Patent SG-11201803741P-A (SG)
Title: Key sequence generation for cryptographic operations
Inventor: VILLEGAS KARINE
IPC: H04L9/06
Filed: 2016-11-02
Abstract: WO 17 /07 69 11 Al (12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (19) World Intellectual Property Organization International Bureau (10) International Publication Number (43) International Publication Date WO 2017/076911 Al 11 May 2017 (11.05.2017) WIPO I PCT 111111111111110111011111111111010111110011111111111111111110111011111111111110111111 (51) International Patent Classification: H04L 9/06 (2006.01) (21) International Application Number: PCT/EP2016/076436 (22) International Filing Date: 2 November 2016 (02.11.2016) (25) Filing Language: English (26) Publication Language: English (30) Priority Data: 1519612.4 6 November 2015 (06.11.2015) GB (71) Applicant: NAGRAVISION SA [CH/CH]; 22-24 Route de Geneve, 1033 Cheseaux-sur-Lausanne (CH). (72) Inventors: VILLEGAS, Karine; c/o Nagravision SA, 22- 24 Route de Geneve, 1033 Cheseaux-sur-Lausanne (CH). WYSEUR, Brecht; c/o Nagravision SA, 22-24 Route de Geneve, 1033 Cheseaux-sur-Lausanne (CH). (74) Agent: KORENBERG, Alexander Tal; Kilburn & Strode LLP, 20 Red Lion Street, London WC1R 4PJ (GB). (81) Designated States (unless otherwise indicated, for every kind of national protection available): AE, AG, AL, AM, AO, AT, AU, AZ, BA, BB, BG, BH, BN, BR, BW, BY, BZ, CA, CH, CL, CN, CO, CR, CU, CZ, DE, DJ, DK, DM, DO, DZ, EC, EE, EG, ES, FI, GB, GD, GE, GH, GM, GT, HN, HR, HU, ID, IL, IN, IR, IS, JP, KE, KG, KN, KP, KR, KW, KZ, LA, LC, LK, LR, LS, LU, LY, MA, MD, ME, MG, MK, MN, MW, MX, MY, MZ, NA, NG, NI, NO, NZ, OM, PA, PE, PG, PH, PL, PT, QA, RO, RS, RU, RW, SA, SC, SD, SE, SG, SK, SL, SM, ST, SV, SY, TH, TJ, TM, TN, TR, TT, TZ, UA, UG, US, UZ, VC, VN, ZA, ZM, ZW. (84) Designated States (unless otherwise indicated, for every kind of regional protection available): ARIPO (BW, GH, GM, KE, LR, LS, MW, MZ, NA, RW, SD, SL, ST, SZ, TZ, UG, ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, RU, TJ, TM), European (AL, AT, BE, BG, CH, CY, CZ, DE, DK, EE, ES, FI, FR, GB, GR, HR, HU, IE, IS, IT, LT, LU, LV, MC, MK, MT, NL, NO, PL, PT, RO, RS, SE, SI, SK, SM, TR), OAPI (BF, BJ, CF, CG, CI, CM, GA, GN, GQ, GW, KM, ML, MR, NE, SN, TD, TG). Published: with international search report (Art. 21(3)) (54) Title: KEY SEQUENCE GENERATION FOR CRYPTOGRAPHIC OPERATIONS Fig. 5 (57) : Methods, system and devices are provided that generate a sequence of sub-keys for cryptographic operations from a main key. The main key is operated on only once to generate the sub-keys of the sequence, with a transformation comprising one or more one-way functions. The respective bit values of the sub-keys of the sequence are set using respective bit values of the one or more one-way functions. Advantageously, deriving sub-key bits from respective output bits of one or more one-way functions re- moves or at least reduces correlations between the main key and the sub-keys, as well as between sub-keys, making it harder or even impossible to recover the main key or other sub-keys from a single sub-key, for example as found using a side-channel attack. At the same time, by using the main key only once (rather than using the main key each time a sub-key is generated), the vulnerability of the main key to a side-channel attack is reduced, because the opportunities for recovering physical information that could lead to the discovery of the main key are reduced. Specific embodiments use parallel or chained execution of sub-functions to generate respect- ive sub-keys. Other specific embodiments generate all sub-keys from a single one-way function in one go.