Aiqin Zhang et al.

Patent Trials and Appeals Board

Jul 29, 2021

2020003799 (P.T.A.B. Jul. 29, 2021)

UNITED STATES PATENT AND TRADEMARK OFFICE
UNITED STATES DEPARTMENT OF COMMERCE
United States Patent and Trademark Office
Address: COMMISSIONER FOR PATENTS
P.O. Box 1450
Alexandria, Virginia 22313-1450
www.uspto.gov
APPLICATION NO. FILING DATE FIRST NAMED INVENTOR ATTORNEY DOCKET NO. CONFIRMATION NO.
13/323,840 12/13/2011 Aiqin Zhang 0911728US 5112
97291 7590 07/29/2021
Huawei Technologies Co., Ltd.
c/o Shuang Liu(Huawei ID 00344817)
Building A10-1, Huawei Industrial Base,
Bantian, Longgang District,
Shenzhen, 518129
CHINA
EXAMINER
DU, HUNG K
ART UNIT PAPER NUMBER
2647
NOTIFICATION DATE DELIVERY MODE
07/29/2021 ELECTRONIC
Please find below and/or attached an Office communication concerning this application or proceeding.
The time period for reply, if any, is set in the attached communication.
Notice of the Office communication was sent electronically on above-indicated "Notification Date" to the
following e-mail address(es):
aipatent@huawei.com
PTOL-90A (Rev. 04/07)
UNITED STATES PATENT AND TRADEMARK OFFICE
____________

BEFORE THE PATENT TRIAL AND APPEAL BOARD
____________

Ex parte AIQIN ZHANG, JING CHEN, and XIAOYU BI
____________

Appeal 2020–003799
Application 13/323,8401
Technology Center 2600
_______________

Before HUNG H. BUI, MIRIAM L. QUINN, and NABEEL U. KHAN,
Administrative Patent Judges.

BUI, Administrative Patent Judge.

DECISION ON APPEAL
Appellant seeks our review under 35 U.S.C. § 134(a) from the
Examiner’s Final rejection of claims 1, 5–7, 37, 38, 40–43, and 47–53, all of
the pending claims. Appeal Br. 9–11 (Claims App.). We have jurisdiction
under 35 U.S.C. § 6(b).
We AFFIRM.2

1 “Appellant” refers to “applicant(s)” as defined in 37 C.F.R. § 1.42.
Appellant identifies Huawei Technologies Co., Ltd., as the real party in
interest. Appeal Br. 2.
2 We refer to the Appellant’s Appeal Brief filed March 28, 2019 (“Appeal
Br.”); the Reply Brief filed September 30, 2019 (“Reply Br.”); the
Examiner’s Answer mailed July 30, 2019 (“Ans.”); the Final Office Action
mailed July 26, 2018 (“Final Act.”); and the Specification filed December
13, 2011 (“Spec.”).
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STATEMENT OF THE CASE
Appellant’s Invention
Appellant’s claimed invention relates to “a method, a device, and a
system for deriving a key for use in the target radio access network” “when a
user equipment [UE] is handed over from a source radio access network
[i.e., an Evolved UTRAN (EUTRAN)] to a target radio access network [i.e.,
a Universal Radio Access Network (UTRAN)] [in a radio access network
system shown in Figure 2].” Spec. ¶¶ 3–8.
According to Appellant, if the same security keys obtained during
handovers between a source network element (i.e., a mobile management
entity “MME”) and a user equipment “UE” and other network elements are
used, the network security would be at risk. Spec. ¶ 7. In order to enhance
the network security, Appellant proposes that “[i]n the case of failure of the
first handover to the second handover” between the MME and UE, as
shown, for example, in Figure 6,
“the key derived on the source MME in the first handover
process of the UE is different from the key derived on the MME
in the second handover process of the UE through changing the
input parameters used in the key derivation, such as . . . changing
the current NAS downlink COUNT value.”

Spec. ¶ 20.
Figure 6 is reproduced below with additional markings for illustration.
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Figure 6 shows a key derivation method during a handover process of
a UE from a source radio access network (EUTRAN) to a target radio access
network (UTRAN).

As shown in Figure 6,
the NAS downlink COUNT value is changed, so that after the
first handover of the UE fails, the NAS downlink COUNT value
saved in step 506 and used by the MME for the key derivation in
the second handover is surely different from the NAS downlink
COUNT value used in the first handover, and therefore the keys
derived and calculated in the two handovers are different, which
achieves the purpose of enhancing the network security.

Spec. ¶ 107 (emphasis added).

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Representative Claim
Claims 1 and 40 are independent claims. Claim 1, reproduced below
with disputed limitations emphasized, is representative:
1. A method for deriving a key, comprising:
receiving, by a mobility management entity (MME), a
handover required message from a base station (BS) of a source
radio access network in a first handover process from the source
radio access network to a target radio access network;
obtaining, by the MME, a first non-access stratum (NAS)
downlink COUNT value in the first handover process;
deriving, by the MME, a first key according to a key
derivation function (KDF), a root key, and the first NAS
downlink COUNT value in the first handover process, the first
key including a ciphering key and an integrity key;
sending, by the MME, at least a portion of a plurality of
bits of the first NAS downlink COUNT value to the UE in the
first handover process; and
obtaining, by the MME in the first handover process, a
second NAS downlink COUNT value by incrementing a value to
the first NAS downlink COUNT value, wherein the second NAS
downlink COUNT value is obtained after deriving the first key.

Appeal Br. 9 (Claims App.).
REJECTIONS AND REFERENCES
(1) Claims 1, 6, 7, 37, 40, 43, 47, and 50 stand rejected under
35 U.S.C. § 103 as obvious over the combined teachings of Forsberg et al.
(US 2011/0092213 A1; published Apr. 21, 2011; “Forsberg”) and
Mizikovsky et al. (US 2008/0137853 A1; published June 12, 2008;
“Mizikovsky”). Final Act. 3–10.
(2) Claims 5, 41, and 51 stand rejected under 35 U.S.C. § 103 as
obvious over the combined teachings of Forsberg, Mizikovsky, and 3GPP
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TSG-SA WG3 Meeting note published Sept. 23–26, 2008. Final Act. 10–
12.
(3) Claims 38 and 42 stand rejected under 35 U.S.C. § 103 as
obvious over the combined teachings of Forsberg, Mizikovsky, and Suumaki
(US 2010/0098247 A1; published Apr. 22, 2010). Final Act. 12–13.
(4) Claims 48, 49, 52, and 53 stand rejected under 35 U.S.C. § 103
as obvious over the combined teachings of Forsberg, Mizikovsky, 3GPP
TSG-SA WG3 Meeting note, and Suumaki. Final Act. 13–14.

ANALYSIS
Claim 1 recites a method for deriving a key, comprising, inter alia,
the disputed limitation:
obtaining, by the MME in the first handover process, a second
NAS downlink COUNT value by incrementing a value to the
first NAS downlink COUNT value, wherein the second NAS
downlink COUNT value is obtained after deriving the first key.

Appeal Br. 9 (Claims App.) (emphasis added). Apparatus claim 40 recites
similar limitations.
In support of the obviousness rejection of method claim 1 and
similarly, apparatus claim 40, the Examiner finds that Forsberg teaches most
limitations of Appellant’s claimed “method for deriving a key,” shown in
Figure 4, including the disputed limitation: “obtaining, by the MME in the
first handover process, a second NAS downlink COUNT value by
incrementing a value to the first NAS downlink COUNT value.” Final Act.
3–5 (citing Forsberg ¶¶ 38, 44, 46, Figures 3, 4).
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Forsberg’s Figure 4 is reproduced below with additional markings for
illustration:

Forsberg’s Figure 4 shows MME 316 (shown outlined in red) [including
handover controller 320, shown in Figure 3] that is configured to receive an
indication of a handover, retrieve a cached security context [including a
master key] for UE 302, determine a current sequence number value [i.e.,
NAS downlink COUNT] (highlighted in yellow above at steps 412 and 414)
that may be “automatically and/or periodically incremented, such as in
response to a communication and/or handover event involving the UE 302.”
Forsberg ¶ 38.
The Examiner finds “Forsberg is silent on whether the sequence
number value, i.e. NAS downlink COUNT, is incremented before the step of
deriving a fresh security context, i.e. fig 4 step 402, or after the step of
deriving the fresh security context.” Ans. 5 (emphasis added). However, the
Examiner relies on Mizikovsky for teaching incrementing the COUNT value
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used in the key derivation after the key derivation step to meet the wherein
clause of Appellant’s claim 1 “wherein the second NAS downlink COUNT
value is obtained after deriving the first key” in order to support the
conclusion of obviousness. Final Act. 5 (citing Mizikovsky ¶¶ 42, 43,
Figure 3, steps 345, 350, 375).
Appellant contends the proposed combination of Forsberg and
Mizikovsky does not teach or suggest the disputed limitation of claim 1 and
similarly, claim 40. Appeal Br. 4–7. In particular, Appellant acknowledges
that Forsberg’s “NAS downlink COUNT is used in deriving the key, and the
NAS downlink COUNT value is maintained as the EUTRAN standards.”
Appeal Br. 5. However, Appellant argues:
Forsberg does not disclose that after deriving the first key in the
first handover process, the MME obtains, in the handover
process, a second NAS downlink COUNT value by incrementing
a value to the first NAS downlink COUNT value. In fact,
Forsberg does not disclose or suggest use of a second NAS
downlink COUNT value for any purpose whatsoever, let alone
deriving a second NAS downlink COUNT value after deriving
the first key, as recited in claim 1.
Appeal Br. 5 (emphasis added). According to Appellant,
[Forsberg’s] scheme is similar to the arrangement described in
the background of the present disclosure (See paragraph [0007]
in page 2 of specification) . . . if the handover of the UE to the
UETRAN fails due to the failure of the connection of an air
interface radio link, the UE returns to the EUTRAN, no NAS
message sent, and the key derivation on the MME in the second
handover process and the key derivation on the MME in the first
handover process are both performed according to the same NAS
downlink COUNT value.
Appeal Br. 5 (emphasis added).
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Appellant also contends that Mizikovsky, as a secondary reference,
does not disclose “‘using the COUNT value in the security operation before
incrementing the COUNT value,’ nor does it disclose the above-highlighted
elements of claim 1.” Appeal Br. 6.
We do not find Appellant’s arguments persuasive. Rather, we find
that the Examiner has provided a comprehensive response to Appellant’s
arguments supported by a preponderance of evidence. Ans. 3–7. Therefore,
we adopt the Examiner’s findings and explanations provided therein. Id.
For additional emphasis, we highlight and address specific arguments and
findings as follows:
First, Forsberg teaches the use of a non-access stratum (NAS)
downlink COUNT in accordance with E-UTRAN standards as the sequence
number value used to derive a fresh mapped security context at both MME
316 and UE 302, shown in Figure 4. For example, during a handover,
MME’s handover controller 320, shown in Figure 3, retrieves a sequence
number value (i.e., a NAS downlink COUNT value) from a cached security
context for UE 302 and derives a fresh mapped security context using key
derivation functions with the current sequence number value (i.e., a NAS
downlink COUNT value) as an input parameter for the key derivation
functions. Forsberg ¶¶ 38, 40, 46. Forsberg also teaches that the sequence
number value (i.e., a NAS downlink COUNT value) “may be automatically
and/or periodically incremented, such as in response to a communication
and/or handover event involving the UE 302.” Forsberg ¶ 38.
Accordingly, since an incrementing sequence number value is
used as an input parameter for deriving a mapped security
context, the mapped security context derived by the handover
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controller 320 may be unique from any previously derived
mapped security context even during the life of the master key.

Forsberg ¶ 40 (emphasis added).
In other words, once the sequence number value (i.e., a NAS
downlink COUNT value) is incremented at MME’s handover controller 320,
the incremented sequence value is sent to UE 302, as shown in Figure 4 (at
step 414), “so that the UE 302 may synchronize its sequence number value
with that used by the source MME 316 so that the UE 302 may derive a
corresponding mapped security.” Forsberg ¶¶ 42, 46. The incremented
sequence value disclosed by Forsberg equates to Appellant’s claimed
“second NAS downlink COUNT value.” See Final Act. 4 (Examiner’s
finding that Forsberg teaches the second NAS downlink COUNT value
because Forsberg discusses incrementing the retrieved NAS downlink
COUNT value in response to the handover event).
Second, we do not agree with Appellant’s contention that Forsberg’s
handover scheme between UE 302 and MME 316, shown in Figure 4, is
“similar to [the] arrangement described in the background of the present
disclosure.” Appeal Br. 5 (citing Spec. ¶ 7). Rather, Forsberg’s handover
scheme addresses the same problem identified by Appellant, i.e., to provide
“a [fresh] mapped security context [during intersystem mobility “handover”
between UE 302 and MME 306, shown in Figure 4] . . . so as to avoid key
stream reuse and consequently to provide for more secure communications.”
Forsberg ¶ 6.
The test for obviousness is not whether the claimed invention is
expressly suggested in the references, but whether the claimed subject matter
would have been obvious to those of ordinary skill in the art in light of the
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combined teachings of those references. See In re Keller, 642 F.2d 413, 425
(CCPA 1981). In an obviousness analysis, it is not necessary to find precise
teachings directed to the specific subject matter claimed because inferences
and creative steps that a person of ordinary skill in the art would employ can
be taken into account. See KSR Int’l Co. v. Teleflex Inc., 550 U.S. 398, 418
(2007). In this regard, “[a] person of ordinary skill is also a person of
ordinary creativity, not an automaton.” Id. at 421.
The Examiner’s rejection relied on the combination of Forsberg’s
incremented NAS downlink COUNT with Mizikovsky’s timing of the
incrementing to be performed after deriving the first key. See Final Act. 5.
Thus arguing that Forsberg alone (or Mizikovsky alone) does not teach
deriving a second NAS downlink COUNT value after deriving the first key
is unpersuasive. As the Examiner finds, and we agree, Mizikovsky teaches
“incrementing the COUNT value used in the key derivation after the key
derivation step,” which supports the conclusion of obviousness. Ans. 5
(citing Mizikovsky, ¶ 40, Figure 3, steps 310, 335, 345, 375)
In the Reply Brief, Appellant raises several new arguments against the
Examiner’s combination, including:
1. “Forsberg does not disclose or teach that there are two NAS
downlink count values in the same handover process, that is,
Forsberg does not disclose or teach ‘obtaining, by the MME in
the first handover process, a second NAS downlink COUNT
value by incrementing a value to the first NAS downlink
COUNT value, wherein the second NAS downlink COUNT
value is obtained after deriving the first key,’ as recited in claim
1”;
2. “substituting Mizikowsly’s timing scheme for that recited in
Forsberg would negate operation of Forsberg’s NAS downlink
COUNT scheme”; and
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3. “ Forsberg pertains to 3GPP,” whereas “the system described in
Mizikovsky pertains to an IEEE 802.l6e system” and, as such,
“there is no motivation to combine Forsberg and Mizikovsky, as
their respective objectives are quite dissimilar and unrelated.”

Reply Br. 2–6.
However, these arguments are not timely. In the absence of a
showing of good cause by Appellant, we can decline to consider these new
argument raised for the first time in the Reply Brief. See 37 C.F.R. §
41.41(b)(2) (2018); In re Hyatt, 211 F.3d 1367, 1373 (Fed. Cir. 2000)
(noting that an argument not first raised in the brief to the Board is waived
on appeal); Ex parte Nakashima, 93 USPQ2d 1834, 1837 (BPAI 2010)
(informative) (explaining that arguments and evidence not timely presented
in the principal Brief, will not be considered when filed in a Reply Brief,
absent a showing of good cause explaining why the argument could not have
been presented in the Principal Brief); Ex parte Borden, 93 USPQ2d 1473,
1477 (BPAI 2010) (informative) (“Properly interpreted, the Rules do not
require the Board to take up a belated argument that has not been addressed
by the Examiner, absent a showing of good cause.”).
Nevertheless, we are not persuaded by these new arguments because
Forsberg teaches the use of two NAS downlink COUNT values during the
same handover process at MME’s handover controller 320, shown in Figure
3, including: a NAS downlink COUNT value determined from a retrieved
security context from MME’s memory 322, and a second NAS downlink
COUNT VALUE representing an incremented NAS downlink COUNT
value in response to a handover event involving the UE 302. Forsberg ¶ 38.
For the reasons set forth above, Appellant has not persuaded us of
Examiner error. Accordingly, we sustain the Examiner’s obviousness
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rejection of independent claims 1 and 40 and their respective dependent
claims 5–7, 37–38, 41–43, and 47–53.

CONCLUSION
On the record before us, we conclude Appellant has not demonstrated
the Examiner erred in rejecting (1) claims 1, 6, 7, 37, 40, 43, 47, and 50 as
obvious over the combined teachings of Forsberg and Mizikovsky; (2)
claims 5, 41, and 51 as obvious over the combined teachings of Forsberg,
Mizikovsky, and 3GPP TSG-SA WG3 Meeting note; (3) claims 38 and 42
as obvious over the combined teachings of Forsberg, Mizikovsky, and
Suumaki; and (4) claims 48, 49, 52, and 53 as obvious over the combined
teachings of Forsberg, Mizikovsky, 3GPP TSG-SA WG3 Meeting note, and
Suumaki.

DECISION SUMMARY
In summary:
Claim(s)
Rejected
35
U.S.C. §
Reference(s)/Basis Affirmed Reversed
1, 6, 7, 37,
40, 43, 47,
50
103(a) Forsberg,
Mizikovsky
1, 6, 7,
37, 40,
43, 47, 50

5, 41, 51 103(a) Forsberg,
Mizikovsky, 3GPP
TSG-SA WG3
5, 41, 51
38, 42 103(a) Forsberg,
Mizikovsky,
Suumaki
38, 42
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Claim(s)
Rejected
35
U.S.C. §
Reference(s)/Basis Affirmed Reversed
48, 49, 52,
53
103(a) Forsberg,
Mizikovsky, 3GPP
TSG-SA WG3,
Suumaki
48, 49,
52, 53

Overall
Outcome
1, 5–7,
37, 38,
40–43,
47–53

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