Paul C. Clark v. Docusign, Inc.

N OTE: This disposition is nonprecedential.
United States Court of Appeals
for the Federal Circuit
______________________
PAUL C. CLARK,
Appellant
v.
DOCUSIGN, INC.,
Appellee
______________________
2024-1301, 2024-1302, 2024-1308
______________________
Appeals from the United States Patent and Trademark
Office, Patent Trial and Appeal Board in Nos. IPR2022-
00923, IPR2022-00924, IPR2022-00925.
______________________
Decided: July 25, 2025
______________________
F REDERICK N GOSI SAMUELS , Cahn & Samuels, LLP,
Washington, DC, argued for appellant. Also represented
by MAURICE U. CAHN.
MICHAEL J OHN SACKSTEDER, Fenwick & West LLP, San
Francisco, CA, argued for appellee. Also represented by
T ODD RICHARD G REGORIAN.
______________________
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CLARK v. DOCUSIGN, INC. 2
Before P ROST , CLEVENGER , and C UNNINGHAM , Circuit
Judges.
CLEVENGER , Circuit Judge.
In three inter partes review (“IPR”) proceedings, the
Patent Trial and Appeal Board (“Board”) determined that
claim 1 of U.S. Patent No. 8,695,066 (the “’066 patent”),
claims 1–3 of U.S. Patent No. 9,391,957 (the “’957 patent”),
and claim 1 of U.S. Patent No. 10,129,214 (the “’214 pa-
tent”) were unpatentable as obvious. J.A. 1–91. Dr. Paul
C. Clark, owner of the challenged patents, seeks to over-
turn the Board’s decisions in all three IPRs. For the fol-
lowing reasons, we affirm.
BACKGROUND
A
The challenged patents purport to improve “security
mechanisms” for “high value business-to-business (B2B)
and Business-to-Consumer (B2C) transactions” on the in-
ternet. ’066 patent, col. 1 ll. 15–18.1 Existing solutions re-
lied on “Secure Socket Layer (SSL) to encrypt traffic
between a client’s browser and a web server” and while SSL
provided “confidentiality . . . at the network level” it did not
“provide authentication or non-repudiation of transac-
tions.” Id., col. 1 ll. 19–22. Thus, internet transactions
lacked complete security because “[m]any applications re-
side on a separate server” from the web server and “[t]raffic
between the web server and the application server [was]
not protected by SSL.” Id., col. 1 ll. 24–27. Further, fire-
walls, which are intended to protect corporate networks
1 The challenged patents share a common specifica-
tion and claim priority through one or more continuation
applications to U.S. Serial No. 09/568,215. We cite to the
specification of the ’066 patent as exemplary of all three
patents.
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CLARK v. DOCUSIGN, INC. 3
from outsiders, still display security vulnerabilities as al-
lowing customers and partners access to the network
means providing access holes through which unauthorized
users can traverse a firewall and attack a web server. See
id., col. 1 ll. 47–53. Therefore, the challenged patents
sought to provide “a system for secure communicat[ion]” on
the internet “that protect[ed] the integrity of data in transit
. . . while allowing the appropriate level of access to author-
ized users.” Id., col. 1 ll. 54–58. To accomplish this, the
alleged invention added one or more conventional security
services to enhance data from a first domain, “translated”
the data to a target protocol, de-enhanced the translated
data, filtered out unauthorized data, and transmitted the
filtered data to a second domain. See id., col. 14 ll. 13–29.
In April 2022, DocuSign, Inc. (“DocuSign”) filed three
IPR petitions, challenging each of the challenged patents
as obvious, and the Board instituted all three challenges in
November 2022. During the IPR proceedings, Dr. Clark
only argued against DocuSign’s claim mappings and asser-
tions for the “translating” claim limitation in each patent,
and conceded that all other claim limitations were obvious
in light of the asserted prior art. See J.A. 13; J.A. 49; J.A.
81–87; J.A. 3176–83; J.A. 4855–64; J.A. 4868–76. The
“translating” claim limitation for each patent reads as fol-
lows:
translating the received data from a first network
application level protocol to a target network appli-
cation level protocol while preserving said data se-
curity enhancements
’066 patent, col. 14 ll. 15–18;
translating the received data from a first network
application level protocol to a target network appli-
cation level protocol while preserving said data se-
curity enhancements
’957 patent, col. 13 ll. 58–61;
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CLARK v. DOCUSIGN, INC. 4
translate the received data from a first network ap-
plication level protocol to a target network applica-
tion level protocol while preserving said data
security enhancements
’214 patent, col. 14 ll. 31–34.
DocuSign asserted U.S. Patent No. 6,163,844 (“Dun-
can”), in combination with other prior art not relevant to
this appeal,2 as rendering the challenged patents obvious.3
Duncan relates to a method for secure communication
on the internet by granting access to information in a dis-
tributed computer system. Duncan, col. 1 ll. 6–9. Duncan
describes a “known network architecture” where the “net-
work line transmits data from [a] browser to [a] host com-
puter via a transfer protocol.” Id., col. 8 ll. 43–44, 55–57.
Duncan specifically calls out the “hypertext transfer proto-
col HTTP” as “an example of such a transfer protocol,” but
Duncan also describes that protocols “can differ
2 In the IPR challenge of the ’066 patent, the Board
held the challenged claims obvious in light of Duncan, with
reference to additional prior art teachings that showed the
“inherent properties of . . . particular features of Duncan.”
J.A. 7.
In the IPR proceedings for the ’957 patent, the Board
held the challenged claims obvious in light of Duncan and
U.S. Patent No. 6,173,399B1. See J.A. 43, 71.
In the IPR proceedings for the ’214 patent, the Board
held the challenged claims obvious in light of Duncan
alone. See J.A. 87, 89.
3 DocuSign asserted additional grounds of unpatent-
ability, which the Board did not reach because it deter-
mined that the challenged claims were obvious in light of
Duncan. J.A. 29; J.A. 35 n.6; J.A. 65; J.A. 71 n.6–7; J.A.
87–88; J.A. 89 n.10.
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CLARK v. DOCUSIGN, INC. 5
fundamentally” from each other. Id., col. 8 ll. 57–58, col. 9
l. 1–3. To transmit the data in a secure manner, Duncan
discloses multiple “protocol converters,” which generally
“convert incoming requests into such a form that they can
be further processed in the server.” Id., col. 10 ll. 36–37.
The protocol converters “convert[] the information accord-
ing to the network protocol employed and according to the
form of the presentation of the information employed in the
browser” and the protocol converters also convert “the data
according to the network protocol of a security network.”
Id., col. 11 ll. 44–46, col. 12 ll. 5–6. They also convert “re-
quests from [a] security network for the proxy browser and
convert[] the replies from the proxy browser for the secu-
rity network.” Id., col. 12 ll. 18–20.
B
The Board held that DocuSign showed by a preponder-
ance of the evidence that the challenged claims in all three
patents would have been obvious in light of either Duncan
alone or in combination with other prior art. J.A. 28.4 The
Board noted that “network application level protocol” was
the “sole term requiring construction” and adopted Dr.
Clark’s suggested construction: “a protocol that functions
at the application level and is intended to transfer data
over a network.” J.A. 9–10. Turning to the merits, the
Board determined that Duncan teaches each limitation of
the challenged patents, spending the majority of its time
analyzing the “translating” claim limitation.
The Board found that Duncan’s disclosure of “protocol
converters” taught “the claimed translating of data.” J.A.
4 Because the Board’s analysis regarding the “trans-
lating” claim limitation was substantially similar in all
three IPRs, see J.A. 16–27; J.A. 51–62; J.A. 82–87, we cite
to the Board’s decision in the IPR for the ’066 patent as
exemplary of all three Final Written Decisions.
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CLARK v. DOCUSIGN, INC. 6
21. The protocol converters, according to the Board, dis-
closed translating “from one protocol to a target protocol”
because Duncan describes protocols that “differ fundamen-
tally.” J.A. 22–23. Further, “[a]lthough [Duncan’s] de-
scription does not specifically address the interactions at
[its] protocol converters” the Board credited the testimony
of DocuSign’s expert, Dr. Black, as supporting the assertion
that “Duncan contemplates conversion to a different proto-
col in appropriate circumstances.” J.A. 23. Therefore, the
Board found that “Duncan teach[es] that a network control
protocol becomes something different by the conversion
performed by its protocol converter,” thus rendering the
“translating” claim limitation obvious. J.A. 24. Based on
this evidence, the Board held that it didn’t need to “address
the parties’ discussion” regarding whether “the two
claimed protocols” needed “to be different from each other.”
J.A. 24 n.4.
The Board rejected Dr. Clark’s argument that Dun-
can’s protocol converters merely “modified” the transfer
protocols rather than “convert[ing]” or “translating” them.
J.A. 23. The Board explained that Duncan did “not use the
term ‘modified’” but instead used “the term ‘converted,’
which the record shows to be interchangeable with the
claimed ‘translating.’” Id. Dr. Clark also argued that Dun-
can does not render all the claim limitations obvious be-
cause it only “describes a single transfer protocol, i.e.,
HTTP.” J.A. 25 (quoting J.A. 3181). The Board dismissed
this argument finding that Dr. Clark’s “discussion of the
nature of Duncan’s ‘modification,’ has confirmed” that
Duncan teaches the required “target network application
protocol.” Id.
Dr. Clark appeals the Board’s decisions. We have ju-
risdiction under 28 U.S.C. § 1295(a)(4)(A).
D ISCUSSION
Claim construction is an issue of law that we review de
novo when based on intrinsic evidence. Personalized
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CLARK v. DOCUSIGN, INC. 7
Media Commc’ns, LLC v. Apple, Inc., 952 F.3d 1336, 1339
(Fed. Cir. 2020). “Obviousness is a question of law, based
on underlying factual determinations.” Kennametal, Inc.
v. Ingersoll Cutting Tool Co., 780 F.3d 1376, 1384 (Fed. Cir.
2015). We review the Board’s “ultimate determination on
obviousness . . . de novo” and any “underlying factual find-
ings . . . for substantial evidence.” Harmonic Inc. v. Avid
Tech., Inc., 815 F.3d 1356, 1363 (Fed. Cir. 2016).
I
Dr. Clark argues that the Board committed legal error
in its claim construction because either the Board failed to
resolve an express claim construction dispute or, in the al-
ternative, the Board’s implicit claim construction is incor-
rect. We reject both arguments.
First, Dr. Clark argues that the Board did not resolve
the parties’ express dispute regarding whether the “target”
and “first” protocols “can be the same protocol . . . or
whether [each] is required to be . . . separate[] [and] inde-
pendent” from the other. Appellant’s Br. 11. However, the
Board was not required to resolve any alleged claim con-
struction dispute because it stated that Duncan disclosed
the “translating” claim limitation under either party’s pro-
posed construction. See J.A. 24 n.4. The Board need “only
construe claim terms that are in controversy, and only to
the extent necessary to resolve the controversy.” Nidec Mo-
tor Corp. v. Zhongshan Broad Ocean Motor Co., 868 F.3d
1013, 1017 (Fed. Cir. 2017) (citing Vivid Techs., Inc. v. Am.
Sci & Eng’g, Inc., 200 F.3d 795, 803 (Fed. Cir. 1999))
(cleaned up). Thus, the Board did not commit legal error
by abstaining from construing the term in dispute where
the Board determined the claim limitations were obvious
under either party’s proposed construction. See Voice Tech
Corp. v. Unified Patents, LLC, 110 F.4th 1331, 1341–42
(Fed. Cir. 2024).
Alternatively, Dr. Clark argues that the Board commit-
ted legal error when it “implicitly determined or assumed
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CLARK v. DOCUSIGN, INC. 8
that” the “translating” claim limitation is met “when the
target . . . protocol is the same protocol as the first . . . pro-
tocol.” Appellant’s Br. 13. According to Dr. Clark, the “tar-
get protocol” must be different from the “first protocol” and
under this interpretation the challenged patents “can avoid
Duncan.” Id. at 12. However, Dr. Clark ignores the fact
that the Board did not implicitly construe “target protocol”
or “first protocol” because the Board’s analysis did not set
the scope and meaning of the patented subject matter. See
Google LLC v. EcoFactor, Inc., 92 F.4th 1049, 1055 (Fed.
Cir. 2024) (explaining that the Board has construed a claim
when its “analysis . . . establishes the scope (e.g., bounda-
ries) and meaning of the patented subject matter”); Sigray,
Inc. v. Carl Zeiss X-Ray Microscopy, Inc., 137 F.4th 1372,
1377 (Fed. Cir. 2025) (same). Rather, the Board explicitly
stated it did not need to determine whether “the two
claimed protocols [need] to be . . . different from each
other,” J.A. 24 n.4, because Duncan “teaches the claimed
translating of data from one protocol to a target protocol”
regardless of whether the protocols are the same or not.
J.A. 24. And the Board’s analysis did not require that the
target protocol and the first protocol be the same. For in-
stance, the Board credited Dr. Black’s testimony that “the
protocol converter converts . . . data from the HTTP appli-
cation protocol of the browser to a network protocol of the
server,” J.A. 23 (citing J.A. 885 ¶ 147), as well as Duncan’s
teaching that the network protocols can “differ fundamen-
tally” from each other. J.A. 23. Thus, the Board explicitly
found that “Duncan contemplates conversion to a different
protocol in appropriate circumstances.” Id.
Because Dr. Clark does not challenge the claim con-
struction the Board did perform and because the Board did
not implicitly construe any claim terms, we reject both of
Dr. Clark’s claim construction arguments.
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CLARK v. DOCUSIGN, INC. 9
II
Dr. Clark also challenges the Board’s obviousness de-
termination. Regarding the obviousness inquiry, the only
issue on appeal is whether Duncan discloses the “translat-
ing” limitation. See Oral Arg. at 10:38–11:00, Clark v.
DocuSign, Inc., Nos. 2024-1301, 2024-1302, 2024-1308
(Fed. Cir. July 14, 2025), https://oralargu-
ments.cafc.uscourts.gov/default.aspx?fl=24-1301_071420
25.mp3 (hereinafter “Oral Arg.”).
We review the Board’s ultimate obviousness determi-
nation de novo, and its underlying factual findings for sub-
stantial evidence. Harmonic Inc., 815 F.3d at 1363. The
Board’s factual determinations include “the scope and con-
tent of the prior art, differences between the prior art and
the claims at issue, the level of ordinary skill in the perti-
nent art, the motivations to modify or combine prior art,
and any objective indicia of non-obviousness.” Corning v.
Fast Felt Corp., 873 F.3d 896, 902 (Fed. Cir. 2017).
Here, the issue is whether the Board’s factual findings
underpinning its obviousness determination are supported
by substantial evidence. See Facebook, Inc. v. Windy City
Innovations, LLC, 973 F.3d 1321, 1343 (Fed. Cir. 2020).
We hold substantial evidence supports the Board’s finding
that “Duncan’s protocol converter perform[s] the claimed
step of translating data from one protocol to another.” J.A.
27. In making its determination, the Board relied on the
following evidence: 1) Duncan’s teaching of protocol con-
verters, Duncan, col. 11 ll. 42–46; 2) Duncan’s description
that, at least in one embodiment, the network protocol can
“differ fundamentally” from another network protocol used
by the server, Duncan, col. 8 ll. 55 to col. 9 ll. 3; 3) Dr.
Black’s testimony that “the protocol converter [] converts
the data from an application protocol of the browser (in this
case HTTP) to a network protocol of Duncan’s network,”
J.A. 885 ¶ 147; 4) the ’066 patent’s interchangeable use of
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CLARK v. DOCUSIGN, INC. 10
the term “convert” and “translate”;5 and 5) Dr. Clark’s use
of the term “convert” interchangeably with “translate” dur-
ing his deposition, where he served as his own expert wit-
ness, J.A. 3226–27, 34:19–35:2. See J.A. 21–24. Taken
together, this evidence serves as substantial evidence that
Duncan discloses a system that utilizes protocol converters
to convert data from one protocol to another, where the pro-
tocols can differ fundamentally from each other. This is all
that the disputed claim limitations require.
Dr. Clark argues that substantial evidence does not ex-
ist because “Duncan identifies only a single transfer proto-
col by name, i.e., HTTP” and Duncan “fails to disclose” a
target protocol “that is a different network application level
protocol from HTTP.” Appellant’s Br. 18–19. However,
Duncan is not limited to only the HTTP protocol. Duncan
states that the network protocols it describes “can differ
fundamentally” from each other. Duncan, col. 9 l. 2. Noth-
ing in Duncan’s specification or claims limits its disclosure
and invention to only the HTTP protocol, especially be-
cause by the ’066 patent’s claimed priority date, “the con-
cept of protocol translation was well-understood and well-
established in the field of computer networking, and the
specific examples used in the ’066 specification . . . were
already embodied in published standards.” J.A. 870 ¶ 117.
There is no reason to read Duncan as narrowly as Dr. Clark
suggests when nothing in Duncan’s specification explicitly
limits the disclosure to only one protocol. See Kinik Co. v.
Int’l Trade Comm’n., 362 F.3d 1359, 1364 (Fed. Cir. 2004)
5 See, e.g., ’066 patent, col. 4 ll. 60–67 (“The protocol
gateway [] is a logical unit that preferably translates cli-
ent/server transactions to and from target/source protocols.
For example, [a] protocol gateway [] can be connected to an
X.25 network. When X.400 requests are received, these
can be converted to a target protocol . . . .”) (emphasis
added).
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CLARK v. DOCUSIGN, INC. 11
(“[W]hen the specification describes the invention in broad
terms, accompanied by specific examples or embodiments,
the claims are generally not restricted to the specific exam-
ples or the preferred embodiments unless that scope was
limited during prosecution.”).
During oral argument, Dr. Clark asserted that the
Board’s conclusion is not supported by substantial evidence
because even if Duncan discloses a translation between dif-
ferent protocols, it does not explain how a network protocol
is operating or functioning at the application level. See
Oral Arg. at 3:18–4:00; 4:38–5:15; 9:20–10:02; 12:25–13:13.
This argument appears to be new and asserted for the first
time at oral argument. When pressed to show support for
this new argument, Dr. Clark pointed to pages 18 and 19
of his opening brief and pages 9 and 10 of his reply brief.
Id. at 21:44–22:02. However, these pages do not recite this
new argument, but rather assert that the Board incorrectly
relied on Duncan because Duncan does not “suggest or dis-
close translation from one network application level proto-
col to another,” the argument we rejected above.
Appellant’s Br. 18. Because Dr. Clark’s argument is pre-
sented for the first time on appeal, we decline to consider
it. See In re Google, 980 F.3d 858, 863 (Fed. Cir. 2020) (“[A]
position not presented in the tribunal under review will not
be considered on appeal in the absence of exceptional cir-
cumstances.”).
CONCLUSION
For the reasons explained above, we affirm the Board’s
determination that the challenged patents are unpatenta-
ble as obvious.
AFFIRMED
COSTS
No costs.
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