Ex Parte BrownDownload PDFPatent Trial and Appeal BoardFeb 12, 201510974802 (P.T.A.B. Feb. 12, 2015) Copy Citation UNITED STATES PATENT AND TRADEMARK OFFICE ____________________ BEFORE THE PATENT TRIAL AND APPEAL BOARD ____________________ Ex parte DANIEL R. BROWN ____________________ Appeal 2012-009560 Application 10/974,802 Technology Center 2400 ____________________ Before CARL W. WHITEHEAD JR., JEFFREY S. SMITH, and WILLIAM M. FINK, Administrative Patent Judges. FINK, Administrative Patent Judge. DECISION ON APPEAL Appellant1 seeks our review under 35 U.S.C. § 134(a) of the Examiner’s final rejection of claims 1–5, 7, 13, 23, and 26. We have jurisdiction under 35 U.S.C. § 6(b). Claims 9–12, 14, 24, 25, 27, and 28 are allowed and claims 6, 8, 29–33 are objected to. Claims 15–22 are cancelled. We affirm. 1 The real party in interest is Certicom Corp. (App. Br. 3.) Appeal 2012-009560 Application 10/974,802 2 STATEMENT OF THE CASE Appellant’s Invention Appellant’s invention relates to generation of public keys in a communication system. (Spec., Abstract.)2 More specifically, Appellant’s invention is directed to verifiable generation of public keys using a self- signed signature message. (Id.) Claims on Appeal Claims 1 is the independent claim on appeal. Claim 1 is illustrative of Appellant’s invention and is reproduced below with disputed limitations emphasized: 1. A computer implemented method of generating a private key and a corresponding public key of a correspondent in a communication system, the correspondent having a cryptographic unit, the method comprising: said cryptographic unit generating a digital signature; said cryptographic unit obtaining message data; said cryptographic unit generating a self-signed signature message by combining said message data and said digital signature; and said cryptographic unit computing said private key using said self-signed signature message and computing said corresponding public key using said private key such that said corresponding public key is verifiable using said digital signature and said self-signed signature message. 2 Our decision refers to Appellant’s Appeal Brief filed March 9, 2012 (“App. Br.”); the Examiner’s Answer mailed April 10, 2012 (“Ans.”); Appellant’s Reply Brief filed June 11, 2012 (“Reply Br.”); and the original Specification filed October 28, 2004 (“Spec.”). Appeal 2012-009560 Application 10/974,802 3 Evidence Considered Diffie US 5,371,794 Dec. 6, 1994 Faucher US 5,515,441 May 7, 1996 Messerges US 2003/0084298 A1 May 1, 2003 Coron US 2003/0152218 A1 Aug. 14, 2003 Chen US 2004/0123098 A1 June 24, 2004 Vanstone WO 01/95068 A2 Dec. 13, 2001 Examiner’s Rejections Claims 1, 2, 4, 5, 13, and 26 stand rejected under 35 U.S.C. § 103(a) as being unpatentable over Messerges and Vanstone, as evidenced by Chen. Ans. 4–7. Claim 3 stands rejected under 35 U.S.C. § 103(a) as being unpatentable over Messerges, Vanstone, and Faucher. Ans. 7–8. Claim 7 stands rejected under 35 U.S.C. § 103(a) as being unpatentable over Messerges, Vanstone, and Coron. Ans. 8–9. Claim 23 stands rejected under 35 U.S.C. § 103(a) as being unpatentable over Messerges, Vanstone, and Diffie. Ans. 9–10. Issues on Appeal Based on Appellant’s arguments, the issues on appeal are (1) whether the combination of Messerges and Vanstone teaches or suggests the limitations of claim 1, including a “cryptographic unit generating a digital signature . . . [and] generating a self-signed signature message,” as claim 1 and similar limitations of claim 13 require (App. Br. 7–8), and (2) whether Messerges and Vanstone are properly combined (id. at 8–10). Appeal 2012-009560 Application 10/974,802 4 ANALYSIS In rejecting claims 1 and 13, the Examiner relies on Messerges and Vanstone, as evidenced by Chen. Ans. 4. Specifically, the Examiner relies on Messerges as teaching a cryptographic unit “generating a digital signature” and “a self-signed signature message,” as the claim requires. Id. at 5 (citing Messerges ¶¶ 8, 10, 30, 38 and Figs. 2, 5, 6), 7 (Messerges ¶¶ 33–34 and Figs. 7–9). The Examiner finds Vanstone teaches: [C]omputing said private key [page 9, line 30: d = a + SA] using said self-signed signature message [page 6, line 26 and page 9, line 28: H( )] and computing said corresponding public key [page 9, lines 30-31 : Q = dP] using said private key [page 9, line 30: d] (page 9, line 25 - page 10, line 2; page 13, lines 14-19). Id. at 5. Appellant disputes the Examiner’s findings. In particular, Appellant argues “the hash values described in Messerges do not disclose a digital signature and the content package, combining the encrypted content and the hash values, does not disclose a self-signed signature message, as recited in claim 1.” App. Br. 8. We are not persuaded by Appellant’s arguments. Although we agree a cryptographic hash of content (e.g., Messerges ¶ 32 (“hash table 142”)) may not necessarily include a digital signature, App. Br. 8, Reply Br. 2–3 (“[A] ‘signature’ binds the information to the party signing . . . .”), this does not address the Examiner’s complete findings. The cited portions of Messerges explain that the hashed content is immediately signed with a digital signature, (Messerges ¶¶ 30, 32), which can operate either on the hash table directly or on an overall hash such as 148 (id. ¶ 30). As the Appeal 2012-009560 Application 10/974,802 5 Examiner points out, Messerges describes how the digital signature can be subsequently verified to ensure authenticity. Ans. 6 (citing Messerges ¶¶ 33–34). Accordingly, we disagree Messerges does not disclose the required digital signature. Based on the foregoing, we also disagree that Messerges does not disclose the required “self-signed signature message by combining said message data and said digital signature . . .,” as claim 1 requires. As the Examiner’s findings show, Messerges describes combining the digital signature with the hashed message content to form a self-signed signature message. Ans. 5 (citing Messerges, Fig. 6 (120 and 140)). Messerges describes block 140 as the secure content package 140, which includes both encrypted content (i.e., “message”) and “rules certificate 20” signed by a trusted authority. Messerges ¶ 32. Appellant also argues Messerges and Vanstone are not properly combined for several reasons. Appellant argues the content package in Messerges is not a self-signed signature, as the claims require, and Vanstone fails to cure this deficiency. App. Br. 9. Appellant also argues the claims require “computing a private key using said self-signed signature message,” whereas Vanstone describes generating the private key, d, then using the private key to generate a digital signature. Id. (citing Vanstone, p. 10, ll. 3– 4). Thus, Appellant contends, Vanstone teaches away from claim 1 by disclosing the opposite of claim 1. Id. We do not find Appellant’s arguments persuasive. As discussed supra, we are not persuaded that Messerges does not disclose a self-signed signature message. With respect to Appellant’s teaching away argument, Appellant relies on a portion of the reference at page 10, line 3 not cited by Appeal 2012-009560 Application 10/974,802 6 the Examiner. Ans. 19. The Examiner finds that the relied-upon portion, ending at page 10, line 2, describes creating private key, d, from secure hash H( ). Id. at 5, 19. While the portion cited by Appellant describes subsequently signing a message, m, with the private key, d, this does not undermine the relied-upon portion’s teaching of creating a private key from a signature, as the Examiner finds. Id. at 6. As such, Appellant’s cited description of what happens after a private key is created does not persuade us that a person of ordinary skill “would be led in a direction divergent from the path that was taken by the applicant.” Galderma Labs., L.P. v. Tolmar, Inc., 737 F.3d 731, 738 (Fed. Cir. 2013). Finally, Appellant argues: [I]t would not be obvious to substitute the hash h(yA || IDA || cP) of Vanstone with the contact [sic] package of Messerges. Appellant notes that the cryptographic unit of the same correspondent generates both the self-signed signature message and the private key, as recited in claim 1. However, the h(yA || IDA || cP) of Vanstone is computed by the CA [(Certificate Authority)] as part of generating sA. . . . The modification suggested by the Examiner of replacing h(yA || IDA || cP) of Vanstone, which is computed by the CA (as part of the computation of sA which can only be generated by the CA), with the content package of Messerges, which is generated by the correspondent, would modify Vanstone in a manner that is unsatisfactory for, and contrary to, its intended purpose of using the CA to compute the hash to generate sA, thus providing no suggestion or motivation to make the proposed modification. App. Br. 9–10 (citations omitted). In responding to Appellant, the Examiner points out that the combination “involve[es] mathematically substitut[ing] one hash value for another value . . . as representative of Messerges[’s] content package which Appeal 2012-009560 Application 10/974,802 7 comprises both encrypted content and a digitally signed certificate wherein the digitally signed certificate comprises a hash value of the encrypted content.” Ans. 23–24. The Examiner finds this is a predictable result of the combination: “private key and the public key are generated based on the equations taught, albeit, substituting one value of the variable for another value of the variable.” Id. at 24. We agree with the Examiner’s findings. “The combination of familiar elements according to known methods is likely to be obvious when it does no more than yield predictable results.” KSR Int’l Co. v. Teleflex, Inc., 550 U.S. 398, 416 (2007). Here, Appellant does not persuasively rebut the Examiner’s findings that combining Messerges and Vanstone involves no more than substituting one hash value for another to create a public key/private key pair using the content package of Messerges (i.e., a self- signed signature message), with predictable results. Although Appellant argues such a change would modify Vanstone in a manner that is unsatisfactory for its intended purpose (App. Br. 6), we agree with the Examiner that Appellant has not persuasively demonstrated how the modification changes the behavior of the mathematical relationships taught by Vanstone (Ans. 25). Accordingly, we are not persuaded that it would not be obvious to combine Messerges and Vanstone consistent with the Examiner’s findings. Because we are not persuaded that the teachings of Messerges and Vanstone, as evidenced by Chen, do not fall within the scope of the claims or are improperly combined, we sustain the Examiner’s rejection of independent claim 1. With respect to dependent claims 2, 4, 5, and 26, which depend from claim 1, and independent claim 13, Appellant presents Appeal 2012-009560 Application 10/974,802 8 no separate arguments. App. Br. 10. Accordingly, we sustain the rejection of these claims for the same reasons. See 37 C.F.R. § 41.37(c)(1)(iv). With respect to claim 3, 7, and 23, rejected separately over Messerges and Vanstone and other references of record, Appellant presents no separate arguments except that the addition of the other references fail to cure the deficiency of the base rejection. App. Br. 10–11. Because we do not agree the base rejection is deficient, we sustain the rejections of these claims as well for the foregoing reasons. DECISION We affirm the Examiner’s final rejection of claims 1–5, 7, 13, 23, and 26. 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 tj Copy with citationCopy as parenthetical citation