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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Downref: Normative reference to an Informational RFC: RFC 2104 ** Downref: Normative reference to an Informational RFC: RFC 6234 -- Possible downref: Non-RFC (?) normative reference: ref. 'SHA' Summary: 2 errors (**), 0 flaws (~~), 1 warning (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 OPSAWG J. Merkle, Ed. 3 Internet-Draft Secunet Security Networks 4 Intended status: Standards Track M. Lochter 5 Expires: April 17, 2016 BSI 6 October 15, 2015 8 HMAC-SHA-2 Authentication Protocols in USM for SNMPv3 9 draft-ietf-opsawg-hmac-sha-2-usm-snmp-new-00 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 April 17, 2016. 33 Copyright Notice 35 Copyright (c) 2015 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 . . . . . . . . . . . . . . . . . . . . . . . . . 11 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 RFC 3414 [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 2. The Internet-Standard Management Framework 96 For a detailed overview of the documents that describe the current 97 Internet-Standard Management Framework, please refer to section 7 of 98 RFC 3410 [RFC3410]. 100 Managed objects are accessed via a virtual information store, termed 101 the Management Information Base or MIB. MIB objects are generally 102 accessed through the Simple Network Management Protocol (SNMP). 103 Objects in the MIB are defined using the mechanisms defined in the 104 Structure of Management Information (SMI). This memo specifies a MIB 105 module that is compliant to the SMIv2, which is described in STD 58, 106 RFC 2578 [RFC2578], STD 58, RFC 2579 [RFC2579] and STD 58, RFC 2580 107 [RFC2580]. 109 3. Conventions 111 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 112 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 113 document are to be interpreted as described in BCP 14, RFC 2119 114 [RFC2119]. 116 4. The HMAC-SHA-2 Authentication Protocols 118 This section describes the HMAC-SHA-2 authentication protocols, which 119 use the SHA-2 hash functions (described in FIPS PUB 180-4 [SHA] and 120 RFC 6234 [RFC6234]) in the HMAC mode (described in RFC 2104 [RFC2104] 121 and RFC 6234), truncating the output to 128 bits for SHA-224, 192 122 bits for SHA-256, 256 bits for SHA-384, and 384 bits for SHA-512. 123 RFC 6234 also provides source code for all the SHA-2 algorithms and 124 HMAC (without truncation). It also includes test harness and 125 standard test vectors for all the defined hash functions and HMAC 126 examples. 128 The following protocols are defined: 130 usmHMAC128SHA224AuthProtocol: uses SHA-224 and truncates the 131 output to 128 bits (16 octets); 133 usmHMAC192SHA256AuthProtocol: uses SHA-256 and truncates the 134 output to 192 bits (24 octets); 136 usmHMAC256SHA384AuthProtocol: uses SHA-384 and truncates the 137 output to 256 bits (32 octets); 139 usmHMAC384SHA512AuthProtocol: uses SHA-512 and truncates the 140 output to 384 bits (48 octets). 142 Implementations conforming to this specification MUST support 143 usmHMAC192SHA256AuthProtocol and SHOULD support 144 usmHMAC384SHA512AuthProtocol. The protocols 145 usmHMAC128SHA224AuthProtocol and usmHMAC256SHA384AuthProtocol are 146 OPTIONAL. 148 4.1. Deviations from the HMAC-SHA-96 Authentication Protocol 150 All the HMAC-SHA-2 authentication protocols are straightforward 151 adaptations of the HMAC-MD5-96 and HMAC-SHA-96 authentication 152 protocols. Specifically, they differ from the HMAC-MD5-96 and HMAC- 153 SHA-96 authentication protocols in the following aspects: 155 o The SHA-2 hash function is used to compute the message digest in 156 the HMAC computation according to RFC 2104 and RFC 6234, as 157 opposed to the MD5 hash function [RFC1321] and SHA-1 hash function 158 [SHA] used in HMAC-MD5-96 and HMAC-SHA-96, respectively. 159 Consequently, the length of the message digest prior to truncation 160 is 224 bits for the SHA-224-based protocol, 256 bits for the 161 SHA-256-based protocol, 384 bits for the SHA-384-based protocol, 162 and 512 bits for the SHA-512-based protocol. 164 o The resulting message digest (output of HMAC) is truncated to 166 * 16 octets for usmHMAC128SHA224AuthProtocol 168 * 24 octets for usmHMAC192SHA256AuthProtocol 170 * 32 octets for usmHMAC256SHA384AuthProtocol 172 * 48 octets for usmHMAC384SHA512AuthProtocol 174 as opposed to the truncation to 12 octets in HMAC-MD5-96 and HMAC- 175 SHA-96. 177 o The user's secret key to be used when calculating a digest MUST be 179 * 28 octets long and derived with SHA-224 for the SHA-224-based 180 protocol usmHMAC128SHA224AuthProtocol 182 * 32 octets long and derived with SHA-256 for the SHA-256-based 183 protocol usmHMAC192SHA256AuthProtocol 185 * 48 octets long and derived with SHA-384 for the SHA-384-based 186 protocol usmHMAC256SHA384AuthProtocol 188 * 64 octets long and derived with SHA-512 for the SHA-512-based 189 protocol usmHMAC384SHA512AuthProtocol 191 as opposed to the keys being 16 and 20 octets long in HMAC-MD5-96 192 and HMAC-SHA-96, respectively. 194 4.2. Processing 196 This section describes the procedures for the HMAC-SHA-2 197 authentication protocols. The descriptions are based on the 198 definition of services and data elements defined for HMAC-SHA-96 in 199 RFC 3414 with the deviations listed in Section 4.1. 201 Values of constants M (the length of the secret key in octets) and N 202 (the length of the Message Authentication Code (MAC) output in 203 octets), and the hash function H used below are: 205 usmHMAC128SHA224AuthProtocol: M=28, N=16, H=SHA-224; 207 usmHMAC192SHA256AuthProtocol: M=32, N=24, H=SHA-256; 209 usmHMAC256SHA384AuthProtocol: M=48, N=32, H=SHA-384; 211 usmHMAC384SHA512AuthProtocol: M=64, N=48, H=SHA-512. 213 4.2.1. Processing an Outgoing Message 215 This section describes the procedure followed by an SNMP engine 216 whenever it must authenticate an outgoing message using one of the 217 authentication protocols defined above. Values of the constants M 218 and N, and the hash function H are as defined in Section 4.2 and are 219 selected based on which authentication protocol is configured for the 220 given USM usmUser Table entry. 222 1. The msgAuthenticationParameters field is set to the serialization 223 of an OCTET STRING containing N zero octets; it is serialized 224 according to the rules in RFC 3417 [RFC3417]. 226 2. Using the secret authKey of M octets, the HMAC is calculated over 227 the wholeMsg according to RFC 6234 with hash function H. 229 3. The N first octets of the above HMAC are taken as the computed 230 MAC value. 232 4. The msgAuthenticationParameters field is replaced with the MAC 233 obtained in the previous step. 235 5. The authenticatedWholeMsg is then returned to the caller together 236 with the statusInformation indicating success. 238 4.2.2. Processing an Incoming Message 240 This section describes the procedure followed by an SNMP engine 241 whenever it must authenticate an incoming message using one of the 242 HMAC-SHA-2 authentication protocols. Values of the constants M and 243 N, and the hash function H are as defined in Section 4.2 and are 244 selected based on which authentication protocol is configured for the 245 given USM usmUser Table entry. 247 1. If the digest received in the msgAuthenticationParameters field 248 is not N octets long, then a failure and an errorIndication 249 (authenticationError) are returned to the calling module. 251 2. The MAC received in the msgAuthenticationParameters field is 252 saved. 254 3. The digest in the msgAuthenticationParameters field is replaced 255 by the N zero octets. 257 4. Using the secret authKey of M octets, the HMAC is calculated over 258 the wholeMsg according to RFC 6234 with hash function H. 260 5. The N first octets of the above HMAC are taken as the computed 261 MAC value. 263 6. The msgAuthenticationParameters field is replaced with the MAC 264 value that was saved in step 2. 266 7. The newly calculated MAC is compared with the MAC saved in step 267 2. If they do not match, then a failure and an errorIndication 268 (authenticationFailure) are returned to the calling module. 270 8. The authenticatedWholeMsg and statusInformation indicating 271 success are then returned to the caller. 273 5. Key Localization and Key Change 275 For any of the protocols defined in Section 4, key localization and 276 key change SHALL be performed according to RFC 3414 [RFC3414] using 277 the same SHA-2 hash function as in the HMAC-SHA-2 authentication 278 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 RFC 3411 [RFC3411] specifies the SNMP-FRAMEWORK-MIB, which defines a 302 subtree snmpAuthProtocols for SNMP authentication protocols. The 303 following 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 snmpModules FROM SNMPv2-SMI -- [RFC2578] 317 snmpAuthProtocols FROM SNMP-FRAMEWORK-MIB; -- [RFC3411] 319 snmpUsmHmacSha2MIB MODULE-IDENTITY 320 LAST-UPDATED "201508130000Z" -- 13 August 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 "201508130000Z" -- 13 August 2015, midnight 357 DESCRIPTION "Initial version, published as RFC 7630" 358 ::= { mib-2 235 } 360 usmHMAC128SHA224AuthProtocol OBJECT-IDENTITY 361 STATUS current 362 DESCRIPTION "The Authentication Protocol 363 usmHMAC128SHA224AuthProtocol uses HMAC-SHA-224 and 364 truncates output to 128 bits." 365 REFERENCE "- Krawczyk, H., Bellare, M., and R. Canetti, HMAC: 366 Keyed-Hashing for Message Authentication, RFC 2104. 367 - National Institute of Standards and Technology, 368 Secure Hash Standard (SHS), FIPS PUB 180-4, 2012." 369 ::= { snmpAuthProtocols 4 } 371 usmHMAC192SHA256AuthProtocol OBJECT-IDENTITY 372 STATUS current 373 DESCRIPTION "The Authentication Protocol 374 usmHMAC192SHA256AuthProtocol uses HMAC-SHA-256 and 375 truncates output to 192 bits." 376 REFERENCE "- Krawczyk, H., Bellare, M., and R. Canetti, HMAC: 377 Keyed-Hashing for Message Authentication, RFC 2104. 378 - National Institute of Standards and Technology, 379 Secure Hash Standard (SHS), FIPS PUB 180-4, 2012." 380 ::= { snmpAuthProtocols 5 } 382 usmHMAC256SHA384AuthProtocol OBJECT-IDENTITY 383 STATUS current 384 DESCRIPTION "The Authentication Protocol 385 usmHMAC256SHA384AuthProtocol uses HMAC-SHA-384 and 386 truncates output to 256 bits." 387 REFERENCE "- Krawczyk, H., Bellare, M., and R. Canetti, HMAC: 388 Keyed-Hashing for Message Authentication, RFC 2104. 389 - National Institute of Standards and Technology, 390 Secure Hash Standard (SHS), FIPS PUB 180-4, 2012." 391 ::= { snmpAuthProtocols 6 } 393 usmHMAC384SHA512AuthProtocol OBJECT-IDENTITY 394 STATUS current 395 DESCRIPTION "The Authentication Protocol 396 usmHMAC384SHA512AuthProtocol uses HMAC-SHA-512 and 397 truncates output to 384 bits." 398 REFERENCE "- Krawczyk, H., Bellare, M., and R. Canetti, HMAC: 399 Keyed-Hashing for Message Authentication, RFC 2104. 400 - National Institute of Standards and Technology, 401 Secure Hash Standard (SHS), FIPS PUB 180-4, 2012." 402 ::= { snmpAuthProtocols 7 } 404 END 406 9. Security Considerations 408 9.1. Use of the HMAC-SHA-2 Authentication Protocols in USM 410 The security considerations of RFC 3414 [RFC3414] also apply to the 411 HMAC-SHA-2 authentication protocols defined in this document. 413 9.2. Cryptographic Strength of the Authentication Protocols 415 At the time of publication of this document, all of the HMAC-SHA-2 416 authentication protocols provide a very high level of security. The 417 security of each HMAC-SHA-2 authentication protocol depends on the 418 parameters used in the corresponding HMAC computation, which are the 419 length of the key (if the key has maximum entropy), the size of the 420 hash function's internal state, and the length of the truncated MAC. 421 For the HMAC-SHA-2 authentication protocols, these values are as 422 follows (values are given in bits). 424 +------------------------------+---------+----------------+---------+ 425 | Protocol | Key | Size of | MAC | 426 | | length | internal state | length | 427 +------------------------------+---------+----------------+---------+ 428 | usmHMAC128SHA224AuthProtocol | 224 | 256 | 128 | 429 | usmHMAC192SHA256AuthProtocol | 256 | 256 | 192 | 430 | usmHMAC256SHA384AuthProtocol | 384 | 512 | 256 | 431 | usmHMAC384SHA512AuthProtocol | 512 | 512 | 384 | 432 +------------------------------+---------+----------------+---------+ 434 Table 1: HMAC Parameters of the HMAC-SHA-2 Authentication Protocols 436 The security of the HMAC scales with both the key length and the size 437 of the internal state: longer keys render key guessing attacks more 438 difficult, and a larger internal state decreases the success 439 probability of MAC forgeries based on internal collisions of the hash 440 function. 442 The role of the truncated output length is more complicated: 443 according to [BCK], there is a trade-off in that 445 by outputting less bits the attacker has less bits to predict in a 446 MAC forgery but, on the other hand, the attacker also learns less 447 about the output of the compression function from seeing the 448 authentication tags computed by legitimate parties. 450 Thus, truncation weakens the HMAC against forgery by guessing but, at 451 the same time, strengthens it against chosen message attacks aiming 452 at MAC forgery based on internal collisions or at key guessing. RFC 453 2104 and [BCK] allow truncation to any length that is not less than 454 half the size of the internal state. 456 Further discussion of the security of the HMAC construction is given 457 in RFC 2104. 459 9.3. Derivation of Keys from Passwords 461 If secret keys to be used for HMAC-SHA-2 authentication protocols are 462 derived from passwords, the derivation SHOULD be performed using the 463 password-to-key algorithm from Appendix A.1 of RFC 3414 with MD5 464 being replaced by the SHA-2 hash function H used in the HMAC-SHA-2 465 authentication protocol. Specifically, the password is converted 466 into the required secret key by the following steps: 468 o forming a string of length 1,048,576 octets by repeating the value 469 of the password as often as necessary, truncating accordingly, and 470 using the resulting string as the input to the hash function H. 471 The resulting digest, termed "digest1", is used in the next step. 473 o forming a second string by concatenating digest1, the SNMP 474 engine's snmpEngineID value, and digest1. This string is used as 475 input to the hash function H. 477 9.4. Access to the SNMP-USM-HMAC-SHA2-MIB 479 The SNMP-USM-HMAC-SHA2-MIB module defines OBJECT IDENTIFIER values 480 for use in other MIB modules. It does not define any objects that 481 can be accessed. As such, the SNMP-USM-HMAC-SHA2-MIB does not, by 482 itself, have any effect on the security of the Internet. 484 The values defined in this module are expected to be used with the 485 usmUserTable defined in the SNMP-USER-BASED-SM-MIB [RFC3414]. The 486 considerations in Section 11.5 of RFC 3414 should be taken into 487 account. 489 10. IANA Considerations 491 IANA has assigned an OID for the MIB as follows. 493 +--------------------+-------------------------+ 494 | Descriptor | OBJECT IDENTIFIER value | 495 +--------------------+-------------------------+ 496 | snmpUsmHmacSha2MIB | { mib-2 235 } | 497 +--------------------+-------------------------+ 499 Table 2: OID of MIB 501 Furthermore, IANA has assigned a value in the SnmpAuthProtocols 502 registry for each of the following protocols. 504 +------------------------------+-------+-----------+ 505 | Description | Value | Reference | 506 +------------------------------+-------+-----------+ 507 | usmHMAC128SHA224AuthProtocol | 4 | RFC 7630 | 508 | usmHMAC192SHA256AuthProtocol | 5 | RFC 7630 | 509 | usmHMAC256SHA384AuthProtocol | 6 | RFC 7630 | 510 | usmHMAC384SHA512AuthProtocol | 7 | RFC 7630 | 511 +------------------------------+-------+-----------+ 513 Table 3: Code Points Assigned to HMAC-SHA-2 Authentication Protocols 515 11. References 516 11.1. Normative References 518 [RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed- 519 Hashing for Message Authentication", RFC 2104, 520 DOI 10.17487/RFC2104, February 1997, 521 . 523 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 524 Requirement Levels", BCP 14, RFC 2119, 525 DOI 10.17487/RFC2119, March 1997, 526 . 528 [RFC2578] McCloghrie, K., Ed., Perkins, D., Ed., and J. 529 Schoenwaelder, Ed., "Structure of Management Information 530 Version 2 (SMIv2)", STD 58, RFC 2578, 531 DOI 10.17487/RFC2578, April 1999, 532 . 534 [RFC2579] McCloghrie, K., Ed., Perkins, D., Ed., and J. 535 Schoenwaelder, Ed., "Textual Conventions for SMIv2", 536 STD 58, RFC 2579, DOI 10.17487/RFC2579, April 1999, 537 . 539 [RFC2580] McCloghrie, K., Ed., Perkins, D., Ed., and J. 540 Schoenwaelder, Ed., "Conformance Statements for SMIv2", 541 STD 58, RFC 2580, DOI 10.17487/RFC2580, April 1999, 542 . 544 [RFC3414] Blumenthal, U. and B. Wijnen, "User-based Security Model 545 (USM) for version 3 of the Simple Network Management 546 Protocol (SNMPv3)", STD 62, RFC 3414, 547 DOI 10.17487/RFC3414, December 2002, 548 . 550 [RFC6234] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms 551 (SHA and SHA-based HMAC and HKDF)", RFC 6234, 552 DOI 10.17487/RFC6234, May 2011, 553 . 555 [SHA] National Institute of Standards and Technology, "Secure 556 Hash Standard (SHS)", FIPS PUB 180-4, 557 DOI 10.6028/NIST.FIPS.180-4, March 2012, 558 . 561 11.2. Informative References 563 [RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, 564 DOI 10.17487/RFC1321, April 1992, 565 . 567 [RFC3410] Case, J., Mundy, R., Partain, D., and B. Stewart, 568 "Introduction and Applicability Statements for Internet- 569 Standard Management Framework", RFC 3410, 570 DOI 10.17487/RFC3410, December 2002, 571 . 573 [RFC3411] Harrington, D., Presuhn, R., and B. Wijnen, "An 574 Architecture for Describing Simple Network Management 575 Protocol (SNMP) Management Frameworks", STD 62, RFC 3411, 576 DOI 10.17487/RFC3411, December 2002, 577 . 579 [RFC3417] Presuhn, R., Ed., "Transport Mappings for the Simple 580 Network Management Protocol (SNMP)", STD 62, RFC 3417, 581 DOI 10.17487/RFC3417, December 2002, 582 . 584 [BCK] Bellare, M., Canetti, R., and H. Krawczyk, "Keyed Hash 585 Functions for Message Authentication", Advances in 586 Cryptology - CRYPTO 96, Lecture Notes in Computer 587 Science 1109, Springer-Verlag Berlin Heidelberg, 588 DOI 10.1007/3-540-68697-5_1, 1996. 590 Authors' Addresses 592 Johannes Merkle (editor) 593 Secunet Security Networks 594 Mergenthaler Allee 77 595 65760 Eschborn 596 Germany 598 Phone: +49 201 5454 3091 599 EMail: johannes.merkle@secunet.com 600 Manfred Lochter 601 BSI 602 Postfach 200363 603 53133 Bonn 604 Germany 606 Phone: +49 228 9582 5643 607 EMail: manfred.lochter@bsi.bund.de