Virnetx, Inc. v. Cisco Systems, Inc. ( 2014 )


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  •   United States Court of Appeals
    for the Federal Circuit
    ______________________
    VIRNETX, INC.,
    Plaintiff-Appellee,
    AND
    SCIENCE APPLICATIONS INTERNATIONAL
    CORPORATION,
    Plaintiff-Appellee,
    v.
    CISCO SYSTEMS, INC.,
    Defendant,
    AND
    APPLE INC.,
    Defendant-Appellant.
    ______________________
    2013-1489
    ______________________
    Appeal from the United States District Court for the
    Eastern District of Texas in No. 10-CV-0417, Chief Judge
    Leonard Davis.
    ______________________
    Decided: September 16, 2014
    ______________________
    2                          VIRNETX, INC.   v. CISCO SYSTEMS, INC.
    WILLIAM F. LEE, Wilmer Cutler Pickering Hale and
    Dorr, LLP, of Boston, Massachusetts, argued for defend-
    ant-appellant. With him on the brief were MARK C.
    FLEMING, LAUREN B. FLETCHER, and REBECCA BACT, of
    Boston, Massachusetts, and JONATHAN G. CEDARBAUM,
    BRITTANY BLUEITT AMADI, and LEAH LITMAN, of Washing-
    ton, DC. Of counsel on the brief was DANNY L. WILLIAMS,
    Williams, Morgan & Amerson, P.C., of Houston, Texas.
    J. MICHAEL JAKES, Finnegan, Henderson, Farabow,
    Garrett & Dunner, LLP, of Washington, DC, argued for
    plaintiffs-appellees. With him on the brief for Virnetx,
    Inc. were KARA F. STOLL and SRIKALA ATLURI, of Washing-
    ton, DC, and BENJAMIN R. SCHLESINGER, of Atlanta,
    Georgia. Of counsel on the brief were BRADLEY W.
    CALDWELL, JASON D. CASSADY, and JOHN AUSTIN CURRY,
    Caldwell, Cassady & Curry, of Dallas, Texas. On the brief
    for Science Applications International Corporation were
    DONALD URRABAZO, ARTURO PADILLA, and RONALD
    WIELKOPOLSKI, Urrabazo Law, P.C., of Los Angeles,
    California; and ANDY TINDEL, Mann, Tindel & Thompson,
    of Tyler, Texas.
    ______________________
    Before PROST, ∗ Chief Judge and CHEN, Circuit Judge. ∗∗
    PROST, Chief Judge.
    Apple Inc. appeals from a final judgment of the U.S.
    District Court for the Eastern District of Texas, in which
    a jury found that Apple infringed U.S. Patent Nos.
    6,502,135 (“’135 patent”), 7,418,504 (“’504 patent”),
    ∗
    Sharon Prost assumed the position of Chief Judge
    on May 31, 2014.
    ∗∗
    Randall R. Rader, who retired from the position of
    Circuit Judge on June 30, 2014, did not participate in this
    decision.
    VIRNETX, INC.   v. CISCO SYSTEMS, INC.                      3
    7,490,151 (“’151 patent”), and 7,921,211 (“’211 patent”).
    The jury further found that none of the infringed claims
    were invalid and awarded damages to plaintiffs-appellees
    VirnetX, Inc. and Science Applications International
    Corporation (“SAIC”) in the amount of $368,160,000.
    For the reasons that follow, we affirm the jury’s find-
    ings that none of the asserted claims are invalid and that
    many of the asserted claims of the ’135 and ’151 patents
    are infringed by Apple’s VPN On Demand product. We
    also affirm the district court’s exclusion of evidence relat-
    ing to the reexamination of the patents-in-suit. However,
    we reverse the jury’s finding that the VPN On Demand
    product infringes claim 1 of the ’151 patent under the
    doctrine of equivalents. We also reverse the district
    court’s construction of the claim term “secure communica-
    tion link” in the ’504 and ’211 patents and remand for
    further proceedings to determine whether the FaceTime
    feature infringes those patents under the correct claim
    construction. Finally, we vacate the jury’s damages
    award and remand for further proceedings consistent
    with this opinion.
    BACKGROUND
    The patents at issue claim technology for providing
    security over networks such as the Internet. The patents
    assert priority to applications filed in the 1990s, originally
    assigned to SAIC. VirnetX, a Nevada-based software
    development and licensing enterprise, acquired the pa-
    tents from SAIC in 2006.
    I. The ’504 and ’211 Patents and FaceTime
    The ’504 and ’211 patents share a common specifica-
    tion disclosing a domain name service (“DNS”) system
    that resolves domain names and facilitates establishing
    “secure communication links.” ’504 patent col. 55 ll. 49–
    50. In one embodiment, an application on the client
    computer sends a query including the domain name to a
    4                           VIRNETX, INC.   v. CISCO SYSTEMS, INC.
    “secure domain name service,” which contains a database
    of secure domain names and corresponding secure net-
    work addresses. 
    Id. at col.
    50 ll. 54–57, col. 51 ll. 11–19,
    col. 51 ll. 29–32. This allows a user to establish a secure
    communication link between a client computer and a
    secure target network address. 
    Id. at col.
    51 ll. 34–40.
    Representative claim 1 of the ’504 patent recites:
    1. A system for providing a domain name service
    for establishing a secure communication link, the
    system comprising:
    a domain name service system configured to be
    connected to a communication network, to store a
    plurality of domain names and corresponding
    network addresses, to receive a query for a net-
    work address, and to comprise an indication that
    the domain name service system supports estab-
    lishing a secure communication link.
    
    Id. at col.
    55 ll. 49–56.
    Before the district court, VirnetX accused Apple of in-
    fringement based on its “FaceTime” feature. Specifically,
    VirnetX accused Apple’s servers that run FaceTime on
    Apple’s iPhone, iPod, iPad (collectively, “iOS devices”),
    and Mac computers of infringing claims 1, 2, 5, 16, 21,
    and 27 of the ’504 patent as well as claims 36, 37, 47, and
    51 of the ’211 patent. In operation, FaceTime allows
    secure video calling between select Apple devices. J.A.
    1443. To use FaceTime, a caller enters an intended
    recipient’s e-mail address or telephone number into the
    caller’s device (e.g., iPhone). J.A. 1451–52. An invitation
    is then sent to Apple’s FaceTime server, which forwards
    the invitation to a network address translator (“NAT”)
    which, in turn, readdresses the invitation and sends it on
    to the receiving device. J.A. 1821, 1824–25. The recipient
    may then accept or decline the call. J.A. 1453. If accept-
    ed, FaceTime servers establish a secure FaceTime call.
    VIRNETX, INC.   v. CISCO SYSTEMS, INC.                    5
    J.A. 1453. Once connected, the devices transmit au-
    dio/video data as packets across the secure communica-
    tion path without passing through the FaceTime server.
    J.A. 1820, 1825.
    II. The ’135 and ’151 Patents and VPN On Demand
    A conventional DNS resolves domain names (e.g.,
    “Yahoo.com”) into Internet Protocol (“IP”) addresses.
    See ’135 patent col. 37 ll. 22–27. A user’s web browser
    then utilizes the IP address to request a website. 
    Id. at col.
    37 ll. 24–29.
    The ’135 and ’151 patents share a common specifica-
    tion disclosing a system in which, instead of a convention-
    al DNS receiving the request, a DNS proxy intercepts it
    and determines whether the request is for a secure site.
    
    Id. at col.
    38 ll. 23–25. If the proxy determines that a
    request is for a secure site, the system automatically
    initiates a virtual private network (“VPN”) between the
    proxy and the secure site. 
    Id. at col.
    38 ll. 30–33. If the
    browser determines that the request was for a non-secure
    website, then the DNS proxy forwards the request to a
    conventional DNS for resolution. 
    Id. at col.
    38 ll. 43–47.
    Representative claim 1 of the ’135 patent recites:
    1. A method of transparently creating a virtual
    private network (VPN) between a client computer
    and a target computer, comprising the steps of:
    (1) generating from the client computer a Domain
    Name Service (DNS) request that requests an IP
    address corresponding to a domain name associat-
    ed with the target computer;
    (2) determining whether the DNS request trans-
    mitted in step (1) is requesting access to a secure
    web site; and
    6                           VIRNETX, INC.   v. CISCO SYSTEMS, INC.
    (3) in response to determining that the DNS re-
    quest in step (2) is requesting access to a secure
    target web site, automatically initiating the VPN
    between the client computer and the target com-
    puter.
    
    Id. at col.
    47 ll. 20–32.
    Claims 1 and 13 of the ’151 patent are similar to claim
    1 of the ’135 patent except that they recite initiating an
    “encrypted channel” and creating a “secure channel,”
    respectively, instead of creating a “VPN.” ’151 patent col.
    46 ll. 55–67, col. 48 ll. 18–29.
    Before the district court, VirnetX accused Apple’s iPh-
    one, iPad, and iPod Touch of infringing claims 1, 3, 7, and
    8 of the ’135 patent and claims 1 and 13 of the ’151 patent
    because they include a feature called “VPN On Demand.”
    When a user enters a domain name into the browser of an
    iOS device, a DNS request is generated. J.A. 1393–94.
    VPN On Demand receives the request and checks a list of
    domain names for which a VPN connection should be
    established, known as a “configuration file.” J.A. 1377. If
    the entered domain name matches a domain name in the
    configuration file, VPN On Demand contacts a VPN
    server to authenticate the user and, if successful, auto-
    matically establishes a VPN between the user’s browser
    and the target computer with which the requested domain
    name is associated. J.A. 1377–78, 1396–98.
    III. Five-Day Jury Trial and Post-Trial Motions
    On August 11, 2010, VirnetX filed this infringement
    action, alleging that Apple’s FaceTime servers infringe
    certain claims of the ’504 and ’211 patents, and that
    Apple’s VPN On Demand feature infringes certain claims
    of the ’135 and ’151 patents. Apple responded that
    FaceTime and VPN On Demand do not infringe, and that
    the asserted claims were invalid as anticipated by a 1996
    publication by Takahiro Kiuchi et al. (“Kiuchi”).
    VIRNETX, INC.   v. CISCO SYSTEMS, INC.                   7
    On April 25, 2012, the district court construed disput-
    ed claim terms, and a jury trial commenced on October
    31, 2012. After a five-day trial, the jury returned its
    verdict, finding all of the asserted claims valid and in-
    fringed. The jury awarded VirnetX $368,160,000 in
    reasonable royalty damages. Apple moved for judgment
    as a matter of law (“JMOL”) or, alternatively, for a new
    trial or remittitur. On February 26, 2013, the district
    court denied Apple’s motions. VirnetX, Inc. v. Apple Inc.,
    
    925 F. Supp. 2d 816
    (E.D. Tex. 2013).
    Apple now appeals the denial of its post-trial motion
    for JMOL or a new trial. This court has jurisdiction
    under 28 U.S.C. § 1295(a)(1).
    DISCUSSION
    I. Claim Construction
    On appeal, Apple argues that the district court erred
    in construing the terms “domain name” and “secure
    communication link,” both recited in the ’504 and ’211
    patents. For the reasons that follow, we affirm the con-
    struction of “domain name” and reverse the construction
    of “secure communication link.”
    Claim construction is a question of law that we review
    de novo. Lighting Ballast Control LLC v. Philips Elecs. N.
    Am. Corp., 
    744 F.3d 1272
    , 1276–77 (Fed. Cir. 2014) (en
    banc); Cybor Corp. v. FAS Techs., Inc., 
    138 F.3d 1448
    ,
    1456 (Fed. Cir. 1998) (en banc). The process of construing
    a claim term begins with the words of the claims them-
    selves. See Vitronics Corp. v. Conceptronic, Inc., 
    90 F.3d 1576
    , 1582 (Fed. Cir. 1996); Phillips v. AWH Corp., 
    415 F.3d 1303
    , 1312–14 (Fed. Cir. 2005) (en banc). However,
    the claims “must be read in view of the specification, of
    which they are a part.” 
    Phillips, 415 F.3d at 1315
    (quot-
    ing Markman v. Westview Instruments, Inc., 
    52 F.3d 967
    ,
    979 (Fed. Cir. 1995) (en banc), aff’d 
    517 U.S. 370
    (1996)).
    Additionally, the doctrine of claim differentiation disfa-
    8                        VIRNETX, INC.   v. CISCO SYSTEMS, INC.
    vors reading a limitation from a dependent claim into an
    independent claim. See InterDigital Commc’ns, LLC v.
    Int’l Trade Comm’n, 
    690 F.3d 1318
    , 1324 (Fed. Cir. 2012).
    Although courts are permitted to consider extrinsic evi-
    dence like expert testimony, dictionaries, and treatises,
    such evidence is generally of less significance than the
    intrinsic record. 
    Phillips, 415 F.3d at 1317
    (citing C.R.
    Bard, Inc. v. U.S. Surgical Corp., 
    388 F.3d 858
    , 862 (Fed.
    Cir. 2004)).
    A. “Domain Name”
    The district court construed “domain name” as “a
    name corresponding to an IP address.” Memorandum
    Opinion & Order at 16, VirnetX, Inc. v. Cisco Sys. Inc., No.
    6:10-cv-416 (E.D. Tex. Apr. 25, 2012), ECF No. 266
    (“Claim Construction Order”). Apple argues, as it did
    below, that the proper construction is “a hierarchical
    sequence of words in decreasing order of specificity that
    corresponds to a numerical IP address.” Apple insists
    that its construction represents the plain and ordinary
    meaning of the term, relying primarily on a technical
    dictionary definition and several examples in the specifi-
    cation (e.g., “Yahoo.com”). We disagree. Intrinsic evi-
    dence supports the district court’s construction of “domain
    name.” The specification of the ’504 and ’211 patents
    suggests the use of the invention for secure communica-
    tions between application programs like “video conferenc-
    ing, e-mail, word processing programs, telephony, and the
    like.” ’504 patent col. 21 ll. 27–29. The disclosure of such
    applications demonstrates that the inventors did not
    intend to limit “domain name” to the particular format-
    ting limitations of websites sought by Apple, i.e., a top-
    level domain, second-level domain, and host name.
    Additionally, fundamental principles of claim differ-
    entiation disfavor reading Apple’s hierarchical limitation
    into the independent claims. Dependent claims in both
    patents require that “at least one” of the domain names
    VIRNETX, INC.   v. CISCO SYSTEMS, INC.                  9
    stored by the system comprise a top-level domain name.
    See, e.g., ’504 patent col. 55 ll. 57–59 (“The system of
    claim 1, wherein at least one of the plurality of domain
    names comprises a top-level domain name.”); ’211 patent
    col. 57 ll. 47–50 (“The non-transitory machine-readable
    medium of claim 36, wherein the instructions comprise
    code for storing the plurality of domain names and corre-
    sponding network addresses including at least one top-
    level domain name.”). The specific limitation of hierar-
    chical formatting in the dependent claims strongly sug-
    gests that the independent claims contemplate domain
    names both with and without the hierarchical format
    exemplified by “Yahoo.com.” See 
    InterDigital, 690 F.3d at 1324
    (“The doctrine of claim differentiation is at its
    strongest . . . ‘where the limitation that is sought to be
    “read into” an independent claim already appears in a
    dependent claim.’” (quoting Liebel-Flarsheim Co. v.
    Medrad, Inc., 
    358 F.3d 898
    , 910 (Fed. Cir. 2004))).
    Such intrinsic evidence is not outweighed by the ex-
    trinsic evidence of one dictionary definition. This is
    particularly true here, where the dictionary definition
    seems to contemplate web addresses on the Internet,
    while the specification makes clear that the claim term in
    question is not so limited. See J.A. 6139–40. Thus, we
    affirm the district court’s construction of the term “do-
    main name” as “a name corresponding to an IP address.”
    B. “Secure Communication Link”
    The district court construed “secure communication
    link” as “a direct communication link that provides data
    security.” Claim Construction Order at 13. Apple argues
    that this term should be construed consistent with “VPN,”
    10                       VIRNETX, INC.   v. CISCO SYSTEMS, INC.
    which the district court construed to require not only data
    security but also anonymity. 1
    As an initial matter, we note that there is no dispute
    that the word “secure” does not have a plain and ordinary
    meaning in this context, and so must be defined by refer-
    ence to the specification. See Oral Arg. 31:50–32:40,
    available at http://www.cafc.uscourts.gov/oral-argument-
    recordings/13-1489/all (acknowledgement by VirnetX’s
    counsel that construction of “secure” requires considera-
    tion of the specification).
    Moreover, we agree with Apple that, when read in
    light of the entire specification, the term “secure commu-
    nication link” requires anonymity. Indeed, the addition of
    anonymity is presented as one of the primary inventive
    contributions of the patent. For example, the Background
    of the Invention states that “[a] tremendous variety of
    methods have been proposed and implemented to provide
    security and anonymity for communications over the
    Internet.” ’504 patent col. 1 ll. 32–35 (emphasis added).
    It goes on to define these two concepts as counterpart
    safeguards against eavesdropping that could occur while
    two computer terminals communicate over the Internet.
    
    Id. at col.
    1 ll. 38–54. Security in this context refers to
    protection of data itself, to preserve the secrecy of its
    contents, while anonymity refers to preventing an eaves-
    dropper from discovering the identity of a participating
    terminal. 
    Id. at col.
    1 ll. 40–54.
    1 The district court construed VPN to mean “a net-
    work of computers which privately and directly communi-
    cate with each other by encrypting traffic on insecure
    paths between the computers where the communication is
    both secure and anonymous.” Claim Construction Order
    at 8.
    VIRNETX, INC.   v. CISCO SYSTEMS, INC.                   11
    Having thus framed the problem, the patent (as ex-
    pected) proposes a solution. Specifically, the Summary of
    the Invention begins by explaining how the invention
    improves security by using a “two-layer encryption for-
    mat” known as the Tunneled Agile Routing Protocol, or
    TARP. 
    Id. at col.
    3 ll. 14–17. First, an “inner layer”
    secures the data itself, 
    id. at col.
    4 ll. 5–7, and then a
    second “outer layer” conceals the data’s “true destination,”
    
    id. at col.
    3 ll. 34–35. The fact that the Summary of the
    Invention gives primacy to these attributes strongly
    indicates that the invention requires more than just data
    security. See, e.g., C.R. 
    Bard, 388 F.3d at 864
    (giving
    particular weight to statements in the Summary of the
    Invention because “[s]tatements that describe the inven-
    tion as a whole, rather than statements that describe only
    preferred embodiments, are more likely to support a
    limiting definition of a claim term”).
    Consistent with this emphasis, the Detailed Descrip-
    tion states that “the message payload is embedded behind
    an inner layer of encryption” and “[e]ach TARP packet’s
    true destination is concealed behind an outer layer of
    encryption.” ’504 patent col. 9 ll. 60–61, col. 11 ll. 2–4.
    The concealment requirement appears throughout the
    specification and is implicated in every embodiment
    associated with the “two-layer encryption” or TARP VPN.
    The fact that anonymity is “repeatedly and consistently”
    used to characterize the invention strongly suggests that
    it should be read as part of the claim. See Eon-Net LP v.
    Flagstar Bancorp., 
    653 F.3d 1314
    , 1321–23 (Fed. Cir.
    2011).
    VirnetX attempts to rebut this suggestion by pointing
    to a single place in the specification where a “secure
    communication path” is referred to as providing only
    security, without anonymity. See ’504 patent col. 39 ll.
    24–35. But that disclosure relates to the “conventional
    architecture” of the prior art that suffers precisely be-
    cause it “hamper[s] anonymous communications on the
    12                       VIRNETX, INC.   v. CISCO SYSTEMS, INC.
    Internet.” 
    Id. at col.
    39 ll. 24, 32–33. And indeed, the
    specification goes on to explain how the invention solves
    that very problem by setting up a VPN, which requires
    anonymity. 
    Id. at col.
    39 ll. 46–62.
    VirnetX also argues that the specification teaches that
    different users have “different needs” such that some
    users need data security while, in other cases, “it may be
    desired” to also have anonymity. Appellee’s Br. 48 (cit-
    ing ’504 patent col. 1 ll. 33–52). Thus, VirnetX insists, the
    TARP protocol (with its requirement of anonymity) is but
    one type of “secure communication link,” and does not
    limit the construction of that term. To be sure, the speci-
    fication mechanically prefaces most passages with the
    phrase “according to one aspect of the present invention.”
    See, e.g., ’504 patent col. 6 l. 36. But the Background and
    Summary of the Invention clearly identify the TARP
    protocol as a key part of the novel solution to the specific
    problem identified in the prior art. Unsurprisingly,
    therefore, VirnetX has not identified even a single embod-
    iment that provides data security but not anonymity.
    Moreover, in several instances the specification ap-
    pears to use the terms “secure communication link” and
    “VPN” interchangeably, suggesting that the inventors
    intended the disputed term to encompass the anonymity
    provided by a VPN. See Nystrom v. Trex Co., 
    424 F.3d 1136
    , 1143 (Fed. Cir. 2005) (“Different terms or phrases in
    separate claims may be construed to cover the same
    subject matter where the written description and prosecu-
    tion history indicate that such a reading of the terms or
    phrases is proper.”). For example, it states that “[w]hen
    software module 3309 is being installed or when the user
    is off-line, the user can optionally specify that all commu-
    nication links established over computer network 3302
    are secure communication links. Thus, anytime that a
    communication link is established, the link is a VPN
    link.” ’504 patent col. 52 ll. 15–19 (emphases added).
    Similarly, in the very next paragraph the specification
    VIRNETX, INC.   v. CISCO SYSTEMS, INC.                  13
    states that “a user at computer 3301 can optionally select
    a secure communication link through proxy computer
    3315. Accordingly, computer 3301 can establish a VPN
    communication link 3323 with secure server computer
    3320 through proxy computer 3315.” 
    Id. at col.
    52 ll. 25–
    29 (emphases added). In both of these instances, the
    specification equates the term “secure communication
    link” with a “VPN.” The only counter-example VirnetX
    can point to is an instance where the specification states,
    in relation to one aspect of the invention, that “[t]he
    secure communication link is a virtual private network
    communication link over the computer network.” 
    Id. at col.
    6 ll. 61–63. But equating the two terms with respect
    to one aspect of the present invention is a far cry from
    expressly divorcing those terms elsewhere, particularly in
    the absence of any embodiment or disclosure that does so.
    Thus, we reverse the district court’s claim construc-
    tion and conclude that the term “secure communication
    link” as used in the ’504 and ’211 patents requires ano-
    nymity. Accordingly, the term should be construed as “a
    direct communication link that provides data security and
    anonymity.”
    II. Infringement
    We review the denial of a motion for JMOL or a new
    trial under the law of the regional circuit. Verizon Servs.
    Corp. v. Cox Fibernet Va., Inc., 
    602 F.3d 1325
    , 1331 (Fed.
    Cir. 2010). The Fifth Circuit requires that a jury’s deter-
    mination must be upheld if it is supported by substantial
    evidence. ClearValue, Inc. v. Pearl River Polymers, Inc.,
    
    668 F.3d 1340
    , 1343 (Fed. Cir. 2012) (citing Med. Care
    Am., Inc. v. Nat’l Union Fire Ins. Co., 
    341 F.3d 415
    , 420
    (5th Cir. 2003)).
    A. ’504 and ’211 Patents
    Apple argues that there was not substantial evidence
    to support the jury’s verdict that its FaceTime servers
    14                       VIRNETX, INC.   v. CISCO SYSTEMS, INC.
    infringe the asserted claims of the ’504 and ’211 patents.
    Apple insists that FaceTime does not infringe the “secure
    communication link” claim term for two reasons: first,
    because when properly construed it requires anonymity,
    which the FaceTime servers do not provide, and second,
    because they do not provide “direct” communication, as
    required by the district court’s claim construction.
    With respect to the first argument, we have now
    construed the disputed claim term so as to require ano-
    nymity. See supra at 13. However, the jury was not
    presented with the question of whether FaceTime infring-
    es the asserted claims under a construction requiring
    anonymity. Thus, we remand for further proceedings to
    determine whether Apple’s FaceTime servers provide
    anonymity.
    With respect to the second argument, Apple argues
    that FaceTime servers do not provide “direct” communica-
    tion because the communications are addressed to a NAT,
    rather than to the receiving device. Appellant’s Br. 43.
    The district court concluded that there was substantial
    evidence to support the jury’s finding that the NAT rout-
    ers used by FaceTime do not impede direct communica-
    tion, 
    VirnetX, 925 F. Supp. 2d at 831
    , and we agree. As
    the district court noted, VirnetX’s expert testified that the
    NAT routers still allow for “end-to-end communication
    between the two devices,” J.A. 1565, because they merely
    translate addresses from the public address space to the
    private address space, but do not terminate the connec-
    tion. J.A. 1465, 1536–37. Even Apple’s expert admitted
    that the connection does not stop at the NAT routers.
    J.A. 1984.
    Apple argues that this testimony cannot support a
    finding of infringement because it is inconsistent with the
    court’s claim construction that required “direct addressa-
    bility.” Appellant’s Br. 43–45. But the district court
    considered this argument and disagreed, noting that its
    VIRNETX, INC.   v. CISCO SYSTEMS, INC.                   15
    claim construction expressly provided that “routers,
    firewalls, and similar servers . . . do not impede ‘direct’
    communication,” and VirnetX presented evidence that
    NATs operate like routers or firewalls. VirnetX, 925 F.
    Supp. 2d at 831.
    Thus, we do not think the district court erred in find-
    ing that there was substantial evidence on which the jury
    could have relied to reach its finding of infringement on
    this element.
    B. ’135 and ’151 Patents
    Apple also argues that there was not substantial
    evidence to support the jury’s verdict that its VPN On
    Demand product infringed the asserted claims of the ’135
    and ’151 patents for several reasons, discussed in turn
    below.
    1. “Determining Whether”
    Apple argues that its VPN On Demand feature does
    not infringe the asserted claims of the ’135 and ’151
    patents because it does not “determine whether” a re-
    quested domain name is a secure website or server.
    Instead, Apple insists that it merely determines whether
    the requested website is listed in the user-created “con-
    figuration file” and initiates a VPN connection for any
    domain name on that list, regardless of whether or not it
    is secure. In response, VirnetX argues that there was
    substantial evidence demonstrating that the VPN On
    Demand system is designed and intended to be used only
    for accessing secure private networks. We agree with
    VirnetX.
    Here, the evidence presented at trial supports the
    conclusion that Apple’s VPN On Demand product infring-
    es the asserted claim limitation in its normal configura-
    tion. In particular, VirnetX’s expert testified that Apple’s
    technical design documents and internal technical presen-
    tations relating to the VPN On Demand system (many of
    16                       VIRNETX, INC.   v. CISCO SYSTEMS, INC.
    which are confidential and cannot be quoted here) make
    clear that a VPN connection should only be established
    for private web addresses. Thus, regardless of whether a
    user could misconfigure the list by entering public domain
    names, Apple’s planning documents, internal emails, and
    presentations all explained that VPN On Demand’s
    primary use is to connect users to secure sites using a
    VPN. That is all that is required. See Hilgraeve Corp. v.
    Symantec Corp., 
    265 F.3d 1336
    , 1343 (Fed. Cir. 2001).
    Moreover, this description of the VPN On Demand
    feature is consistent with how the claimed functionality is
    described in the specification. For example, in one embod-
    iment, the DNS proxy determines whether a request is for
    a secure site by checking the domain name against a table
    or list of domain names. ’135 patent col. 38 ll. 23–30. In
    other words, the proxy identifies a request for “access to a
    secure site . . . by reference to an internal table of such
    sites.” 
    Id. That is
    precisely how the VPN On Demand
    feature operates.
    We therefore conclude that the jury’s finding that the
    VPN On Demand product infringes the “determining
    whether” limitation was supported by substantial evi-
    dence.
    2. “Between”
    a. Literal Infringement of Claim 1 of the ’135 Patent and
    Claim 13 of the ’151 Patent
    Claim 1 of the ’135 patent requires creating a “VPN”
    “between” the client and a target computer. ’135 patent
    col. 47 ll. 20–22. Similarly, claim 13 of the ’151 patent
    requires creating a “secure channel” “between” the client
    and the secure server. ’151 patent col. 48 ll. 28–29. For
    both claims, the district court construed “between” to
    mean “extending from” the client to the target computer.
    Claim Construction Order at 26.
    VIRNETX, INC.   v. CISCO SYSTEMS, INC.                     17
    Apple argues that its VPN On Demand product fails
    to meet this limitation because it only secures communi-
    cations between the iPhone and the VPN server, but not
    between the VPN server and the target computer. Vir-
    netX responds that Apple’s product is intended to be used
    with private networks, which are generally configured to
    be both secure and anonymous. In other words, VirnetX
    argues that the secure channel between the VPN server
    and the target computer is provided by the target com-
    puter itself. After considering the record as a whole, we
    conclude that there was substantial evidence to support
    the jury’s verdict of infringement on this limitation.
    At trial, VirnetX presented evidence and testimony to
    the jury that “the virtual private network extend[s] from
    the client computer to the target computer . . . because it’s
    encrypted on the insecure paths, and it’s secure within
    the corporate network.” J.A. 1400–01. VirnetX’s expert
    testified that one of ordinary skill would understand that
    the path extending from the VPN server to the target
    computer, i.e., within the private network, would be
    secure and anonymous owing to protection provided by
    the private network. J.A. 1080 (“That network is secure,
    because it’s been physically secured; and it also has
    what’s called a firewall between its network and the
    public network. So it keeps the bad guys out.”); J.A. 1379
    (“If that’s a private network of the company that they’ve
    set up behind a VPN server, the company would have
    configured that to be secure.”); J.A. 1396 (“[T]hese are . . .
    private networks that are not to be accessed by others.
    They require authorization for access.”). The jury also
    heard testimony that while in some situations traffic
    could be unsecured behind the VPN server, J.A. 1997–98,
    this scenario would be “atypical.” J.A. 1992–93. For
    example, VirnetX presented evidence to the jury that
    Apple itself advertised that VPN On Demand is designed
    to connect with “private corporate networks” and “works
    with a variety of authentication methods.” J.A. 20001.
    18                       VIRNETX, INC.   v. CISCO SYSTEMS, INC.
    And, more to the point, the jury heard that the “private
    corporate networks” to which VPN On Demand is intend-
    ed to connect employ security measures including VPN
    servers, VPN authentication servers, proxy servers, and
    firewalls which regulate access to private resources and
    prevent unauthorized users from breaching. J.A. 1080,
    1379, 1401.
    Apple argues that this finding of infringement neces-
    sarily rests on a series of “assumptions” about how all
    private networks operate in order to conclude that VPN
    On Demand is “typically” configured to operate in the
    manner accused of infringement. Appellant’s Br. 30–31.
    However, VirnetX’s expert relied on Apple’s own internal
    technical documentation, product specifications, and
    marketing presentations, several of which describe specif-
    ic security measures used by the private networks to
    which VPN On Demand is intended to connect. This
    evidence demonstrates not only that VPN On Demand
    may be configured to interact with private networks, but
    that this was apparently Apple’s primary objective. Apple
    would have VirnetX prove that VPN On Demand has no
    non-infringing modes of operation. But, as noted above,
    VirnetX bears no such burden. See supra at 15–16; see
    also z4 Techs., Inc. v. Microsoft Corp., 
    507 F.3d 1340
    , 1350
    (Fed. Cir. 2007) (“[I]nfringement is not avoided merely
    because a non-infringing mode of operation is possible.”).
    We cannot agree that the jury’s finding lacks substantial
    evidence because VirnetX did not specifically disprove
    that VPN On Demand can, in atypical situations, estab-
    lish a VPN with insecure networks.
    Apple also responds that this evidence is insufficient
    because VirnetX’s expert testified that VPN On Demand
    only encrypts communications between the iPhone and
    the VPN server—by implication leaving the path from the
    VPN server to the target unencrypted. Appellant’s Br. 29
    (quoting J.A. 1392). However, the district court’s con-
    struction of “VPN” does not require that traffic on a
    VIRNETX, INC.   v. CISCO SYSTEMS, INC.                   19
    secure path be encrypted. Rather, the construction only
    requires encryption of traffic “on insecure paths.” Claim
    Construction Order at 8. Moreover, as indicated by
    the ’135 patent, encryption is just one possible way to
    address data security. ’135 patent col. 1 ll. 38–39 (“Data
    security is usually tackled using some form of data en-
    cryption.” (emphasis added)).      And VirnetX provided
    substantial evidence for the jury to conclude that paths
    beyond the VPN server may be rendered secure and
    anonymous by means of “physical security” present in the
    private corporate networks connected to by VPN On
    Demand. See, e.g., J.A. 1401.
    Accordingly, we conclude that the jury’s finding that
    the VPN On Demand feature creates a “VPN” or a “secure
    channel” that extends from the client to the target com-
    puter was supported by substantial evidence. We there-
    fore affirm the district court’s denial of JMOL as to claim
    1 of the ’135 patent and claim 13 of the ’151 patent.
    b. Infringement of Claim 1 of the ’151 Patent Under the
    Doctrine of Equivalents
    Claim 1 of the ’151 patent is similar to claim 13 except
    that it requires initiating an “encrypted channel”—rather
    than a “secure channel”—“between” the client and the
    secure server. ’151 patent col. 46 ll. 66–67. With respect
    to infringement, VirnetX conceded that VPN On Demand
    does not literally practice this limitation because the
    private network between the VPN server and the target is
    “not necessarily encrypted” from end to end. J.A. 1420–
    21. Rather, VirnetX asserted that VPN On Demand
    infringes under the doctrine of equivalents because the
    difference between secure communication via encryption
    and secure communication in general is insubstantial.
    J.A. 1421–24. Apple argues that VirnetX’s theory of
    equivalents is legally insufficient because it vitiates the
    “encrypted channel” element. Appellant’s Br. 32–33.
    20                       VIRNETX, INC.   v. CISCO SYSTEMS, INC.
    To find infringement under the doctrine of equiva-
    lents, any differences between the claimed invention and
    the accused product must be insubstantial. See Graver
    Tank & Mfg. Co. v. Linde Air Prods. Co., 
    339 U.S. 605
    ,
    608 (1950).     Insubstantiality may be determined by
    whether the accused device performs substantially the
    same function in substantially the same way to obtain
    substantially the same result as the claim limitation.
    Crown Packaging Tech., Inc. v. Rexam Beverage Can Co.,
    
    559 F.3d 1308
    , 1312 (Fed. Cir. 2009). This is a question of
    fact. Anchor Wall Sys., Inc. v. Rockwood Retaining Walls,
    Inc., 
    340 F.3d 1298
    , 1313 (Fed. Cir. 2003). Vitiation is not
    an exception to the doctrine of equivalents. Deere & Co. v.
    Bush Hog, LLC, 
    703 F.3d 1349
    , 1356 (Fed. Cir. 2012).
    Rather, it is a legal determination that “the evidence is
    such that no reasonable jury could determine two ele-
    ments to be equivalent.” 
    Id. (citation omitted).
        After considering the record as a whole, we conclude
    that the evidence presented at trial does not support the
    jury’s finding of infringement under the doctrine of equiv-
    alents. VirnetX’s expert testified that VPN On Demand
    (a) performs substantially the same function because it
    secures the communication between the client and the
    secure server, (b) does so in substantially the same way
    by protecting data through encryption on insecure paths
    that are vulnerable to eavesdroppers, and (c) achieves
    substantially the same result of successfully protecting
    the entire communication path from potential eavesdrop-
    pers. See J.A. 1424.
    Notably, in explaining the “way” that VPN On De-
    mand secures communications, the expert did not testify
    that VPN On Demand provides encryption on the alleged-
    ly secure pathway between the VPN server and the pri-
    vate network, but only on the insecure portion of the
    pathway. Thus, his testimony effectively equates the
    “security” of the private network with the “encryption”
    provided by the VPN server. But the patent consistently
    VIRNETX, INC.   v. CISCO SYSTEMS, INC.                   21
    differentiates between “security” and “encryption.” Both
    the claims and the specification of the ’151 patent make
    clear that encryption is a narrower, more specific re-
    quirement than security. For example, the specification
    states that encryption is just one possible way to address
    data security. ’151 patent col. 1 ll. 49–50 (“Data security
    is usually tackled using some form of data encryption.”
    (emphasis added)). Additionally, one of the primary
    differences between the steps performed in claim 1 of
    the ’151 patent and the steps performed in claim 13 is
    that claim 13 requires creating a “secure” channel, while
    claim 1 specifically requires that the channel be “encrypt-
    ed.”
    In light of these distinctions in the patent itself, the
    jury’s implicit finding that VPN On Demand achieves the
    result of protecting communications from eavesdropping
    in “substantially the same way” as contemplated by the
    “encrypted channel” claim limitation was not supported
    by VirnetX’s expert’s testimony. See Crown 
    Packaging, 559 F.3d at 1312
    . No reasonable jury could have deter-
    mined that the security provided by the VPN On Demand
    system—which includes encryption on the insecure paths
    but otherwise relies on the security provided by private
    networks—is equivalent to the “encrypted channel”
    required by claim 1 of the ’151 patent. The district court’s
    denial of JMOL as to that claim must therefore be re-
    versed.
    III. Invalidity
    A party challenging the validity of a patent must es-
    tablish invalidity by clear and convincing evidence. See
    Microsoft Corp. v. i4i Ltd. P’ship, 
    131 S. Ct. 2238
    , 2242
    (2011). Anticipation is a factual question that we review
    for substantial evidence. SynQor, Inc. v. Artesyn Techs.,
    Inc., 
    709 F.3d 1365
    , 1373 (Fed. Cir. 2013). A claim is
    anticipated only if each and every element is found within
    a single prior art reference, arranged as claimed. See
    22                       VIRNETX, INC.   v. CISCO SYSTEMS, INC.
    NetMoneyIN, Inc. v. VeriSign, Inc., 
    545 F.3d 1359
    , 1369
    (Fed. Cir. 2008).
    Apple argues that the asserted claims are anticipated
    by the Kiuchi reference. However, we conclude that the
    jury heard substantial evidence that at least one element
    of each asserted claim was missing from that reference.
    With respect to the ’135, ’504, and ’211 patents, the jury
    heard evidence that Kiuchi’s proxy servers at least do not
    teach “direct communication” between a client and target
    computer, which is sufficient to defeat a claim of anticipa-
    tion. J.A. 2343–44. Specifically, the jury heard expert
    testimony that Kiuchi’s client-side and server-side proxies
    terminate the connection, process information, and create
    a new connection—actions that are not “direct” within the
    meaning of the asserted claims. J.A. 2334–35. VirnetX
    distinguished such proxy activities from the operation of
    NAT routers which—unlike proxy servers in the prior
    art—do not terminate the connection.
    Additionally, with respect to the ’151 patent, there
    was substantial evidence to support VirnetX’s argument
    that Kiuchi fails to disclose the requirement that the DNS
    request be “sent by a client.” ’151 patent col. 46 l. 57.
    Apple argued that the “client-side proxy” of Kiuchi meets
    the “client” limitation, but there was evidence that the
    “client” of Kiuchi is actually a web browser, a component
    that is distinguishable from the client-side proxy. See
    J.A. 2341. Thus, the district court did not err in denying
    Apple’s JMOL motion with respect to invalidity.
    IV. Exclusion of Evidence
    At trial, to prove induced infringement, VirnetX at-
    tempted to show that Apple knew or was willfully blind to
    the fact that its customers’ use of its products would
    infringe valid patent claims. In defense, Apple sought to
    inform the jury that, after learning of VirnetX’s allega-
    tions, Apple initiated reexaminations against the asserted
    patents. Apple’s requests for reexamination resulted in
    VIRNETX, INC.   v. CISCO SYSTEMS, INC.                     23
    initial rejections of the asserted claims at the United
    States Patent and Trademark Office (“PTO”). Apple
    offered these rejections as evidence of Apple’s reasonably-
    held belief that the patents were invalid. The district
    court, however, excluded this proffer, concluding that
    such non-final actions in pending reexaminations would
    be “highly prejudicial evidence that risks misleading the
    jury.” 
    VirnetX, 925 F. Supp. at 842
    .
    We apply regional circuit law to evidentiary issues.
    The Fifth Circuit reviews a district court’s exclusion of
    evidence under Federal Rule of Evidence 403 for “clear
    abuse of discretion” resulting in substantial prejudice.
    Wellogix, Inc. v. Accenture, L.L.P., 
    716 F.3d 867
    , 882 (5th
    Cir. 2013). In this case, we cannot say that the district
    court abused its discretion in excluding this evidence.
    Apple asserts that the rejections are relevant because
    they establish its good faith belief that the asserted
    claims are invalid, thereby negating the requisite intent
    for inducement. Appellant’s Br. 50 (citing Commil USA,
    LLC v. Cisco Sys., Inc., 
    720 F.3d 1361
    , 1368–69 (Fed. Cir.
    2013)). As an initial matter, we note that this court’s
    precedent has often warned of the limited value of actions
    by the PTO when used for such purposes. See, e.g.,
    Hoechst Celanese Corp. v. BP Chems. Ltd., 
    78 F.3d 1575
    ,
    1584 (Fed. Cir. 1996) (“[G]rant by the examiner of a
    request for reexamination is not probative of unpatenta-
    bility.”); Acoustical Design, Inc. v. Control Elecs. Co., 
    932 F.2d 939
    , 942 (Fed. Cir. 1991) (“[I]nitial rejection by the
    [PTO] . . . hardly justifies a good faith belief in the inva-
    lidity of the claims.”). However, in this case we need not
    decide whether our opinion in Commil justifies reliance
    on reexamination evidence to establish a good faith belief
    of invalidity. Instead, we conclude that, regardless of the
    evidence’s relevance to a fact at issue at trial, the district
    court would still not have abused its discretion in finding
    that the probative value was substantially outweighed by
    the risk of unfair prejudice to the patentee, confusion with
    24                       VIRNETX, INC.   v. CISCO SYSTEMS, INC.
    invalidity (on the merits), or misleading the jury, thereby
    justifying exclusion under Federal Rule of Evidence 403.
    See, e.g., 
    SynQor, 709 F.3d at 1380
    (finding no abuse of
    discretion for excluding non-final reexamination evidence
    as being “confusing and more prejudicial than probative”);
    Callaway Golf Co. v. Acushnet Co., 
    576 F.3d 1331
    , 1342–
    43 (Fed. Cir. 2009) (finding the probative value of a co-
    pending reexamination marginal and the effect likely to
    be highly prejudicial). Thus, we affirm the district court’s
    exclusion of this evidence.
    V. Damages
    At trial, VirnetX’s damages expert, Mr. Roy Wein-
    stein, provided three reasonable royalty theories, which
    the district court admitted over Apple’s challenges under
    Daubert v. Merrell Dow Pharmaceuticals, Inc., 
    509 U.S. 579
    (1993).
    Weinstein’s first approach began with the lowest sale
    price of each model of the accused iOS devices containing
    the accused features. J.A. 1616–23. Weinstein then
    applied a 1% royalty rate to the base, derived from a
    VirnetX policy of seeking to license its patents for at least
    1–2% of the entire value of products sold and several
    allegedly comparable licenses. J.A. 1595, 1613–14. This
    theory yielded a $708 million demand, consisting of $566
    million for products including both FaceTime and VPN
    On Demand, and $142 million for those including only
    VPN On Demand. J.A. 1622–24, 1644.
    Weinstein also offered a second damages theory, re-
    garding FaceTime alone, relying on a mathematical
    theorem proved by John Nash, a mathematician who
    proved a number of results in game theory that have
    become important in economics and other fields. J.A.
    1628–29. Nash was a co-winner of the 1994 Nobel Prize
    in Economics for some of this work, though not the theo-
    rem at issue here—published as “The Bargaining Prob-
    lem” in 18 Econometrica 155–62 (Apr. 1950). Like other
    VIRNETX, INC.   v. CISCO SYSTEMS, INC.                  25
    mathematical theorems, this theorem states a number of
    premises and establishes a conclusion that follows from
    those premises. In particular, under the conditions stated
    in the premises, where two persons bargain over a matter,
    there is a “solution” to the negotiation problem satisfying
    stated conditions on a desirable result (bargain). That
    solution—in which “each bargainer get[s] the same money
    profit,” 
    id. at 162—has
    come to be called the Nash Bar-
    gaining Solution.
    Weinstein, invoking the Nash Bargaining Solution,
    testified that “the parties [would have] split between
    themselves the incremental or additional profits that are
    associated with the use of the patented technology.” J.A.
    1630. Weinstein derived the profits associated with
    FaceTime from the revenue generated by the addition of a
    “front-facing” camera on Apple’s mobile devices. Without
    examining the applicability to this case of all the precon-
    ditions for the Nash Bargaining Solution, he invoked the
    Solution as suggesting a 50/50 split of those profits, and
    then modified that result by 10%, explaining that VirnetX
    would have received only 45% of the profit because of its
    weaker bargaining position, leaving 55% for Apple. J.A.
    1633, 1709. This calculation amounted to $588 million in
    damages for infringement by FaceTime. J.A. 1633–38.
    Finally, Weinstein offered yet another theory for
    FaceTime, again relying on the Nash Bargaining Solu-
    tion. This time, he claimed that FaceTime “drove sales”
    for Apple iOS products. J.A. 1639. Weinstein extrapolat-
    ed from a customer survey to assert that 18% of all iOS
    device sales would not have occurred without the addition
    of FaceTime. J.A. 1641. From that figure, he determined
    the amount of Apple’s profits that he believed were at-
    tributable to the FaceTime feature, and apportioned 45%
    of the profits to VirnetX, consistent with his previous
    application of the Nash theory. Using this approach,
    Weinstein arrived at damages of $5.13 per unit, totaling
    $606 million in damages for FaceTime. J.A. 1643.
    26                        VIRNETX, INC.   v. CISCO SYSTEMS, INC.
    Ultimately, the jury awarded VirnetX $368 million in
    damages. Apple now challenges each of Weinstein’s
    damages theories, as well as the district court’s jury
    instruction on damages. For the reasons stated below, we
    vacate the jury’s damages award and remand for further
    proceedings consistent with this opinion.
    A. Jury Instruction
    Upon a finding of infringement, “the court shall award
    the claimant damages adequate to compensate for the
    infringement, but in no event less than a reasonable
    royalty for the use made of the invention by the infring-
    er.” 35 U.S.C. § 284. The most common method for
    determining a reasonable royalty is the hypothetical
    negotiation approach, which “attempts to ascertain the
    royalty upon which the parties would have agreed had
    they successfully negotiated an agreement just before
    infringement began.” Lucent Techs., Inc. v. Gateway, Inc.,
    
    580 F.3d 1301
    , 1324 (Fed. Cir. 2009). A reasonable royal-
    ty may be a lump-sum payment not calculated on a per-
    unit basis, but it may also be, and often is, a running
    payment that varies with the number of infringing units.
    In that event, it generally has two prongs: a royalty base
    and a royalty rate.
    No matter what the form of the royalty, a patentee
    must take care to seek only those damages attributable to
    the infringing features. Indeed, the Supreme Court long
    ago observed that a patentee
    must in every case give evidence tending to sepa-
    rate or apportion the defendant’s profits and the
    patentee’s damages between the patented feature
    and the unpatented features, and such evidence
    must be reliable and tangible, and not conjectural
    or speculative; or he must show, by equally relia-
    ble and satisfactory evidence, that the profits and
    damages are to be calculated on the whole ma-
    chine, for the reason that the entire value of the
    VIRNETX, INC.   v. CISCO SYSTEMS, INC.                     27
    whole machine, as a marketable article, is proper-
    ly and legally attributable to the patented feature.
    Garretson v. Clark, 
    111 U.S. 120
    , 121 (1884).
    Thus, when claims are drawn to an individual compo-
    nent of a multi-component product, it is the exception, not
    the rule, that damages may be based upon the value of
    the multi-component product. LaserDynamics, Inc. v.
    Quanta Computer, Inc., 
    694 F.3d 51
    , 67–68 (Fed. Cir.
    2012). Indeed, we recently reaffirmed that “[a] patentee
    may assess damages based on the entire market value of
    the accused product only where the patented feature
    creates the basis for customer demand or substantially
    creates the value of the component parts.” Versata Soft-
    ware, Inc. v. SAP Am., Inc., 
    717 F.3d 1255
    , 1268 (Fed. Cir.
    2013) (emphasis added) (quoting 
    SynQor, 709 F.3d at 1383
    ). In the absence of such a showing, principles of
    apportionment apply.
    These strict requirements limiting the entire market
    value exception ensure that a reasonable royalty “does not
    overreach and encompass components not covered by the
    patent.” 
    LaserDynamics, 694 F.3d at 70
    ; see also Garret-
    
    son, 111 U.S. at 121
    (“[T]he patentee must show in what
    particulars his improvement has added to the usefulness
    of the machine or contrivance.”). Thus, “[i]t is not enough
    to merely show that the [patented feature] is viewed as
    valuable, important, or even essential to the use of the
    [overall product].”   
    LaserDynamics, 694 F.3d at 68
    .
    Instead, this court has consistently held that “a reasona-
    ble royalty analysis requires a court to . . . carefully tie
    proof of damages to the claimed invention’s footprint in
    the market place.” ResQNet.com, Inc. v. Lansa, Inc., 
    594 F.3d 860
    , 869 (Fed. Cir. 2010); see also Cornell Univ. v.
    Hewlett-Packard Co., 
    609 F. Supp. 2d 279
    , 285 (N.D.N.Y.
    2009) (“The entire market value rule indeed permits
    damages on technology beyond the scope of the claimed
    invention, but only upon proof that damages on the un-
    28                       VIRNETX, INC.   v. CISCO SYSTEMS, INC.
    patented components or technology is necessary to fully
    compensate for infringement of the patented invention.”).
    Additionally, we have also cautioned against reliance on
    the entire market value of the accused products because it
    “cannot help but skew the damages horizon for the jury,
    regardless of the contribution of the patented component
    to this revenue.” Uniloc USA, Inc. v. Microsoft Corp., 
    632 F.3d 1292
    , 1320 (Fed. Cir. 2011).
    Apple argues that the district court misstated this law
    on the entire market value rule in its jury instruction.
    The district court instructed the jury as follows:
    In determining a royalty base, you should not use
    the value of the entire apparatus or product un-
    less either: (1) the patented feature creates the
    basis for the customers’ demand for the product,
    or the patented feature substantially creates the
    value of the other component parts of the product;
    or (2) the product in question constitutes the
    smallest saleable unit containing the patented
    feature.
    J.A. 2515–16. Apple argues that this instruction inappro-
    priately created a second exception that would allow a
    patentee to rely on the entire market value of a multi-
    component product so long as that product is the smallest
    salable unit containing the patented feature.
    We agree with Apple that the district court’s instruc-
    tion misstates our law. To be sure, we have previously
    permitted patentees to base royalties on the “smallest
    salable patent-practicing unit.” 
    LaserDynamics, 694 F.3d at 67
    . However, the instruction mistakenly suggests that
    when the smallest salable unit is used as the royalty base,
    there is necessarily no further constraint on the selection
    of the base. That is wrong. For one thing, the fundamen-
    tal concern about skewing the damages horizon—of using
    a base that misleadingly suggests an inappropriate
    VIRNETX, INC.   v. CISCO SYSTEMS, INC.                  29
    range—does not disappear simply because the smallest
    salable unit is used.
    Moreover, the smallest salable unit approach was in-
    tended to produce a royalty base much more closely tied
    to the claimed invention than the entire market value of
    the accused products. Indeed, that language first arose in
    the Cornell case, where the district court noted that,
    rather than pursuing a “royalty base claim encompassing
    a product with significant non-infringing components,”
    the patentee should have based its damages on “the
    smallest salable infringing unit with close relation to the
    claimed 
    invention.” 609 F. Supp. 2d at 287
    –88 (emphasis
    added). In other words, the requirement that a patentee
    identify damages associated with the smallest salable
    patent-practicing unit is simply a step toward meeting the
    requirement of apportionment.         Where the smallest
    salable unit is, in fact, a multi-component product con-
    taining several non-infringing features with no relation to
    the patented feature (as VirnetX claims it was here), the
    patentee must do more to estimate what portion of the
    value of that product is attributable to the patented
    technology. To hold otherwise would permit the entire
    market value exception to swallow the rule of apportion-
    ment. 2
    In reaching this conclusion, we are cognizant of the
    difficulty that patentees may face in assigning value to a
    feature that may not have ever been individually sold.
    However, we note that we have never required absolute
    precision in this task; on the contrary, it is well-
    understood that this process may involve some degree of
    2   As, indeed, it did in this case, where VirnetX ef-
    fectively relied on the entire market value of the iOS
    devices without showing that the patented features drove
    demand for those devices, simply by asserting that they
    were the smallest salable units.
    30                       VIRNETX, INC.   v. CISCO SYSTEMS, INC.
    approximation and uncertainty. See generally Unisplay,
    S.A. v. Am. Elec. Sign Co., 
    69 F.3d 512
    , 517 (Fed. Cir.
    1995).
    We conclude that the district court’s jury instruction
    regarding the entire market value rule was legally erro-
    neous. Moreover, that error cannot be considered harm-
    less, as VirnetX’s expert relied on the entire value of the
    iOS devices as the “smallest salable units,” without at-
    tempting to apportion the value attributable to the VPN
    On Demand and FaceTime features. Thus, it is clear that
    the jury’s verdict was tainted by the erroneous jury in-
    struction.
    B. Weinstein’s First Approach: Royalty Base
    In addition to the erroneous jury instruction, Apple
    argues that the testimony of VirnetX’s expert on the
    proper royalty base should have been excluded because it
    relied on the entire market value of Apple’s products
    without demonstrating that the patented features drove
    the demand for those products. For similar reasons to
    those stated above, we agree.
    The admissibility of expert testimony is governed by
    the Federal Rules of Evidence and the principles laid out
    in Daubert v. Merrell Dow Pharmaceuticals, Inc., 
    509 U.S. 579
    (1993). The district court’s “gatekeeping obligation”
    applies to all types of expert testimony. Kumho Tire Co.
    v. Carmichael, 
    526 U.S. 137
    , 147 (1999). While questions
    regarding which facts are most relevant for calculating a
    reasonable royalty are properly left to the jury, a critical
    prerequisite is that the underlying methodology be sound.
    Here, it was not, and the district court should have exer-
    cised its gatekeeping authority to ensure that only theo-
    ries comporting with settled principles of apportionment
    were allowed to reach the jury.
    Under Weinstein’s first damages theory, he undisput-
    edly based his calculations on the entire cost of the iOS
    VIRNETX, INC.   v. CISCO SYSTEMS, INC.                   31
    devices, ranging in value from $199 for the iPod Touch to
    $649 for the iPhone 4S. Weinstein used the base price at
    which each product was sold, excluding only charges for
    additional memory sold separately. He called this the
    smallest salable unit. However, when asked whether this
    “remove[d] features that aren’t accused in this case,”
    Weinstein answered as follows:
    To the extent that the products that we’re talking
    about here contain additional features, like addi-
    tional memory, for instance, that Apple was charg-
    ing for, by using the lowest saleable unit, I’m
    doing as much as I can to remove payments for
    those features . . . .
    J.A. 1620 (emphasis added). This testimony confirms that
    Weinstein did not even attempt to subtract any other
    unpatented elements from the base, which therefore
    included various features indisputably not claimed by
    VirnetX, e.g., touchscreen, camera, processor, speaker,
    and microphone, to name but a few. J.A. 1143–44.
    VirnetX defends Weinstein’s approach by insisting
    that “software creates the largest share of the product’s
    value” for these popular iOS products. Appellee’s Br. 60.
    But this misses the point. Whether “viewed as valuable,
    important, or even essential,” the patented feature must
    be separated. 
    LaserDynamics, 694 F.3d at 68
    . Weinstein
    made no attempt to separate software from hardware,
    much less to separate the FaceTime software from other
    valuable software components.
    Indeed, the record supports Apple’s contention that
    Weinstein could have apportioned a smaller per unit
    figure for FaceTime; namely, for the use of FaceTime on
    Mac computers he used a royalty base of $29—the cost of
    the software upgrade. J.A. 1619. And he used an even
    lower estimate to represent the patentable contributions
    to iOS devices in his application of the Nash Bargaining
    Solution, calculating incremental revenues due to
    32                        VIRNETX, INC.   v. CISCO SYSTEMS, INC.
    FaceTime at $15 per iOS device. J.A. 1634–36. The only
    reason Weinstein gave for not using the $29 as the base
    for other iOS products was that Apple does not actually
    charge separately for FaceTime on those devices. J.A.
    1673–74. But, as explained above, a patentee’s obligation
    to apportion damages only to the patented features does
    not end with the identification of the smallest salable unit
    if that unit still contains significant unpatented features. 3
    Thus, VirnetX cannot simply hide behind Apple’s
    sales model to avoid the task of apportionment. This
    court rejects the excuse that “practical and economic
    necessity compelled [the patentee] to base its royalty on
    the price of an entire [device].” 
    LaserDynamics, 694 F.3d at 69
    . There is no “necessity-based exception to the entire
    market value rule.” 
    Id. at 70.
    On the contrary, a patent-
    ee must be reasonable (though may be approximate) when
    seeking to identify a patent-practicing unit, tangible or
    intangible, with a close relation to the patented feature.
    In the end, VirnetX should have identified a patent-
    practicing feature with a sufficiently close relation to the
    claimed functionality. The law requires patentees to
    apportion the royalty down to a reasonable estimate of the
    value of its claimed technology, or else establish that its
    patented technology drove demand for the entire product.
    VirnetX did neither. As we noted in LaserDynamics:
    Whether called “product value apportionment” or
    anything else, the fact remains that the royalty
    was expressly calculated as a percentage of the
    entire market value of a [multi-component prod-
    3  Because Apple has not challenged it, we offer no
    opinion on whether the $29 software upgrade is itself so
    closely related to the patented feature that VirnetX may
    rely on its entire value in determining the proper royalty
    base for the FaceTime feature.
    VIRNETX, INC.   v. CISCO SYSTEMS, INC.                     33
    uct] rather than a patent-practicing [component]
    alone. This, by definition, is an application of the
    entire market value rule.
    
    Id. at 68.
    In calculating the royalty base, Weinstein did
    not even try to link demand for the accused device to the
    patented feature, and failed to apportion value between
    the patented features and the vast number of non-
    patented features contained in the accused products.
    Because Weinstein did not “carefully tie proof of damages
    to the claimed invention’s footprint in the market place,”
    
    Uniloc, 632 F.3d at 1317
    (quoting 
    ResQNet, 594 F.3d at 869
    ), his testimony on the royalty base under this ap-
    proach was inadmissible and should have been excluded.
    C. Weinstein’s First Approach: Royalty Rate
    In addition to challenging Weinstein’s testimony with
    respect to the royalty base, Apple argues that his testi-
    mony with respect to the royalty rate should also have
    been excluded.
    After determining the royalty base, Weinstein applied
    a 1% royalty rate, based on six allegedly comparable
    licenses, as well as his understanding that VirnetX had a
    “policy” of licensing its patents for 1–2%. Apple argues
    that the licenses on which Weinstein relied were not
    sufficiently comparable to the license that would have
    resulted from the hypothetical negotiation. In particular,
    Apple points out that two of the licenses predated the
    patents-in-suit. Both of those agreements related to
    technology leading to the claimed invention, and one
    contained a software license in addition to a license for
    various patent applications. Apple further complains that
    three of the other licenses were entered into in 2012, a full
    three years after the date of the “hypothetical negotia-
    tion,” set in June 2009. Apple argues that at the time
    those licenses were entered into, VirnetX was in a much
    better financial position (and therefore a better bargain-
    ing position) than it was in 2009. Finally, Apple notes
    34                       VIRNETX, INC.   v. CISCO SYSTEMS, INC.
    that the sixth license covered sixty-eight VirnetX patents,
    and was therefore much broader than the license to four
    patents Apple would be seeking in the hypothetical nego-
    tiation. It also equated to a 0.24% royalty rate, which is
    significantly lower than the 1–2% rate Weinstein testified
    VirnetX would accept.
    We have held that in attempting to establish a rea-
    sonable royalty, the “licenses relied on by the patentee in
    proving damages [must be] sufficiently comparable to the
    hypothetical license at issue in suit.” 
    Lucent, 580 F.3d at 1325
    . “When relying on licenses to prove a reasonable
    royalty, alleging a loose or vague comparability between
    different technologies or licenses does not suffice.” La-
    
    serDynamics, 694 F.3d at 79
    . However, we have never
    required identity of circumstances; on the contrary, we
    have long acknowledged that “any reasonable royalty
    analysis ‘necessarily involves an element of approxima-
    tion and uncertainty.’” 
    Lucent, 580 F.3d at 1325
    (quoting
    
    Unisplay, 69 F.3d at 517
    ). Thus, we have cautioned that
    “district courts performing reasonable royalty calculations
    [must] exercise vigilance when considering past licenses
    to technologies other than the patent in suit,” 
    ResQNet, 594 F.3d at 869
    , and “must account for differences in the
    technologies and economic circumstances of the contract-
    ing parties,” Finjan, Inc. v. Secure Computing Corp., 
    626 F.3d 1197
    , 1211 (Fed. Cir. 2010).
    With those principles in mind, we conclude that the
    district court here did not abuse its discretion in permit-
    ting Weinstein to rely on the six challenged licenses. To
    begin with, four of those licenses did indeed relate to the
    actual patents-in-suit, while the others were drawn to
    related technology. Moreover, all of the other differences
    that Apple complains of were presented to the jury, allow-
    ing the jury to fully evaluate the relevance of the licenses.
    See J.A. 1600, 1650, 1678–82. No more is required in
    these circumstances.
    VIRNETX, INC.   v. CISCO SYSTEMS, INC.                    35
    Our case law does not compel a contrary result. In
    ResQNet, we faulted the district court for relying on
    licenses with “no relationship to the claimed invention,”
    nor even a “discernible link to the claimed 
    technology.” 594 F.3d at 870
    . And in Lucent, we rejected reliance on
    licenses from “vastly different situation[s]” or where the
    subject matter of certain agreements was not even ascer-
    tainable from the evidence presented at 
    trial. 580 F.3d at 1327
    –28. The licenses in this case—though not immune
    from challenge—bear a closer relationship to the hypo-
    thetical negotiation that would have occurred.
    This case is therefore much more akin to the circum-
    stances in Finjan and ActiveVideo Networks, Inc. v. Veri-
    zon Communications, Inc., 
    694 F.3d 1312
    (Fed. Cir. 2012).
    In Finjan, there were several differences between the
    single license relied upon and the hypothetical negotia-
    tion, most notably that Finjan did not compete with the
    licensee as it did with the defendant in the case, and that
    the license involved a lump sum rather than a running
    
    royalty. 626 F.3d at 1212
    . Nevertheless, we affirmed the
    damages award based on that license because “[those]
    differences permitted the jury to properly discount the . . .
    license.” 
    Id. And in
    ActiveVideo, the damages expert
    relied on two agreements, one of which post-dated the
    hypothetical negotiations by two years, did not involve the
    patents-in-suit, and did not cover the technologies in the
    case, while the other agreement covered both patents and
    software 
    services. 694 F.3d at 1333
    . Nevertheless, we
    concluded that the “degree of comparability” of the license
    agreements was “[a] factual issue[] best addressed by
    cross examination and not by exclusion.” 
    Id. Similarly, here,
    though there were undoubtedly differences between
    the licenses at issue and the circumstances of the hypo-
    thetical negotiation, “[t]he jury was entitled to hear the
    expert testimony and decide for itself what to accept or
    reject.” i4i Ltd. P’ship v. Microsoft Corp., 
    598 F.3d 831
    ,
    856 (Fed. Cir. 2010), aff’d 
    131 S. Ct. 2238
    (2011).
    36                       VIRNETX, INC.   v. CISCO SYSTEMS, INC.
    Thus, we do not believe the district court abused its
    discretion by permitting Weinstein’s testimony regarding
    the proper royalty rate based on these allegedly compara-
    ble licenses.
    D. Weinstein’s Second and Third Approaches:
    Nash Bargaining Solution
    Weinstein also offered two other estimates of the
    damages attributable to the FaceTime feature. Both of
    these estimates relied on the Nash Bargaining Solution.
    Weinstein began by determining “incremental or addi-
    tional profits that are associated with the use of the
    patented technology.” J.A. 1630. Weinstein used two
    different methods to estimate the incremental profits
    associated with the FaceTime feature. First, he used the
    front-facing camera as a proxy for the FaceTime feature,
    and calculated the profits that he believed were attribut-
    able to the addition of the front-facing camera to certain
    Apple products. And second, he relied on customer sur-
    veys to assert that 18% of iOS device sales would not have
    occurred but for the inclusion of FaceTime, and deter-
    mined the profits attributable to those sales.
    Having thus purported to determine those profits,
    Weinstein then testified about how the parties would split
    those incremental profits. To do this, he began with the
    assumption that each party would take 50% of the incre-
    mental profits, invoking the Nash Bargaining Solution,
    and then adjusted that split based on “the relative bar-
    gaining power of the two entities.” J.A. 1632.
    Apple challenges both steps of Weinstein’s analysis.
    First, Apple insists that Weinstein did not adequately
    isolate the incremental profits attributable to the patent-
    ed technology under either approach. And second, Apple
    argues that the invocation of a 50/50 starting point based
    on the Nash Bargaining Solution is akin to the “25 per-
    cent rule of thumb” that we rejected in Uniloc as being
    insufficiently grounded in the specific facts of the case.
    VIRNETX, INC.   v. CISCO SYSTEMS, INC.                   37
    Because we agree with Apple on the second point, we need
    not reach the first.
    In recent years, numerous district courts have con-
    fronted experts’ invocations of the Nash Bargaining
    Solution as a model for reasonable royalty damages, with
    varying results. Compare Robocast, Inc. v. Microsoft
    Corp., No. 10-1055, 
    2014 WL 350062
    (D. Del. Jan. 29,
    2014) (excluding expert testimony based on Nash Bar-
    gaining Solution because it was not sufficiently tied to the
    facts of the case); Dynetix Design Solutions, Inc. v. Synop-
    sys, Inc., No. 11-5973, 
    2013 WL 4538210
    , at *4–5 (N.D.
    Cal. Aug. 22, 2013) (excluding expert testimony on royalty
    rate that began from a starting point of a 50/50 split
    because the expert’s methodology was “indistinguishable
    from 25% rule”); Oracle Am., Inc. v. Google Inc., 798 F.
    Supp. 2d 1111, 1119–21 (N.D. Cal. 2011) (excluding
    testimony based on Nash Bargaining Solution because it
    “would invite a miscarriage of justice by clothing a fifty-
    percent assumption in an impenetrable façade of mathe-
    matics”) with Mformation Techs., Inc. v. Research in
    Motion Ltd., No. 08-4990, 
    2012 WL 1142537
    , at *3 n.19
    (N.D. Cal. Mar. 29, 2012) (declining to exclude Wein-
    stein’s testimony based on Nash Bargaining Solution
    because he used it only “as a check” in addition to the
    Georgia-Pacific analysis, rather than in lieu of it); Gen-
    Probe Inc. v. Becton Dickinson & Co., No. 09-2319, 
    2012 WL 9335913
    , at *3 (S.D. Cal. Nov. 26, 2012) (permitting
    testimony based on Nash Bargaining Solution because
    calculation was sufficiently tied to the facts of the case,
    “including the competitive environment and Gen-Probe’s
    policy of exploiting its own patents”); Sanofi-Aventis
    Deutschland Gmbh v. Glenmark Pharms. Inc., USA, No.
    07-5855, 
    2011 WL 383861
    , at *12–13 (D.N.J. Feb. 3, 2011)
    (determining that expert’s testimony asserting a 50/50
    profit split was based on the specific facts of the case);
    Amakua Dev. LLC v. Warner, No. 05-3082, 
    2007 WL 2028186
    , at *20 (N.D. Ill. July 10, 2007) (permitting
    38                       VIRNETX, INC.   v. CISCO SYSTEMS, INC.
    reliance on Nash because the “[d]efendants ha[d] not
    challenged the reliability of Nash’s theories, and the
    assessment of whether the theory persuasively can be
    applied in the context of this case is for the jury”).
    For the reasons that follow, we agree with the courts
    that have rejected invocations of the Nash theorem with-
    out sufficiently establishing that the premises of the
    theorem actually apply to the facts of the case at hand.
    The use here was just such an inappropriate “rule of
    thumb.”
    Previously, damages experts often relied on the “25
    percent rule of thumb” in determining a reasonable
    royalty rate in a hypothetical negotiation. That rule
    hypothesized that 25% of the value of the infringing
    product would remain with the patentee, while the re-
    maining 75% would go to the licensee. In Uniloc, howev-
    er, we held the “25 percent rule of thumb” to be
    inadmissible “because it fails to tie a reasonable royalty
    base to the facts of the case at 
    issue.” 632 F.3d at 1315
    .
    In so doing, we noted that the rule did not differentiate
    between different industries, technologies, or parties. 
    Id. at 1317.
    Rather, it assumed the same 25/75 royalty split
    regardless of the size of the patent portfolio in question or
    the value of the patented technology. 
    Id. The problem
    was that the 25% rule made too crude a generalization
    about a vastly more complicated world.
    The problem with Weinstein’s use of the Nash Bar-
    gaining Solution, though somewhat different, is related,
    and just as fatal to the soundness of the testimony. The
    Nash theorem arrives at a result that follows from a
    certain set of premises. It itself asserts nothing about
    what situations in the real world fit those premises.
    Anyone seeking to invoke the theorem as applicable to a
    particular situation must establish that fit, because the
    50/50 profit-split result is proven by the theorem only on
    those premises. Weinstein did not do so. This was an
    VIRNETX, INC.   v. CISCO SYSTEMS, INC.                   39
    essential failing in invoking the Solution. Moreover, we
    do not believe that the reliability of this methodology is
    saved by Weinstein’s attempts to account for the unique
    facts of the case in deviating from the 50/50 starting
    point. As we noted in Uniloc:
    It is of no moment that the 25 percent rule of
    thumb is offered merely as a starting point to
    which the Georgia-Pacific factors are then applied
    to bring the rate up or down. Beginning from a
    fundamentally flawed premise and adjusting it
    based on legitimate considerations specific to the
    facts of the case nevertheless results in a funda-
    mentally flawed 
    conclusion. 632 F.3d at 1317
    . Indeed, Weinstein’s thin attempts to
    explain his 10% deviation from the 50/50 baseline in this
    case demonstrates how this methodology is subject to
    abuse. His only testimony on the matter was that alt-
    hough he “considered other splits,” he ultimately deter-
    mined that a 10% deviation—resulting in a 45/55 split—
    was appropriate “to reflect the fact that Apple would have
    additional bargaining power over VirnetX back in . . .
    2009.” JA. 1708–09. Such conclusory assertions cannot
    form the basis of a jury’s verdict. See Gen. Elec. Co. v.
    Joiner, 
    522 U.S. 136
    , 146 (1997) (noting that where an
    expert considers relevant material but fails to provide an
    opinion explaining how that material leads to his conclu-
    sion, “[a] court may conclude that there is simply too
    great an analytical gap between the data and the opinion
    proffered”).
    More importantly, even if an expert could identify all
    of the factors that would cause negotiating parties to
    deviate from the 50/50 baseline in a particular case, the
    use of this methodology would nevertheless run the
    significant risk of inappropriately skewing the jury’s
    verdict. This same concern underlies our rule that a
    patentee may not balance out an unreasonably high
    40                       VIRNETX, INC.   v. CISCO SYSTEMS, INC.
    royalty base simply by asserting a low enough royalty
    rate. See 
    Uniloc, 632 F.3d at 1320
    . Although the result of
    that equation would be mathematically sound if properly
    applied by the jury, there is concern that the high royalty
    base would cause the jury to deviate upward from the
    proper outcome. 
    Id. Thus, in
    Uniloc, we noted that “[t]he
    disclosure that a company has made $19 billion dollars in
    revenue from an infringing product cannot help but skew
    the damages horizon for the jury, regardless of the contri-
    bution of the patented component to this revenue.” 
    Id. Similarly, here,
    the use of a 50/50 starting point—itself
    unjustified by evidence about the particular facts—
    provides a baseline from which juries might hesitate to
    stray, even if the evidence supported a radically different
    split.
    Even the 25% rule had its share of support in the lit-
    erature, which had observed that, at least as an anecdotal
    matter, a 25% royalty rate was a common starting point—
    and not far off from a common end point—of licensing
    negotiations across numerous industries. See 
    Uniloc, 632 F.3d at 1313
    (citing Robert Goldscheider, John Jarosz and
    Carla Mulhern, Use of the 25 Per Cent Rule in Valuing IP,
    37 les Nouvelles 123, 132–33 (Dec. 2002); Stephen A.
    Degnan & Corwin Horton, A Survey of Licensed Royalties,
    32 les Nouvelles 91, 95 (June 1997)). Nevertheless, we
    rejected it, insisting on testimony tied to the particular
    facts. The same insistence is vital here.
    We note that the Nash Bargaining Solution does offer
    at least one noticeable improvement over the 25% rule:
    where the 25% rule was applied to the entire profits
    associated with the allegedly infringing product, the Nash
    theory focuses only on the incremental profits earned by
    the infringer from the use of the asserted patents. But
    while we commend parties for using a theory that more
    appropriately (and narrowly) defines the universe of
    profits to be split, the suggestion that those profits be
    split on a 50/50 basis—even when adjusted to account for
    VIRNETX, INC.   v. CISCO SYSTEMS, INC.                 41
    certain individual circumstances—is insufficiently tied to
    the facts of the case, and cannot be supported.
    For each of the reasons stated above, we vacate the
    damages award and remand for further proceedings
    consistent with this opinion.
    AFFIRMED-IN-PART, REVERSED-IN-PART,
    VACATED-IN-PART and REMANDED
    COSTS
    Each party shall bear its own costs.