US 4316055

I'll search for authoritative information on US patent 4316055, including any litigation/docket references.

Let me check for any litigation or Federal Circuit docket activity involving this patent.

US Patent 4,316,055 (as identified in the query: "4316055")

Verification note (literal ID handling): The identifier 4316055 maps to US 4,316,055 A. It should not be confused with a Soviet application number 4316055/2о33 that appears in an unrelated 1987 USSR inventor's certificate for a fiber-bundle cutting device (poleznayamodel.ru) — that is a different jurisdiction, different subject matter, and not a US patent. The US patent is discussed below.

Bibliographic data

Source: Google Patents, https://patents.google.com/patent/US4316055/en (fetched 2026‑09‑24); uspto.report/patent/grant/4316055.

Abstract (verbatim)

"The system disclosed comprises a dual function cryptographic system capable of operating in either a stream or block cipher mode. Further, with minimal alteration the system is capable of performing either encoding or decoding functions. The system requires three inputs, the first of which is the raw data, and the second two inputs comprise a first and a second unique user supplied key. One of the keys is utilized to control a permutation function for both the stream and block cipher mode and the other key is combined directly with the data in the block cipher mode prior to a series of non-linear transformations. In the stream encipherment mode of operation the second key is entered in its entirety into the system where it is successively and continuously transformed as a function of said first key whereby the function of said system becomes a pseudo-random number generator whose output is serially combined with the raw data to form the stream enciphered cryptogram."

Plain-language overview of the independent claims

The patent has 14 claims total, of which two are independent: claim 1 and claim 11. (All other claims depend from one of these.)

Claim 1 — the broad "dual-mode crypto engine" claim.
A key-controlled cryptographic system that can be switched between stream and block operation on incoming data. It must include:

• a store for a user-supplied key;
• a means to enter the data set into the system;
• a "main reconfiguration means" implemented as a shift register, whose input is a function of the user key (i.e., the register is loaded/seeded using the key);
• a transformation element wired to the shift register that cryptographically transforms data already in the register;
• control means that cause the transformation element to run consecutive transformations for a predetermined number of cycles; and
• selection means that let the system output either the full contents of the register as a complete transformed data block (block mode) or a pseudo-random number stream that is combined serially with the incoming data using an inverse mathematical function (stream mode).

In substance: one piece of hardware (the loading register + transformation element + iteration loop) is reused either as a block cipher or as a key-stream generator, chosen by a mode control.

Claim 11 — the narrower "two-key, non-affine + keyed-permutation" claim.
Also a key-controlled system selectable between stream and block mode, but with more specific structure:

• accepts and stores two user-supplied binary keys;
• data enters in stream or block form depending on mode;
• the main reconfiguration means is a shift register loaded with data that is a function of one of the keys;
• the transformation element extracts data from a source field of the register, applies a non-affine transformation (in the spec, a substitution/mapping table), and returns the result to a destination field through a permutation means controlled by the other key;
• the transformation is actuated each time the shift register is shifted one bit position; and
• the output is selectively used as a full transformed block (block mode) or as a pseudo-random stream cryptographically combined with the input data (stream mode).

Dependent claims (context): Claims 2–10 build on claim 1 — a transformation element that extracts from one portion and returns transformed data to a second location, combined there by a linear (modulo‑2) operation (cl. 2–3); substitution device as a data-dependent mapping table (cl. 4); keyed permutation/transposition (cl. 5); two-key storage and split control of loading vs. permutation (cl. 6); circular shifting with one bit tapped per shift to form the pseudo-random stream (cl. 7); a modulo‑2 adder mixing that stream with the data (cl. 8); block-mode initial loading and a set number of transformation cycles (cl. 9–10). Claims 12–14 build on claim 11 — modulo‑2 combination of the destination-field contents with the permutation output (cl. 12); stream-mode single-bit output mixed via modulo‑2 adder with identical encrypt/decrypt operation (cl. 13); and block-mode specifics, including encryption loading the register with the modulo‑2 sum of input data and one key, while decryption loads the ciphertext directly and adds the key as the final modulo‑2 step (cl. 14).

Litigation / CAFC 2026 docket check

• I searched for U.S. litigation and Federal Circuit activity tied to 4,316,055 / 4316055. No CAFC 2026 docket entry, district-court case, or appeal involving this patent was found. Searches of general web and patent-citation sources returned only technical citation material (e.g., the EPO search report for EP 1 292 067 cites "US 4 316 055 A (FEISTEL) 16 Feb 1982" as category X against claims 1, 9, 10, and the search report for EP 0 618 701 cites it as background art).
• Confidence caveat: I do not have direct query access to the USPTO PatentCenter/PTAB or CAFC docket systems in this session, so I cannot state definitively that no recent filing exists. However, this is strongly expected: the patent's term expired February 16, 1999 (20 years from the 1976 filing), and it is listed as "Expired – Lifetime." A 2026 CAFC appeal on this patent would therefore be anomalous, and any apparent hit should be treated as a false positive (e.g., the Soviet 4316055/2о33 application number noted above, or a similarity to the later dual-use block/stream cipher patent US 7,068,786 B1, which is a different, unrelated document).
• Uncertainty flag: If a specific 2026 docket number was expected, please supply it. Based on the evidence available, there is no authoritative record of such a proceeding, and I will not fabricate one.

Historical context

US 4,316,055 is one of the foundational Lucifer-family patents by Horst Feistel, the inventor of the "Feistel network." It pre-dates the DES standard and describes essentially the same round-function architecture (keyed substitution + keyed permutation + modulo‑2 addition over a 64‑bit shift register) but generalized so the same engine can act either as a block cipher or as a pseudo-random keystream generator for a stream cipher.

Sources: https://patents.google.com/patent/US4316055/en ; https://uspto.report/patent/grant/4316055 ; http://data.epo.org/gpi/EP0618701A3.pdf ; EP 1 292 067 A1 search report (patentimages.storage.googleapis.com).

I'll research litigation involving US Patent 4,316,055. Let me run several targeted searches.

Let me search dedicated litigation databases for this patent number.

Litigation Search Results: US Patent 4,316,055

Bottom line: No litigation is known involving US Patent 4,316,055. My searches of patent-litigation sources (Unified Patents litigation portal, CourtListener/RECAP, and general web searches keyed to the exact number) returned no district court, ITC, PTAB, or Federal Circuit proceedings in which US 4,316,055 was asserted, challenged, or otherwise at issue.

What the patent is

• Patent: US 4,316,055 — "Stream/block cipher cryptographic system"
• Inventor: Horst Feistel
• Assignee: International Business Machines Corp. (IBM)
• Filing date / priority: 1976-12-30 (App. No. 05/755,898)
• Grant date: 1982-02-16
• Status: Expired — Lifetime; anticipated expiration 1999-02-16

A patent that expired in 1999 predates the modern patent-assertion (NPE) era and the AIA post-grant review regime, which is consistent with the absence of any recorded litigation.

Negative-search caveats

1. The identifier appears in prosecution/citation contexts, not litigation. US 4,316,055 shows up as a cited prior-art reference in later patent documents — e.g., as a citation in EP 0618701 (NTT) and in WO 1998/036525 — and in an EPO search report. Being cited as prior art is not litigation and means only that examiners or applicants referenced it.
2. Do not confuse it with unrelated "431"/"605" patents that did appear in my searches. Results included matters involving a Senju/Bausch & Lomb patent referred to as the "'431 patent" (a different patent, litigated in D.N.J., C.A. Nos. 1:14-cv-00667 and 1:14-cv-03962), a Wang Laboratories "'605 patent" (SIMM case against Mitsubishi), and a Safoco "'605 patent" (Cameron litigation). None of these is US 4,316,055; I have not conflated them.
3. Coverage limits. Unified Patents' portal and CourtListener/RECAP have incomplete historical coverage (RECAP depends on PACER pulls; Unified's portal is oriented to the modern era). A pre-1999-expiring IBM patent would in any event fall well outside the periods these tools cover densely, and any 1980s–1990s litigation would likely not be digitized there. So I can say affirmatively that no litigation was found, but I cannot certify that none ever existed — only that it is absent from the sources searched.

Recommended verification if you need certainty

• CourtListener / RECAP docket search: https://www.courtlistener.com/?q=%224316055%22
• Unified Patents litigation portal: https://portal.unifiedpatents.com/litigation/caselist (search the patent number)
• USPTO Patent Public Search / Patent Assignment records and the patent's "Cited By" and "Litigation" tabs on Google Patents
• Derwent/LexisNexis/Docket Navigator for pre-2000 federal dockets not captured in free tools

If you'd like, I can attempt a more targeted search of an individual source (e.g., Docket Navigator or a specific PACER district) if you can provide access, since the public tools I reached exhausted their useful returns on this number.

PTAB / AIA Trial Landscape — US 4,316,055

Patent: US 4,316,055 — "Stream/block cipher crytographic system"
Inventor: Horst Feistel | Assignee: International Business Machines Corp.
App. No.: US05/755,898 | Filed: 1976-12-30 | Granted: 1982-02-16
Claims: 14 (independent claims 1 and 11; 2–10 depend from 1, 12–14 depend from 11)
Legal status (Google Patents / ODP): Expired – Lifetime | Anticipated expiration: 1999-02-16

Proceedings overview

The structured "PTAB proceedings on file" block returns zero AIA trial proceedings — no IPR, no PGR, no CBM has ever been instituted, instituted-and-decided, or filed against US 4,316,055 as reflected in the USPTO Open Data Portal as of the most recent ingest (breakdown: 0 active / 0 claims invalidated / 0 claims sustained / 0 settled / 0 institution denials). My independent web searches (PTAB petition PDFs indexed by PTAB E2E/PTACTS, CourtListener, Google Patents' litigation and "Cited By" records) surfaced no AIA trial petition naming this patent, and I found no Federal Circuit appeal arising from a PTAB proceeding on it. This is not a hardened-patent story and it is not a killed-patent story — it is a dead-patent story: the patent's entire term ended on 1999-02-16, roughly thirteen years before the AIA created IPR/PGR/CBM. A defendant receiving an assertion of this patent today has an absolute, dispositive defense that has nothing to do with PTAB at all: the patent has been expired for more than a quarter century and cannot be infringed.

For each proceeding

There are none to enumerate. I am deliberately not manufacturing proceeding numbers, panel rosters, or FWD dispositions, because doing so would be fabrication. The section below records what I checked and why the absence is structural rather than a reporting gap.

No proceeding on file — verification trail

• Type: N/A (no IPR / PGR / CBM)
• Filed: N/A
• Status: Per the canonical ODP block: no AIA trial proceedings returned. Plain-English gloss: never petitioned, never instituted, never decided.
• Judge panel: N/A — no panel ever assigned.
• Petition grounds: N/A — no petition. (For completeness: even if one had been filed, only IPR would have been legally available. PGR under § 321 requires a first-inventor-to-file patent with a filing date on or after 2013-03-16; this patent's 1976-12-30 effective filing date disqualifies it. CBM under § 18 of the AIA was limited to patents with at least one claim directed to a financial-services practice, and the CBM program sunset for new petitions on 2020-09-16 — neither condition is met here.)
• Institution decision: None issued.
• Final Written Decision: None issued. Consequently no claim of US 4,316,055 has ever been canceled, confirmed, or held unpatentable by the Board. All 14 claims stand exactly as granted on 1982-02-16 (subject only to routine post-issuance certificate-of-correction practice, which I could not confirm either way from the sources available to me).
• Settlement / termination: N/A.
• Appeal: None identified. I specifically looked for CAFC opinions and CourtListener dockets naming the '055 patent in a PTAB-appeal posture and found none.
• Defensive value: Not a PTAB-defense situation. The controlling defense is 35 U.S.C. § 271 + the expiration date: an expired patent supports no injunctive relief, and under 35 U.S.C. § 286 damages reach back only six years from the filing of the complaint — i.e., no earlier than 2020-09-30 for a complaint filed today (2026-09-30), which is twenty-one years after the patent's last day of enforceable term (1999-02-16). There is no window of compensable infringement.

Strategic summary

What is canceled vs. sustained vs. untested. Using the terms the Board uses: claims 1–14 are all UNTESTED. Zero claims are canceled; zero are sustained by any PTAB ruling. The patent emerged from prosecution in 1982 with a 64-bit shift-register- and key-controlled transformation architecture — substitution boxes SF0/SF1, key-controlled permutation multiplexers MPXC/MPXD, mod-2 adders 9/16/17/18, a micro-programmed sequential controller, and a stream/block mode switch — and it was never challenged in an AIA forum. The only "adjudication" of note post-issuance is negative for confidence in live assertion: the patent is cited in 133 forward citations on Google Patents, and shows up as an X-category reference against later filers (e.g., EP 1 292 067 A1, where US 4,316,055 alone is cited as X against claims 1, 9 and 10, and EP 0 618 701 A3, where it appears in the search report). That is the profile of foundational prior art, not of a patent still being enforced.

Estoppel landscape. There is none, and that is the honest answer. § 315(e)(2) estoppel only attaches to a petitioner that obtained a final written decision — no FWD exists here, so no party is estopped, and no party needs to be. Equally, there is no IPR-created "safe harbor" record of canceled claims that a defendant could point to. If a defendant wanted to invalidate this patent prophylactically (for example, because a demand letter invokes it descriptively), the full universe of prior art remains available — including the very references the patent itself distinguishes: US 3,798,359 and US 3,796,830 (Feistel/IBM product-cipher patents referenced in the Background), US 3,250,855 and US 3,364,308 (stream generators), US 3,506,783 and US 3,522,374 (key-material generation / cycle control), US 3,411,089 and US 3,188,390, and Shannon, "Communication Theory of Secrecy Systems," Bell System Technical Journal, Vol. 28, pp. 656–715 (Oct. 1949), whose product-cipher teaching the specification expressly builds on. But note the futility: an IPR on an expired patent yields no practical benefit to a defendant because there is nothing left to be liable for.

Pattern signals. None of the usual ones are present. There is no serial petitioner (no party has filed even one IPR, let alone multiple). There is no aggressive PTAB-appeal posture by the patent owner — IBM, the original assignee, never had a PTAB ruling to appeal on this patent. There is no defensive aggregator in the chain; my searches surfaced no Unified Patents, RPX, or similar involvement, and the patent's status as "Expired – Lifetime" would defeat the standing case any aggregator would need. The absence of IPRs here is fully explained by the calendar: the AIA trial regime began on 2012-09-16, more than thirteen years after this patent's term ended.

Recommended next steps

• If you are a defendant or demand-letter recipient: the disposition is expiration, not invalidation, so there is no FWD to link or quote. Your response should cite the patent's own bibliographic record — the anticipated expiration of 1999-02-16 and "Expired – Lifetime" status on the Google Patents record and the corresponding USPTO PatentCenter file for application US05/755,898. Pair that with 35 U.S.C. § 286 (six-year damages lookback) to show that no compensable infringement window can exist. If the demand letter affirmatively alleges present infringement, that is a Rule 11 exposure issue, not a licensing negotiation.
• If you are evaluating this patent as prior art (the far more likely real-world use, given the 133 forward citations): rely on the 1982-02-16 grant date and the 1976-12-30 filing date as its prior-art dates. It is a § 102(b)/§ 102(a) reference against anything filed after those dates, and its disclosure of a key-controlled substitution–permutation–mod-2 product cipher with selectable stream/block modes is broad.
• If you were expecting active proceedings: please re-verify against PTAB E2E (PTACTS) and the PTAB Decisions page before relying on this memo for a filing deadline. My conclusion of "no PTAB activity on file" rests on the ODP block supplied above plus web verification, and while I found nothing contradicting it, I could not inspect every historical paper docket from the pre-E2E era.

Caveats and confidence level. I have high confidence that no AIA trial proceeding exists on US 4,316,055 — the term expired before the AIA trial regime existed, and nothing in the ODP data or in web-accessible petition, decision, or docket material indicates otherwise. I have lower confidence on two peripheral points and flag them rather than guess: (1) whether any post-issuance certificate of correction, disclaimer, or ex parte reexamination touched the claims — these are not the kind of event reliably surfaced by the searches I ran; and (2) whether any district court litigation naming the '055 patent occurred during its 1982–1999 term. Neither would change the bottom line. I did not locate any proceeding number, judge panel, FWD, settlement, or CAFC docket for this patent, and I have not invented any.

I'll research the assignment record for US 4,316,055.

Let me try to reach the USPTO assignment records directly.

Let me check the patent front page and Google Patents legal events data.

Assignment & Ownership Reconstruction — US 4,316,055

Access limitation stated up front (important): I could not execute a working query against the USPTO Assignment Center in this session. Assignment Center (assignmentcenter.uspto.gov) is a JavaScript single-page application backed by a JSON API (.../ipas/search/api/v2/public/...) that is not exposed to ordinary web indexing; general web searches keyed to 4316055, 4,316,055, Feistel, IBM and reel frame returned only citation hits (EPO search reports, later US patents listing it as prior art) and no "Assignment Abstract of Title" for this patent. That is a failure to retrieve, not a confirmed finding of "no records." I flag the distinction because the two carry different weight for your chain analysis, and I will not fabricate reel/frame numbers to fill the gap.

What I can ground: the patent's own front-page data (via Google Patents, as reproduced authoritatively in the source text supplied for this analysis) lists Original Assignee: International Business Machines Corp. and the Specification describes the invention as IBM work referencing earlier Feistel/IBM product-cipher patents (U.S. Pat. Nos. 3,798,359 and 3,796,830) — so at least one assignment document from Feistel to IBM exists by definition of that [73] field.

Inventors

Unusual-pattern check — nothing anomalous, with one nuance:

• Single inventor. No co-inventor departures to track; the "all inventors left within 12 months" fire-sale precursor is structurally inapplicable here.
• Timing nuance worth noting but not over-reading: the application was filed 1976-12-30, and public biographical accounts place Feistel's formal retirement from IBM in the early-to-mid 1970s with continued consulting. If correct, the 1976 filing would be a post-employment / consultancy-era filing still assigned to IBM under the inventor's obligations to his former employer. I could not verify Feistel's exact separation date from primary-source personnel records, so treat this as a research lead, not a finding. It has no assignment-chain consequence: the [73] Assignee field establishes IBM's title regardless.
• Feistel died in 1990. He was never a named assignee of anything other than IBM on this family.

Original assignee

• Entity: International Business Machines Corporation, Old Orchard Road, Armonk, N.Y. 10504 (address form used on IBM's contemporaneous European filings, e.g. EP 0 114 356).
• Primary line of business: computing hardware, software, and services — an operating industrial company, not a holding entity.
• Did they ship a product embodying the claims? Unclear / not established. US 4,316,055 claims a dual-mode architecture (one shift-register-plus-transformation-element engine switched between block cipher and keystream generator). IBM's Feistel-family research did feed directly into the Lucifer cipher and thence into the NBS DES standard (FIPS PUB 46, January 1977), and IBM shipped crypto hardware and software implementing Feistel-type rounds. But I found no evidence that the specific stream/block selectable reconfiguration claimed in the '055 patent was commercialized as a discrete IBM product. I will not assert embodiment.
• Current status: Operating. IBM remains an active NYSE-listed company; it has never been in bankruptcy and has not changed its corporate name in any way that would generate a "Change of Name" recording against this patent.
• Assertion posture: IBM is not known ever to have asserted US 4,316,055. The patent expired 1999-02-16 (20 years from the 1976-12-30 filing; Google Patents status "Expired – Lifetime"), so it had no assertable value for essentially the entire modern NPE era.

Assignment timeline

No post-issuance assignment could be retrieved, and I found no evidence that any exists. The most probable state of the record is a single pre-issue assignment and nothing more. Presented without invented reel/frame data:

• 1976-12-30 (filing date) or shortly thereafter — executed date unknown / recorded date unknown — Reel/Frame: NOT RETRIEVED

  • Conveyance: Assignment (inferred; not confirmed)
  • Assignor: Horst Feistel
  • Assignee: International Business Machines Corporation, Armonk, N.Y.
  • Correspondent: Not retrieved. For calibration only — the attorney of record named on the closely related Feistel patent US 3,798,359 is Victor Siber, and IBM assignments of this era were typically recorded through IBM in-house IP counsel (Armonk, N.Y. / Yorktown Heights, N.Y. addresses). Do not treat "Victor Siber" as the correspondent on this patent — I have not seen the recording document and am supplying it only so you know what to look for.
  • Context: Original employment/inventor assignment to the filing employer — routine, pre-issue, not a transfer-to-asserter.

• 1982-02-16 — Patent issued (US 4,316,055 A). No assignment event; publication date only.

• 1999-02-16 — Term expires. Anticipated expiration recorded in Google Patents legal events. After this date the asset is unenforceable, so any hypothetical later transfer is economically meaningless as an assertion vehicle.

If your review requires the reel/frame, the single authoritative path is a Patent Assignment Search by patent number at https://assignmentcenter.uspto.gov/ (and the legacy index at https://assignment.uspto.gov/patent/index.html). A 1976/1977-era IBM recording will sit in the paper-era reel series, so the search must be run against the patent number rather than by assignee name.

Timeline diagram

timeline
    title Ownership of US 4316055
    1976 : Application filed by Horst Feistel
         : Assigned to IBM Armonk NY
    1982 : Patent issued as US 4316055 A
    1999 : Patent term expires

Note: the "Assigned to IBM" event reflects the patent's [73] Assignee field. The exact execution date, recording date and reel/frame for that single recorded assignment have not been verified against Assignment Center. No post-issue events are shown because none were found.

NPE / troll-pattern signals

1. Shell-entity transfer — Not present. No evidence of any transfer out of IBM. The only assignee is a large publicly traded operating company; the patent's term expired before the modern licensing-LLC era, and its legal-status record terminates at expiration rather than at a corporate transfer.

2. Known asserter in the chain — Not present. Neither the original nor any successor assignee matches Acacia, Marathon, Intellectual Ventures, IPNav, Wi-LAN, Mosaid/Conversant, Vringo, Pendrell, Innovatio, MPHJ, Lumen View, Round Rock, Document Generation Corp, or any Spangenberg entity. Google Patents' "Cited By" list is populated by technologists citing it as art (NTT/EP 0618701, Ericsson cellular encryption filings, WO 98/36525, and later US 10,348,485 to Fornetix LLC), not by asserters acquiring it.

3. Repeat correspondent across the chain — Unclear / not assessable. One would expect a single IBM in-house attorney of record, but with only one link and no retrieved recording document there is nothing to test for recurrence, and no correspondent name has been matched to any Unified Patents / RPX / Patent Progress assertor roster. (Cross-reference for your records: the related Feistel patent US 3,798,359 names Victor Siber as attorney of record — a calibration data point only.)

4. Cascading transfers — Not present. No chain of LLC-to-LLC assignments within any 24-month window; no evidence of shared correspondent addresses or common principals because there is no chain at all.

5. Pre-litigation transfer — Not present. No infringement suit naming US 4,316,055 was found in any source (Unified Patents portal, CourtListener/RECAP, general web). With no litigation, there is no transfer timed to precede one.

6. Bankruptcy fire-sale — Not present. IBM has no Chapter 7/11 history; there is no Kodak/Nortel/Polaroid-style sale event associated with this patent.

7. Privateering — Not present. No SEC disclosure, Patent Progress, or EFF coverage ties this patent to an operating company funding assertions through an NPE proxy.

8. Defensive aggregator — Not present. The chain does not terminate at RPX, AST, LOT Network, Unified Patents, or OIN. IBM is a large LOT Network participant, but participation in LOT is a prospective commitment covering future transfers — it is not a recorded assignment against this patent and should not be recorded as one.

Verdict

Insufficient data (within the meaning of the rubric: "no records, or only the original assignment").

Justification: The only ownership record I can substantiate is the original [73] assignment from Horst Feistel to International Business Machines Corporation at/near the 1976-12-30 filing; I could not retrieve the reel/frame, execution date, recording date, or correspondent because Assignment Center was not queryable in this session, and no assignment abstract of title for 4316055 surfaced in any indexed source. Every NPE signal therefore resolves to not present or not assessable on the available evidence — there is no shell LLC, no known asserter, no cascading transfer, no pre-litigation transfer, and no litigation; the patent expired 1999-02-16, twenty years before an NPE could have exploited it. Because the surviving-record hypothesis (IBM retained title to expiration) is inferred from the patent's own front-page assignee field and legal-status record rather than verified from a recorded reel/frame, the honest verdict is Insufficient data rather than "Defensive / non-asserting" — nothing in the evidence shows a deliberate anti-NPE transfer, only a never-transferred, long-expired IBM asset.

Verify at: https://assignmentcenter.uspto.gov/ (search by patent number 4316055) — expect a single paper-era assignment, Feistel → IBM, recorded 1976–1977; if the search instead returns zero assignment records, that still means IBM held title by operation of the inventor's employment agreement, and the front-page "Original Assignee" field should be treated as the operative ownership evidence.

Contradiction flagged for your file: none with the prior sections, but note one cross-reference hazard already identified upstream — do not conflate (a) the Soviet application number 4316055/2о33 (unrelated fiber-cutting inventor's certificate), (b) the Senju/Bausch & Lomb " '431 patent," (c) the Wang Laboratories and Safoco " '605 patents," or (d) Fornetix's US 10,348,485 (which merely cites US 4,316,055 as prior art and is a for-profit assignee of its own unrelated portfolio) with this patent's ownership chain. None of them touches the Feistel → IBM record.

I'll research the prior-art citations for this specific patent. Let me search multiple sources in parallel.

Let me dig into the front-page "References Cited" (the examiner/applicant-cited prior art) for this specific patent.

Prior-Art Analysis — US 4,316,055 (Feistel)

Identifier handling (literal): I searched on the exact string 4316055, which resolves to US 4,316,055 A, "Stream/block cipher crytographic system," Horst Feistel, IBM, filed 1976‑12‑30, issued 1982‑02‑16. I did not substitute any similar number (e.g., US 4,316,245 Luu, US 4,315,282 Schumacher, US 4,315,055, or the Soviet application 4316055/2о33 noted in the earlier section). Any "431…" or "…605" hits from unrelated matters are excluded.

1. Important scoping correction before the reference list

There are three different citation sets associated with this document, and conflating them produces invalid §102 conclusions:

Two of the earlier sections treat the "Cited By" material as though it were relevant art. It is not prior art to '055 and I flag that as a correction to the framing.

Retrieval caveat (stated explicitly rather than papered over): I was able to reach the USPTO/Google-hosted authoritative PDF (https://patentimages.storage.googleapis.com/4d/dd/52/4572efbe038994/US4316055.pdf) and the Google Patents record (https://patents.google.com/patent/US4316055/en), but the search returns surfaced the specification text, not the complete front-page (56) column. I therefore base the substantive list on the references the patent itself cites in its Background section (authoritative, from the full text supplied), and I state plainly that I could not independently enumerate every item in the front-page (56) list. I will not reconstruct that column from memory, because I do not have high confidence in its exact contents.

2. Prior-art references cited within US 4,316,055 (Background section)

All of the following are cited and characterized by the applicant in the patent's own "Background of the Invention." Dates shown are the filing/issue dates as recited in the patent text where given; I mark my own uncertainty where the patent omits them.

Discrepancy flag (cross‑reference to the prior section): the supplied full text reads "copending application Ser. No. 552,685," whereas an OCR snippet of the same PDF surfaced in search reads "552,655." The authoritative full text in this session says 552,685; the other is a probable OCR error. I note it rather than silently picking one, and I could not identify the resulting patent with confidence.

Corroborating source for P9: I retrieved the full text of US 3,798,359 (Feistel) — front page confirms Block Cipher Cryptographic System, filed June 30, 1971, issued Mar 19, 1974, and its own (56) cites US 3,657,699, US 2,984,700, US 3,170,033, US 2,995,624, US 2,917,579. Source: https://luca-giuzzi.unibs.it/corsi/Support/papers-cryptography/US3798359.pdf

3. §102 anticipation analysis — reference by reference

Governing principle: anticipation under §102 requires a single reference disclosing every limitation of the claim, arranged as claimed, including all limitations of any claim from which it depends. A reference that discloses only a subset is §103 material, not §102 material.

The pivotal limitation in this patent is the dual-mode selectivity. Every independent claim (1 and 11) requires means to selectively use the main reconfiguration means either as a full block cipher output or as a pseudo-random stream combined with the incoming data. That is the point of novelty the applicant argues throughout.

Bottom line on anticipation

On the record available, none of the references cited in US 4,316,055 anticipates any of claims 1–14 under §102. The reason is structural, not incidental: the claimed invention is defined by the selective dual‑mode operation, and every cited reference is a single‑mode device (or a theory paper). This is consistent with the fact that the claims were allowed. If a §102 challenge were to be constructed, the only realistic path would be to find a single reference disclosing both a shift‑register block cipher round function and a mode‑selectable keystream output — none of the cited art does that.

Where the real risk lies (§103, noted for completeness)

The strongest obviousness combination on this record would be P9 (US 3,798,359) + P3/P4 or P6 (block‑cipher round function + stream generator/mod‑2 keystream mixing), with N1/N2 as evidence that combining substitution and transposition into a product cipher, and reusing it as a keystream source, was known. That is a §103 analysis, not §102, and I flag it as such rather than miscasting it as anticipation.

4. What I could not verify (explicit confidence statement)

1. The complete front-page (56) "References Cited" column of US 4,316,055 was not retrievable in this session. The prior sections and this one rely on the specification's own citations. If a claim-by-claim §102 chart against the examiner-cited art is required, the (56) column should be pulled directly from the PDF front page or from USPTO Patent Public Search (the OCR of the front page is where the exact examiner citations reside).
2. Copending application Ser. No. 552,685 is unidentified; I will not guess which patent issued from it.
3. Dates for P1–P8 are the filing dates the patent recites. I did not independently confirm their issue dates; they are not material to the conclusion above (all predate the 1976 filing by well over a year, so all are §102(b) art regardless).

5. Sources used

• US 4,316,055 full text and claims — https://patents.google.com/patent/US4316055/en ; https://uspto.report/patent/grant/[4316055](/patent/4316055)
• US 4,316,055 published PDF (USPTO/Google‑hosted) — https://patentimages.storage.googleapis.com/4d/dd/52/4572efbe038994/US4316055.pdf
• US 3,798,359 (Feistel) full text — https://luca-giuzzi.unibs.it/corsi/Support/papers-cryptography/US3798359.pdf
• EPO/search‑report treatment of '055 as a citation (confirming it is cited as art by later documents, not litigated) — EP 1 292 067 A1 search report; EP 0 618 701 A3.

Recommendation: if you need a defensible §102 table, supply or permit retrieval of the front‑page (56) column; on the presently available record the answer is that the cited art is close but anticipatorily insufficient, and the appropriate challenge theory is §103.

I'll ground this analysis in the prior-art references the patent itself cites. Let me verify what each cited reference actually discloses.

Obviousness Analysis — US 4,316,055 A under 35 U.S.C. § 103

0. Scope, framing, and what "Prior Art" is actually available here

Legal standard applied. Because US 4,316,055 was filed December 30, 1976, pre‑AIA § 103(a) governs, and the Graham v. John Deere framework applies: (1) scope and content of the prior art, (2) differences between the prior art and the claims, (3) level of ordinary skill, and (4) secondary considerations. KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007) supplies the motivation‑to‑combine methodology (the "familiar elements / known method" and "finite number of identified, predictable solutions" rationales), which is fully applicable to pre‑AIA claims.

Two threshold observations on the available prior art (important, and they constrain the analysis):

1. The only true prior art on this page is the set the '055 specification itself cites. The Google Patents "Prior Art" tab content for this document is essentially the applicant's own Background section. Because the application was filed 1976‑12‑30, every cited patent issued 1966–1974, i.e. all are § 102(b) art (published more than one year before filing). Shannon (1949) and Feistel's Scientific American article (May 1973) are also § 102(b) printed publications.
2. The "Cited By (133)" list cannot be used. Every entry in it post‑dates the 1976‑12‑30 filing (earliest visible: US 4,399,323, priority 1981‑02‑09). Those documents are later art and are inadmissible for § 103 purposes against these claims. I note that several of them (e.g. US 4,471,164, "Stream cipher operation using public key cryptosystem"; US 4,815,130, "Stream cipher system with feedback") show the industry later converging on the exact block‑cipher‑as‑keystream‑generator idea — but using them would be classic hindsight and I do not rely on them.

Non‑prior art to exclude expressly: US 4,157,454 and its EP counterpart EP 0 035 048 B1 (variant‑key‑matrix cipher, Feistel) — the EP filing is 1980‑03‑04, well after the '055 filing date; that reference is cited by the later document against others, and it is not available against '055.

The reference set relied upon

1. Level of ordinary skill (ECU)

A PHOSITA in December 1976: a B.S. in EE/CS plus 2–3 years in digital‑logic and data‑security design, familiar with (a) shift‑register sequence generators and their use as key streams combined by mod‑2 addition, and (b) the IBM/Lucifer product‑cipher family (S‑boxes + keyed permutation + mod‑2 combination over recirculating shift registers), and (c) the standard trade‑off that block ciphers are stronger but slower (many cycles per block) while stream ciphers are fast but weaker. Both F‑359 and S‑830 were assigned to the applicant's own company and are in the same technical lineage, which strongly supports combining them (a PHOSITA working in this group would have both on the desk).

2. Grounds of rejection

Ground 1 — Claims 1, 2, 3, 5, 6, 11, 12 obvious over S‑830 in view of F‑359

S‑830 alone supplies, with near‑literal correspondence:

• Claim 1 — "main reconfiguration means comprising a shift register": S‑830 cl. 7, "a plurality of recirculating shift registers, each register having associated therewith a set of logic means interposed between storage cells." "Transformation element… cryptographically transforming data located in said main reconfiguration means": S‑830 cl. 2–6 + Fig. 3. "Consecutive cryptographic transformations… for a predetermined number of cycles": S‑830 cl. 8 (cycle‑count counter, incremented per shift until 128 is reached) — this is the predetermined number of cycles recitation. "Means for selectively utilizing the complete contents … as a full cryptographically transformed block": S‑830 output control 110 gating the 32‑bit block out.
• Claim 2 — extraction from a first portion and return to a second location: S‑830 source registers → adder 50 → S‑box 52 → XOR gates 60–67 in the convolution registers; plus recirculation ("shifted to itself reconfigure the contents").
• Claim 3 — return to a second location and concurrent linear combination with data already there: S‑830 cl. 6, "each of said logic means comprises an exclusive‑or gate for performing a modulo‑2 addition of said T signals and the binary signal values contained in the store cells." This is the claim almost verbatim.
• Claim 6 — two keys, one loading the register, one controlling the permutation: F‑359 cl. 5 (a plurality of key‑segment storage means controlling the transformations) combined with S‑830's key‑segment role assignment (TCR minibyte vs. permutation‑control minibyte). Splitting one 64‑bit key into two independent user keys and assigning one to register loading and one to permutation control is an obvious change in the number/nature of parts with no new result (In re Harza; In re Kuhle).
• Claim 11 — non‑affine transformation from a source field returned via a permutation controlled by the other key: F‑359 cl. 1–4 (nonlinear substitution means + linear rearranging means, both under key control) and S‑830 (keyed S‑box + keyed permutation of T). "Each time said main reconfiguration means is shifted a bit position": S‑830's crypt cycle = one shift per transformed minibyte, i.e., a transformation is interleaved with every shift.
• Claim 12 — mod‑2 addition of the destination‑field contents with the permutation output: S‑830 cl. 6, as above.

Why combine F‑359 with S‑830? Both are IBM product‑cipher patents of the same architecture; F‑359 supplies the express substitution + transposition product‑cipher statement of the transformation element (and its cl. 4 fixed‑wire permutation means), while S‑830 supplies the recirculating shift register with in‑register XOR combination and cycle counter. A PHOSITA seeking to build a hardware product cipher would treat them as two publications of the same design family and would freely take the register topology from one and the cipher‑element characterization from the other.

Ground 2 — Claims 1, 7, 8, 9, 10, 13, 14, and the "stream mode" limitation obvious over S‑830 and/or F‑359 in view of V‑855 and/or V‑308, further in view of A‑374 and A‑783

This is the ground that reaches the dual‑mode feature — the only feature not found in F‑359/S‑830 alone.

• "Selectively … stream or block mode" (cl. 1, 11) — V‑855 and V‑308 are, on the applicant's own characterization in the Background, stream generators whose sequence is mod‑2 summed with the clear message. Combining a known block‑cipher engine (F‑359/S‑830) with a known stream‑generator/combiner (V‑855/V‑308) under a mode switch is a combination of two known, independently complete cryptographic subsystems. The Background of '055 itself states the motivation: "in many communication and/or closely related computer systems where differing security levels exist, it would be a great advantage to be able to utilize full block ciphering techniques for highly secure data transmissions and stream enciphering techniques for data transmissions having a requirement of lower security."
• Claims 7, 8, 13 (stream mode: circular shifting, one bit tapped per shift, mod‑2 adder) — A‑783 is literally a "Key Material Generator" producing "a very long pseudo‑random sequence"; V‑855/V‑308 show the mod‑2 combiner. Tapping the register output bit and adding it to the data with a mod‑2 adder is the standard stream‑cipher architecture the applicant concedes as prior art.
• Claims 9, 10 (block‑mode loading and iteration) — S‑830 cl. 1 (means for loading message segments into store means) and cl. 4 ("adder means for performing a modulo addition on information contained in said first and third store means," i.e., combining message and key before the nonlinear transformation) teach the substance of claim 10 even though the S‑830 adder is mod‑16 rather than mod‑2; the mod‑2 instantiation is suggested by S‑830's own XOR gates.
• Claim 14 (asymmetric encipher/decipher handling: encipher loads the mod‑2 sum of data + key; decipher loads the ciphertext directly and applies the key as the final mod‑2 step) — the applicant's own specification states this is simply the mathematical inverse and that "encryption and decryption sequence of operations is identical with the exception of… shift direction." F‑359 and S‑830 already teach both encipher and decipher by the same hardware (S‑830: "the cryptographic system does not distinguish between an encipher or decipher mode of operation"; cl. 9 process claimed as enciphering or deciphering). Once the mod‑2 combination with key‑2 is adopted at the input (claim 10), the inverse placement at the output for decipherment is the only remaining mathematically valid position — a "finite number of identified, predictable solutions" situation (KSR).
• A‑374 supplies the explicit teaching that a key‑material generator can control the number of cycles for enciphering and deciphering — i.e., it links the stream‑generator concept to the cycle count control recitation in claims 1/9/11.

Ground 3 — Shannon in view of F‑359 / S‑830 and F‑SA, as a corroborating motivation ground

Shannon supplies the generalized product‑cipher doctrine and the canonical substitution‑then‑transposition construction, and F‑SA asserts product ciphers' superiority and frames the efficiency trade‑off. A PHOSITA starting from Shannon and F‑359 would arrive at a keyed substitution + keyed permutation + mod‑2 adder round function; the only step left is choosing whether to iterate it as a block transform or as a keystream generator, which is a use of the same apparatus for a known alternative purpose (In re Hack, KSR).

3. Motivation to combine — explicit KSR rationales

1. The problem itself supplied the motivation. The '055 Background expressly identifies the desideratum: one device that can do high‑security block encipherment when needed and fast stream encipherment when adequate, and gives the banking‑terminal example. Under KSR, the motivation may be found in "the nature of the problem to be solved."
2. Hardware‑reuse / cost‑reduction engineering. The same building blocks (recirculating shift register, S‑box, keyed permutation, mod‑2 adder, cycle counter) are common to F‑359/S‑830 and to V‑855/V‑308/A‑783. One engine performing both is a "combination of familiar elements according to known methods" yielding no more than predictable results.
3. Same physical primitive. Both modes in '055 ship a bit out of the same register and mod‑2 combine it with data. A single tap and one adder serve either the block data path or the keystream path, with the only difference being whether the data symbol comes from the input stream or from the register. That is the very definition of a design choice between two known configurations.
4. Known reversibility. F‑359/S‑830 already teach that the same hardware enciphers and deciphers (same key schedule, reversed access). The '055 encrypt/decipher duality therefore adds nothing that the art did not already reward.
5. No teaching away. Nothing in F‑359, S‑830, V‑855, V‑308, A‑374, or A‑783 disparages the other cipher family; S‑830's Background criticizes "memory protection," not stream ciphers. There is no "teach away" to rebut.

4. Where the obviousness case is genuinely weaker (do not overstate it)

I want to be explicit about the limits of this analysis rather than assert a blanket § 103 rejection.

• Claims 7, 8 and 13 (and the stream‑mode "pseudo‑random number stream" recitation generally) are the hardest. The art cited supplies keystream generators that are shift‑register/LFSR sequence generators (V‑855/V‑308; A‑783 "key material generator") and it supplies block ciphers that iterate a substitution‑permutation round over the whole register. As of 1976‑12‑30 I have no verified reference that teaches operating a full product‑cipher round function on the register to produce one keystream bit per cycle — i.e., the "output‑feedback/one‑round‑per‑keystream‑bit" idea later formalized for DES. The patent's own claims 7/13 emphasize exactly this ("sequentially shifted in a circular mode," "cryptographic transformation… between each shift cycle"). A patentee defending those claims could argue that the cited references teach two different kinds of generator (algebraic LFSR vs. nonlinear product cipher), and that swapping one for the other was not routine. That is a real, non‑frivolous argument. It is answerable under KSR's "obvious to try" branch (one predictable, identified substitution), but it is not a slam dunk.
• No secondary considerations were located. I found no record of commercial success, licensing, copying, or industry praise attributable to this patent; the previously generated sections of this analysis likewise found no litigation. So there is no objective indicia evidence on either side.
• Prosecution‑history / § 282 weight. The references relied on here are cited on the face of the patent — the examiner considered them and still allowed the claims. Under 35 U.S.C. § 282 that carries a rebuttable presumption of validity, and in a § 103 challenge the burden of showing why the combination was beyond the PHOSITA's ordinary creativity rests on the challenger. That said, the applicant's own "Conclusions" section offers only the conclusory assertion that reuse of the same hardware "is considered to be basically unique" — a statement of novelty, not a technical teaching away from combination.
• Practical relevance. 4,316,055 expired February 16, 1999 (20 years from the 1976 filing) and is listed "Expired – Lifetime." The productive framing is therefore not "is the patent invalid," but using '055 as § 102(b) prior art with a Dec. 30, 1976 date against later claims — which is how the EPO actually used it (EP 0 618 701 as background; and the EP 1 292 067 search report cited "US 4 316 055 A (FEISTEL)" as category X against claims 1, 9 and 10 of that later application, per the earlier generated summary).

5. Bottom line

Confidence: high that Grounds 1–3 establish a prima facie § 103 case for the block‑mode and dual‑mode‑selection claims (1–6, 9–12, 14); moderate for the stream‑generator‑specific claims 7, 8, 13, which would likely require an additional reference (an OFB/CFB‑type keystream teaching) that is not available as pre‑1976 art on this record and that I will not fabricate.

6. Flags and contradictions to surface (per the cross‑reference instruction)

1. Secondary‑source identifier discrepancy (not auto‑corrected). A Cryptologia article ("The Impetus to Creativity in Technology," Konheim 2015) refers to "U.S. Patent #3798539A … filed by the IBM Corporation in 1971." The number 3,798,539 does not correspond to the Feistel block‑cipher patent; the patent actually cited by '055, and confirmed by Espacenet/Google Patents/uspto.report, is US 3,798,359. I have preserved the literal string 3798539 from the source and used 3,798,359 (the number the '055 specification itself recites). The secondary source appears to contain a transposition typo.
2. Unverified copending application. The '055 Background cites "the copending application Ser. No. 552,685" as a product‑cipher reference. Its identity is not established from the material supplied. If it issued as a US patent, it would be § 102(e) art with a constructive date of its filing (~1975, given the numbering between app. 194,836 of Nov. 1971 and app. 755,898 of Dec. 1976). It should be verified in Patent Public Search before being relied on. I have not assumed it corresponds to US 4,157,454.
3. Secondary‑source date inconsistency. The same Cryptologia article states that "US #3,962,539 'Product Block Cipher System for Data Security'" was "filed by IBM Kingston on 28 June 1976." A patent numbered 3,962,5xx would normally have issued in 1976, which is inconsistent with a June 1976 filing date. Either the number or the filing date in that secondary source is wrong. I therefore do not rely on US 3,962,539 as prior art here and flag it for verification (its correct § 102(e) date, if it pre‑dates 1976‑12‑30, could add an independent ground for the block‑mode claims).
4. No contradiction was found between the previously generated summary/litigation sections and the full patent text on bibliographic data, claim structure (two independents: claims 1 and 11; 14 claims total), or the "Expired – Lifetime" status. The "Cited By" list and the EPO category‑X usage are about '055 as prior art, not about its validity, and should not be conflated with the § 103 analysis above.
5. Potential § 112 note (outside the § 103 task, but worth recording). Claim 4 recites "said non‑affine transformation device" although its parent claim 2 does not introduce such a device — a possible antecedent‑basis/indefiniteness defect. It does not affect the § 103 combination above, but it is a secondary vulnerability.