesting entity is permitted to access a specific version of a data item (Compl. ¶¶33-34; '310 Patent, col. 3:10-4:44).

Key Claims at a Glance

  • The complaint asserts at least independent claims 20 and 69 (Compl. ¶63).
  • Independent Claim 20 recites a method with the following essential elements:
    • Controlling the distribution of content from a first computer to another in response to a request from a second device.
    • The request includes a content-dependent name of a data item, where the name is generated by a hash or message digest function of the item's data.
    • Based on that content-dependent name, the first device either permits access if the content is not determined to be unauthorized/unlicensed or does not permit access if it is.
  • Independent Claim 69 recites a system with the following essential elements:
    • Hardware and software configured to receive a request at a first computer from a second computer, where the request includes a content-dependent name for a data item.
    • In response, the system causes the content-dependent name to be compared to a plurality of values.
    • Based on the comparison, the system determines if access is authorized and allows the data item to be provided if access is not determined to be unauthorized.

U.S. Patent No. 7,945,544 - "Similarity-Based Access Control of Data in a Data Processing System," Issued May 17, 2011

  • Technology Synopsis: The patent describes a hierarchical method for creating a content-based identifier ("digital key") for a file composed of multiple parts. A first hash function is applied to each part to generate "part values," and a second hash function is applied to the collection of part values to generate the final digital key for the entire file (’544 Patent, Abstract). This structure facilitates efficient comparison and access control for complex data files by allowing checks at both the whole-file and individual-part levels (Compl. ¶¶75-76).
  • Asserted Claims: At least claims 46, 48, 52, and 55, with claim 46 being independent (Compl. ¶73).
  • Accused Features: The complaint alleges infringement by Defendant's system of generating ETag values for webpage base files (the "digital key") by applying a hash function to the base file's contents, where those contents include URIs containing content-based fingerprints of individual asset files (the "part values") (Compl. ¶¶75-76).

U.S. Patent No. 8,099,420 - "Accessing Data in a Data Processing System," Issued January 17, 2012

  • Technology Synopsis: The patent claims a system for selectively permitting access to data items using content-dependent identifiers. The system determines one or more such identifiers for a data item and resolves whether access should be granted by checking if the identifier corresponds to an entry in a database of authorized identifiers (’420 Patent, Abstract).
  • Asserted Claims: At least claims 25, 26, 27, 29, 30, 32, 34-36, and 166, with claim 166 being independent (Compl. ¶84).
  • Accused Features: Defendant's system is accused of applying hash functions to generate content-dependent identifiers (ETags and fingerprints) for its webpage files. These identifiers are then allegedly used to selectively permit access by comparing an ETag received in an HTTP request with a database of ETag values to determine if the requesting computer is authorized to use its cached content (Compl. ¶¶87-89).

III. The Accused Instrumentality

Product Identification

  • The twitch.tv website and its associated content distribution system (Compl. ¶29).

Functionality and Market Context

  • The complaint alleges that Defendant's system controls the distribution of webpage content to users by employing a caching mechanism that relies on content-based identifiers (Compl. ¶30). The system is alleged to generate "ETag" values for webpage base files and asset files by applying a hash function to the files' contents (Compl. ¶¶31, 42). It is also alleged to generate content-based "fingerprints" that are inserted into the filenames of asset files, with these modified filenames being referenced by URIs within the main webpage files (Compl. ¶¶32, 36).
  • When a browser or intermediate cache possessing a stored version of a file requests it again, it allegedly sends a conditional HTTP GET request containing an "If-None-Match" header with the file's associated ETag value (Compl. ¶¶44, 47). Defendant's servers allegedly use this ETag to verify whether the cached content is still the authorized version; a match results in an HTTP 304 (Not Modified) response, while a mismatch results in an HTTP 200 (OK) response with the new content (Compl. ¶¶49-50). This system is alleged to reduce bandwidth and server load by serving full content only when it has changed (Compl. ¶34). No probative visual evidence provided in complaint.

IV. Analysis of Infringement Allegations

U.S. Patent No. 6,928,442 Infringement Allegations

Claim Element (from Independent Claim 10) Alleged Infringing Functionality Complaint Citation Patent Citation
obtaining a name for a data file, the name being based at least in part on a given function of the data, wherein the data used by the function comprises the contents of the particular file Defendant generates or obtains ETags for its webpage files using a hash function, where the ETags are based on the contents of those files. ¶57 col. 13:7-14
determining, using at least the name, whether a copy of the data file is present on at least one of said computers Defendant's origin servers and intermediate cache servers respond to a conditional GET request containing an ETag by determining if a file matching the URI and ETag is present. ¶58 col. 15:32-41
determining whether a copy of the data file that is present on a at least one of said computers is an unauthorized copy or an unlicensed copy of the data file If the received ETag matches the server's current ETag, the copy is determined to be authorized; if there is no match, it is determined to be unauthorized. ¶59 col. 1:1-4

U.S. Patent No. 7,802,310 Infringement Allegations

Claim Element (from Independent Claim 20) Alleged Infringing Functionality Complaint Citation Patent Citation
controlling distribution of content from a first computer to at least one other computer, in response to a request obtained by a first device...from a second device..., the request including at least a content-dependent name of a particular data item... An upstream server (first computer) receives a conditional GET request from a downstream browser or cache (second computer), which includes an ETag (the content-dependent name). ¶65 col. 4:50-58
based at least in part on said content-dependent name...the first device (A) permitting the content to be provided...if it is not determined that the content is unauthorized or unlicensed, otherwise, (B)...not permitting the content to be provided... The upstream server compares the received ETag to its stored ETag. A match results in an HTTP 304 response (permitting use of cached content), while a mismatch results in an HTTP 200 response with new content (not permitting use of old content). ¶66 col. 23:42-51

Identified Points of Contention

  • Scope Questions: The infringement theory hinges on equating an "ETag" used in the HTTP protocol with the "name for a data file" described in the patents. A potential point of contention is whether an ephemeral cache-validation token used in a communication protocol falls within the scope of a "name" as taught by the patents, which describe a more persistent "True Name" integrated into a data management and registry system ('442 Patent, col. 7:29-35).
  • Technical Questions: A central question will be whether the function of checking for stale content via an ETag mismatch is technically and legally equivalent to the claimed function of determining if a file is "unauthorized or unlicensed." The patents' specification links this determination to "licensed content" and "licensed users," which may suggest a digital rights management or access control context rather than a cache coherency mechanism ('442 Patent, col. 8:52-56).

V. Key Claim Terms for Construction

  • The Term: "name for a data file" ('442 Patent, Claim 10)

    • Context and Importance: The viability of the infringement allegations for multiple patents depends on whether an ETag or a URI containing a content-based fingerprint constitutes a "name" under the patents' claims. Practitioners may focus on this term because the accused functionality is rooted in the standard HTTP protocol's use of ETags for caching, which may differ from the patents' description of a comprehensive data management system built around "True Names."
    • Intrinsic Evidence for Interpretation:
      • Evidence for a Broader Interpretation: The patent specification broadly defines a "True Name" as a "substantially unique data identifier for a particular data item" generated by a function of its content ('442 Patent, col. 5:7-11). This functional definition could be argued to encompass any content-based hash, including an ETag.
      • Evidence for a Narrower Interpretation: The detailed description repeatedly discusses the "True Name" in the context of a "True File registry," a specific data structure for managing files, their locations, and dependencies ('442 Patent, col. 7:29-44). This context may support a narrower construction where a "name" is not merely a hash but an identifier used within such a registry system.

  • The Term: "unauthorized copy or an unlicensed copy" ('442 Patent, Claim 10)

    • Context and Importance: The allegation of infringement requires mapping the technical result of a failed cache-coherency check (an ETag mismatch) to the legal statuses of "unauthorized" or "unlicensed."
    • Intrinsic Evidence for Interpretation:
      • Evidence for a Broader Interpretation: The '442 patent is titled "Enforcement and Policing of Licensed Content," and the abstract states a copy is "only provided to licensed (or authorized) parties." This could be read broadly to mean any copy not explicitly permitted by the content owner at that moment, including a stale cached copy.
      • Evidence for a Narrower Interpretation: The specification discusses a "license table...identifying files, which may only be used by licensed users" ('442 Patent, col. 8:52-56). This language suggests a focus on user-based permissions and digital rights management, which may be functionally distinct from a technical check to determine if a public web asset is the most current version.

VI. Other Allegations

  • Indirect Infringement: The complaint alleges Defendant "caused" its servers and intermediate caches to perform certain steps (Compl. ¶¶57, 58, 65). These allegations may form the basis for a theory of induced or contributory infringement, although the complaint does not separately plead the specific elements of knowledge and intent typically required for such claims.
  • Willful Infringement: The complaint does not contain allegations of willful infringement.

VII. Analyst’s Conclusion: Key Questions for the Case

  • A core issue will be one of definitional scope: can an "ETag", an ephemeral cache-validation token within the HTTP protocol, be construed as a "name for a data file" as contemplated by the patents, which describe a system of persistent, content-based "True Names" for managing data across a network?
  • A key evidentiary question will be one of functional equivalence: does the accused system's technical process for ensuring cache coherency—determining if a cached file is stale via an ETag mismatch—perform the same function as the patented method of determining if a file is "unauthorized or unlicensed," a concept the patents appear to frame in the context of content policing and access rights management?