Invalidity dossier
US 5638443
System for controlling the distribution and use of composite digital works
Current assignee: Contentguard Holdings Inc
Added 9/23/2026, 5:28:09 PM
Active provider: DeepSeek · deepseek-flash
Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview — US 5,638,443 A
Title: System for controlling the distribution and use of composite digital works
Patent number: US 5,638,443 A (application US 08/344,776)
Inventors: Mark J. Stefik, Daniel G. Bobrow, Peter L. T. Pirolli
Original assignee: Xerox Corp. Current assignee (per source, listed assignees may be inaccurate): Contentguard Holdings Inc.
Key dates: Prior art date and filing date 1994-11-23; publication/grant 1997-06-10; anticipated expiration 2014-11-23. Legal status: Expired – Lifetime.
Purpose / plain-language scope (based only on the supplied text): The patent concerns a system for controlling the distribution and use of composite digital works. The recurring "prior art keywords" are repository, digital work, work, rights, and digital — indicating a repository-based scheme in which rights governing a digital work are enforced. Classifications place it in digital rights management (G06F21/10), network security for access control (H04L63/08–63/10, including multiple levels of security), and selective content distribution/client-server content handling (H04N21/xx). The network-security classes reference encrypted or encapsulated payloads and asymmetric encryption (H04L63/0442), and certificate-based entity authentication (H04L63/0823), suggesting encrypted content and credential-based control.
Source: https://patents.google.com/patent/US5638443/en (fetched 2026-09-23). Also cited in the source: related family filings including EP0715246B1, JP H08263439 A, and others.
What the excerpt does not establish: It provides no claim language, no written description, no drawings text, and no abstract, so the precise claimed scope, claim count, dependencies, and limitations cannot be stated. It does not specify what "composite" means in the specification, how rights are represented or enforced, or the actual architecture. It does not establish inventorship validity, claim coverage, examination history, or the accuracy of the listed assignees or priority dates (the source itself flags these as assumptions, not legal conclusions). It also does not confirm or deny later ownership transfers, litigation, validity, or prior art; consistent with instructions, those were not researched. The classification codes are administrative metadata, not a statement of claimed subject matter.
Generated 10/1/2026, 9:43:34 PM
Cases on file (0)
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Litigation summary
Past and pending lawsuits — plaintiffs, defendants, jurisdictions, outcomes, and notable rulings.
Proceedings on file (0)
All PTAB activity →AIA trial proceedings (IPR / PGR / CBM) filed at the USPTO Patent Trial and Appeal Board against this patent. Sourced from the USPTO Open Data Portal and refreshed every six hours; each proceeding number deep-links to the PTAB E2E docket.
No PTAB proceedings on file. This patent has not been challenged via IPR, PGR, or CBM. The absence is itself a signal — well-asserted patents eventually attract IPRs. The LLM analysis below may surface filings the ODP feed hasn’t indexed yet.
PTAB challenges
AIA trial proceedings at the USPTO Patent Trial and Appeal Board — IPR, PGR, and CBM. Petitioners, judge panels, claim-level invalidation outcomes from Final Written Decisions, and Federal Circuit appeals. The single most important defensive datapoint after litigation history.
Assignment history
Inventors, original assignee, and the chain of ownership recorded with the USPTO — including the correspondent attorney who recorded each assignment, since shell-LLC chains often share one repeat-player attorney even when the entity names look unrelated. Surfaces NPE / patent-troll patterns: shell-entity transfers, known asserters in the chain, repeat correspondent fingerprints, pre-litigation assignments, and bankruptcy fire-sales.
Prior art
Earlier patents, publications, and products that may anticipate or render the claims unpatentable.
Obviousness
Combinations of prior art that suggest the claimed invention would have been obvious under 35 U.S.C. § 103.
Extensions
Patent term adjustments, term extensions, continuations, divisionals, family members, and expiration dates.
Derivative works
Defensive disclosure: derivative variations of each claim designed to render future incremental improvements obvious or non-novel.