Aiqin Zhang et al.Download PDFPatent Trials and Appeals BoardJul 29, 20212020003799 (P.T.A.B. Jul. 29, 2021) Copy Citation 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.”). Appeal 2020–003799 Application 13/323,840 2 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. Appeal 2020–003799 Application 13/323,840 3 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). Appeal 2020–003799 Application 13/323,840 4 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 Appeal 2020–003799 Application 13/323,840 5 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). Appeal 2020–003799 Application 13/323,840 6 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 Appeal 2020–003799 Application 13/323,840 7 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). Appeal 2020–003799 Application 13/323,840 8 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 Appeal 2020–003799 Application 13/323,840 9 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 Appeal 2020–003799 Application 13/323,840 10 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 Appeal 2020–003799 Application 13/323,840 11 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 Appeal 2020–003799 Application 13/323,840 12 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 Appeal 2020–003799 Application 13/323,840 13 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 Copy with citationCopy as parenthetical citation