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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IETF K. Moriarty 3 Internet-Draft Dell EMC 4 Intended status: Standards Track May 30, 2019 5 Expires: December 1, 2019 7 ACME End User Client and Code Signing Certificates 8 draft-moriarty-acme-client-01 10 Abstract 12 Automated Certificate Management Environment (ACME) core protocol 13 addresses the use case of web server certificates for TLS. This 14 document extends the ACME protocol to support end user client, device 15 client, and code signing certificates. 17 Status of This Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF). Note that other groups may also distribute 24 working documents as Internet-Drafts. The list of current Internet- 25 Drafts is at https://datatracker.ietf.org/drafts/current/. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 This Internet-Draft will expire on December 1, 2019. 34 Copyright Notice 36 Copyright (c) 2019 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents 41 (https://trustee.ietf.org/license-info) in effect on the date of 42 publication of this document. Please review these documents 43 carefully, as they describe your rights and restrictions with respect 44 to this document. Code Components extracted from this document must 45 include Simplified BSD License text as described in Section 4.e of 46 the Trust Legal Provisions and are provided without warranty as 47 described in the Simplified BSD License. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 52 2. Identity Proofing for Client Certificates . . . . . . . . . . 2 53 3. Device Certificates . . . . . . . . . . . . . . . . . . . . . 4 54 4. End User Client Certificates . . . . . . . . . . . . . . . . 5 55 5. CodeSigning Certificates . . . . . . . . . . . . . . . . . . 6 56 6. Pre-authorization . . . . . . . . . . . . . . . . . . . . . . 9 57 7. Challenge Types . . . . . . . . . . . . . . . . . . . . . . . 9 58 7.1. One Time Password (OTP) . . . . . . . . . . . . . . . . . 10 59 7.2. Certificate . . . . . . . . . . . . . . . . . . . . . . . 10 60 7.3. FIDO or Public/Private Key Pairs . . . . . . . . . . . . 11 61 8. Security Considerations . . . . . . . . . . . . . . . . . . . 12 62 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 63 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 12 64 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 65 11.1. Normative References . . . . . . . . . . . . . . . . . . 12 66 11.2. Informative References . . . . . . . . . . . . . . . . . 12 67 11.3. URL References . . . . . . . . . . . . . . . . . . . . . 12 68 Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 14 69 Appendix B. Open Issues . . . . . . . . . . . . . . . . . . . . 14 70 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 14 72 1. Introduction 74 ACME [RFC8555] is a mechanism for automating certificate management 75 on the Internet. It enables administrative entities to prove 76 effective control over resources like domain names, and automates the 77 process of generating and issuing certificates. 79 The core ACME protocol defined challenge types specific to web server 80 certificates with the possibility to create extensions, or additional 81 challenge types for other use cases and certificate types. Client 82 certificates, such as end user and Code SIgning may also benefit from 83 automated management to ease the deployment and maintenance of these 84 certificates type, thus the definition of this extension defining 85 challenge types specific to that usage. 87 2. Identity Proofing for Client Certificates 89 As with the TLS certificates defined in the core ACME document, 90 identity proofing for ACME issued end user client, device client, and 91 code signing certificates was not covered in RFC8555. 93 Identity proofing for these certificate types present some challenges 94 for process automation. NIST SP 800-63 r3 [NIST800-63r3] serves as 95 guidance for identity proofing further detailed in NIST SP 800-63A 96 [NIST800-63A] that may occur prior to the ability to automate 97 certificate management via ACME or may obviate the need for it 98 weighing end user privacy as a higher concern and allowing for 99 credential issuance to be decoupled from identity proofing (IAL1). 100 Using this guidance, a CA might select from the identity proofing 101 levels to assert claims on the issued certificates as follows from 102 NIST SP 800-63 r3 [NIST800-63r3]: 104 "IAL1: There is no requirement to link the applicant to a specific 105 real-life identity. Any attributes provided in conjunction with the 106 authentication process are self-asserted or should be treated as such 107 (including attributes a Credential Service Provider, or CSP, asserts 108 to an RP). 110 IAL2: Evidence supports the real-world existence of the claimed 111 identity and verifies that the applicant is appropriately associated 112 with this real-world identity. IAL2 introduces the need for either 113 remote or physically-present identity proofing. Attributes can be 114 asserted by CSPs to RPs in support of pseudonymous identity with 115 verified attributes. 117 IAL3: Physical presence is required for identity proofing. 118 Identifying attributes must be verified by an authorized and trained 119 representative of the CSP. As with IAL2, attributes can be asserted 120 by CSPs to RPs in support of pseudonymous identity with verified 121 attributes." 123 The certificate issuing CA may make this choice by certificate type 124 issued. Once identity proofing has been performed, in cases where 125 this is part of the process, and certificates have been issued, NIST 126 SP 800-63 r3 [NIST800-63r3] has the following recommendations for 127 authentication or in the context of ACME, management of issuance for 128 subsequent client, device, or code-signing certificates: 130 "For services in which return visits are applicable, a successful 131 authentication provides reasonable risk-based assurances that the 132 subscriber accessing the service today is the same as that which 133 accessed the service previously. The robustness of this confidence 134 is described by an AAL categorization. NIST SP 800-63 B 135 [NIST800-63B] addresses how an individual can securely authenticate 136 to a CSP to access a digital service or set of digital services. SP 137 800-63B contains both normative and informative material. 139 The three AALs define the subsets of options agencies can select 140 based on their risk profile and the potential harm caused by an 141 attacker taking control of an authenticator and accessing agencies? 142 systems. The AALs are as follows: 144 AAL1: AAL1 provides some assurance that the claimant controls an 145 authenticator bound to the subscriber's account. AAL1 requires 146 either single-factor or multi-factor authentication using a wide 147 range of available authentication technologies. Successful 148 authentication requires that the claimant prove possession and 149 control of the authenticator through a secure authentication 150 protocol. 152 AAL2: AAL2 provides high confidence that the claimant controls 153 authenticator(s) bound to the subscriber's account. Proof of 154 possession and control of two distinct authentication factors is 155 required through secure authentication protocol(s). Approved 156 cryptographic techniques are required at AAL2 and above. 158 AAL3: AAL3 provides very high confidence that the claimant controls 159 authenticator(s) bound to the subscriber's account. Authentication 160 at AAL3 is based on proof of possession of a key through a 161 cryptographic protocol. AAL3 authentication SHALL use a hardware- 162 based authenticator and an authenticator that provides verifier 163 impersonation resistance; the same device MAY fulfill both these 164 requirements. In order to authenticate at AAL3, claimants SHALL 165 prove possession and control of two distinct authentication factors 166 through secure authentication protocol(s). Approved cryptographic 167 techniques are required." 169 If federations and assertions are used for authorizing certificate 170 issuance, NIST SP 800-63 C [NIST800-63C] may be referenced for 171 guidance on levels of assurance. 173 Existing PKI certification authorities (CAs) tend to use a set of ad 174 hoc protocols for certificate issuance and identity verification. 175 For each certificate usage type, a basic process will be described to 176 obtain an initial certificate and for the certificate renewal 177 process. If higher assurance levels are desired, the guidance from 178 NIST SP 800-63 r3 [NIST800-63r3] may be useful and out-of-band 179 identity proofing options are possible options for pre-authorization 180 challenges or notifications. 182 3. Device Certificates 184 A device certificate is a client certificate issued to a device 185 identified through device credentials such as an IP address, 186 hostname, or MAC address. This process is separate from an end user 187 client certificate that may be stored on a device, but identifies a 188 person using the device described in the next subsection. While 189 there are automated processes in place today for device certificate 190 renewal, most are specific to the CA and not open standards. The 191 general workflow is similar to that described in RFC8555 with the 192 differences being in the CSR, requesting a client certificate. [IP 193 addresses may be necessary for some devices and it may be best to 194 extend [I-D.ietf-acme-ip] to cover varying CSR types that include 195 client certificates for devices explicitly.] 197 A typical process to obtain a device certificate may be similar to 198 the following workflow described in the introduction of RFC8555 with 199 the exception of certificate type and usage. 201 [There is some work happening in possibly 2 different drafts on 202 device certificates, so no further definition is provided here at 203 this time.] 205 [Is an additional type definition helpful to distinguish that this is 206 for a client certificate?] 208 4. End User Client Certificates 210 A client certificate used to authenticate an end user may be used for 211 mutual authentication in TLS, EAP-TLS, or messaging. The client 212 certificate in this case may be stored in a browser, PKCS-#11 213 container, KMIP, or another key container. To obtain an end user 214 client certificate, there are several possibilities to automate 215 authentication of an identity credential presumably tied to an end 216 user. 218 [We need to determine if it is important in ACME to define an 219 automated method that tests the identity or the user or to just have 220 consistent credentials for the authentication challenges. The 221 credentials may be distributed through an out-of-band method that 222 involves identity proofing.] 224 [Several authentication options with identity proofing are 225 intentionally provided for review and discussion by the ACME working 226 group.] 228 A trusted federated service that ties the user to an email address 229 with a reputation of the user attached to the email may be possible. 230 One such example might be the use of a JWT signed OAuth token. 232 Risk based authentication used for identity proofing with red herring 233 questions is a third option that could utilize public information on 234 individuals to authenticate. This would be similar to the signup 235 process used in some financial applications. 237 Existing credentials - for instance, FIDO. FIDO uses a public key 238 pair and does not perform identity proofing. FIDO authentication 239 provides a different key pair to each service using FIDO for 240 authentication, which are generated at the client and registered by 241 the server. This may require using the FIDO credentials from a 242 specific service for authentication to gain ACME issued crededentials 243 (not advised based on how FIDO credentials are supposed to be used). 244 Are there instances where the same provider would issue both sets of 245 credentials? You wouldn't want to expose your FIDO credentials to a 246 different party, that's why each service has their own. Would you 247 set up a mechanism to get FIDO credentials to then obtain a 248 certificate? (What use cases would this be necessary? When do you 249 need a certificate where you already have a specific public/private 250 key pair?) This can be defined as an auth type, but should it be? 252 One-time password (OTP) authentication is a secure option. In cases 253 where a higher assurance level is needed, OTP may be a good choice 254 and many options exist today for OTP that could use an app on a phone 255 for instance tied to an existing (or newly established) password. 256 The OTP may be tied to an out-of-band process and may be associated 257 with a username/password and other accounts. 259 One consideration is to understand if the use case could just use 260 FIDO and not create anything new (ACME client certificates). FIDO 261 provides a mechanism to have unique public key pair based access for 262 client authentication to web sites and they are working on non-web. 263 Identity proofing is intentionally decoupled from authentication in 264 this model as that is in line with NIST 800-63r3 recommendations for 265 privacy protections of the user. The credential in this case is 266 authenticated and would be consistent for it's use, but the identity 267 proofing for that credential is not performed. Obviously, identity 268 proofing is more important for some services, like financial 269 applications where tying the user to the identity for access to 270 financial information is important. However, is automated identity 271 proofing important for any user certificate or should it remain 272 decoupled where it could be automated by a service offering or is 273 there a need for a standardized mechanism to support it for user 274 certificates? 276 Three methods for ACME client authentication, not identity proofing, 277 are proposed in the Challenge Type Section. 279 5. CodeSigning Certificates 281 The process to retrieve a code signing certificate is similar to that 282 of a web server certificate, with differences primarily in the CSR 283 request and the resulting certificate properties. [The storage and 284 access of a code signing certificate must be protected and is 285 typically done through hardware, a hardware security module (HSM), 286 which likely has a PKCS#11 interface. A code signing certificate may 287 either be a standard one or an extended validation (EV) certificate.] 288 For automation purposes, the process described in this document will 289 follow the standard process and any out-of-band preprocessing can 290 increase the level of the issued certificate if the CA offers such 291 options and has additional identity proofing mechanisms (in band or 292 out-of-band). 294 Strict vetting processes are necessary for many code signing 295 certificates to provide a high assurance on the signer. In some 296 cases, issuance of a standard CodeSigning certificate will be 297 appropriate and no additional "challenges" [RFC8555 Section 8] will 298 be necessary. In this case, the standard option could be automated 299 very similar to Web server certificates with the only changes being 300 in the CSR properties. However, this may not apply to all scenarios, 301 such as those requiring EV certificates with the possibility for 302 required out-of-band initial authentication and identity proofing. 304 Organization validation is required for standard code signing 305 certificates from most issuers. The CSR is used to identify the 306 organization from the included domain name in the request. The 307 resulting certificate, however, instead contains the organization's 308 name and for EV certificates, other identifying information for the 309 organization. For EV certificates, this typically requires that the 310 domain is registered with the Certificate Authority provider, listed 311 in CAA [RFC6844], and administrators for the account are named with 312 provided portal access for certificate issuance and management 313 options. 315 While ACME allows for the client to directly establish an account 316 with a CA, an initial out-of-band process for this step may assist 317 with the additional requirements for EV certificates and assurance 318 levels typically required for code signing certificates. For 319 standard certificates, with a recommendation for additional vetting 320 through extended challenge options to enable ACME to establish the 321 account directly. In cases where code signing certificates are used 322 heavily for an organization, having the portal access accessible 323 replaced with ACME authenticated client access with extra challenges 324 for authentication may be an option to automate the functionality. 326 [For standard certificates, is it worth defining SMS and email for 327 the challenge? Obviously, EV needs more, so a few choices are 328 suggested in this revision.] 330 To improve the vetting process, ACME's optional use of CAA [RFC6844] 331 with the Directory "meta" data "caaIdentities" ([RFC8555] 332 Section 9.7.6) assists with the validation that a CA may have issue 333 certificates for any particular domain and is RECOMMENDED for use 334 with code signing certificates for this additional level of 335 validation checking on issued certificates. 337 CAA helps as anyone verifying a certificate used for code signing can 338 verify that the CA used has been authorized to issue certificates for 339 that organization. CSR requests for code signing certificates 340 typically contain a Common Name (CN) using a domain name that is 341 replaced with the organization name to have the expected details 342 displayed in the resulting certificate. Since this work flow already 343 occurs, there is a path to automation and validation via an existing 344 ACME type, "dns". 346 As noted in RFC8555, "the external account binding feature (see 347 Section 7.3.4) can allow an ACME account to use authorizations that 348 have been granted to an external, non-ACME account. This allows ACME 349 to address issuance scenarios that cannot yet be fully automated, 350 such as the issuance of "Extended Validation" certificates." 352 The ACME challenge object, [RFC8555] Section 7.1.5 is RECOMMENDED for 353 use for Pre-authorization ([RFC8555] Section 7.4.1). Additional 354 challenge types are added to provide higher levels of security for 355 this issuance verification step. The use of OTP, FIDO credentials 356 (public/private key pairs), or validation from a certificate issued 357 at account setup time are defined in Section 8. Pre-Authoriziation. 359 Questions for reviewers: 361 [Is there interest to set a specific or default challenge object for 362 CodeSigning Certificates? Or should this be left to individual CAs 363 to decide and differentiate? The current challenge types defined in 364 RFC8555 include HTTPS (provisioning HTTP resources) and DNS 365 (provisioning a TXT resource record). Use of DNS may be possible, 366 but the HTTP resource doesn't necessarily make sense. Since the 367 process to retrieve an EV CodeSigning certificate usually requires 368 proof of the organization and validation from one of 2 named 369 administrators, some other challenge type like public/private key 370 pairs or OTP may be needed as defined challenge types. An 371 organization may want to tie this contact to a role rather than a 372 person and that consideration should be made in the design as well as 373 implementation by organizations.] 375 ACME provides an option for notification of the operator via email or 376 SMS upon issuance/renewal of a certificate after the domain has been 377 validated as owned by the requestor. This option is RECOMMENDED due 378 to the security considerations of code signing certificates as a way 379 to limit or reduce the possibility of a third party gaining access to 380 a code signing certificate inappropriately. Development of 381 additional challenge types is included in this document to support 382 this for pre-authorization, which would better match the security 383 considerations for this certificate type. Additional types may be 384 added if agreed upon by the working group. 386 Since DNS is used to identify the organization in the request, the 387 identifier "type" ([RFC8555]Section 7.4) is set to dns, not requiring 388 any additions to the ACME protocol for this type of certificate. The 389 distinction lies in the CSR, where the values are set to request a 390 CodeSigning certificate for a client certificate. [Question: Is it 391 helpful to define an identifier for the administrator or for the 392 developer to distinguish the certificate type in ACME and not just 393 the CSR?] 395 KeyUsage (DigitalSignature) and ExtendedKeyUsage (CodeSigning) in the 396 CSR MUST be set to the correct values for the CA to see the request 397 is for a Code Signing certificate. The Enhanced Key Usage SHOULD be 398 set to show this is a client certificate., using OID 399 "1.3.6.1.5.5.7.3.2". The CN MUST be set to the expected registered 400 domain with the CA account. 402 An advantage of ACME is the ability to automate rollover to allow for 403 easy management of short expiry times on certificates. The lifetime 404 of CodeSigning certificates is typically a year or two, but 405 automation could allow for shorter expiry times becoming feasible. 407 Automation of storage to an HSM, which typically requires 408 authentication is intentionally left out-of-scope. 410 6. Pre-authorization 412 Additional challenge types are defined here for the verification of 413 administrors at an organization requesting CodeSigning certificates. 414 SMS and email are both defined and may be used singularly or in 415 combination as the ACME protocol allows for multiple pre- 416 authorization challenges to be issued. Additional pre-authorization 417 types are defined that provide a higher level of assurance to 418 authorize a request. 420 7. Challenge Types 422 The challenge types are defined in the following subsections are for 423 use to authenticate individuals or holders of specific pre-issued 424 credentials (users acting in roles for an organization). The 425 challenge types can be used to obtain end user certificate types or 426 as a pre-authorization challenges with certificate types such as the 427 Code Signing Certificate. Please note that the pre-authorization 428 challenge is also coupled with the account certificate in ACME for 429 verification. The process for obtaining EV Code Signing Certificates 430 typically requires authorization from one or more individuals in a 431 role for the organization. The use of pre-issued secure credentials, 432 at an assurance level appropriate for the certificate type being 433 issued, provides a way to automate the issuance and renewal process. 435 7.1. One Time Password (OTP) 437 There are numerous one time password technologies with slight 438 variations between implementations. The response to the challenge is 439 entered in the provided URL, offering flexibility to those using this 440 challenge type to accomodate the specific requirements of their 441 solution. Looking at 2 OTP solutions, the challenge response is 442 provided via a tool or app without any user interaction of 443 information required from the server to generate the challenge. The 444 2 solutions that operate in this manner include SecureID and Duo 445 Security. If a challenge is required to generate the reponse to be 446 provided in the URL, the token can supply the challenge. 448 type (required, string): The string "otp-01". 450 token (required, string): A random value that uniquely identifies 451 the challenge. OTP types and input vary between technologies. 452 The token value will match the type expected for the pre-issued 453 OTP credential. The user will be able to supply a response in the 454 provided URL from this challenge. It MUST NOT contain any 455 characters outside the base64url alphabet and MUST NOT include 456 base64 padding characters ("="). 458 { 459 "type": "otp-01", 460 "url": "https://example.com/acme/chall/WrV_H87EyD3", 461 "status": "pending", 462 "token": "challenge" 463 } 465 7.2. Certificate 467 Certificates may be pre-issued and stored according to assurance 468 level requirements for the purpose of identiying a user's identity. 469 If a higher assurance level is needed for a user serving in a 470 specific role or for that individual, it is posisble for identity 471 proofing to occur in person using identifiers acceptable for the 472 specified process and then stored appropriately for the required 473 assurance level. PKCS#11 software or hardware tokens are both 474 possible options. This model assumes that there may be multiple 475 authorized users with different certificates that can be used for the 476 authorization or pre-authentication challenge. As such, the user 477 first provides the digital signature, so the account management can 478 determine if one of the acceptable certificates was used to digitally 479 sign the token. 481 type (required, string): The string "cert-01". 483 token (required, string): A random value that uniquely identifies 484 the challenge. The token for a certificate authentication 485 challenge includes a value for the recipeint to digitally sign 486 using their private key and post to the provided URL. The ACME 487 server then uses the digitally signed content to verify that the 488 challenge was signed using authorized credentials (certificate 489 issued and authorized for this challenge type). It MUST NOT 490 contain any characters outside the base64url alphabet and MUST NOT 491 include base64 padding characters ("="). 493 { 494 "type": "cert-01", 495 "url": "https://example.com/acme/chall/WrV_H87EyD3", 496 "status": "pending", 497 "token": "Some challenge to digitally sign" 498 } 500 7.3. FIDO or Public/Private Key Pairs 502 FIDO uses public/private key pairs that are issued specific to a 503 service. If FIDO or public/private key pairs (PPKP) are selected as 504 the challenge type, the account and credential issuance will have to 505 occur prior to use of this challenge type. The FIDO or public/ 506 private key pair credentials would be specific to the certificate 507 management account and would be created by the client, then 508 registered with the service as occurs with normal FIDO regisration of 509 credentials. As with normal FIDO and puiblic/private key pairs, the 510 token or challenge is digitally signed to prove possession of the 511 private key. 513 type (required, string): The string "ppkp-01". 515 token (required, string): A random value that uniquely identifies 516 the challenge. This challenge will operate much in the same way 517 as the certificate challenge as the operations are largely the 518 same. The user will be able to supply a response in the provided 519 URL from this challenge. It MUST NOT contain any characters 520 outside the base64url alphabet and MUST NOT include base64 padding 521 characters ("="). 523 { 524 "type": "ppkp-01", 525 "url": "https://example.com/acme/chall/WrV_H87EyD3", 526 "status": "pending", 527 "token": "Some challenge to sign" 528 } 530 8. Security Considerations 532 This will likely be full of considerations and is TBD for this 533 revision until challenge types are settled. 535 9. IANA Considerations 537 This memo includes no request to IANA, yet. 539 10. Contributors 541 11. References 543 11.1. Normative References 545 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 546 Requirement Levels", BCP 14, RFC 2119, 547 DOI 10.17487/RFC2119, March 1997, 548 . 550 [RFC7030] Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed., 551 "Enrollment over Secure Transport", RFC 7030, 552 DOI 10.17487/RFC7030, October 2013, 553 . 555 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 556 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 557 May 2017, . 559 [RFC8555] Barnes, R., Hoffman-Andrews, J., McCarney, D., and J. 560 Kasten, "Automatic Certificate Management Environment 561 (ACME)", RFC 8555, DOI 10.17487/RFC8555, March 2019, 562 . 564 11.2. Informative References 566 [I-D.ietf-acme-ip] 567 Shoemaker, R., "ACME IP Identifier Validation Extension", 568 draft-ietf-acme-ip-06 (work in progress), May 2019. 570 11.3. URL References 572 [NIST800-63A] 573 US National Institute of Standards and Technology, 574 "https://nvlpubs.nist.gov/nistpubs/SpecialPublications/ 575 NIST.SP.800-63a.pdf". 577 [NIST800-63B] 578 US National Institute of Standards and Technology, 579 "https://nvlpubs.nist.gov/nistpubs/SpecialPublications/ 580 NIST.SP.800-63b.pdf". 582 [NIST800-63C] 583 US National Institute of Standards and Technology, 584 "https://nvlpubs.nist.gov/nistpubs/SpecialPublications/ 585 NIST.SP.800-63c.pdf". 587 [NIST800-63r3] 588 US National Institute of Standards and Technology, 589 "https://nvlpubs.nist.gov/nistpubs/SpecialPublications/ 590 NIST.SP.800-63-3.pdf". 592 Appendix A. Change Log 594 Note to RFC Editor: if this document does not obsolete an existing 595 RFC, please remove this appendix before publication as an RFC. 597 Appendix B. Open Issues 599 Note to RFC Editor: please remove this appendix before publication as 600 an RFC. 602 Author's Address 604 Kathleen M. Moriarty 605 Dell EMC 606 176 South Street 607 Hopkinton 608 US 610 EMail: Kathleen.Moriarty@dell.com