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Merkle, Ed. 3 Internet-Draft Secunet Security Networks 4 Obsoletes: 7630 (if approved) M. Lochter 5 Intended status: Standards Track BSI 6 Expires: July 29, 2016 January 26, 2016 8 HMAC-SHA-2 Authentication Protocols in USM for SNMPv3 9 draft-ietf-opsawg-hmac-sha-2-usm-snmp-new-03 11 Abstract 13 This memo specifies new HMAC-SHA-2 authentication protocols for the 14 User-based Security Model (USM) for SNMPv3 defined in RFC 3414. 16 Status of This Memo 18 This Internet-Draft is submitted in full conformance with the 19 provisions of BCP 78 and BCP 79. 21 Internet-Drafts are working documents of the Internet Engineering 22 Task Force (IETF). Note that other groups may also distribute 23 working documents as Internet-Drafts. The list of current Internet- 24 Drafts is at http://datatracker.ietf.org/drafts/current/. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 This Internet-Draft will expire on July 29, 2016. 33 Copyright Notice 35 Copyright (c) 2016 IETF Trust and the persons identified as the 36 document authors. All rights reserved. 38 This document is subject to BCP 78 and the IETF Trust's Legal 39 Provisions Relating to IETF Documents 40 (http://trustee.ietf.org/license-info) in effect on the date of 41 publication of this document. Please review these documents 42 carefully, as they describe your rights and restrictions with respect 43 to this document. Code Components extracted from this document must 44 include Simplified BSD License text as described in Section 4.e of 45 the Trust Legal Provisions and are provided without warranty as 46 described in the Simplified BSD License. 48 Table of Contents 50 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 51 2. The Internet-Standard Management Framework . . . . . . . . . 3 52 3. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3 53 4. The HMAC-SHA-2 Authentication Protocols . . . . . . . . . . . 3 54 4.1. Deviations from the HMAC-SHA-96 Authentication Protocol . 4 55 4.2. Processing . . . . . . . . . . . . . . . . . . . . . . . 5 56 4.2.1. Processing an Outgoing Message . . . . . . . . . . . 5 57 4.2.2. Processing an Incoming Message . . . . . . . . . . . 6 58 5. Key Localization and Key Change . . . . . . . . . . . . . . . 6 59 6. Structure of the MIB Module . . . . . . . . . . . . . . . . . 6 60 7. Relationship to Other MIB Modules . . . . . . . . . . . . . . 7 61 7.1. Relationship to SNMP-USER-BASED-SM-MIB . . . . . . . . . 7 62 7.2. Relationship to SNMP-FRAMEWORK-MIB . . . . . . . . . . . 7 63 7.3. MIB Modules Required for IMPORTS . . . . . . . . . . . . 7 64 8. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 7 65 9. Security Considerations . . . . . . . . . . . . . . . . . . . 9 66 9.1. Use of the HMAC-SHA-2 Authentication Protocols in USM . . 9 67 9.2. Cryptographic Strength of the Authentication Protocols . 9 68 9.3. Derivation of Keys from Passwords . . . . . . . . . . . . 10 69 9.4. Access to the SNMP-USM-HMAC-SHA2-MIB . . . . . . . . . . 11 70 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 71 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 72 11.1. Normative References . . . . . . . . . . . . . . . . . . 12 73 11.2. Informative References . . . . . . . . . . . . . . . . . 13 74 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 76 1. Introduction 78 This memo defines a portion of the Management Information Base (MIB) 79 for use with network management protocols. In particular, it defines 80 additional authentication protocols for the User-based Security Model 81 (USM) for the Simple Network Management Protocol version 3 (SNMPv3) 82 specified in [RFC3414]. 84 In RFC 3414, two different authentication protocols, HMAC-MD5-96 and 85 HMAC-SHA-96, are defined based on the hash functions MD5 and SHA-1, 86 respectively. This memo specifies new HMAC-SHA-2 authentication 87 protocols for USM using a Hashed Message Authentication Code (HMAC) 88 based on the SHA-2 family of hash functions [SHA] and truncated to 89 128 bits for SHA-224, to 192 bits for SHA-256, to 256 bits for 90 SHA-384, and to 384 bits for SHA-512. These protocols are 91 straightforward adaptations of the authentication protocols HMAC- 92 MD5-96 and HMAC-SHA-96 to the SHA-2-based HMAC. 94 This document obsoletes RFC 7630, in which the MIB MODULE-IDENTITY 95 value was incorrectly specified. 97 2. The Internet-Standard Management Framework 99 For a detailed overview of the documents that describe the current 100 Internet-Standard Management Framework, please refer to section 7 of 101 [RFC3410]. 103 Managed objects are accessed via a virtual information store, termed 104 the Management Information Base or MIB. MIB objects are generally 105 accessed through the Simple Network Management Protocol (SNMP). 106 Objects in the MIB are defined using the mechanisms defined in the 107 Structure of Management Information (SMI). This memo specifies a MIB 108 module that is compliant to the SMIv2, which is described in 109 [RFC2578], [RFC2579], and [RFC2580]. 111 3. Conventions 113 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 114 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 115 document are to be interpreted as described in BCP 14, RFC 2119 116 [RFC2119]. 118 4. The HMAC-SHA-2 Authentication Protocols 120 This section describes the HMAC-SHA-2 authentication protocols, which 121 use the SHA-2 hash functions (described in FIPS PUB 180-4 [SHA] and 122 [RFC6234]) in the HMAC mode (described in [RFC2104] and RFC 6234), 123 truncating the output to 128 bits for SHA-224, 192 bits for SHA-256, 124 256 bits for SHA-384, and 384 bits for SHA-512. RFC 6234 also 125 provides source code for all the SHA-2 algorithms and HMAC (without 126 truncation). It also includes test harness and standard test vectors 127 for all the defined hash functions and HMAC examples. 129 The following protocols are defined: 131 usmHMAC128SHA224AuthProtocol: uses SHA-224 and truncates the 132 output to 128 bits (16 octets); 134 usmHMAC192SHA256AuthProtocol: uses SHA-256 and truncates the 135 output to 192 bits (24 octets); 137 usmHMAC256SHA384AuthProtocol: uses SHA-384 and truncates the 138 output to 256 bits (32 octets); 140 usmHMAC384SHA512AuthProtocol: uses SHA-512 and truncates the 141 output to 384 bits (48 octets). 143 Implementations conforming to this specification MUST support 144 usmHMAC192SHA256AuthProtocol and SHOULD support 145 usmHMAC384SHA512AuthProtocol. The protocols 146 usmHMAC128SHA224AuthProtocol and usmHMAC256SHA384AuthProtocol are 147 OPTIONAL. 149 4.1. Deviations from the HMAC-SHA-96 Authentication Protocol 151 All the HMAC-SHA-2 authentication protocols are straightforward 152 adaptations of the HMAC-MD5-96 and HMAC-SHA-96 authentication 153 protocols. Specifically, they differ from the HMAC-MD5-96 and HMAC- 154 SHA-96 authentication protocols in the following aspects: 156 o The SHA-2 hash function is used to compute the message digest in 157 the HMAC computation according to RFC 2104 and RFC 6234, as 158 opposed to the MD5 hash function [RFC1321] and SHA-1 hash function 159 [SHA] used in HMAC-MD5-96 and HMAC-SHA-96, respectively. 160 Consequently, the length of the message digest prior to truncation 161 is 224 bits for the SHA-224-based protocol, 256 bits for the 162 SHA-256-based protocol, 384 bits for the SHA-384-based protocol, 163 and 512 bits for the SHA-512-based protocol. 165 o The resulting message digest (output of HMAC) is truncated to 167 * 16 octets for usmHMAC128SHA224AuthProtocol 169 * 24 octets for usmHMAC192SHA256AuthProtocol 171 * 32 octets for usmHMAC256SHA384AuthProtocol 173 * 48 octets for usmHMAC384SHA512AuthProtocol 175 as opposed to the truncation to 12 octets in HMAC-MD5-96 and HMAC- 176 SHA-96. 178 o The user's secret key to be used when calculating a digest MUST be 180 * 28 octets long and derived with SHA-224 for the SHA-224-based 181 protocol usmHMAC128SHA224AuthProtocol 183 * 32 octets long and derived with SHA-256 for the SHA-256-based 184 protocol usmHMAC192SHA256AuthProtocol 186 * 48 octets long and derived with SHA-384 for the SHA-384-based 187 protocol usmHMAC256SHA384AuthProtocol 189 * 64 octets long and derived with SHA-512 for the SHA-512-based 190 protocol usmHMAC384SHA512AuthProtocol 192 as opposed to the keys being 16 and 20 octets long in HMAC-MD5-96 193 and HMAC-SHA-96, respectively. 195 4.2. Processing 197 This section describes the procedures for the HMAC-SHA-2 198 authentication protocols. The descriptions are based on the 199 definition of services and data elements defined for HMAC-SHA-96 in 200 RFC 3414 with the deviations listed in Section 4.1. 202 Values of constants M (the length of the secret key in octets) and N 203 (the length of the Message Authentication Code (MAC) output in 204 octets), and the hash function H used below are: 206 usmHMAC128SHA224AuthProtocol: M=28, N=16, H=SHA-224; 208 usmHMAC192SHA256AuthProtocol: M=32, N=24, H=SHA-256; 210 usmHMAC256SHA384AuthProtocol: M=48, N=32, H=SHA-384; 212 usmHMAC384SHA512AuthProtocol: M=64, N=48, H=SHA-512. 214 4.2.1. Processing an Outgoing Message 216 This section describes the procedure followed by an SNMP engine 217 whenever it must authenticate an outgoing message using one of the 218 authentication protocols defined above. Values of the constants M 219 and N, and the hash function H are as defined in Section 4.2 and are 220 selected based on which authentication protocol is configured for the 221 given USM usmUser Table entry. 223 1. The msgAuthenticationParameters field is set to the serialization 224 of an OCTET STRING containing N zero octets; it is serialized 225 according to the rules in [RFC3417]. 227 2. Using the secret authKey of M octets, the HMAC is calculated over 228 the wholeMsg according to RFC 6234 with hash function H. 230 3. The N first octets of the above HMAC are taken as the computed 231 MAC value. 233 4. The msgAuthenticationParameters field is replaced with the MAC 234 obtained in the previous step. 236 5. The authenticatedWholeMsg is then returned to the caller together 237 with the statusInformation indicating success. 239 4.2.2. Processing an Incoming Message 241 This section describes the procedure followed by an SNMP engine 242 whenever it must authenticate an incoming message using one of the 243 HMAC-SHA-2 authentication protocols. Values of the constants M and 244 N, and the hash function H are as defined in Section 4.2 and are 245 selected based on which authentication protocol is configured for the 246 given USM usmUser Table entry. 248 1. If the digest received in the msgAuthenticationParameters field 249 is not N octets long, then a failure and an errorIndication 250 (authenticationError) are returned to the calling module. 252 2. The MAC received in the msgAuthenticationParameters field is 253 saved. 255 3. The digest in the msgAuthenticationParameters field is replaced 256 by the N zero octets. 258 4. Using the secret authKey of M octets, the HMAC is calculated over 259 the wholeMsg according to RFC 6234 with hash function H. 261 5. The N first octets of the above HMAC are taken as the computed 262 MAC value. 264 6. The msgAuthenticationParameters field is replaced with the MAC 265 value that was saved in step 2. 267 7. The newly calculated MAC is compared with the MAC saved in step 268 2. If they do not match, then a failure and an errorIndication 269 (authenticationFailure) are returned to the calling module. 271 8. The authenticatedWholeMsg and statusInformation indicating 272 success are then returned to the caller. 274 5. Key Localization and Key Change 276 For any of the protocols defined in Section 4, key localization and 277 key change SHALL be performed according to [RFC3414] using the same 278 SHA-2 hash function as in the HMAC-SHA-2 authentication protocol. 280 6. Structure of the MIB Module 282 The MIB module specified in this memo does not define any managed 283 objects, subtrees, notifications, or tables; rather, it only defines 284 object identities (for authentication protocols) under a subtree of 285 an existing MIB. 287 7. Relationship to Other MIB Modules 289 7.1. Relationship to SNMP-USER-BASED-SM-MIB 291 RFC 3414 specifies the MIB module for USM for SNMPv3 (SNMP-USER- 292 BASED-SM-MIB), which defines authentication protocols for USM based 293 on the hash functions MD5 and SHA-1, respectively. The following MIB 294 module defines new HMAC-SHA2 authentication protocols for USM based 295 on the SHA-2 hash functions [SHA]. The use of the HMAC-SHA2 296 authentication protocols requires the usage of the objects defined in 297 the SNMP-USER-BASED-SM-MIB. 299 7.2. Relationship to SNMP-FRAMEWORK-MIB 301 [RFC3411] specifies the SNMP-FRAMEWORK-MIB, which defines a subtree 302 snmpAuthProtocols for SNMP authentication protocols. The following 303 MIB module defines new authentication protocols in the 304 snmpAuthProtocols subtree. 306 7.3. MIB Modules Required for IMPORTS 308 The following MIB module IMPORTS definitions from SNMPv2-SMI 309 [RFC2578] and SNMP-FRAMEWORK-MIB [RFC3411]. 311 8. Definitions 313 SNMP-USM-HMAC-SHA2-MIB DEFINITIONS ::= BEGIN 314 IMPORTS 315 MODULE-IDENTITY, OBJECT-IDENTITY, 316 mib-2 FROM SNMPv2-SMI -- [RFC2578] 317 snmpAuthProtocols FROM SNMP-FRAMEWORK-MIB; -- [RFC3411] 319 snmpUsmHmacSha2MIB MODULE-IDENTITY 320 LAST-UPDATED "201510210000Z" -- 21 October 2015, midnight 321 ORGANIZATION "SNMPv3 Working Group" 322 CONTACT-INFO "WG email: OPSAWG@ietf.org 323 Subscribe: 324 https://www.ietf.org/mailman/listinfo/opsawg 325 Editor: Johannes Merkle 326 secunet Security Networks 327 Postal: Mergenthaler Allee 77 328 D-65760 Eschborn 329 Germany 330 Phone: +49 20154543091 331 Email: johannes.merkle@secunet.com 333 Co-Editor: Manfred Lochter 334 Bundesamt fuer Sicherheit in der 335 Informationstechnik (BSI) 336 Postal: Postfach 200363 337 D-53133 Bonn 338 Germany 339 Phone: +49 228 9582 5643 340 Email: manfred.lochter@bsi.bund.de" 342 DESCRIPTION "Definitions of Object Identities needed 343 for the use of HMAC-SHA2 by SNMP's User-based 344 Security Model. 346 Copyright (c) 2015 IETF Trust and the persons identified 347 as authors of the code. All rights reserved. 349 Redistribution and use in source and binary forms, with 350 or without modification, is permitted pursuant to, and 351 subject to the license terms contained in, the Simplified 352 BSD License set forth in Section 4.c of the IETF Trust's 353 Legal Provisions Relating to IETF Documents 354 (http://trustee.ietf.org/license-info)." 356 REVISION "201510210000Z" -- 21 October 2015, midnight 357 DESCRIPTION "Version correcting the MODULE-IDENTITY value, published as RFC TBD" 358 -- RFC Ed.: replace TBD with actual RFC number & remove this line 359 REVISION "201508130000Z" -- 13 August 2015, midnight 360 DESCRIPTION "Initial version, published as RFC 7630" 362 ::= { mib-2 235 } 364 usmHMAC128SHA224AuthProtocol OBJECT-IDENTITY 365 STATUS current 366 DESCRIPTION "The Authentication Protocol 367 usmHMAC128SHA224AuthProtocol uses HMAC-SHA-224 and 368 truncates output to 128 bits." 369 REFERENCE "- Krawczyk, H., Bellare, M., and R. Canetti, HMAC: 370 Keyed-Hashing for Message Authentication, RFC 2104. 371 - National Institute of Standards and Technology, 372 Secure Hash Standard (SHS), FIPS PUB 180-4, 2012." 373 ::= { snmpAuthProtocols 4 } 375 usmHMAC192SHA256AuthProtocol OBJECT-IDENTITY 376 STATUS current 377 DESCRIPTION "The Authentication Protocol 378 usmHMAC192SHA256AuthProtocol uses HMAC-SHA-256 and 379 truncates output to 192 bits." 380 REFERENCE "- Krawczyk, H., Bellare, M., and R. Canetti, HMAC: 381 Keyed-Hashing for Message Authentication, RFC 2104. 382 - National Institute of Standards and Technology, 383 Secure Hash Standard (SHS), FIPS PUB 180-4, 2012." 384 ::= { snmpAuthProtocols 5 } 386 usmHMAC256SHA384AuthProtocol OBJECT-IDENTITY 387 STATUS current 388 DESCRIPTION "The Authentication Protocol 389 usmHMAC256SHA384AuthProtocol uses HMAC-SHA-384 and 390 truncates output to 256 bits." 391 REFERENCE "- Krawczyk, H., Bellare, M., and R. Canetti, HMAC: 392 Keyed-Hashing for Message Authentication, RFC 2104. 393 - National Institute of Standards and Technology, 394 Secure Hash Standard (SHS), FIPS PUB 180-4, 2012." 395 ::= { snmpAuthProtocols 6 } 397 usmHMAC384SHA512AuthProtocol OBJECT-IDENTITY 398 STATUS current 399 DESCRIPTION "The Authentication Protocol 400 usmHMAC384SHA512AuthProtocol uses HMAC-SHA-512 and 401 truncates output to 384 bits." 402 REFERENCE "- Krawczyk, H., Bellare, M., and R. Canetti, HMAC: 403 Keyed-Hashing for Message Authentication, RFC 2104. 404 - National Institute of Standards and Technology, 405 Secure Hash Standard (SHS), FIPS PUB 180-4, 2012." 406 ::= { snmpAuthProtocols 7 } 408 END 410 9. Security Considerations 412 9.1. Use of the HMAC-SHA-2 Authentication Protocols in USM 414 The security considerations of [RFC3414] also apply to the HMAC-SHA-2 415 authentication protocols defined in this document. 417 9.2. Cryptographic Strength of the Authentication Protocols 419 At the time of publication of this document, all of the HMAC-SHA-2 420 authentication protocols provide a very high level of security. The 421 security of each HMAC-SHA-2 authentication protocol depends on the 422 parameters used in the corresponding HMAC computation, which are the 423 length of the key (if the key has maximum entropy), the size of the 424 hash function's internal state, and the length of the truncated MAC. 425 For the HMAC-SHA-2 authentication protocols, these values are as 426 follows (values are given in bits). 428 +------------------------------+---------+----------------+---------+ 429 | Protocol | Key | Size of | MAC | 430 | | length | internal state | length | 431 +------------------------------+---------+----------------+---------+ 432 | usmHMAC128SHA224AuthProtocol | 224 | 256 | 128 | 433 | usmHMAC192SHA256AuthProtocol | 256 | 256 | 192 | 434 | usmHMAC256SHA384AuthProtocol | 384 | 512 | 256 | 435 | usmHMAC384SHA512AuthProtocol | 512 | 512 | 384 | 436 +------------------------------+---------+----------------+---------+ 438 Table 1: HMAC Parameters of the HMAC-SHA-2 Authentication Protocols 440 The security of the HMAC scales with both the key length and the size 441 of the internal state: longer keys render key guessing attacks more 442 difficult, and a larger internal state decreases the success 443 probability of MAC forgeries based on internal collisions of the hash 444 function. 446 The role of the truncated output length is more complicated: 447 according to [BCK], there is a trade-off in that 449 by outputting less bits the attacker has less bits to predict in a 450 MAC forgery but, on the other hand, the attacker also learns less 451 about the output of the compression function from seeing the 452 authentication tags computed by legitimate parties. 454 Thus, truncation weakens the HMAC against forgery by guessing but, at 455 the same time, strengthens it against chosen message attacks aiming 456 at MAC forgery based on internal collisions or at key guessing. RFC 457 2104 and [BCK] allow truncation to any length that is not less than 458 half the size of the internal state. 460 Further discussion of the security of the HMAC construction is given 461 in RFC 2104. 463 9.3. Derivation of Keys from Passwords 465 If secret keys to be used for HMAC-SHA-2 authentication protocols are 466 derived from passwords, the derivation SHOULD be performed using the 467 password-to-key algorithm from Appendix A.1 of RFC 3414 with MD5 468 being replaced by the SHA-2 hash function H used in the HMAC-SHA-2 469 authentication protocol. Specifically, the password is converted 470 into the required secret key by the following steps: 472 o forming a string of length 1,048,576 octets by repeating the value 473 of the password as often as necessary, truncating accordingly, and 474 using the resulting string as the input to the hash function H. 475 The resulting digest, termed "digest1", is used in the next step. 477 o forming a second string by concatenating digest1, the SNMP 478 engine's snmpEngineID value, and digest1. This string is used as 479 input to the hash function H. 481 9.4. Access to the SNMP-USM-HMAC-SHA2-MIB 483 The SNMP-USM-HMAC-SHA2-MIB module defines OBJECT IDENTIFIER values 484 for use in other MIB modules. It does not define any objects that 485 can be accessed. As such, the SNMP-USM-HMAC-SHA2-MIB does not, by 486 itself, have any effect on the security of the Internet. 488 The values defined in this module are expected to be used with the 489 usmUserTable defined in the SNMP-USER-BASED-SM-MIB [RFC3414]. The 490 considerations in Section 11.5 of RFC 3414 should be taken into 491 account. 493 10. IANA Considerations 495 IANA has assigned an OID for the MIB as follows. 497 +--------------------+-------------------------+ 498 | Descriptor | OBJECT IDENTIFIER value | 499 +--------------------+-------------------------+ 500 | snmpUsmHmacSha2MIB | { mib-2 235 } | 501 +--------------------+-------------------------+ 503 Table 2: OID of MIB 505 Furthermore, IANA has assigned a value in the SnmpAuthProtocols 506 registry for each of the following protocols. 508 +------------------------------+-------+-----------+ 509 | Description | Value | Reference | 510 +------------------------------+-------+-----------+ 511 | usmHMAC128SHA224AuthProtocol | 4 | RFC XXX | 512 | usmHMAC192SHA256AuthProtocol | 5 | RFC XXX | 513 | usmHMAC256SHA384AuthProtocol | 6 | RFC XXX | 514 | usmHMAC384SHA512AuthProtocol | 7 | RFC XXX | 515 +------------------------------+-------+-----------+ 517 Table 3: Code Points Assigned to HMAC-SHA-2 Authentication Protocols 519 -- RFC Ed.: replace XXX with actual RFC number and remove this line 521 11. References 523 11.1. Normative References 525 [RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed- 526 Hashing for Message Authentication", RFC 2104, 527 DOI 10.17487/RFC2104, February 1997, 528 . 530 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 531 Requirement Levels", BCP 14, RFC 2119, 532 DOI 10.17487/RFC2119, March 1997, 533 . 535 [RFC2578] McCloghrie, K., Ed., Perkins, D., Ed., and J. 536 Schoenwaelder, Ed., "Structure of Management Information 537 Version 2 (SMIv2)", STD 58, RFC 2578, 538 DOI 10.17487/RFC2578, April 1999, 539 . 541 [RFC2579] McCloghrie, K., Ed., Perkins, D., Ed., and J. 542 Schoenwaelder, Ed., "Textual Conventions for SMIv2", 543 STD 58, RFC 2579, DOI 10.17487/RFC2579, April 1999, 544 . 546 [RFC2580] McCloghrie, K., Ed., Perkins, D., Ed., and J. 547 Schoenwaelder, Ed., "Conformance Statements for SMIv2", 548 STD 58, RFC 2580, DOI 10.17487/RFC2580, April 1999, 549 . 551 [RFC3414] Blumenthal, U. and B. Wijnen, "User-based Security Model 552 (USM) for version 3 of the Simple Network Management 553 Protocol (SNMPv3)", STD 62, RFC 3414, 554 DOI 10.17487/RFC3414, December 2002, 555 . 557 [RFC6234] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms 558 (SHA and SHA-based HMAC and HKDF)", RFC 6234, 559 DOI 10.17487/RFC6234, May 2011, 560 . 562 [SHA] National Institute of Standards and Technology, "Secure 563 Hash Standard (SHS)", FIPS PUB 180-4, 564 DOI 10.6028/NIST.FIPS.180-4, March 2012, 565 . 568 11.2. Informative References 570 [RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, 571 DOI 10.17487/RFC1321, April 1992, 572 . 574 [RFC3410] Case, J., Mundy, R., Partain, D., and B. Stewart, 575 "Introduction and Applicability Statements for Internet- 576 Standard Management Framework", RFC 3410, 577 DOI 10.17487/RFC3410, December 2002, 578 . 580 [RFC3411] Harrington, D., Presuhn, R., and B. Wijnen, "An 581 Architecture for Describing Simple Network Management 582 Protocol (SNMP) Management Frameworks", STD 62, RFC 3411, 583 DOI 10.17487/RFC3411, December 2002, 584 . 586 [RFC3417] Presuhn, R., Ed., "Transport Mappings for the Simple 587 Network Management Protocol (SNMP)", STD 62, RFC 3417, 588 DOI 10.17487/RFC3417, December 2002, 589 . 591 [BCK] Bellare, M., Canetti, R., and H. Krawczyk, "Keyed Hash 592 Functions for Message Authentication", Advances in 593 Cryptology - CRYPTO 96, Lecture Notes in Computer 594 Science 1109, Springer-Verlag Berlin Heidelberg, 595 DOI 10.1007/3-540-68697-5_1, 1996. 597 Authors' Addresses 599 Johannes Merkle (editor) 600 Secunet Security Networks 601 Mergenthaler Allee 77 602 65760 Eschborn 603 Germany 605 Phone: +49 201 5454 3091 606 EMail: johannes.merkle@secunet.com 607 Manfred Lochter 608 BSI 609 Postfach 200363 610 53133 Bonn 611 Germany 613 Phone: +49 228 9582 5643 614 EMail: manfred.lochter@bsi.bund.de