US 6434535

I'll search for this specific patent number across USPTO and litigation sources.

Let me dig deeper on the assignee and any litigation.

US 6,434,535 B1 — Verified Bibliographic Data

I searched for the literal identifier 6434535 / 6,434,535. What follows is grounded in the Google Patents record (which matches the authoritative full text) and in litigation databases I could actually retrieve. I did not locate any CAFC 2026 docket, or any CAFC docket at all, involving US 6,434,535 — see the caveats section below, which is important because of a number-confusion risk.

Bibliographic summary

Abstract (verbatim)

"A system and method for distribution of electronic content over a network infrastructure and compensation of vendors of such data using prepaid media that includes a client device for operation by a user desiring to receive the electronic content and server that contains the electronic content and offering the electronic content for downloading to the client device via the network infrastructure. The client device communicates a unique identifier associated with a particular piece of media to which the electronic content is to be stored to the server. The server contacts a media tracking sever to determine if the media is valid and a remaining balance of the prepaid media. The cost of the electronic content to be downloaded is deducted from the remaining balance and credited to the vendor's account. The server then encrypts the electronic content using the unique identifier as a key and downloads the encrypted electronic content to the client computer, where the client computer writes the encrypted electronic content to the particular piece of media such that the encrypted electronic content may only be accessed from the particular piece of media. The electronic content is only accessible from only the one piece of media having the unique identifier and is not accessible from any other media having a different or no identifier."

Plain-language overview of the independent claims

⚠️ Uncertainty flag up front: the fetched record was truncated before the numbered claim set, so I do not have verbatim claim text or exact independent-claim numbers (e.g., "claim 1," "claim 22"). The overviews below are reconstructed from the Summary of the Invention and the claim-derived "Definitions" section of the record, which track the claim language closely. Claim numbers should be treated as unverified. Based on that material, the patent appears to contain four independent claims, in four families:

1. Independent method claim — prepaid media distribution (the "basic" embodiment).
A method of distributing electronic content from a vendor server to a client device over a network, where (a) the destination medium's unique identifier ties the content to that one piece of media, and (b) a prepaid stored value on the media pays for the content. Steps: contact the vendor server; transmit the media's unique identifier to it; have the vendor server query a media tracking server to validate the identifier and look up the remaining balance; deliver the content in encrypted form; and write it to the media so it can only be used from that media.

2. Independent method claim — compound-key variant.
Same overall flow, but the client additionally reads the unique identifier (from a predetermined location/track), obtains vendor information and user information, and builds a "compound key" via a predetermined operation (specification's preferred form: CK = S XOR (V interleaved U)). The content and/or its encryption key is encrypted with that compound key, so decryption requires the right media plus the right vendor-licensed software plus the right user credential.

3. Independent system/apparatus claim — networked distribution system.
An apparatus/system claim covering a vendor server holding content and offering it for download, a client device running an application program with a prepaid, uniquely-identified piece of media, and a media tracking server holding the balance keyed to the unique identifier. The identifier flows to the vendor server, which queries the tracking server for the balance, then encrypts and downloads content so it is only accessible from that media.

4. Independent claim — media tracking server per se.
A claim to the tracking server itself: a processor, a database, and a network communication interface, where the server maintains a remaining balance associated with a given media identifier, is adapted to receive the identifier (and the prepaid amount) from the media manufacturer, and is adapted to receive a balance-verification request from a vendor server — including debiting the balance and crediting the vendor's account.

Representative dependent features recited across these families (per the Definitions section): debiting price from balance and returning an acknowledgment before download; crediting the vendor's account; insufficient-balance handling with an offer to replenish (credit card / bank transfer); media-full handling with a swap to a second prepaid disk and transfer of the remaining balance to the new disk's identifier; reading the identifier via a predetermined track (Iomega ZIP® disk serial number via the "Iomega Ready API" / SCSI 0x06 Non-Sense command, Disk Status Page 0x02, offset bytes 20–59); browser→CGI→"IPM" metatag transaction-file handshake that launches a client program and may point to a dynamically loadable download server; and encryption choice of Blowfish over the content and/or its data key.

Litigation / CAFC search results — what I actually found, and an important caution

• No lawsuit or Federal Circuit appeal asserting US 6,434,535 was found. The patent's term expired 2018-11-13, and it is recorded as "Expired – Lifetime."
• No CAFC 2026 docket for 6,434,535 was found. Searches of Federal Circuit 2026 materials surfaced unrelated appeals (e.g., Woodway/LifeCORE treadmills, Teva v. Lilly, inventorship cases) with no reference to this patent.
• Number-confusion caution per your strict-literal rule: the entity named in this patent's chain of title — Hanger Solutions, LLC — is an active patent assertion entity that filed numerous suits (D. Del. 2021; W.D. Tex. 2022; M.D. Ga. 2022) against Extreme Networks, Charter Communications, Cequel Communications, Mediacom, and others. Those suits asserted different patents — US 6,430,623, 6,609,159, 6,772,227, 6,119,171, 6,098,098, and 6,868,160 — not 6,434,535. I am not treating "6,430,623" as the same as "6,434,535"; they are distinct numbers and I have not merged them. Note also that the "Hanger Solutions"-branded suits involve US 6,430,623, which is a different patent from the one you asked about.
• Sources: Google Patents US6434535B1; Hanger Solutions, LLC v. Extreme Networks, Inc., 1:21-cv-00040 (D. Del.); Hanger Solutions LLC v. Cequel Communications, LLC, 6:22-cv-00330 (W.D. Tex.); Hanger Solutions, LLC v. Mediacom Communications Corp., 4:22-cv-00152 (M.D. Ga.).

Bottom line

US 6,434,535 is an Iomega-originated 1998 invention by Kupka and Lundgren, issued in 2002, covering downloadable-content prepayment via a uniquely-identified removable disk combined with encryption keyed to that disk's serial number (optionally a compound key of serial + vendor + user data). Ownership passed through Bozak Investments → Xylon → Hanger Solutions, and the patent expired in November 2018. I found no evidence of any live 2025–2026 CAFC appeal or district-court assertion of this specific patent, and I explicitly did not substitute the similarly-numbered Hanger Solutions patents for it. If you need verified verbatim independent-claim text with exact claim numbers, the USPTO Patent Center / Patent Public Search full-text or the issued patent PDF would be the authoritative source — the accessible record I retrieved did not include the numbered claims.

I'll search litigation databases for US patent 6434535.

The general searches didn't isolate this patent. Let me search with the proper comma-formatted number and the specific owners.

Let me search more specifically, including the Xylon LLC / Hanger Solutions campaigns and IPR activity.

Summary: No litigation specifically asserting US 6,434,535 found

Based on my searches of litigation-oriented sources (Unified Patents‑style docket aggregators, Justia/CourtListener, UniCourt dockets, PTAB filings, and Google/JUSTIA patent pages), I did not locate any lawsuit, IPR/PGR, or other contested proceeding that names US Patent No. 6,434,535 as a patent‑in‑suit. I want to be explicit about this rather than fabricate cases.

Why I'm reasonably (not absolutely) confident it's not in a public campaign

The patent's provenance is well documented, and its owners are NPE‑type entities whose other assertions I could find — but those cases assert different patents, not this one:

• Ownership chain of 6,434,535 (per the Google Patents record): Iomega Corp (original assignee) → Bozak Investments, LLC (2006) → Xylon LLC (2015, merger) → Hanger Solutions, LLC (2020). Anticipated expiration 2018‑11‑13.
• Hanger Solutions, LLC ran a 2022 campaign in W.D. Tex. (Judge Alan D. Albright) against cable/telecom defendants — e.g., Hanger Solutions LLC v. Charter Communications, Inc., No. 6:22‑cv‑00070 (W.D. Tex., filed 01/18/2022) and Hanger Solutions LLC v. Cequel Communications, LLC, No. 6:22‑cv‑00330 (W.D. Tex., filed 03/29/2022). However, the patents asserted there were U.S. 6,430,623; 6,609,159; 6,772,227; and 6,119,171 — not 6,434,535. (Note the close numeric neighborships; I am not treating 6,430,623 as 6,434,535.)
• Xylon Licensing LLC (an NPE that is not the "Xylon LLC" that held 6,434,535) sued banks (e.g., Xylon Licensing LLC v. Lone Star National Bancshares Texas Inc, No. 6:21‑cv‑00302, W.D. Tex.) asserting U.S. 8,719,165 — again, not this patent.

So the two candidates that superficially look relevant (Hanger Solutions; "Xylon") are asserting other patents. I found no docket tying 6,434,535 to either.

Important caveats and limitations

• This is not a certified clearance search. My tool calls were cut off before I could exhaustively query the Unified Patents litigation caselist, Docket Navigator, PACER, and the Google Patents "Litigation" tab for this exact number. It is possible a short-lived or small case exists that did not surface in these queries.
• The patent expired 2018‑11‑13, which reduces (but does not eliminate) the likelihood of recent assertions; any suit would likely predate that expiration.
• I am explicitly flagging low-to-moderate confidence in "no litigation" rather than asserting it as definitive fact.

Recommended next steps to confirm

To verify authoritatively, I suggest these fee/free sources keyed to the exact number 6,434,535:

1. PACER / CourtListener RECAP — search docket text for "6,434,535."
2. Docket Navigator — "patent" search on 6,434,535 for both district court and PTAB.
3. Unified Patents Portal — https://portal.unifiedpatents.com/litigation/caselist (search patent number).
4. Google Patents page for US6434535B1 — the "Litigation" / "Similar Documents" panel sometimes lists co‑asserted cases.
5. USPTO Patent Trial and Appeal Board — search for the patent number in IPR/PGR/CBM proceedings.

Bottom line: I could not identify any case — plaintiff, defendant, jurisdiction, case number, or outcome — involving US 6,434,535. The known litigation campaigns by its successor owners (Hanger Solutions, Xylon) concern other patent numbers. If you need a definitive "none exists" statement for a legal purpose, please run the five sources above, since my search coverage was incomplete.

I'll verify the ODP's "no proceedings" result with targeted searches before concluding.

Initial searches surfaced nothing relevant. Let me try the patent number in several litigation/trial contexts.

Let me check the Unified Patents portal and PTAB-specific sources directly.

Proceedings overview

Total AIA trial proceedings on file: 0. The USPTO Open Data Portal returns no IPR, PGR, or CBM proceedings for US 6,434,535. I could not corroborate any PTAB filing through independent search either — queries against the "Hanger Solutions" / Xylon LLC / Iomega ownership chain and the patent number surfaced district court litigation and prosecution citations, but no petition, institution decision, or Final Written Decision naming this patent. Bottom line for a defendant: the ODP default controls — this patent has never been tested at the PTAB, so you get none of the "claims canceled, troll has no case" benefit, and you will be building any invalidity case from scratch in district court under a pre-AIA statute.

Important negative-data caveat: zero proceedings is not the same as zero exposure. This is a 1998-filed Iomega patent that passed to Bozak Investments → Xylon LLC → Hanger Solutions LLC (assignment recorded 2020-01-05), and Hanger is a serial filer. The absence of an IPR on this patent most likely reflects its expired status rather than its strength or weakness.

Per-proceeding detail

Not applicable — there are no proceedings to detail. I will not manufacture proceeding numbers, panels, or claim-level dispositions. Per your instruction, the structured ODP block is the canonical list, and it is empty.

What I did find (context, not proceedings)

• Ownership chain (from the structured record): Iomega Corp (original assignee) → Bozak Investments, LLC (assignment recorded 2006-11-02) → Xylon LLC (merger, 2015-08-04) → Hanger Solutions, LLC (assignment recorded 2020-01-05, from Intellectual Ventures Assets 161 LLC).
• Statutory dates: priority/filing 1998-11-13; granted 2002-08-13; anticipated expiration 2018-11-13 ("Expired – Lifetime").
• Litigation footprint of the same owner: Hanger Solutions asserted a different set of patents — US 6,119,171; US 6,430,623; US 6,609,159; US 6,772,227; US 6,868,160 — in cases including Hanger Solutions, LLC v. Extreme Networks, Inc., No. 1:21-cv-00040 (D. Del., filed 2021-01-14, voluntarily dismissed 2021-04-09) and Hanger Solutions LLC v. Cequel Communications, LLC, No. 6:22-cv-00330 (W.D. Tex., filed 2022-03-29, stayed then contemplated dismissal). Those cases were stayed/extended and largely resolved without PTAB involvement.
• Do not conflate US 6,430,623 with US 6,434,535. The numbers are adjacent and both are Iomega-lineage patents asserted in the same Hanger campaigns. Everything I found about PTAB-adjacent activity traces to 6,430,623, not to the patent at issue here. Treat any citation to a 6,430,623 CBM/IPR as concerning a different patent.

Strategic summary

Claim status: entirely UNTESTED. No claim of US 6,434,535 has been canceled, confirmed, or construed by the PTAB. If you are mapping claim charts, you are working from the issued claims as written, and the only binding construction you will see is whatever the district court adopts. The specification's key claim-differentiating concepts — tying content to a media unique identifier read from a predetermined track, and the compound key built by XOR of the serial number with byte-interleaved vendor/user information (CK = S XOR (V interleaved U)) — are exactly the kind of "generic computer + conventional network" limitations that have been vulnerable in § 101 and § 103 challenges elsewhere, but that is a litigation theory, not a PTAB result.

Estoppel landscape: there is none. 35 U.S.C. § 315(e)(2) estoppel only arises from a petition that reaches a Final Written Decision. With zero proceedings, there are no estoppel bars on any petitioner or privy, and every prior-art ground remains fully available — § 102(a)/(b)/(g) and § 103(a) under pre-AIA law (the application was filed 1998-11-13, so pre-AIA §§ 102/103 govern, including the pre-AIA on-sale/public-use bars and the § 102(b) one-year critical date of 1997-11-13). Practically, that is the one real gift here: no adversary has burned art.

Pattern signals: no aggregator, no serial PTAB challenger. I found no indication that Unified Patents or any defensive aggregator has touched this patent, and no repeat petitioner. Hanger's own playbook in the related cases was to file, obtain stays or extensions, and dismiss — a cost-of-defense model, not a trial-tested model. Conversely, there is no evidence Hanger has ever had to defend a claim in an AIA trial, so it has no PTAB track record on this family either way.

The dominant fact is expiration, not PTAB. The patent expired 2018-11-13. Under 35 U.S.C. § 286, damages are limited to infringement within six years before suit (subject to the notice provisions of § 287), so you are negotiating over a closed historical window, not prospective injunctive relief. That also explains the empty PTAB docket: post-expiration IPRs are generally poor value, and PGR/CBM routes are gone (PGR window closed ~2003; CBM review sunset for new petitions on 2020-09-16, and the patent expired in any event).

Recommended next steps

1. Treat the demand letter as a backwards-looking damages demand. Confirm whether the accuser points to pre-2018-11-13 conduct. If all accused conduct postdates expiration, the § 286 window and § 271(a) "during the term" requirement are dispositive. Ask for the accused-act proof of pre-expiration infringement before spending on invalidity.
2. Because there is no FWD to cite, build the invalidity case in-house. The best PTAB-adjacent assets you can use are the prosecution history and the pre-AIA art already cited in the Iomega/IV family. Do not import claim-level conclusions from any 6,430,623 or 6,119,171 CBM/IPR — different patents, no preclusive or issue-preclusive effect on 6,434,535.
3. Screen for a § 101/Alice and § 112 written-description attack at the claim-construction stage. The "compound key" and "unique identifier from a predetermined track" limitations are the natural battleground — narrow constructions there are your best non-invalidity defense, since Iomega Ready-style API-derived serial numbers are read "from a predetermined track" (SCSI 0x06 Non-Sense, Disk Status Page 0x02, offset bytes 20–59 per the spec).
4. Verification step I could not complete: I was unable to run an exhaustive PTAB E2E / Docket Alarm party-name sweep before hitting my search limit. Before relying on "no PTAB activity," run a name-based search in PTAB E2E and Docket Alarm for "Hanger Solutions," "Xylon LLC," "Bozak Investments," and "Intellectual Ventures Assets 161," plus a patent-number search on 6,434,535. Party-name searches catch proceedings the ODP patent-keyed ingest can miss.

Citations: Patent record — https://patents.google.com/patent/[US6434535B1](/patent/US6434535B1)/en. Related litigation — https://dockets.justia.com/docket/delaware/dedce/1:2021cv00040/74292 and https://dockets.justia.com/docket/texas/txwdce/6:2022cv00330/[1167358](/patent/1167358). PTAB E2E (for the verification sweep) — https://ptab.uspto.gov/.

I'll start by pulling the assignment and litigation records from multiple sources.

Now let me pull the specific assignment records and check whether this patent itself was asserted.

Ownership chain — US 6,434,535 B1

Patent: "System for prepayment of electronic content using removable media and for prevention of unauthorized copying of same"
App. 09/191,976 · filed 1998‑11‑13 · issued 2002‑08‑13 · term expired 2018‑11‑13
Source of record used here: Google Patents legal‑events panel for US6434535B1, cross‑checked against RPX / Mondaq / court dockets and PlainSite assignment records.

Evidentiary caveat up front: the Assignment Center / assignment.uspto.gov record pages did not return in my retrievals, so reel/frame numbers, executed‑vs‑recorded dates, and the correspondent of record for each of this patent's four assignments are NOT verified. I have deliberately left those fields marked "not retrieved" rather than guessing. Everything else below is grounded in the record I did retrieve. Reel/frame must be pulled from Assignment Center before this analysis is used for anything adversarial.

Inventors

Pattern notes. No unusual inventor‑departure signal is determinable. Both inventors assigned to the same operating employer (Iomega) and the assignment was filed roughly eight months after filing, which is ordinary corporate practice, not a fire‑sale tell. I found no evidence that either inventor left Iomega within 12 months of filing — I simply cannot date their departures from the sources retrieved, and I am not going to infer it. This is unclear / not determinable, not "not present."

Original assignee

Iomega Corporation (Roy, Utah) — assignee on the issued patent.

• Product embodying the claims: I have no evidence that Iomega ever shipped a commercial product practicing the claimed prepaid‑content system. The spec is written around Iomega's own hardware (ZIP® drive, ZIP® disks, the Iomega Ready API, the "Iomega store web server," and Iomega Prepaid Media "IPM" files), which shows the system was built out at least to an internal/pilot stage. But the claim is directed to the prepaid download and tracking architecture, and there is no evidence in the record of a shipping Iomega prepaid‑media product. The company's actual revenue product was ZIP drives and ZIP disks.
• Primary line of business: removable magnetic storage — ZIP® drives and disks, later also Jaz, Click, and CD/DVD writers. Iomega was a publicly traded US company (NYSE: IOM).
• Current status: not an operating company today. My understanding is that Iomega was acquired by EMC Corporation (2008) and the brand was subsequently divested to Lenovo (2013) — I am confident on the EMC acquisition and less confident on the exact Lenovo date, so treat the Lenovo leg as needing verification from SEC filings. Note the sequencing point: this patent left Iomega in 2006, two years before the EMC deal, so the EMC/Lenovo events are not the cause of the transfer and are not a "bankruptcy fire‑sale" analogue.

Assignment timeline

Reel/frame and correspondent fields below are unverified. The dates shown are the reassignment dates surfaced by Google Patents' legal‑events panel; on Google's data these are typically recording dates, not execution dates.

• Executed: not retrieved / recorded 1999‑07‑13 — Reel not retrieved/NNNN

  • Conveyance: Assignment of Assignors' Interest
  • Assignor: Michael S. Kupka; Michael G. Lundgren (individually)
  • Assignee: Iomega Corporation
  • Correspondent: not retrieved
  • Context: Standard inventor‑to‑employer assignment perfecting the original corporate ownership.

• Executed: not retrieved / recorded 2006‑11‑02 — Reel not retrieved/NNNN

  • Conveyance: Assignment of Assignors' Interest
  • Assignor: Iomega Corporation
  • Assignee: Bozak Investments, LLC
  • Correspondent: not retrieved
  • Context: Portfolio divestiture by an operating company to a non‑operating holding LLC — the pivotal link that removes the patent from the operating side.

• Executed: not retrieved / recorded 2015‑08‑04 — Reel not retrieved/NNNN

  • Conveyance: Merger
  • Assignor: Bozak Investments LLC
  • Assignee: Xylon LLC
  • Correspondent: not retrieved
  • Context: Internal reorg/consolidation — the merger‑type conveyance is itself the evidence that Bozak Investments LLC was a constituent entity inside the Intellectual Ventures holding structure that was merged into Xylon LLC.
  • Related‑patent data point (not this patent's record): PlainSite shows a different Xylon LLC merger assignment, Assignment 63264/507 (executed 2015‑08‑13, recorded 2023‑04‑05, assignor Intellectual Ventures Holding 35 LLC → Xylon LLC, address 2215‑B Renaissance Drive, Suite 5, Las Vegas, NV 89119), with correspondent Sterne Kessler Goldstein & Fox, PLLC, 1100 New York Avenue NW, Washington, DC 20005. Cite this only as an indication of who ran Xylon filings generally — do not attribute it to this patent's reel/frame without pulling the actual record.

• Executed c. Dec 2019 / recorded 2020‑01‑05 — Reel not retrieved/NNNN

  • Conveyance: Assignment of Assignors' Interest
  • Assignor: Intellectual Ventures Assets 161 LLC
  • Assignee: Hanger Solutions, LLC
  • Correspondent: not retrieved
  • Context: Bulk transfer‑to‑asserter — Hanger Solutions is a Georgia litigation vehicle affiliated with IP Investments Group LLC / Brainbox Innovations LLC that took thousands of IV assets in late 2019 and has filed multiple infringement campaigns since.

Recorded gap you should chase at Assignment Center. The 2015 link lands on Xylon LLC, but the 2020 link's assignor is Intellectual Ventures Assets 161 LLC, not Xylon. There is therefore an intermediate Xylon → IV Assets 161 LLC conveyance that the Google legal‑events panel does not display. That intermediate link is a classic IV "shuffle into a numbered asset LLC" step (cf. Xylon LLC → Intellectual Ventures Assets 75 LLC, Assignment 45305/268, executed 2018‑03‑07, recorded 2018‑03‑21, assignee address 251 Little Falls Drive, Wilmington, DE 19808 — a mass‑registration agent address). Get it from Assignment Center; it will likely add a 2018–2019 entry to this timeline.

No security agreement, license, release, correction, or change‑of‑name recording appears in this chain on the retrieved record. I found no recorded security interest.

Timeline diagram

timeline
    title Ownership of US 6434535
    1998 : Filed by Kupka and Lundgren
         : Rights assigned to Iomega Corp
    2002 : Patent issues as US 6434535
    2006 : Assigned to Bozak Investments LLC
    2015 : Merged into Xylon LLC
    2018 : Patent term ends
    2019 : IV Assets 161 assigns to Hanger
    2020 : Hanger assignment recorded

NPE / troll‑pattern signals

1. Shell‑entity transfer — PRESENT.
The chain leaves an operating company and never returns: Iomega Corporation (operating, ZIP drives) → Bozak Investments, LLC (recorded 2006‑11‑02) → Xylon LLC (recorded 2015‑08‑04, by merger) → Intellectual Ventures Assets 161 LLC → Hanger Solutions, LLC (recorded 2020‑01‑05). Every post‑2006 holder is a licensing/litigation vehicle: Xylon LLC is IV's holding company, and the merger‑type conveyance of Bozak into Xylon places Bozak inside that same structure. Corroborating address evidence from the same family (not this patent's reel): Intellectual Ventures Assets 75 LLC, 251 Little Falls Drive, Wilmington, DE 19808 (Assignment 45305/268) — a bulk registered‑agent address. Hanger Solutions' Rule 7.1 corporate disclosure identifies its parent as Brainbox Innovations LLC, and its only visible activity is patent litigation. Caveat: I could not retrieve the address of record for Bozak Investments LLC itself.

2. Known asserter in the chain — PRESENT.
Intellectual Ventures is on the enumerated NPE list and occupies two links (Xylon LLC, 2015; IV Assets 161 LLC, 2019/2020). The terminal holder, Hanger Solutions, LLC, is a high‑frequency plaintiff surfaced by RPX: at least Hanger Solutions v. Extreme Networks (D. Del. 1:21‑cv‑00040, filed 2021‑01‑14), v. Squarespace (D. Del. 1:21‑cv‑00774), v. Charter Communications (W.D. Tex. 6:22‑cv‑00070, filed 2022‑01‑18, voluntarily dismissed 2022‑06‑10), v. Cequel Communications/Altice (W.D. Tex. 6:22‑cv‑00330, filed 2022‑03‑29), v. Mediacom (M.D. Ga. 4:22‑cv‑00152, filed 2022‑09‑28). RPX describes Hanger as an IP Investments Group LLC NPE that received thousands of IV assets in late 2019 and has both litigated directly and passed assets to other NPEs (Kioba Processing, 21st Century Garage, and entities of Equitable IP Corporation). Important: none of those campaigns asserted US 6,434,535.

3. Repeat correspondent across the chain — UNCLEAR (data not retrieved).
This is the signal the brief flags as the highest‑value tell, and it is precisely the data I could not obtain: no correspondent of record was retrieved for any of the four recordings on this patent. I therefore cannot say whether one attorney/firm ran the Bozak, Xylon, IV Assets 161, and Hanger filings. The one correspondent I did see — Sterne Kessler Goldstein & Fox, PLLC (1100 New York Avenue NW, Washington, DC 20005), on IV Holding 35 LLC → Xylon LLC, Assignment 63264/507 — is a different patent and a different link, so it is at most a lead, not a finding. Action item: pull all four correspondent blocks from Assignment Center. If Sterne Kessler (or a single IV‑regular firm) recurs across them, this flips to PRESENT and is a strong recurrence finding, since these are four facially unrelated LLC names.

4. Cascading transfers — NOT PRESENT (for this patent).
The links are 2006 → 2015 → 2019/2020: nine and four‑plus years apart, with no <24‑month run of chained LLC‑to‑LLC hops on this asset. The IV "Assets NNN LLC" shuffling is real and prolific across the IV portfolio, but on this patent's own chronology it does not present as cascading. (The 2006→2015 gap also means there is no evidence the 2015 merger was staged for this asset.)

5. Pre‑litigation transfer — NOT PRESENT.
Not only did I find no infringement suit naming US 6,434,535, the timing forecloses one: the patent's term expired 2018‑11‑13 per Google's legal events, and the Hanger Solutions assignment was executed c. December 2019 / recorded 2020‑01‑05 — i.e., Hanger took title to an already‑expired patent. The 2020 link reads as a bulk‑portfolio conveyance, not an assertion‑enabling transfer.
Numbering trap worth flagging: US 6,430,623 — a different patent (sole inventor Hasan S. Alkhatib; originally IP Dynamics; assigned to IV 2008) that Hanger Solutions did assert against Extreme Networks and others — is one digit‑transposition away from 6,434,535. Any "Hanger asserted '535" hit is almost certainly a conflation of these two. Do not carry that error into a claim chart or a diligence memo.

6. Bankruptcy fire‑sale — NOT PRESENT.
No evidence Iomega filed Chapter 7/11, and no evidence this patent was sold in a bankruptcy proceeding. The 2006 departure predates Iomega's EMC acquisition and is a straight corporate divestiture, not an estate sale.

7. Privateering — UNCLEAR.
Iomega transferred to Bozak Investments LLC (recorded 2006‑11‑02) two years before EMC acquired Iomega, and the next link runs into the IV structure. That shape is consistent with an operating company handing patents to a monetization vehicle, but I retrieved no SEC 10‑K/8‑K disclosure from Iomega documenting the sale, and no Patent Progress / EFF coverage naming this patent. Without that documentary link, calling it privateering would be speculation. Marked unclear.

8. Defensive aggregator — NOT PRESENT.
The chain terminates at Hanger Solutions, LLC, an asserting NPE — the inverse of the RPX/AST/LOT/Unified/OIN endpoint. The patent was not neutralized; it simply ran out of term while parked in the IV structure.

Verdict

NPE — high confidence.

Two strong signals are documented on the record: (a) shell‑entity transfer — Iomega Corporation (2006‑11‑02) → Bozak Investments, LLC → Xylon LLC by merger (2015‑08‑04) → Intellectual Ventures Assets 161 LLC → Hanger Solutions, LLC (2020‑01‑05), an unbroken run of non‑operating vehicles; and (b) known asserter in the chain — Intellectual Ventures occupies the 2015 and 2019/2020 links, and the terminal holder Hanger Solutions is an RPX‑documented serial plaintiff affiliated with IP Investments Group / Brainbox Innovations LLC. The caveats are material and should travel with the verdict: the correspondent of record was not retrieved for any recording (so the highest‑value recurrence test is unresolved), an intermediate Xylon → IV Assets 161 LLC conveyance is missing from the retrieved event list, and US 6,434,535 itself was never asserted in any case I could find — it expired 2018‑11‑13, before Hanger even acquired it, so this is an ownership‑chain characterization rather than an active campaign.

Verify at: https://assignmentcenter.uspto.gov/ (search patent number 6,434,535) — pull reel/frame, executed‑vs‑recorded dates, and all four correspondent blocks. Also cross‑check USPTO Patent Center for the patent's maintenance‑fee history to confirm the 2018‑11‑13 full‑term expiry.

I'll pull the citation records for US 6,434,535 B1 from USPTO/Google Patents and other patent databases.

Let me get the specific "References Cited" list from the patent record.

I need the "References Cited" appearing on the face of US 6,434,535 itself. Let me query several patent databases.

I hit the tool-call limit mid-search, so let me give you what I verified, clearly separated from what I could not verify — because for this task the distinction is decisive.

Prior-art / citation analysis — US 6,434,535 B1

(Kupka & Lundgren, Iomega Corp., app. 09/191,976, filed & priority 1998-11-13, granted 2002-08-13. Building on the earlier bibliographic section; not repeating it.)

0. A threshold point that changes the whole answer: "citations" runs two directions

Because 6,434,535 was filed in 1998, pre-AIA § 102 governs: § 102(a) (known/used/patented/published before invention), § 102(b) (patented or published more than one year before 1998-11-13, i.e., before 1997-11-13 — statutory bar), and § 102(e) (earlier-filed U.S. application by another). Anticipation requires every element of a claim in a single reference. Anything issued after 1998-11-13 in my tables below is therefore not § 102 art against this patent.

1. Verified citation data I actually retrieved

Table A — Forward citations of US 6,434,535 B1 (verified in this session; NOT § 102 art)

Sources: Google Patents US6434535B1; US 6,748,539 (Google Patents); US 2002/0087870 (Google Patents); US 10,860,290 (Justia); GB 2536449 A search report (PDF).

Table B — Citation list of US 6,748,539 B1 (a forward citer), retrieved for field context only. These are its citations, not 6,434,535's — I am not attributing them to 6,434,535:

US 4,694,491 A; US 5,345,505 A; US 5,592,552 A; US 5,734,719 A; US 5,636,276 A; US 6,020,883 A; US 5,910,987 A; US 5,754,648 A; US 6,061,451 A; US 2001/0032088 A1; US 6,434,535 B1; JP 2002-150056 A. (source)

2. What I could NOT verify — and I will not paper over it

I was unable to retrieve the front-page "(56) References Cited" list of US 6,434,535 B1 itself. My searches returned forward-citation lists and third-party search reports, not the applicant-cited art. Concretely, I could not verify which prior-art patents the applicant/examiner listed on its face, their numbers, or their dates.

Per the operating rule against fabrication, I am not going to invent a (56) list. The entries that many analyses would expect to see in this field (Freeny, Hirsch, Stefik/Xerox, Payne/Open Market, Hellman, Shear, etc.) are given below only as field-context candidates with explicit confidence labels — not as confirmed citations of 6,434,535.

3. § 102 mapping — candidate prior art by claim family

Recall the four independent-claim families reconstructed in the earlier section (claim numbers still unverified):

• F1 — Method: prepaid media distribution (serial-tied content + prepaid stored value + tracking-server balance + encrypted delivery)
• F2 — Method: compound key (serial ⊕ vendor ⊕ user)
• F3 — System: vendor server + client app + media tracking server
• F4 — Media tracking server per se (manufacturer supplies serial + prepaid amount; vendor queries balance)

Key analytical point for whoever finalizes this: the novelty of 6,434,535 sits almost entirely in the combination — (i) prepaid stored value on removable media settled by a tracking server, and (ii) content delivered encrypted with that media's unique serial number so it is unreadable from any other medium. The individual components (point-of-sale reproduction, network payment, rights management, prepaid account servers) were all pre-1998. So expect § 102 exposure to be claim-family-specific (especially F4 and the payment sub-claims), with § 103 as the more realistic attack surface for F1/F3.

4. Carry-forward caution: number confusion (per the strict-literal rule)

• US 6,434,535 ≠ US 6,430,623. The Hanger Solutions, LLC-branded suits that surfaced in the prior section asserted 6,430,623, 6,609,159, 6,772,227, 6,119,171, 6,098,098, and 6,868,160 — none of which is 6,434,535. Do not merge these numbers.
• Likewise, Table B entries belong to US 6,748,539, not to 6,434,535.
• The GB 2 536 449 A "X" citation treats US6434535 B1 as prior art against that application — a forward use, not art against 6,434,535.

5. To close the verified gap (authoritative sources)

I could not reach these within the tool budget; they are the right places for the exact (56) list:

1. USPTO Patent Public Search / Patent Center — patent number 6434535, "References Cited" (the issued-PDF front page and Form PTO/SB/08).
2. Espacenet — "Cited documents" tab for US6434535B1.
3. The issued patent PDF on Google Patents — front page (56) list (the HTML rendering I fetched was truncated and omitted it).

Bottom line

• Verified: 6,434,535 is Iomega's Kupka/Lundgren prepaid-removable-media DRM patent; it is cited by US 6,748,539, US 2002/0087870, US 10,860,290, and (as "X" art) GB 2 536 449 A. None of those can anticipate it — they post-date the 1998-11-13 filing.
• Not verified: the actual front-page references cited on 6,434,535 — and therefore the only references that can support a § 102 count. An honest § 102 chart requires that list; I have flagged it rather than guessed it.
• Best-supported § 102 exposure (subject to confirmation): the media-tracking-server-per-se claim family (F4) against pre-1998 prepaid/stored-value account-server art, and the basic method family (F1) against point-of-sale reproduction art (Hirsch, Freeny).

I need the actual cited prior art for this patent. The full text I was given includes "Prior art keywords" but not the front-page reference list, so let me pull it from the record and related sources.

Let me get the rest of the cited reference list (page 2 of the front matter) and confirm a few key references.

Preliminary note on the prior-art record (read this first)

The material you supplied as "the results from the Prior Art section of this page" contains only the Google Patents "Prior art keywords" string (media; electronic content; piece; unique identifier; recited) — it does not contain the actual front-page reference list, and the fetched full text was truncated before the numbered claims. To do a § 103 analysis I therefore had to retrieve the cited references myself. Two important corrections/additions to the earlier sections:

1. I recovered verbatim claim 1 (the earlier Litigation/Summary sections flagged that they could not). From the Indiana University Virtual Docket Library rendering of the issued patent: US 6,434,535 B1, Int. Cl. G06F 17/00, U.S. Cl. 705–24, 38 claims. Claim 1 reads (verbatim, emphasis added):

"1. A method of distributing electronic content from a vendor server to a client device via a network infrastructure which includes a Transmission Control Protocol/Internet Protocol Network and for payment to a vendor of the electronic content, said method utilizing a permanent unique identifier stored on a piece of destination media on which the electronic content is to be stored to associate the electronic content with only said piece of media and utilizing a predetermined value stored on said piece of media as payment for the electronic content, said method comprising: contacting the vendor server via the network infrastructure; transmitting said unique identifier of said piece of destination media to the vendor server; communicating, via said network infrastructure information from said vendor server to media tracking server to determine if said unique identifier is valid and to determine a remaining balance of said predetermined value of said piece of media; encrypting said electronic content into an encrypted format having said unique identifier as a key; communicating, via the network infrastructure, said encrypted format of said electronic content to said piece of media; and writing the electronic content to said piece of media in accordance with said unique identifier such that the electronic content may be accessed for use from only said piece of media having said unique identifier."
— Indiana University Virtual Docket Library, US 6,434,535

1. The front-page (56) reference list I could retrieve (the list was truncated mid-way in the OCR at "5,715,313," so this is a partial but verified set) includes: US 4,977,594 Shear; 5,010,571 Katznelson; 5,050,213 Shear; 5,058,162 Santon et al.; 5,291,598 Grundy; 5,319,705 Haller et al.; 5,379,433 Yamagishi; 5,400,319 Fite et al.; 5,450,489 Ostrover et al.; 5,469,564 Junga; 5,479,510 Olsen et al.; 5,490,216 Richardson III; 5,533,125 Bensimon et al.; 5,555,304 Hasebe et al.; 5,563,946 Cooper et al.; 5,590,197 Chen et al.; 5,629,980 Stefik et al.; 5,634,012 Stefik et al.; 5,638,443 Stefik et al.; 5,682,428 Johnson; and (as foreign art) EP 0 302 710; EP 0 561 685; EP 0 665 486; EP 0 679 980; WO 96/35158; WO 97/14067; WO 97/29416; WO 98/02793; WO 98/43398.

— US006434535B1 front page (Google Patents PDF)

Confidence note: the reference numbers and dates below for the front-page citations are read from the OCR of that front page and are reliable; the substance I attribute to each reference (e.g., that Stefik '980 is a Xerox "digital works repository" patent) is from my own knowledge of those references and secondary sources, and where I am inferring rather than quoting I say so. This is an analyst's obviousness opinion, not a clearance or validity opinion.

1. The invention, reduced to an element list

Claim 1 (and the parallel independent claims — the system claim, the compound-key method claim, and the media-tracking-server claim) can be decomposed into five technical elements:

The key insight for § 103: each of A–E was, by November 1998, an independently known technique; the patent is a combination invention.

2. Person of ordinary skill in the art (POSITA)

For a FY1998 priority date, the POSITA would have had a bachelor's degree in EE/CS (or equivalent) plus ~2 years in digital-content security, DRM, and/or network commerce, and would have been familiar with: (i) network payment protocols and HTTP/CGI forms (Open Market, CyberCash, First Virtual were live commercial products); (ii) software copy-protection using media/device serial numbers; (iii) symmetric ciphers and key-derivation from identifiers; and (iv) prepaid stored-value cards (telecom, transit, vending). This is consonant with how the PTAB/parties framed the analogous art in the contemporaneous DRM cases. (USPTO — Apple & Google v. Contentguard briefing, POSITA discussion)

3. What each prior-art reference supplies

Note on Ginter: US 5,892,900 granted after the '535 filing date, but because its application was filed 1996-08-30 (before 1998-11-13) it qualifies as prior art under pre-AIA § 102(e). I flag that it does not appear in the partial (56) list I retrieved, so I cannot confirm it was cited during '535's prosecution. Treat its use as examiner-reachable art rather than confirmed-of-record art.

4. The obviousness case (35 U.S.C. § 103)

4.1 Primary rejection: Stefik '980/'012 + Lang '611 + Olsen '510 (or Chen '197) + Payne '314

Applied to claim 1:

• A / "contacting the vendor server… TCP/IP" — Payne '314 expressly teaches a network sales system in which a purchaser's computer contacts a vendor server and orders goods over a network; Stefik '980 teaches the content-server half.
• B / "payment to a vendor" from "a predetermined value stored on said piece of media," debited via a tracking server — Chen '197 (electronic/stored-value payment) and Olsen '510 (prepaid token decremented per transaction) supply prepaid stored value as the payment medium; Stefik '012 supplies the central fee-accounting authority (the "media tracking server").
• C / "permanent unique identifier stored on the media" binding content to that media — Shear '594 and Richardson '216 teach exactly this binding pattern for software on physical media.
• D / "encrypting said electronic content … having said unique identifier as a key" — Lang '611 teaches encrypting material on storage media so that it is usable only via the correct medium/key.
• E — not present in claim 1.

Motivation to combine (KSR / "known problem, known solution"):

1. The patent itself states the problem to be solved — "a limitation in credit card transactions is that small transactions (e.g., those less than a dollar) are not efficient due to fees charged … by the credit card issuers," and "many buyers are concerned about transmitting credit card information over the Internet." Stefik/Chen/Olsen directly solve that stated problem by replacing per-transaction card authorization with a pre-decremented stored value. Where the specification identifies the problem, the art that solves it is combinable. (KSR Int'l v. Teleflex, 550 U.S. 398 (2007).)
2. All references are in the same field of endeavor (digital-content distribution + rights/payment), so they are analogous art.
3. The "unique media identifier as the encryption key" step is a known, predictable use of an identifier the media already carries for copy-protection (Shear; Lang). Substituting "the encryption key is the media's existing serial number" for Lang's user/system key is a predictable substitution of one known identifier for another, with the predictable result that the file opens only on that medium.
4. A central server that tracks balances per identifier is the natural, predictable extension of Stefik's fee-reporting repository and Richardson's remote license server. Nothing in the combination changes the principle of operation of any reference.

4.2 Secondary rejection of the media-tracking-server independent claim (family 4)

That claim is essentially: processor + database + network interface; maintains a per-identifier balance; receives the identifier/prepaid value from a manufacturer; receives a balance-check request from a vendor server; debits the balance and credits the vendor.

• Stefik '012 (fee reporting / accounting authority) + Richardson '216 (central licensing server keyed to an identifier) + Chen '197/Olsen '510 (stored value) disclose every functional limitation. "Maintains a balance in a database" is ordinary database programming; the manufacturer pre-loading the value is the well-known prepaid-card issuance model (carrier/value issuer loads the balance). The motivation is again the patent's own stated goal: enable small, anonymous purchases without card fees.

4.3 Secondary rejection of the compound-key family

Claim scope (per the Specification) requires key = f(S, V, U), e.g. CK = S XOR (V interleaved U).

• D (media-ID key) comes from Lang '611 / Shear.
• Adding a vendor/application identifier and a user credential to the key is a routine key-derivation: Ginter '900 expressly describes keying content access to both an appliance/user identity and a content-provider/clearinghouse identity in a rights-management system; Richardson '216 ties licenses to specific users/machines.
• The specific arithmetic (S XOR (V interleaved U)) is a predictable mathematical combination of known identifiers, producing only the expected result (three-way binding). Under KSR and In re KSR-style reasoning, a claim to a particular mixing function that yields no unexpected property is not patentably distinct from the obvious combination of the underlying identifiers.

4.4 Why the "browser metatag launches a client program" sub-limitation does not save the claim

The Content-Type: application/x-ipm → download-and-execute-a-helper-program mechanism is the standard MIME/content-type handler behavior that Netscape Navigator/Internet Explorer supported in the period, and Payne '314's network-sales flow uses the browser/vendor-server interaction. Using a registered MIME type to invoke a downloader is routine implementation detail, not an inventive contribution. (This maps to dependent-claim scope, not to claim 1, so it does not affect the § 103 result for the independent claim.)

5. Secondary considerations — likely unavailing, but note the vulnerabilities

• Long-felt need / failure of others: the patent's own background describes decades of failed copy-protection (hardware dongles, master floppy, special-format CDs). A patentee could argue the industry long sought and failed to achieve content that is both portable and non-copyable, and that '535 achieved it. This is the strongest non-obviousness argument, but it is undercut because '535's claimed mechanism (bind to the media's own ID + encrypt with that ID) is precisely the art (Shear/Lang/Richardson) that the background dismisses as "limited success."
• Commercial success: I found no evidence of a commercialized Iomega "prepaid ZIP" product reading on the claims; the record shows only litigation/licensing by successor NPEs. If no nexus, this factor drops out.
• Unexpected results: the patent claims none.

6. Bottom line

• The strongest § 103 combination is Stefik '980/'012 (and '443) in view of Lang '611, further in view of Olsen '510 or Chen '197, and further in view of Payne '314 — which discloses every element of claim 1 and provides an express motivation (small-transaction efficiency + buyer privacy) drawn from the patent's own admitted problem.
• The media-tracking-server claim falls to Stefik '012 + Richardson '216 + Chen '197/Olsen '510.
• The compound-key claims fall to Lang '611/Shear (media-ID key) + Ginter '900 or Richardson '216 (user/vendor identifiers added to the key), with the specific XOR/interleave being a predictable arithmetic combination.
• My overall view: claim 1 and the system/server independent claims would have been obvious under § 103; the compound-key claims are closer but still likely obvious because the additional "vendor ID + user ID" inputs and their combination function were known key-derivation techniques yielding only predictable results.

Caveats (stated explicitly, per your rules):

1. The (56) reference list I retrieved is partial (OCR truncated at 5,715,313); I cannot confirm whether Ginter '900 or Payne '314 appear on '535's face, so those two should be treated as available-to-an-examiner art, not cited art.
2. I could not retrieve the full verbatim text of independent claims 2–4 (compound-key method, system, tracking server); the claim-4 and compound-key analyses rest on the Specification's Summary/Definitions language, which tracks claim language closely but is not a substitute for claim text.
3. Reference dates/numbers for front-page citations are from OCR and are reliable; substantive characterizations of some references (e.g., exact scope of Chen '197, Olsen '510, Haller '705) are from my knowledge and secondary sources and should be verified against the documents themselves before use in any filing.
4. No IPR/PGR/CBM or district-court invalidity ruling on '535 was found (consistent with the earlier Litigation section), so there is no adjudicated validity determination to rely on either way.