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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group A. Cooper 3 Internet-Draft Cisco 4 Intended status: Informational F. Gont 5 Expires: August 18, 2014 Huawei Technologies 6 D. Thaler 7 Microsoft 8 February 14, 2014 10 Privacy Considerations for IPv6 Address Generation Mechanisms 11 draft-ietf-6man-ipv6-address-generation-privacy-01.txt 13 Abstract 15 This document discusses privacy and security considerations for 16 several IPv6 address generation mechanisms, both standardized and 17 non-standardized. It evaluates how different mechanisms mitigate 18 different threats and the trade-offs that implementors, developers, 19 and users face in choosing different addresses or address generation 20 mechanisms. 22 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on August 18, 2014. 39 Copyright Notice 41 Copyright (c) 2014 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 58 3. Weaknesses in IEEE-identifier-based IIDs . . . . . . . . . . 4 59 3.1. Correlation of activities over time . . . . . . . . . . . 5 60 3.2. Location tracking . . . . . . . . . . . . . . . . . . . . 6 61 3.3. Address scanning . . . . . . . . . . . . . . . . . . . . 6 62 3.4. Device-specific vulnerability exploitation . . . . . . . 6 63 4. Privacy and security properties of address generation 64 mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . 7 65 4.1. IEEE-identifier-based IIDs . . . . . . . . . . . . . . . 9 66 4.2. Static, manually configured IIDs . . . . . . . . . . . . 10 67 4.3. Constant, semantically opaque IIDs . . . . . . . . . . . 10 68 4.4. Cryptographically generated IIDs . . . . . . . . . . . . 10 69 4.5. Stable, semantically opaque IIDs . . . . . . . . . . . . 10 70 4.6. Temporary IIDs . . . . . . . . . . . . . . . . . . . . . 11 71 4.7. DHCPv6 generation of IIDs . . . . . . . . . . . . . . . . 12 72 4.8. Transition/co-existence technologies . . . . . . . . . . 12 73 5. Miscellaneous Issues with IPv6 addressing . . . . . . . . . . 12 74 5.1. Geographic Location . . . . . . . . . . . . . . . . . . . 12 75 5.2. Network Operation . . . . . . . . . . . . . . . . . . . . 12 76 5.3. Compliance . . . . . . . . . . . . . . . . . . . . . . . 13 77 5.4. Intellectual Property Rights (IPRs) . . . . . . . . . . . 13 78 6. Security Considerations . . . . . . . . . . . . . . . . . . . 13 79 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 80 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13 81 9. Informative References . . . . . . . . . . . . . . . . . . . 13 82 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 84 1. Introduction 86 IPv6 was designed to improve upon IPv4 in many respects, and 87 mechanisms for address assignment were one such area for improvement. 88 In addition to static address assignment and DHCP, stateless 89 autoconfiguration was developed as a less intensive, fate-shared 90 means of performing address assignment. With stateless 91 autoconfiguration, routers advertise on-link prefixes and hosts 92 generate their own interface identifiers (IIDs) to complete their 93 addresses. Over the years, many interface identifier generation 94 techniques have been defined, both standardized and non-standardized: 96 o Manual configuration 97 * IPv4 address 99 * Service port 101 * Wordy 103 * Low-byte 105 o Stateless Address Auto-Cofiguration (SLAAC) 107 * IEEE 802 48-bit MAC or IEEE EUI-64 identifier 108 [RFC1972][RFC2464] 110 * Cryptographically generated [RFC3972] 112 * Temporary (also known as "privacy addresses") [RFC4941] 114 * Constant, semantically opaque (also known as random) 115 [Microsoft] 117 * Stable, semantically opaque 118 [I-D.ietf-6man-stable-privacy-addresses] 120 o DHCPv6-based [RFC3315] 122 o Specified by transition/co-existence technologies 124 * IPv4 address and port [RFC4380] 126 Deriving the IID from a globally unique IEEE identifier [RFC2462] was 127 one of the earliest mechanisms developed. A number of privacy and 128 security issues related to the interface IDs derived from IEEE 129 identifiers were discovered after their standardization, and many of 130 the mechanisms developed later aimed to mitigate some or all of these 131 weaknesses. This document identifies four types of threats against 132 IEEE-identifier-based IIDs, and discusses how other existing 133 techniques for generating IIDs do or do not mitigate those threats. 134 The discussion in this document is limited to global addresses and 135 does not address link-local addresses. [Do we need to say something 136 about unique-local being in or out of scope?] 138 2. Terminology 140 This section clarifies the terminology used throughout this document. 142 Public address: 143 An address that has been published in a directory or other public 144 location, such as the DNS, a SIP proxy, an application-specific 145 DHT, or a publicly available URI. A host's public addresses are 146 intended to be discoverable by third parties. 148 Stable address: 149 An address that does not vary over time within the same network. 150 Note that [RFC4941] refers to these as "public" addresses, but 151 "stable" is used here for reasons explained in Section 4. 153 Temporary address: 154 An address that varies over time within the same network. 156 Constant IID: 157 An IPv6 Interface Identifier that is globally stable. That is, 158 the Interface ID will remain constant even if the node moves from 159 one network to another. 161 Stable IID: 162 An IPv6 Interface Identifier that is stable within some specified 163 context. For example, an Interface ID can be globally stable 164 (constant), or could be stable per network (meaning that the 165 Interface ID will remain unchanged as long as a the node stays on 166 the same network, but may change when the node moves from one 167 network to another). 169 Temporary IID: 170 An IPv6 Interface Identifier that varies over time. 172 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 173 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 174 "OPTIONAL" in this document are to be interpreted as described in 175 [RFC2119]. These words take their normative meanings only when they 176 are presented in ALL UPPERCASE. 178 3. Weaknesses in IEEE-identifier-based IIDs 180 There are a number of privacy and security implications that exist 181 for hosts that use IEEE-identifier-based IIDs. This section 182 discusses four generic attack types: correlation of activities over 183 time, location tracking, address scanning, and device-specific 184 vulnerability exploitation. The first three of these rely on the 185 attacker first gaining knowledge of the target host's IID. This can 186 be achieved by a number of different attackers: the operator of a 187 server to which the host connects, such as a web server or a peer-to- 188 peer server; an entity that connects to the same network as the 189 target (such as a conference network or any public network); or an 190 entity that is on-path to the destinations with which the host 191 communicates, such as a network operator. 193 3.1. Correlation of activities over time 195 As with other identifiers, an IPv6 address can be used to correlate 196 the activities of a host for at least as long as the lifetime of the 197 address. The correlation made possible by IEEE-identifier-based IIDs 198 is of particular concern because MAC addresses are much more 199 permanent than, say, DHCP leases. MAC addresses tend to last roughly 200 the lifetime of a device's network interface, allowing correlation on 201 the order of years, compared to days for DHCP. 203 As [RFC4941] explains, 205 "[t]he use of a non-changing interface identifier to form 206 addresses is a specific instance of the more general case where a 207 constant identifier is reused over an extended period of time and 208 in multiple independent activities. Anytime the same identifier 209 is used in multiple contexts, it becomes possible for that 210 identifier to be used to correlate seemingly unrelated activity. 211 ... The use of a constant identifier within an address is of 212 special concern because addresses are a fundamental requirement of 213 communication and cannot easily be hidden from eavesdroppers and 214 other parties. Even when higher layers encrypt their payloads, 215 addresses in packet headers appear in the clear." 217 IP addresses are just one example of information that can be used to 218 correlate activities over time. DNS names, cookies [RFC6265], 219 browser fingerprints [Panopticlick], and application-layer usernames 220 can all be used to link a host's activities together. Although IEEE- 221 identifier-based IIDs are likely to last at least as long or longer 222 than these other identifiers, IIDs generated in other ways may have 223 shorter or longer lifetimes than these identifiers depending on how 224 they are generated. Therefore, the extent to which a host's 225 activities can be correlated depends on whether the host uses 226 multiple identifiers together and the lifetimes of all of those 227 identifiers. Frequently refreshing an IPv6 address may not mitigate 228 correlation if an attacker has access to other longer lived 229 identifiers for a particular host. This is an important caveat to 230 keep in mind throughout the discussion of correlation in this 231 document. For further discussion of correlation, see Section 5.2.1 232 of [RFC6973]. 234 As noted in [RFC4941], in some cases correlation is just as feasible 235 for a host using an IPv4 address as for a host using an IEEE 236 identifier to generate its IID in its IPv6 address. Hosts that use 237 static IPv4 addressing or who are consistently allocated the same 238 address via DHCPv4 can be tracked as described above. However, the 239 widespread use of both NAT and DHCPv4 implementations that assign the 240 same host a different address upon lease expiration mitigates this 241 threat in the IPv4 case as compared to the IEEE identifier case in 242 IPv6. 244 3.2. Location tracking 246 Because the IPv6 address structure is divided between a topological 247 portion and an interface identifier portion, an interface identifier 248 that remains constant when a host connects to different networks (as 249 an IEEE-identifier-based IID does) provides a way for observers to 250 track the movements of that host. In a passive attack on a mobile 251 host, a server that receives connections from the same host over time 252 would be able to determine the host's movements as its prefix 253 changes. 255 Active attacks are also possible. An attacker that first learns the 256 host's interface identifier by being connected to the same network 257 segment, running a server that the host connects to, or being on-path 258 to the host's communications could subsequently probe other networks 259 for the presence of the same interface identifier by sending a probe 260 packet (ICMPv6 Echo Request, or any other probe packet). Even if the 261 host does not respond, the first hop router will usually respond with 262 an ICMP Address Unreachable when the host is not present, and be 263 silent when the host is present. 265 Location tracking based on IP address is generally not possible in 266 IPv4 since hosts get assigned wholly new addresses when they change 267 networks. 269 3.3. Address scanning 271 The structure of IEEE-based identifiers used for address generation 272 can be leveraged by an attacker to reduce the target search space 273 [I-D.ietf-opsec-ipv6-host-scanning]. The 24-bit Organizationally 274 Unique Identifier (OUI) of MAC addresses, together with the fixed 275 value (0xff, 0xfe) used to form a Modified EUI-64 Interface 276 Identifier, greatly help to reduce the search space, making it easier 277 for an attacker to scan for individual addresses using widely-known 278 popular OUIs. This erases much of the protection against address 279 scanning that the larger IPv6 address space was supposed to provide 280 as compared to IPv4. 282 3.4. Device-specific vulnerability exploitation 284 IPv6 addresses that embed IEEE identifiers leak information about the 285 device (Network Interface Card vendor, or even Operating System and/ 286 or software type), which could be leveraged by an attacker with 287 knowledge of device/software-specific vulnerabilities to quickly find 288 possible targets. Attackers can exploit vulnerabilities in hosts 289 whose IIDs they have previously obtained, or scan an address space to 290 find potential targets. 292 4. Privacy and security properties of address generation mechanisms 294 Analysis of the extent to which a particular host is protected 295 against the threats described in Section 3 depends on how each of a 296 host's addresses is generated and used. In some scenarios, a host 297 configures a single global address and uses it for all 298 communications. In other scenarios, a host configures multiple 299 addresses using different mechanisms and may use any or all of them. 301 [RFC3041] (later obsoleted by [RFC4941]) sought to address some of 302 the problems described in Section 3 by defining "temporary addresses" 303 for outbound connections. Temporary addresses are meant to 304 supplement the other addresses that a device might use, not to 305 replace them. They use IIDs that are randomly generated and change 306 daily by default. The idea was for temporary addresses to be used 307 for outgoing connections (e.g., web browsing) while maintaining the 308 ability to use a stable address when more address stability is 309 desired (e.g., in DNS advertisements). 311 [RFC3484] originally specified that stable addresses be used for 312 outbound connections unless an application explicitly prefers 313 temporary addresses. The default preference for stable addresses was 314 established to avoid applications potentially failing due to the 315 short lifetime of temporary addresses or the possibility of a reverse 316 look-up failure or error. However, [RFC3484] allowed that 317 "implementations for which privacy considerations outweigh these 318 application compatibility concerns MAY reverse the sense of this 319 rule" and instead prefer by default temporary addresses rather than 320 stable addresses. Indeed most implementations (notably including 321 Windows) chose to default to temporary addresses for outbound 322 connections since privacy was considered more important (and few 323 applications supported IPv6 at the time, so application compatibility 324 concerns were minimal). [RFC6724] then obsoleted [RFC3484] and 325 changed the default to match what implementations actually did. 327 The envisioned relationship in [RFC3484] between stability of an 328 address and its use in "public" can be misleading when conducting 329 privacy analysis. The stability of an address and the extent to 330 which it is linkable to some other public identifier are independent 331 of one another. For example, there is nothing that prevents a host 332 from publishing a temporary address in a public place, such as the 333 DNS. Publishing both a stable address and a temporary address in the 334 DNS or elsewhere where they can be linked together by a public 335 identifier allows the host's activities when using either address to 336 be correlated together. 338 Moreover, because temporary addresses were designed to supplement 339 other addresses generated by a host, the host may still configure a 340 more stable address even if it only ever intentionally uses temporary 341 addresses (as source addresses) for communication to off-link 342 destinations. An attacker can probe for the stable address even if 343 it is never used as such a source address or advertised (e.g., in DNS 344 or SIP) outside the link. 346 This section compares the privacy and security properties of a 347 variety of IID generation mechanisms and their possible usage 348 scenarios, including scenarios in which a single mechanism is used to 349 generate all of a host's IIDs and those in which temporary addresses 350 are used together with addresses generated using a different IID 351 generation mechanism. The analysis of the exposure of each IID type 352 to correlation assumes that IPv6 prefixes are shared by a reasonably 353 large number of nodes. As [RFC4941] notes, if a very small number of 354 nodes (say, only one) use a particular prefix for an extended period 355 of time, the prefix itself can be used to correlate the host's 356 activities regardless of how the IID is generated. For example, 357 [RFC3314] recommends that prefixes be uniquely assigned to mobile 358 handsets where IPv6 is used within GPRS. In cases where this advice 359 is followed and prefixes persist for extended periods of time (or get 360 reassigned to the same handsets whenever those handsets reconnect to 361 the same network router), hosts' activities could be correlatable for 362 longer periods than the analysis below would suggest. 364 The table below provides a summary of the whole analysis. 366 +--------------+-------------+----------+-------------+-------------+ 367 | Mechanism(s) | Correlation | Location | Address | Device | 368 | | | tracking | scanning | exploits | 369 +--------------+-------------+----------+-------------+-------------+ 370 | IEEE | For device | For | Possible | Possible | 371 | identifier | lifetime | device | | | 372 | | | lifetime | | | 373 | | | | | | 374 | Static | For address | For | Depends on | Depends on | 375 | manual | lifetime | address | generation | generation | 376 | | | lifetime | mechanism | mechanism | 377 | | | | | | 378 | Constant, | For address | For | No | No | 379 | semantically | lifetime | address | | | 380 | opaque | | lifetime | | | 381 | | | | | | 382 | CGA | For | No | No | No | 383 | | lifetime of | | | | 384 | | (public key | | | | 385 | | + modifier | | | | 386 | | block) | | | | 387 | | | | | | 388 | Stable, | Within | No | No | No | 389 | semantically | single | | | | 390 | opaque | network | | | | 391 | | | | | | 392 | Temporary | For temp | No | No | No | 393 | | address | | | | 394 | | lifetime | | | | 395 | | | | | | 396 | DHCPv6 | For lease | No | Depends on | No | 397 | | lifetime | | generation | | 398 | | | | mechanism | | 399 +--------------+-------------+----------+-------------+-------------+ 401 Table 1: Privacy and security properties of IID generation mechanisms 403 4.1. IEEE-identifier-based IIDs 405 As discussed in Section 3, addresses that use IIDs based on IEEE 406 identifiers are vulnerable to all four threats. They allow 407 correlation and location tracking for the lifetime of the device 408 since IEEE identifiers last that long and their structure makes 409 address scanning and device exploits possible. 411 4.2. Static, manually configured IIDs 413 Because static, manually configured IIDs are stable, both correlation 414 and location tracking are possible for the life of the address. 416 The extent to which location tracking can be successfully performed 417 depends, to a some extent, on the uniqueness of the employed 418 Interface ID. For example, one would expect "low byte" Interface IDs 419 to be more widely reused than, for example, Interface IDs where the 420 whole 64-bits follow some pattern that is unique to a specific 421 organization. Widely reused Interface IDs will typically lead to 422 false positives when performing location tracking. 424 Whether manually configured addresses are vulnerable to address 425 scanning and device exploits depends on the specifics of how the IIDs 426 are generated. 428 4.3. Constant, semantically opaque IIDs 430 Although a mechanism to generate a constant, semantically opaque IID 431 has not been standardized, it has been in wide use for many years on 432 at least one platform (Windows). Windows uses the [RFC4941] random 433 generation mechanism in lieu of generating an IEEE-identifier-based 434 IID. This mitigates the device-specific exploitation and address 435 scanning attacks, but still allows correlation and location tracking 436 because the IID is constant across networks and time. 438 4.4. Cryptographically generated IIDs 440 Cryptographically generated addresses (CGAs) [RFC3972] bind a hash of 441 the host's public key to an IPv6 address in the SEcure Neighbor 442 Discovery (SEND) [RFC3971] protocol. CGAs may be regenerated for 443 each subnet prefix, but this is not required given that they are 444 computationally expensive to generate. A host using a CGA can be 445 correlated for as long as the lifetime of the combination of the 446 public key and the chosen modifier block, since it is possible to 447 rotate modifier blocks without generating new public keys. Because 448 the cryptographic hash of the host's public key uses the subnet 449 prefix as an input, even if the host does not generate a new public 450 key or modifier block when it moves to a different network, its 451 location cannot be tracked via the IID. CGAs do not allow device- 452 specific exploitation or address scanning attacks. 454 4.5. Stable, semantically opaque IIDs 456 [I-D.ietf-6man-stable-privacy-addresses] specifies a mechanism that 457 generates a unique random IID for each network. A host that stays 458 connected to the same network could therefore be tracked at length, 459 whereas a mobile host's activities could only be correlated for the 460 duration of each network connection. Location tracking is not 461 possible with these addresses. They also do not allow device- 462 specific exploitation or address scanning attacks. 464 4.6. Temporary IIDs 466 A host that uses only a temporary address mitigates all four threats. 467 Its activities may only be correlated for the lifetime a single 468 temporary address. 470 A host that configures both an IEEE-identifier-based IID and 471 temporary addresses makes the host vulnerable to the same attacks as 472 if temporary addresses were not in use, although the viability of 473 some of them depends on how the host uses each address. An attacker 474 can correlate all of the host's activities for which it uses its 475 IEEE-identifier-based IID. Once an attacker has obtained the IEEE- 476 identifier-based IID, location tracking becomes possible on other 477 networks even if the host only makes use of temporary addresses on 478 those other networks; the attacker can actively probe the other 479 networks for the presence of the IEEE-identifier-based IID. Device- 480 specific vulnerabilities can still be exploited. Address scanning is 481 also still possible because the IEEE-identifier-based address can be 482 probed. 484 If the host instead generates a constant, semantically opaque IID to 485 use in a stable address for server-like connections together with 486 temporary addresses for outbound connections (as is the default in 487 Windows), it sees some improvements over the previous scenario. The 488 address scanning and device-specific exploitation attacks are no 489 longer possible because the OUI is no longer embedded in any of the 490 host's addresses. However, correlation of some activities across 491 time and location tracking are both still possible because the 492 semantically opaque IID is constant. And once an attacker has 493 obtained the host's semantically opaque IID, location tracking is 494 possible on any network by probing for that IID, even if the host 495 only uses temporary addresses on those networks. However, if the 496 host generates but never uses a constant, semantically opaque IID, it 497 mitigates all four threats. 499 When used together with temporary addresses, the stable, semantically 500 opaque IID generation mechanism 501 [I-D.ietf-6man-stable-privacy-addresses] improves upon the previous 502 scenario by limiting the potential for correlation to the lifetime of 503 the stable address (which may still be lengthy for hosts that are not 504 mobile) and by eliminating the possibility for location tracking 505 (since a different IID is generated for each subnet prefix). As in 506 the previous scenario, a host that configures but does not use a 507 stable, semantically opaque address mitigates all four threats. 509 4.7. DHCPv6 generation of IIDs 511 The security/privacy implications of DHCPv6-based addresses will 512 typically depend on the specific DHCPv6 server software being 513 employed. We note that recent releases of most popular DHCPv6 server 514 software typically lease random addresses with a similar lease time 515 as that of IPv4. Thus, these addresses can be considered to be 516 "stable, semantically opaque." 518 On the other hand, some DHCPv6 software leases sequential addresses 519 (typically low-byte addresses). These addresses can be considered to 520 be stable addresses. The drawback of this address generation scheme 521 compared to "stable, semantically opaque" addresses is that, since 522 they follow specific patterns, they enable IPv6 address scans. 524 4.8. Transition/co-existence technologies 526 Addresses specified based on transition/co-existence technologies 527 that embed an IPv4 address within an IPv6 address are not included in 528 Table 1 because their privacy and security properties are inherited 529 from the embedded address. For example, Teredo [RFC4380] specifies a 530 means to generate an IPv6 address from the underlying IPv4 address 531 and port, leaving many other bits set to zero. This makes it 532 relatively easy for an attacker to scan for IPv6 addresses by 533 guessing the Teredo client's IPv4 address and port (which for many 534 NATs is not randomized). For this reason, popular implementations 535 (e.g., Windows), began deviating from the standard by including 12 536 random bits in place of zero bits. This modification was later 537 standardized in [RFC5991]. 539 5. Miscellaneous Issues with IPv6 addressing 541 5.1. Geographic Location 543 Since IPv6 subnets have unique prefixes, they reveal some information 544 about the location of the subnet, just as IPv4 addresses do. Hiding 545 this information is one motivation for using NAT in IPv6 (see RFC 546 5902 section 2.4). 548 5.2. Network Operation 550 It is generally agreed that IPv6 addresses that vary over time in a 551 specific network tend to increase the complexity of event logging, 552 trouble-shooting, enforcement of access controls and quality of 553 service, etc. As a result, some organizations disable the use of 554 temporary addresses [RFC4941] even at the expense of reduced privacy 555 [Broersma]. 557 5.3. Compliance 559 Major IPv6 compliance testing suites required (and still require) 560 implementations to support MAC-derived suffixes in order to be 561 approved as compliant. Implementations that fail to support MAC- 562 derived suffixes are therefore largely not eligible to receive the 563 benefits of compliance certification (e.g., use of the IPv6 logo, 564 eligibility for government contracts, etc.). This document 565 recommends that these be relaxed to allow other forms of address 566 generation that are more amenable to privacy. 568 5.4. Intellectual Property Rights (IPRs) 570 Some IPv6 addressing techniques might be covered by Intellectual 571 Property rights, which might limit their implementation in different 572 Operating Systems. [CGA-IPR] and [KAME-CGA] discuss the IPRs on 573 CGAs. 575 6. Security Considerations 577 This whole document concerns the privacy and security properties of 578 different IPv6 address generation mechanisms. 580 7. IANA Considerations 582 This document does not require actions by IANA. 584 8. Acknowledgements 586 The authors would like to thank Bernard Aboba, Rich Draves, and James 587 Woodyatt. 589 9. Informative References 591 [Broersma] 592 Broersma, R., "IPv6 Everywhere: Living with a Fully 593 IPv6-enabled environment", Australian IPv6 Summit 2010, 594 Melbourne, VIC Australia, October 2010, October 2010, 595 . 598 [CGA-IPR] IETF, "Intellectual Property Rights on RFC 3972", 2005. 600 [I-D.ietf-6man-stable-privacy-addresses] 601 Gont, F., "A Method for Generating Semantically Opaque 602 Interface Identifiers with IPv6 Stateless Address 603 Autoconfiguration (SLAAC)", draft-ietf-6man-stable- 604 privacy-addresses-17 (work in progress), January 2014. 606 [I-D.ietf-opsec-ipv6-host-scanning] 607 Gont, F. and T. Chown, "Network Reconnaissance in IPv6 608 Networks", draft-ietf-opsec-ipv6-host-scanning-03 (work in 609 progress), January 2014. 611 [KAME-CGA] 612 KAME, "The KAME IPR policy and concerns of some 613 technologies which have IPR claims", 2005. 615 [Microsoft] 616 Microsoft, "IPv6 interface identifiers", 2013. 618 [Panopticlick] 619 Electronic Frontier Foundation, "Panopticlick", 2011. 621 [RFC1972] Crawford, M., "A Method for the Transmission of IPv6 622 Packets over Ethernet Networks", RFC 1972, August 1996. 624 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 625 Requirement Levels", BCP 14, RFC 2119, March 1997. 627 [RFC2462] Thomson, S. and T. Narten, "IPv6 Stateless Address 628 Autoconfiguration", RFC 2462, December 1998. 630 [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet 631 Networks", RFC 2464, December 1998. 633 [RFC3041] Narten, T. and R. Draves, "Privacy Extensions for 634 Stateless Address Autoconfiguration in IPv6", RFC 3041, 635 January 2001. 637 [RFC3314] Wasserman, M., "Recommendations for IPv6 in Third 638 Generation Partnership Project (3GPP) Standards", RFC 639 3314, September 2002. 641 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., 642 and M. Carney, "Dynamic Host Configuration Protocol for 643 IPv6 (DHCPv6)", RFC 3315, July 2003. 645 [RFC3484] Draves, R., "Default Address Selection for Internet 646 Protocol version 6 (IPv6)", RFC 3484, February 2003. 648 [RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure 649 Neighbor Discovery (SEND)", RFC 3971, March 2005. 651 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", 652 RFC 3972, March 2005. 654 [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through 655 Network Address Translations (NATs)", RFC 4380, February 656 2006. 658 [RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy 659 Extensions for Stateless Address Autoconfiguration in 660 IPv6", RFC 4941, September 2007. 662 [RFC5991] Thaler, D., Krishnan, S., and J. Hoagland, "Teredo 663 Security Updates", RFC 5991, September 2010. 665 [RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265, 666 April 2011. 668 [RFC6724] Thaler, D., Draves, R., Matsumoto, A., and T. Chown, 669 "Default Address Selection for Internet Protocol Version 6 670 (IPv6)", RFC 6724, September 2012. 672 [RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J., 673 Morris, J., Hansen, M., and R. Smith, "Privacy 674 Considerations for Internet Protocols", RFC 6973, July 675 2013. 677 Authors' Addresses 679 Alissa Cooper 680 Cisco 681 707 Tasman Drive 682 Milpitas, CA 95035 683 US 685 Phone: +1-408-902-3950 686 Email: alcoop@cisco.com 687 URI: https://www.cisco.com/ 688 Fernando Gont 689 Huawei Technologies 690 Evaristo Carriego 2644 691 Haedo, Provincia de Buenos Aires 1706 692 Argentina 694 Phone: +54 11 4650 8472 695 Email: fgont@si6networks.com 696 URI: http://www.si6networks.com 698 Dave Thaler 699 Microsoft 700 Microsoft Corporation 701 One Microsoft Way 702 Redmond, WA 98052 704 Phone: +1 425 703 8835 705 Email: dthaler@microsoft.com