Ex Parte Billhartz

Board of Patent Appeals and Interferences

Jan 15, 2009

10197148 (B.P.A.I. Jan. 15, 2009)

UNITED STATES PATENT AND TRADEMARK OFFICE
____________________

BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
____________________

Ex parte THOMAS JAY BILLHARTZ

Appeal 2008-2526
Application 10/197,1481
Technology Center 2400
____________________

Decided: January 15, 2009
____________________

Before JAMES D. THOMAS, KENNETH W. HAIRSTON, and
JEAN R. HOMERE, Administrative Patent Judges.

HOMERE, Administrative Patent Judge.

DECISION ON APPEAL
I. STATEMENT OF THE CASE
Appellant appeals under 35 U.S.C. § 134(a) from the Examiner’s final
rejection of claims 1 through 4, 6 through 24, 26, 27, 29 through 34, and 36
through 42. Claims 5, 25, 28, and 35 have been canceled. We have
jurisdiction under 35 U.S.C. § 6(b). We affirm.

1 Filed on July 17, 2002. The real party in interest is Harris Corp.
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The Invention
Appellant invented a mobile ad-hoc network (MANET) for
authenticating mobile nodes thereon sharing a common radio channel.
(Spec. 1.) As shown in Figure 1, the MANET includes a first node having a
first public key and a first private key; a second node (12) having a second
public key and a second private key; and a certifying authority (14) having a
public authentication key, and a private authentication key. Upon generating
an authentication request, the first node (11) receives from the certifying
authority (14) a certificate of authenticity along with a second public key.
The first node then decrypts the certificate of authenticity to verify that the
received second public key belongs to the second node. Upon such
verification, the first node sends challenge data to the second node. The
second node uses its private key to encrypt the challenge data before
returning it to the first node. The first node uses the verified second public
key to decrypt the encrypted challenge data received from the second node.
If the decrypted challenge data matches the original challenge data, the first
node sends a session key encrypted with the second public key to the second
node for exchanging data. (Spec. 13-15, para. [0033]-[0037].)

Illustrative Claim
Independent claim 1 further illustrates the invention. It reads as
follows:
1. A mobile ad-hoc network comprising:
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a first node for generating an authentication request, said first node
having a first public key and a first private key associated therewith; and

a second node having a second public key and a second private key
associated therewith;

said first node receiving a certificate of authenticity responsive to the
authentication request, the certificate of authenticity being generated by a
certifying authority and comprising the second public key, the certifying
authority having a public authentication key and a private authentication key
associated therewith and generating the certificate of authenticity using the
private authentication key;

said first node decrypting the certificate of authenticity using the
public authentication key and verifying that the second public key belongs to
said second node based upon the decrypted certificate of authenticity;

said first node sending challenge data to said second node upon
verification that the second public key belongs to said second node;

said second node encrypting the challenge data using the second
private key and returning the encrypted challenge data back to said first
node;

said first node decrypting the encrypted challenge data using the
verified second public key and authenticating said second node if the
decryption of the encrypted challenge data yields the original challenge data;

said first node sending a session key encrypted with the second public
key to said second node for use with subsequent data transfers therebetween
upon authenticating said second node.

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Prior Art Relied Upon

The Examiner relies on the following prior art as evidence of
unpatentability:
Hanson US 6,546,425 B1 Apr. 8, 2003
(filed Jun. 11, 1999)

William Stallings, Cryptography and Network Security, Prentice-Hall, Inc.,
2ed. Chapters 5, 6, and 10, (1999) available at http://www.loc-gov/cgi-
bin/lormprocessor/copyright/locis.pt.

Dan Nguyen et al., Security Routing Analysis for Mobile Ad Hoc Networks,
Department of Interdisciplinary Telecommunications, University of
Colorado at Boulder, 1-11, (2000).

Rejections on Appeal
The Examiner rejects the claims on appeal as follows:
A. Claims 1 through 4, 6, 8 through 17, 19 through 24, 27, 29 through
34, 36, and 38 through 42 stand rejected under 35 U.S.C. § 103(a) as being
unpatentable over the combination of Stallings and Nguyen.
B. Claims 7, 18, 26, and 37 stand rejected under 35 U.S.C. § 103(a) as
being unpatentable over the combination of Stallings, Nguyen, and Hanson.

Appellant’s Contentions
Appellant argues that the combination of Stallings and Nguyen does
not render independent claim 1 unpatentable. (App. Br. 6-12, Reply Br. 1-
3.) Particularly, Appellant argues that Nguyen teaches performing public
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key encryption on a message hash digest rather than on the entire message
itself to increase authentication speed. Thus, one of ordinary skill in the art
would not find sufficient rationale to perform the additional authentication
operation, such as the claimed challenge-response, in Nguyen since it would
increase the length of the authentication process in the resulting Stallings-
Nguyen’s communications system where speed is critical among the
different nodes. (App. Br. 9-11, Reply Br. 2.) Appellant therefore
concludes that Nguyen teaches away from Stallings. (Id.)
Examiner’s Findings/Conclusions
The Examiner finds that Stallings’ disclosure of a sender using nonce
values and the valid public key of a receiver to verify the identity of the
receiver, and to then securely share a secret key with the receiver
substantially teaches the challenge-response operation, as recited in
independent claim 1. (Ans. 14.) Further, the Examiner recognizes that
Nguyen discloses performing a public key encryption on a hash digest of a
message, as opposed to encrypting the entire message, as a way to expedite
the authentication process in the MANET. (Ans. 15.) However, the
Examiner also finds that the MANET environment disclosed in Nguyen can
be used for implementing the authentication process of the mobile nodes
disclosed in Stallings. Therefore, the Examiner concludes that Stallings and
Nguyen are properly combined to render claim 1 unpatentable. (Id.)

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II. ISSUE
Did Appellant show the Examiner erred in concluding that the
combination of Stallings and Nguyen renders the claimed invention
unpatentable. Particularly, the issue turns on whether the ordinarily skilled
artisan would have found sufficient rationale to combine the cited references
to teach in a MANET (1) encrypting challenge data using a second private
key at a second node, and (2) decrypting the challenge data using a second
public key at a first node to thereby authenticate the second node if the
original challenge data matches the decrypted challenge data, as recited in
independent claim 1.

III. FINDINGS OF FACT
The following findings of fact (FF) are supported by a preponderance
of the evidence.
Stallings
1a. As shown in Figure 6.12, Stallings discloses a communication
network having a plurality of nodes including an initiator node A, a
responder node B and a public key authority that are exchanging messages.
(P. 184.)
1b. Particularly, node A submits to the public key authority a
request for the current public key of node B. The authority uses its private
key to encrypt a message, and transmits the encrypted message to node A.
(P. 185.)
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1c. Initiator A decrypts the message using the authority’s public
key. Node A then uses node B’s public key to encrypt a message destined
for node B. (Id.)
1d. Responder B retrieves node A’s public key from the public key
authority to decrypt node A’s message, and to then encrypt a new response
message including a nonce destined for initiator A. (Id.)
2. Stallings also discloses that both nodes A and B submit a public
key and a certificate request to the certificate authority. In response, each of
the nodes receives from the certificate authority the requested certificate
along with the authority’s public key. (P. 186.)
3a. Initiator node A uses responder node B’s public key to encrypt
a message destined for node B. The encrypted message includes a challenge
nonce (N1), and an identifier of node A to uniquely identify a particular
transaction. (P. 188.)
3b. Upon receiving the encrypted message from initiator node A,
responder node B decrypts it, and uses node A’s public key to encrypt a
response message including the challenge nonce (N1) received from node A,
as well as a new nonce (N2) generated by node B. (P. 188.)
3c. Upon receiving the response message including the original
nonce (N1), node A can confirm that it originates from node B by using node
B’s public key to encrypt the new nonce (N2), and subsequently return it to
node B. (P. 189.)
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3d. Node A then selects a secret key and uses it with a node B’s
public key to encrypt a message destined for node B such that only node B
can decrypt it. (P. 189.)

Nguyen
4. Nguyen discloses a MANET having a plurality of nodes for
securely exchanging messages with one another through public key
encryption. Particularly, a signer encrypts the message with its private key,
and sends the encrypted message to an intended recipient who decrypts it
using the sender’s public key. Nguyen discloses, however, that such public
key encryption approach is relatively slow, and can take up a lot of space in
an ad hoc network. (Para. 4.2.)
5. Alternatively, Nguyen discloses a one-way hash function
scheme to remedy the space and speed constraints of the public key
encryption approach. Particularly, Nguyen discloses using a one-way hash
function with the public key encryption to provide an efficient digital
signature. The sender can thus use the one-way hash function on the
message, and then encrypt the hash value with his/her private key. The
encrypted hash value and the message are then sent to the recipient who
independently calculates another hash value on the message. Subsequently,
the recipient decrypts the received hash value, and compares it with the
calculated hash value to authenticate the user’s signature if the two hash
values match. (Para 4.2.)
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IV. PRINCIPLES OF LAW
Obviousness
Appellant has the burden on appeal to the Board to demonstrate error
in the Examiner’s position. See In re Kahn, 441 F.3d 977, 985-86 (Fed. Cir.
2006) (“On appeal to the Board, an applicant can overcome a rejection
[under § 103] by showing insufficient evidence of prima facie obviousness
or by rebutting the prima facie case with evidence of secondary indicia of
nonobviousness.”) (quoting In re Rouffet, 149 F.3d 1350, 1355 (Fed. Cir.
1998)).
Section 103 forbids issuance of a patent when “the differences
between the subject matter sought to be patented and the prior art are
such that the subject matter as a whole would have been obvious at
the time the invention was made to a person having ordinary skill in
the art to which said subject matter pertains.”

KSR Int'l Co. v. Teleflex Inc., 127 S. Ct. 1727, 1734 (2007).

In KSR, the Supreme Court emphasized "the need for caution in
granting a patent based on the combination of elements found in the prior
art," and discussed circumstances in which a patent might be determined to
be obvious. KSR, 127 S. Ct. at 1739 (citing Graham v. John Deere Co., 383
U.S. 1, 12 (1966)). The Court reaffirmed principles based on its precedent
that "[t]he combination of familiar elements according to known methods is
likely to be obvious when it does no more than yield predictable results." Id.
The operative question in this "functional approach" is thus "whether the
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improvement is more than the predictable use of prior art elements according
to their established functions." Id. at 1740.
The Federal Circuit recently recognized that "[a]n obviousness
determination is not the result of a rigid formula disassociated from the
consideration of the facts of a case. Indeed, the common sense of those
skilled in the art demonstrates why some combinations would have been
obvious where others would not." Leapfrog Enters., Inc. v. Fisher-Price,
Inc., 485 F.3d 1157, 1161 (Fed. Cir. 2007) (citing KSR, 127 S. Ct. 1727,
1739 (2007)). The Federal Circuit relied in part on the fact that Leapfrog
had presented no evidence that the inclusion of a reader in the combined
device was “uniquely challenging or difficult for one of ordinary skill in the
art” or “represented an unobvious step over the prior art." Id. at 1162 (citing
KSR, 127 S. Ct. at 1740-41).
One cannot show nonobviousness by attacking references individually
where the rejections are based on combinations of references. In re Merck
& Co., Inc., 800 F.2d 1091, 1097 (Fed. Cir. 1986).
The test for obviousness is what the combined teachings of the
references would have suggested to one of ordinary skill in the art. See In re
Kahn, 441 F.3d at 987-988 (Fed. Cir. 2006), In re Young, 927 F.2d 588, 591
(Fed. Cir. 1991) and In re Keller, 642 F.2d 413, 425 (CCPA 1981).
Moreover, in evaluating such references it is proper to take into account not
only the specific teachings of the references but also the inferences which
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one skilled in the art would reasonably be expected to draw therefrom. In re
Preda, 401 F.2d 825, 826 (CCPA 1968).

V. ANALYSIS
Independent claim 1 recites in relevant part a MANET wherein a first
mobile node and a second mobile node encrypt and decrypt received
challenge-response data in order to authenticate the parties before they can
be allowed to securely exchange data. As set forth in the Findings of Facts
section, Stallings discloses a communications network having an initiator
and a responder encrypting and decrypting nonce challenge data to
authenticate the parties before they can share a secret key to exchange
messages. (FF. 3a-3d.) We find that Stallings’ disclosure reasonably
teaches the challenge-response data between the first and second nodes as
recited in independent claim 1. As noted above, the Examiner similarly
finds that the disclosed nonce exchange between the parties teaches the
claimed challenge-response. However, Appellant’s arguments nowhere
dispute such findings as advanced by the Examiner. Rather, Appellant’s
arguments focus on the combinability of Stallings’ teachings with Nguyen’s
as being allegedly improper. While Nguyen does discuss the space and
speed shortcomings of the public key encryption approach, it does recognize
such approach as being known and widely used in the art. (FF. 4.) In other
words, Nguyen does recognize the public key encryption approach as being
an alternative encryption scheme, although it may not be as viable as the
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one-way hash function encryption approach when it comes to enhancing
speed and space in a MANET. (FF. 4-5.) We note nonetheless, it is offered
as an alternative that is known to have been used in the MANET
environment. Furthermore, we note that Appellant appears to have
overlooked the fact that the Examiner only relies upon Nguyen for its
teaching of providing the necessary environment for implementing the
claimed MANET using the different nodes disclosed in Stallings. We
therefore conclude that one of ordinary skill in the art would readily
appreciate that Stallings and Nguyen disclose prior art elements that perform
their ordinary functions to predictably result in a MANET that uses
challenge-response nonce data to authenticate the mobile nodes thereon
before they can be allowed to securely transfer exchange messages. We
therefore do not agree with Appellant that the combination of Stallings and
Nguyen is improper. For these same reasons, we do not agree with
Appellant that Nguyen teaches away from Stallings.
Additionally, it is worth noting that the mobile ad hoc network
(MANET) limitation is only recited in the preamble of the claim, and
appears nowhere in the body of the claim. In general, a preamble is
construed as a limitation “if it recites essential structure or steps, or if it is
‘necessary to give life, meaning, and vitality’ to the claim.” Catalina Mktg.
Int'l, Inc. v. Coolsavings.com, Inc., 289 F.3d 801, 808 (Fed. Cir. 2002)
(quoting Pitney Bowes, Inc. v. Hewlett-Packard Co., 182 F.3d 1298, 1305
(Fed. Cir. 1999)). A preamble is not limiting, however, “‘where a patentee
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defines a structurally complete invention in the claim body and uses the
preamble only to state a purpose or intended use for the invention.’” Id.
(quoting Rowe v. Dror, 112 F.3d 473, 478 (Fed. Cir. 1997)). Symantec
Corp. v. Computer Associates International Inc., 86 USPQ2d 1449, 1453-54
(Fed. Cir. 2008). We therefore find the mobile ad hoc network recitation to
be a mere statement of intended use. We thus decline to give any patentable
weight to the cited recitation. Consequently, we find that alternatively
Stallings anticipates the claimed invention.
It follows that Appellant has not shown that the Examiner erred in
concluding that the combination of Stallings and Nguyen renders claim 1
unpatentable.
Appellant did not provide separate arguments with respect to the
rejections of claims 2 through 4, 6 through 24, 26, 27, 29 through 34, and 36
through 42. Consequently, these claims fall together with representative
claim 1. 37 C.F.R. § 41.37(c)(1)(vii).

VI. CONCLUSIONS OF LAW
Appellant has not shown that the Examiner erred in concluding that
the combination of:
1. Stallings and Nguyen renders claims 1-4, 6, 8-17, 19-24, 27,
29-34, 36, and 38-42 unpatentable under 35 U.S.C. § 103(a).
2. Stallings, Nguyen, and Hanson renders claims 7, 18, 26, and 37
unpatentable under 35 U.S.C. § 103(a).
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VII. DECISION
We affirm the Examiner’s decision to reject claims 1 through 4, 6
through 24, 26, 27, 29 through 34, and 36 through 42.
No time period for taking any subsequent action in connection with
this appeal may be extended under 37 C.F.R. § 1.136(a)(1)(iv).

AFFIRMED

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