idnits 2.17.1 draft-oiwa-httpauth-mutual-algo-00.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (July 1, 2013) is 3950 days in the past. Is this intentional? -- Found something which looks like a code comment -- if you have code sections in the document, please surround them with '' and '' lines. Checking references for intended status: Experimental ---------------------------------------------------------------------------- -- Looks like a reference, but probably isn't: '4' on line 265 == Outdated reference: A later version (-11) exists of draft-ietf-httpauth-mutual-00 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 HTTPAUTH Working Group Y. Oiwa 3 Internet-Draft H. Watanabe 4 Intended status: Experimental H. Takagi 5 Expires: January 2, 2014 RISEC, AIST 6 B. Kihara 7 T. Hayashi 8 Lepidum 9 Y. Ioku 10 Yahoo! Japan 11 July 1, 2013 13 Mutual Authentication Protocol for HTTP: KAM3-based Cryptographic 14 Algorithms 15 draft-oiwa-httpauth-mutual-algo-00 17 Abstract 19 This document specifies some cryptographic algorithms which will be 20 used for the Mutual user authentication method for the Hyper-text 21 Transport Protocol (HTTP). 23 Status of this Memo 25 This Internet-Draft is submitted in full conformance with the 26 provisions of BCP 78 and BCP 79. 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF). Note that other groups may also distribute 30 working documents as Internet-Drafts. The list of current Internet- 31 Drafts is at http://datatracker.ietf.org/drafts/current/. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 This Internet-Draft will expire on January 2, 2014. 40 Copyright Notice 42 Copyright (c) 2013 IETF Trust and the persons identified as the 43 document authors. All rights reserved. 45 This document is subject to BCP 78 and the IETF Trust's Legal 46 Provisions Relating to IETF Documents 47 (http://trustee.ietf.org/license-info) in effect on the date of 48 publication of this document. Please review these documents 49 carefully, as they describe your rights and restrictions with respect 50 to this document. Code Components extracted from this document must 51 include Simplified BSD License text as described in Section 4.e of 52 the Trust Legal Provisions and are provided without warranty as 53 described in the Simplified BSD License. 55 Table of Contents 57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 58 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 59 2. Authentication Algorithms . . . . . . . . . . . . . . . . . . 3 60 2.1. Support Functions and Notations . . . . . . . . . . . . . 4 61 2.2. Functions for Discrete-Logarithm Settings . . . . . . . . 4 62 2.3. Functions for Elliptic-Curve Settings . . . . . . . . . . 6 63 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 64 4. Security Considerations . . . . . . . . . . . . . . . . . . . 7 65 5. Notice on intellectual properties . . . . . . . . . . . . . . 7 66 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 67 6.1. Normative References . . . . . . . . . . . . . . . . . . . 8 68 6.2. Informative References . . . . . . . . . . . . . . . . . . 8 69 Appendix A. (Informative) Group Parameters for 70 Discrete-Logarithm Based Algorithms . . . . . . . . . 9 71 Appendix B. (Informative) Derived Numerical Values . . . . . . . 11 72 Appendix C. (Informative) Draft Change Log . . . . . . . . . . . 12 73 C.1. Changes in revision 02 . . . . . . . . . . . . . . . . . . 12 74 C.2. Changes in revision 01 . . . . . . . . . . . . . . . . . . 12 75 C.3. Changes in revision 00 . . . . . . . . . . . . . . . . . . 12 76 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12 78 1. Introduction 80 This document specifies some algorithms for Mutual authentication 81 protocol for Hyper-Text Transport Protocol (HTTP) 82 [I-D.ietf-httpauth-mutual]. 84 1.1. Terminology 86 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 87 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 88 "OPTIONAL" in this document are to be interpreted as described in 89 [RFC2119]. 91 The terms "encouraged" and "advised" are used for suggestions that do 92 not constitute "SHOULD"-level requirements. People MAY freely choose 93 not to include the suggested items regarding [RFC2119], but complying 94 with those suggestions would be a best practice; it will improve the 95 security, interoperability, and/or operational performance. 97 The term "natural numbers" refers to the non-negative integers 98 (including zero) throughout this document. 100 This document treats target (codomain) of hash functions to be 101 natural numbers. The notation OCTETS(H(s)) gives a usual octet- 102 string output of hash function H applied to string s. 104 2. Authentication Algorithms 106 This document specifies only one family of the authentication 107 algorithm. The family consists of four authentication algorithms, 108 which only differ in their underlying mathematical groups and 109 security parameters. The algorithms do not add any additional 110 parameters. The tokens for these algorithms are 112 o iso-kam3-dl-2048-sha256: for the 2048-bit discrete-logarithm 113 setting with the SHA-256 hash function. 115 o iso-kam3-dl-4096-sha512: for the 4096-bit discrete-logarithm 116 setting with the SHA-512 hash function. 118 o iso-kam3-ec-p256-sha256: for the 256-bit prime-field elliptic- 119 curve setting with the SHA-256 hash function. 121 o iso-kam3-ec-p521-sha512: for the 521-bit prime-field elliptic- 122 curve setting with the SHA-512 hash function. 124 For discrete-logarithm settings, the underlying groups are the 2048- 125 bit and 4096-bit MODP groups defined in [RFC3526], respectively. See 126 Appendix A for the exact specifications of the groups and associated 127 parameters. The hash functions H are SHA-256 for the 2048-bit group 128 and SHA-512 for the 4096-bit group, respectively, defined in FIPS PUB 129 180-2 [FIPS.180-2.2002]. The representation of the parameters kc1, 130 ks1, vkc, and vks is base64-fixed-number. 132 For the elliptic-curve settings, the underlying groups are the 133 elliptic curves over the prime fields P-256 and P-521, respectively, 134 specified in the appendix D.1.2 of FIPS PUB 186-3 [FIPS.186-3.2009] 135 specification. The hash functions H, which are referenced by the 136 core document, are SHA-256 for the P-256 curve and SHA-512 for the 137 P-521 curve, respectively. The representation of the parameters kc1, 138 ks1, vkc, and vks is hex-fixed-number. 140 Note: This algorithm is based on the Key Agreement Mechanism 3 (KAM3) 141 defined in Section 6.3 of ISO/IEC 11770-4 [ISO.11770-4.2006] with a 142 few modifications/improvements. However, implementers should use 143 this document as the normative reference, because the algorithm has 144 been changed in several minor details as well as major improvements. 146 2.1. Support Functions and Notations 148 The algorithm definitions use several support functions and notations 149 defined below: 151 The integers in the specification are in decimal, or in hexadecimal 152 when prefixed with "0x". 154 The two functions named octet() and OCTETS() are those defined in the 155 core specification [I-D.ietf-httpauth-mutual]. 157 Note: The definition of OCTETS() is different from the function 158 GE2OS_x in the original ISO specification, which takes the shortest 159 representation without preceding zeros. 161 All of the algorithms defined in this specification use the default 162 functions defined in the core specification for computing the values 163 pi, VK_c and VK_s. 165 2.2. Functions for Discrete-Logarithm Settings 167 In this section, an equation (x / y mod z) denotes a natural number w 168 less than z that satisfies (w * y) mod z = x mod z. 170 For the discrete-logarithm, we refer to some of the domain parameters 171 by using the following symbols: 173 o q: for "the prime" defining the MODP group. 175 o g: for "the generator" associated with the group. 177 o r: for the order of the subgroup generated by g. 179 The function J is defined as 181 J(pi) = g^(pi) mod q. 183 The value of K_c1 is derived as 185 K_c1 = g^(S_c1) mod q, 187 where S_c1 is a random integer within range [1, r-1] and r is the 188 size of the subgroup generated by g. In addition, S_c1 MUST be 189 larger than log(q)/log(g) (so that g^(S_c1) > q). 191 The value of K_c1 SHALL satisfy 1 < K_c1 < q-1. The server MUST 192 check this condition upon reception. 194 Let an intermediate value t_1 be 196 t_1 = H(octet(1) | OCTETS(K_c1)), 198 the value of K_s1 is derived from J(pi) and K_c1 as: 200 K_s1 = (J(pi) * K_c1^(t_1))^(S_s1) mod q 202 where S_s1 is a random number within range [1, r-1]. The value of 203 K_s1 MUST satisfy 1 < K_s1 < q-1. If this condition is not held, the 204 server MUST retry using another value for S_s1. The client MUST 205 check this condition upon reception. 207 Let an intermediate value t_2 be 209 t_2 = H(octet(2) | OCTETS(K_c1) | OCTETS(K_s1)), 211 the value z on the client side is derived by the following equation: 213 z = K_s1^((S_c1 + t_2) / (S_c1 * t_1 + pi) mod r) mod q. 215 The value z on the server side is derived by the following equation: 217 z = (K_c1 * g^(t_2))^(S_s1) mod q. 219 2.3. Functions for Elliptic-Curve Settings 221 For the elliptic-curve setting, we refer to some of the domain 222 parameters by the following symbols: 224 o q: for the prime used to define the group. 226 o G: for the defined point called the generator. 228 o r: for the order of the subgroup generated by G. 230 The function P(p) converts a curve point p into an integer 231 representing point p, by computing x * 2 + (y mod 2), where (x, y) 232 are the coordinates of point p. P'(z) is the inverse of function P, 233 that is, it converts an integer z to a point p that satisfies P(p) = 234 z. If such p exists, it is uniquely defined. Otherwise, z does not 235 represent a valid curve point. The operator + indicates the 236 elliptic-curve group operation, and the operation [x] * p denotes an 237 integer-multiplication of point p: it calculates p + p + ... (x 238 times) ... + p. See the literatures on elliptic-curve cryptography 239 for the exact algorithms used for those functions (e.g. Section 3 of 240 [RFC6090], which uses different notations, though.) 0_E represents 241 the infinity point. The equation (x / y mod z) denotes a natural 242 number w less than z that satisfies (w * y) mod z = x mod z. 244 The function J is defined as 246 J(pi) = [pi] * G. 248 The value of K_c1 is derived as 250 K_c1 = P(K_c1'), where K_c1' = [S_c1] * G, 252 where S_c1 is a random number within range [1, r-1]. The value of 253 K_c1 MUST represent a valid curve point, and K_c1' SHALL NOT be 0_E. 254 The server MUST check this condition upon reception. 256 Let an intermediate integer t_1 be 258 t_1 = H(octet(1) | OCTETS(K_c1)), 260 the value of K_s1 is derived from J(pi) and K_c1' = P'(K_c1) as: 262 K_s1 = P([S_s1] * (J(pi) + [t_1] * K_c1')), 264 where S_s1 is a random number within range [1, r-1]. The value of 265 K_s1 MUST represent a valid curve point and satisfy [4] * P'(K_s1) <> 266 0_E. If this condition is not satisfied, the server MUST retry using 267 another value for S_s1. The client MUST check this condition upon 268 reception. 270 Let an intermediate integer t_2 be 272 t_2 = H(octet(2) | OCTETS(K_c1) | OCTETS(K_s1)), 274 the value z on the client side is derived by the following equation: 276 z = P([(S_c1 + t_2) / (S_c1 * t_1 + pi) mod r] * P'(K_s1)). 278 The value z on the server side is derived by the following equation: 280 z = P([S_s1] * (P'(K_c1) + [t_2] * G)). 282 3. IANA Considerations 284 Four tokens iso-kam3-dl-2048-sha256, iso-kam3-dl-4096-sha512, 285 iso-kam3-ec-p256-sha256 and iso-kam3-ec-p521-sha512 shall be 286 allocated and registered according to the provision of the core 287 documentation when this document is promoted to an RFC. 289 Note: More formal declarations will be added in the future drafts to 290 meet the RFC 5226 requirements. 292 4. Security Considerations 294 Refer the corresponding section of the core specification for 295 algorithm-independent, generic considerations. 297 o All random numbers used in these algorithms MUST be at least 298 cryptographically computationally secure against forward and 299 backward guessing attacks. 301 o Computation times of all numerical operations on discrete- 302 logarithm group elements and elliptic-curve points MUST be 303 normalized and made independent of the exact values, to prevent 304 timing-based side-channel attacks. 306 5. Notice on intellectual properties 308 The National Institute of Advanced Industrial Science and Technology 309 (AIST) and Yahoo! Japan, Inc. has jointly submitted a patent 310 application on the protocol proposed in this documentation to the 311 Patent Office of Japan. The patent is intended to be open to any 312 implementors of this protocol and its variants under non-exclusive 313 royalty-free manner. For the details of the patent application and 314 its status, please contact the author of this document. 316 The elliptic-curve based authentication algorithms might involve 317 several existing third-party patents. The authors of the document 318 take no position regarding the validity or scope of such patents, and 319 other patents as well. 321 6. References 323 6.1. Normative References 325 [FIPS.180-2.2002] 326 National Institute of Standards and Technology, "Secure 327 Hash Standard", FIPS PUB 180-2, August 2002, . 330 [FIPS.186-3.2009] 331 National Institute of Standards and Technology, "Digital 332 Signature Standard (DSS)", FIPS PUB 186-3, June 2009, . 336 [I-D.ietf-httpauth-mutual] 337 Oiwa, Y., Watanabe, H., Takagi, H., Kihara, B., Hayashi, 338 T., and Y. Ioku, "Mutual Authentication Protocol for 339 HTTP", draft-ietf-httpauth-mutual-00 (work in progress), 340 July 2013. 342 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 343 Requirement Levels", BCP 14, RFC 2119, March 1997. 345 [RFC3526] Kivinen, T. and M. Kojo, "More Modular Exponential (MODP) 346 Diffie-Hellman groups for Internet Key Exchange (IKE)", 347 RFC 3526, May 2003. 349 6.2. Informative References 351 [ISO.11770-4.2006] 352 International Organization for Standardization, 353 "Information technology - Security techniques - Key 354 management - Part 4: Mechanisms based on weak secrets", 355 ISO Standard 11770-4, May 2006. 357 [RFC6090] McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic 358 Curve Cryptography Algorithms", RFC 6090, February 2011. 360 Appendix A. (Informative) Group Parameters for Discrete-Logarithm Based 361 Algorithms 363 The MODP group used for the iso-kam3-dl-2048-sha256 algorithm is 364 defined by the following parameters. 366 The prime is: 368 q = 0xFFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1 369 29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD 370 EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245 371 E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED 372 EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE45B3D 373 C2007CB8 A163BF05 98DA4836 1C55D39A 69163FA8 FD24CF5F 374 83655D23 DCA3AD96 1C62F356 208552BB 9ED52907 7096966D 375 670C354E 4ABC9804 F1746C08 CA18217C 32905E46 2E36CE3B 376 E39E772C 180E8603 9B2783A2 EC07A28F B5C55DF0 6F4C52C9 377 DE2BCBF6 95581718 3995497C EA956AE5 15D22618 98FA0510 378 15728E5A 8AACAA68 FFFFFFFF FFFFFFFF. 380 The generator is: 382 g = 2. 384 The size of the subgroup generated by g is: 386 r = (q - 1) / 2 = 387 0x7FFFFFFF FFFFFFFF E487ED51 10B4611A 62633145 C06E0E68 388 94812704 4533E63A 0105DF53 1D89CD91 28A5043C C71A026E 389 F7CA8CD9 E69D218D 98158536 F92F8A1B A7F09AB6 B6A8E122 390 F242DABB 312F3F63 7A262174 D31BF6B5 85FFAE5B 7A035BF6 391 F71C35FD AD44CFD2 D74F9208 BE258FF3 24943328 F6722D9E 392 E1003E5C 50B1DF82 CC6D241B 0E2AE9CD 348B1FD4 7E9267AF 393 C1B2AE91 EE51D6CB 0E3179AB 1042A95D CF6A9483 B84B4B36 394 B3861AA7 255E4C02 78BA3604 650C10BE 19482F23 171B671D 395 F1CF3B96 0C074301 CD93C1D1 7603D147 DAE2AEF8 37A62964 396 EF15E5FB 4AAC0B8C 1CCAA4BE 754AB572 8AE9130C 4C7D0288 397 0AB9472D 45565534 7FFFFFFF FFFFFFFF. 399 The MODP group used for the iso-kam3-dl-4096-sha512 algorithm is 400 defined by the following parameters. 402 The prime is: 404 q = 0xFFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1 405 29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD 406 EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245 407 E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED 408 EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE45B3D 409 C2007CB8 A163BF05 98DA4836 1C55D39A 69163FA8 FD24CF5F 410 83655D23 DCA3AD96 1C62F356 208552BB 9ED52907 7096966D 411 670C354E 4ABC9804 F1746C08 CA18217C 32905E46 2E36CE3B 412 E39E772C 180E8603 9B2783A2 EC07A28F B5C55DF0 6F4C52C9 413 DE2BCBF6 95581718 3995497C EA956AE5 15D22618 98FA0510 414 15728E5A 8AAAC42D AD33170D 04507A33 A85521AB DF1CBA64 415 ECFB8504 58DBEF0A 8AEA7157 5D060C7D B3970F85 A6E1E4C7 416 ABF5AE8C DB0933D7 1E8C94E0 4A25619D CEE3D226 1AD2EE6B 417 F12FFA06 D98A0864 D8760273 3EC86A64 521F2B18 177B200C 418 BBE11757 7A615D6C 770988C0 BAD946E2 08E24FA0 74E5AB31 419 43DB5BFC E0FD108E 4B82D120 A9210801 1A723C12 A787E6D7 420 88719A10 BDBA5B26 99C32718 6AF4E23C 1A946834 B6150BDA 421 2583E9CA 2AD44CE8 DBBBC2DB 04DE8EF9 2E8EFC14 1FBECAA6 422 287C5947 4E6BC05D 99B2964F A090C3A2 233BA186 515BE7ED 423 1F612970 CEE2D7AF B81BDD76 2170481C D0069127 D5B05AA9 424 93B4EA98 8D8FDDC1 86FFB7DC 90A6C08F 4DF435C9 34063199 425 FFFFFFFF FFFFFFFF. 427 The generator is: 429 g = 2. 431 The size of the subgroup generated by g is: 433 r = (q - 1) / 2 = 434 0x7FFFFFFF FFFFFFFF E487ED51 10B4611A 62633145 C06E0E68 435 94812704 4533E63A 0105DF53 1D89CD91 28A5043C C71A026E 436 F7CA8CD9 E69D218D 98158536 F92F8A1B A7F09AB6 B6A8E122 437 F242DABB 312F3F63 7A262174 D31BF6B5 85FFAE5B 7A035BF6 438 F71C35FD AD44CFD2 D74F9208 BE258FF3 24943328 F6722D9E 439 E1003E5C 50B1DF82 CC6D241B 0E2AE9CD 348B1FD4 7E9267AF 440 C1B2AE91 EE51D6CB 0E3179AB 1042A95D CF6A9483 B84B4B36 441 B3861AA7 255E4C02 78BA3604 650C10BE 19482F23 171B671D 442 F1CF3B96 0C074301 CD93C1D1 7603D147 DAE2AEF8 37A62964 443 EF15E5FB 4AAC0B8C 1CCAA4BE 754AB572 8AE9130C 4C7D0288 444 0AB9472D 45556216 D6998B86 82283D19 D42A90D5 EF8E5D32 445 767DC282 2C6DF785 457538AB AE83063E D9CB87C2 D370F263 446 D5FAD746 6D8499EB 8F464A70 2512B0CE E771E913 0D697735 447 F897FD03 6CC50432 6C3B0139 9F643532 290F958C 0BBD9006 448 5DF08BAB BD30AEB6 3B84C460 5D6CA371 047127D0 3A72D598 449 A1EDADFE 707E8847 25C16890 54908400 8D391E09 53C3F36B 450 C438CD08 5EDD2D93 4CE1938C 357A711E 0D4A341A 5B0A85ED 451 12C1F4E5 156A2674 6DDDE16D 826F477C 97477E0A 0FDF6553 452 143E2CA3 A735E02E CCD94B27 D04861D1 119DD0C3 28ADF3F6 453 8FB094B8 67716BD7 DC0DEEBB 10B8240E 68034893 EAD82D54 454 C9DA754C 46C7EEE0 C37FDBEE 48536047 A6FA1AE4 9A0318CC 455 FFFFFFFF FFFFFFFF. 457 Appendix B. (Informative) Derived Numerical Values 459 This section provides several numerical values for implementing this 460 protocol, derived from the above specifications. The values shown in 461 this section are for informative purposes only. 463 +----------------+---------+---------+---------+---------+----------+ 464 | | dl-2048 | dl-4096 | ec-p256 | ec-p521 | | 465 +----------------+---------+---------+---------+---------+----------+ 466 | Size of K_c1 | 2048 | 4096 | 257 | 522 | (bits) | 467 | etc. | | | | | | 468 | Size of H(...) | 256 | 512 | 256 | 512 | (bits) | 469 | length of | 256 | 512 | 33 | 66 | (octets) | 470 | OCTETS(K_c1) | | | | | | 471 | etc. | | | | | | 472 | length of kc1, | 344 * | 684 * | 66 | 132 | (octets) | 473 | ks1 param. | | | | | | 474 | values. | | | | | | 475 | length of vkc, | 44 * | 88 * | 64 | 128 | (octets) | 476 | vks param. | | | | | | 477 | values. | | | | | | 478 | minimum | 2048 | 4096 | 1 | 1 | | 479 | allowed S_c1 | | | | | | 480 +----------------+---------+---------+---------+---------+----------+ 482 (The numbers marked with an * do not include any enclosing quotation 483 marks.) 485 Appendix C. (Informative) Draft Change Log 487 C.1. Changes in revision 02 489 o Implementation hints in appendix changed (number of characters for 490 base64-fixed-number does not contain double-quotes). 492 C.2. Changes in revision 01 494 o Parameter names renamed. 496 o Some expressions clarified without changing the value. 498 C.3. Changes in revision 00 500 The document is separated from the revision 08 of the core 501 documentation. 503 Authors' Addresses 505 Yutaka Oiwa 506 National Institute of Advanced Industrial Science and Technology 507 Research Institute for Secure Systems 508 Tsukuba Central 2 509 1-1-1 Umezono 510 Tsukuba-shi, Ibaraki 511 JP 513 Email: mutual-auth-contact-ml@aist.go.jp 514 Hajime Watanabe 515 National Institute of Advanced Industrial Science and Technology 516 Research Institute for Secure Systems 517 Tsukuba Central 2 518 1-1-1 Umezono 519 Tsukuba-shi, Ibaraki 520 JP 522 Hiromitsu Takagi 523 National Institute of Advanced Industrial Science and Technology 524 Research Institute for Secure Systems 525 Tsukuba Central 2 526 1-1-1 Umezono 527 Tsukuba-shi, Ibaraki 528 JP 530 Boku Kihara 531 Lepidum Co. Ltd. 532 #602, Village Sasazuka 3 533 1-30-3 Sasazuka 534 Shibuya-ku, Tokyo 535 JP 537 Tatsuya Hayashi 538 Lepidum Co. Ltd. 539 #602, Village Sasazuka 3 540 1-30-3 Sasazuka 541 Shibuya-ku, Tokyo 542 JP 544 Yuichi Ioku 545 Yahoo! Japan, Inc. 546 Midtown Tower 547 9-7-1 Akasaka 548 Minato-ku, Tokyo 549 JP