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Checking references for intended status: Informational ---------------------------------------------------------------------------- == Outdated reference: A later version (-05) exists of draft-ietf-dnssd-privacy-00 -- Obsolete informational reference (is this intentional?): RFC 3315 (Obsoleted by RFC 8415) -- Obsolete informational reference (is this intentional?): RFC 4941 (Obsoleted by RFC 8981) Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force R. Winter 3 Internet-Draft University of Applied Sciences Augsburg 4 Intended status: Informational M. Faath 5 Expires: July 19, 2018 Conntac GmbH 6 F. Weisshaar 7 University of Applied Sciences Augsburg 8 January 15, 2018 10 Privacy considerations for protocols relying on IP broadcast and 11 multicast 12 draft-ietf-intarea-broadcast-consider-06 14 Abstract 16 A number of application-layer protocols make use of IP broadcasts or 17 multicast messages for functions like local service discovery or name 18 resolution. Some of these functions can only be implemented 19 efficiently using such mechanisms. When using broadcasts or 20 multicast messages, a passive observer in the same broadcast/ 21 multicast domain can trivially record these messages and analyze 22 their content. Therefore, designers of protocols that make use 23 broadcast/multicast messages need to take special care when designing 24 their protocols. 26 Status of This Memo 28 This Internet-Draft is submitted in full conformance with the 29 provisions of BCP 78 and BCP 79. 31 Internet-Drafts are working documents of the Internet Engineering 32 Task Force (IETF). Note that other groups may also distribute 33 working documents as Internet-Drafts. The list of current Internet- 34 Drafts is at http://datatracker.ietf.org/drafts/current/. 36 Internet-Drafts are draft documents valid for a maximum of six months 37 and may be updated, replaced, or obsoleted by other documents at any 38 time. It is inappropriate to use Internet-Drafts as reference 39 material or to cite them other than as "work in progress." 41 This Internet-Draft will expire on July 19, 2018. 43 Copyright Notice 45 Copyright (c) 2018 IETF Trust and the persons identified as the 46 document authors. All rights reserved. 48 This document is subject to BCP 78 and the IETF Trust's Legal 49 Provisions Relating to IETF Documents 50 (http://trustee.ietf.org/license-info) in effect on the date of 51 publication of this document. Please review these documents 52 carefully, as they describe your rights and restrictions with respect 53 to this document. Code Components extracted from this document must 54 include Simplified BSD License text as described in Section 4.e of 55 the Trust Legal Provisions and are provided without warranty as 56 described in the Simplified BSD License. 58 Table of Contents 60 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 61 1.1. Types and usage of broadcast and multicast . . . . . . . 4 62 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 4 63 2. Privacy considerations . . . . . . . . . . . . . . . . . . . 4 64 2.1. Message frequency . . . . . . . . . . . . . . . . . . . . 5 65 2.2. Persistent identifiers . . . . . . . . . . . . . . . . . 5 66 2.3. Anticipate user behavior . . . . . . . . . . . . . . . . 6 67 2.4. Consider potential correlation . . . . . . . . . . . . . 7 68 2.5. Configurability . . . . . . . . . . . . . . . . . . . . . 7 69 3. Operational considerations . . . . . . . . . . . . . . . . . 8 70 4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 71 5. Other considerations . . . . . . . . . . . . . . . . . . . . 9 72 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9 73 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 74 8. Security Considerations . . . . . . . . . . . . . . . . . . . 10 75 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 76 9.1. Normative References . . . . . . . . . . . . . . . . . . 10 77 9.2. Informative References . . . . . . . . . . . . . . . . . 10 78 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 80 1. Introduction 82 Broadcast and multicast messages have a large (and to the sender 83 unknown) receiver group by design. Because of that, these two 84 mechanisms are vital for a number of basic network functions such as 85 auto-configuration or link-layer address lookup. Also application 86 developers use broadcast/multicast messages to implement things like 87 local service or peer discovery. It appears that an increasing 88 number of applications make use of it as suggested by experimental 89 results obtained on campus networks including the IETF meeting 90 network [TRAC2016]. This trend is not entirely surprising. As RFC 91 919 [RFC0919] puts it, "The use of broadcasts [...] is a good base 92 for many applications". Broadcast and multicast functionality in a 93 subnetwork are therefore important as a lack thereof renders the 94 protocols relying on these mechanisms inoperable [RFC3819]. 96 Using broadcast/multicast can become problematic if the information 97 that is being distributed can be regarded as sensitive or when the 98 information that is distributed by multiple of these protocols can be 99 correlated in a way that sensitive data can be derived. This is 100 clearly true for any protocol, but broadcast/multicast is special in 101 at least two respects: 103 (a) The aforementioned large receiver group, consisting of receivers 104 unknown to the sender. This makes eavesdropping without special 105 privileges or a special location in the network trivial for 106 anybody in the broadcast/multicast domain. 108 (b) Encryption is more difficult when broadcast/multicast messages, 109 leaving content of these messages in the clear and making it 110 easier to spoof and replay them. 112 Given the above, privacy protection for protocols based on broadcast 113 or multicast communication is significantly more difficult compared 114 to unicast communication and at the same time invading the privacy is 115 much easier. 117 Privacy considerations of IETF-specified protocols have received some 118 attention in the recent past (e.g. RFC 7721 [RFC7721] or RFC 7819 119 [RFC7819]). There is also general guidance available for document 120 authors on when and how to include a privacy considerations section 121 in their documents and on how to evaluate the privacy implications of 122 Internet protocols [RFC6973]. RFC6973 also describes potential 123 threats to privacy in great detail and lists terminology that is also 124 used in this document. In contrast to RFC6973, this document 125 contains a number of privacy considerations especially for protocols 126 that rely on broadcast/multicast, intended to reduce the likelihood 127 that a broadcast/multicast protocol can be misused to collect 128 sensitive data about devices, users and groups of users on a 129 broadcast/multicast domain. 131 The above mentioned considerations particularly apply to protocols 132 designed outside the IETF - for two reasons. For one, non-standard 133 protocols will likely not receive operational attention and support 134 in making them more secure such as e.g. DHCP snooping does for DHCP 135 because they typically are not documented. The other reason is that 136 these protocols have been designed in isolation, where a set of 137 considerations to follow is useful in the absence of a larger 138 community providing feedback. In particular, carelessly designed 139 protocols that use broadcast/multicast can break privacy efforts at 140 different layers of the protocol stack such as MAC address or IP 141 address randomization [RFC4941]. 143 1.1. Types and usage of broadcast and multicast 145 In IPv4, two major types of broadcast addresses exist, the limited 146 broadcast which is defined as all-ones (255.255.255.255, defined in 147 section 5.3.5.1 of [RFC1812]) and the directed broadcast with the 148 given network prefix of an IP address and the host part of all-ones 149 (defined in section 5.3.5.2. of [RFC1812]). Broadcast packets are 150 received by all nodes in a subnetwork. Limited broadcasts never 151 transit a router. The same is true for directed broadcasts by 152 default, but routers MAY provide an option to do this [RFC2644]. 153 IPv6 on the other hand does not provide broadcast addresses but 154 solely relies on multicast [RFC4291]. 156 In contrast to broadcast addresses, multicast addresses represent an 157 identifier for a set of interfaces that can be a set different from 158 all nodes in the subnetwork. All interfaces that are identified by a 159 given multicast address receive packets destined towards that address 160 and are called a multicast group. In both IPv4 and IPv6, multiple 161 pre-defined multicast addresses exist. The ones most relevant for 162 this document are the ones with subnet scope. For IPv4, an IP prefix 163 is reserved for this purpose called the Local Network Control Block 164 (224.0.0.0/24, defined in section 4 of [RFC5771]). For IPv6, the 165 relevant multicast addresses are the two All Nodes Addresses, which 166 every IPv6-capable host is required to recognize as identifying 167 itself (see section 2.7.1 of [RFC4291]). 169 Typical usage of these addresses include local service discovery 170 (e.g. mDNS [RFC6762] and LLMNR [RFC4795] make use of multicast), 171 autoconfiguration (e.g. DHCPv4 [RFC2131] uses broadcasts and DHCPv6 172 [RFC3315] uses multicast addresses) and other vital network services 173 such as address resolution or duplicate address detection. But 174 besides these core network functions, also applications make use of 175 broadcast and multicast functionality, often implementing proprietary 176 protocols. In sum, these protocols distribute a diverse set of 177 potentially privacy sensitive information to a large receiver group. 179 1.2. Requirements Language 181 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 182 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 183 document are to be interpreted as described in RFC 2119 [RFC2119]. 185 2. Privacy considerations 187 There are a few obvious and a few not necessarily obvious things 188 designers of protocols utilizing broadcast/multicast should consider 189 in respect to the privacy implications of their protocol. Most of 190 these items are based on protocol behavior observed as part of 191 experiments on operational networks [TRAC2016]. 193 2.1. Message frequency 195 Frequent broadcast/multicast traffic caused by an application can 196 give away user behavior and online connection times. This allows a 197 passive observer to potentially deduce a user's current activity 198 (e.g. a game) and it allows to create an online profile (i.e. times 199 the user is on the network). The higher the frequency of these 200 messages and the duration of time these messages are sent, the more 201 accurate this profile will be. Given that broadcasts/multicasts are 202 only visible in the same broadcast/multicast domain, these messages 203 also give the rough location of the user away (e.g. a campus or 204 building). 206 This behavior has e.g. been observed by a synchronization mechanism 207 of a popular application, where multiple messages have been sent per 208 minute via broadcast. Given this behavior, it is possible to record 209 a device's time on the network with a sub-minute accuracy given only 210 the traffic of this single application installed on the device. But 211 also services used for local name resolution in modern operating 212 systems utilize broadcast/multicast protocols (e.g. mDNS, LLMNR or 213 NetBIOS) to announce for example their shares regularly and allow a 214 tracking of the online time of a device. 216 If a protocol relies on frequent or periodic broadcast/multicast 217 messages, the frequency SHOULD be chosen conservatively, in 218 particular if the messages contain persistent identifiers (see next 219 subsection). Also, intelligent message suppression mechanisms such 220 as the ones employed in mDNS [RFC6762] SHOULD be implemented. The 221 lower the frequency of broadcast messages, the harder passive traffic 222 analysis and surveillance becomes. 224 2.2. Persistent identifiers 226 A few protocols that make use of broadcast/multicast messages 227 observed in the wild make use of persistent identifiers. This 228 includes the use of host names or more abstract persistent 229 identifiers such as a universally unique identifiers (UUID) or 230 similar. These IDs, which e.g. identify the installation of a 231 certain application might not change across updates of the software 232 and are therefore extremely long lived. This allows a passive 233 observer to track a user precisely if broadcast/multicast messages 234 are frequent. This is even true in case the IP and/or MAC address 235 changes. Such identifiers also allow two different interfaces (e.g. 236 WiFi and Ethernet) to be correlated to the same device. If the 237 application makes use of persistent identifiers for multiple 238 installations of the same application for the same user, this even 239 allows to infer that different devices belong to the same user. 241 The aforementioned broadcast messages from a synchronization 242 mechanism of a popular application also included a persistent 243 identifier in every broadcast. This identifier did never change 244 after the application was installed and allowed to track a device 245 even when it changed its network interface or when it connected to a 246 different network. 248 Persistent IDs are considered bad practice in general for broadcast 249 and multicast communication, as persistent application layer IDs will 250 make efforts on lower layers to randomize identifiers (e.g. 251 [I-D.huitema-6man-random-addresses]) useless. When protocols that 252 make use of broadcast/multicast need to make use of IDs, frequent 253 rotations of these IDs SHOULD be considered to make user tracking 254 more difficult. 256 2.3. Anticipate user behavior 258 A large number of users name their device after themselves, either 259 using their first name, last name or both. Often a host name 260 includes the type, model or maker of a device, its function or 261 includes language specific information. Based on data gathered 262 during experiments performed at IETF meetings and at a large campus 263 network, this appears currently to be prevalent user behavior 264 [TRAC2016]. For protocols using the host name as part of the 265 messages, this clearly will reveal personally identifiable 266 information to everyone on the local network. This information can 267 also be used to mount more sophisticated attacks, when e.g. the owner 268 of a device is identified (as an interesting target) or properties of 269 the device are known (e.g. known vulnerabilities). 271 Some of the most commonly used operating systems include the name the 272 user chooses for the user account during the installation process as 273 part of the host name of the device. The name of the operating 274 system can also be included, revealing therefore two pieces of 275 information, which can be regarded as private information if the host 276 name is used in broadcast/multicast messages. 278 Where possible, the use of host names and other user-provided 279 information in protocols making use of broadcast/multicast SHOULD be 280 avoided. If all that is required is a persistent identifier (which 281 SHOULD be avoided, see Section 2.2), this SHOULD be generated 282 randomly. An application might want to display the information it 283 will broadcast on the LAN at install/config time, so the user is at 284 least aware of the application's behavior. More host name 285 considerations can be found in [RFC8117]. More information on user 286 participation can be found in RFC 6973 [RFC6973]. 288 2.4. Consider potential correlation 290 A large number of services and applications make use of the 291 broadcast/multicast mechanism. That means there are various sources 292 of information that are easily accessible by a passive observer. In 293 isolation, the information these protocols reveal might seem 294 harmless, but given multiple such protocols, it might be possible to 295 correlate this information. E.g. a protocol that uses frequent 296 messages including a UUID to identify the particular installation 297 does not give the identity of the user away. But a single message 298 including the user's host name might just do that and it can be 299 correlated using e.g. the MAC address of the device's interface. 301 In the experiments described in [TRAC2016], it was possible to 302 correlate frequently sent broadcast messages that included a unique 303 identifier with other broadcast/multicast messages containing 304 usernames (e.g. mDNS, LLMNR or NetBIOS), but also relationships to 305 other users. This allowed to reveal the real identity of the users 306 of many devices but it also gave some information about their social 307 environment away. 309 A designer of a protocol that makes use of broadcast/multicast needs 310 to be aware of the fact that even if - in isolation - the information 311 a protocol leaks seems harmless, there might be ways to correlate 312 that information with information from other protocols to reveal 313 sensitive information about a user. 315 2.5. Configurability 317 A lot of applications and services relying on broadcast/multicast 318 protocols do not include the means to declare "safe" environments 319 (e.g. based on the SSID of a WiFi network and the MAC addresses of 320 the access points). E.g. a device connected to a public WiFi will 321 likely broadcast the same information as when connected to the home 322 network. It would be beneficial if certain behavior could be 323 restricted to "safe" environments. 325 A popular operating system e.g. allows the user to specify the trust 326 level of the network the device connects to, which for example 327 restricts specific system services (using broadcast/multicast 328 messages for their normal operation) to be used in trusted networks 329 only. Such functionality could implemented as part of an 330 application. 332 An application developer making use of broadcasts/multicasts as part 333 of the application SHOULD make the broadcast feature, if possible, 334 configurable, so that potentially sensitive information does not leak 335 on public networks, where the threat to privacy is much larger. 337 3. Operational considerations 339 Besides changing end-user behavior, choosing sensible defaults as an 340 operating system vendor (e.g. for suggesting host names) and the 341 considerations for protocol designers mentioned in this document, 342 there are things that the network administrators/operators can do to 343 limit the above mentioned problems. 345 A feature not uncommonly found on access points e.g. is to filter 346 broadcast and multicast traffic. This will potentially break certain 347 applications or some of their functionality but will also protect the 348 users from potentially leaking sensitive information. 350 4. Summary 352 Increasingly, applications rely on protocols that send and receive 353 broadcast and multicast messages. For some, broadcasts/multicasts 354 are the basis of their application logic, others use broadcasts/ 355 multicasts to improve certain aspects of the application but are 356 fully functional in case broadcasts/multicasts fail. Irrespective of 357 the role of broadcast and multicast messages for the application, the 358 designers of protocols that make use of them should be very careful 359 in their protocol design because of the special nature of broadcast 360 and multicast. 362 It is not always possible to implement certain functionality via 363 unicast, but in case a protocol designer chooses to rely on 364 broadcast/multicast, the following should be carefully considered: 366 o IETF-specified protocols, such as mDNS [RFC6762], SHOULD be used 367 if possible as operational support might exist to protect against 368 the leakage of private information. Also, for some protocols 369 privacy extensions are being specified, which can be used if 370 implemented. E.g. for DNS-SD privacy extensions are documented in 371 [I-D.ietf-dnssd-privacy] 373 o Using user-specified information inside broadcast/multicast 374 messages SHOULD be avoided, as users will often use personal 375 information or other information aiding attackers, in particular 376 if the user is unaware about how that information is being used 378 o The use of persistent IDs in messages SHOULD be avoided, as this 379 allows user tracking, correlation and potentially has a 380 devastating effect on other privacy protection mechanisms 382 o If one really must design a new protocol relying on broadcast/ 383 multicast and cannot use an IETF-specified protocol, then: 385 * You SHOULD be very conservative in how frequently you send 386 messages as an effort in data minimization 388 * You SHOULD seek advice from IETF-specified protocols such as 389 message suppression in mDNS 391 * You SHOULD try to design the protocol in a way that information 392 sent in broadcast/multicast messages cannot be correlated with 393 information from other protocols using broadcast/multicast 395 * You SHOULD let the user configure safe environments if possible 396 (e.g. based on the SSID) 398 5. Other considerations 400 Besides privacy implications, frequent broadcasting also represents a 401 performance problem. In particular in certain wireless technologies 402 such as 802.11, broadcast and multicast are transmitted at a much 403 lower rate (the lowest common denominator rate) compared to unicast 404 and therefore have a much bigger impact on the overall available 405 airtime [I-D.perkins-intarea-multicast-ieee802]. Further, it will 406 limit the ability for devices to go to sleep if frequent broadcasts 407 are being sent. A similar problem in respect to Router 408 Advertisements is addressed in 409 [I-D.ietf-v6ops-reducing-ra-energy-consumption]. In that respect 410 broadcasts/multicast can be used for another class of attacks that is 411 not related to privacy. The potential impact on network performance 412 should nevertheless be considered when designing a protocol that 413 makes use of broadcast/multicast. 415 6. Acknowledgments 417 We would like to thank Eliot Lear, Joe Touch and Stephane Bortzmeyer 418 for their valuable input to this document. 420 This work was partly supported by the European Commission under grant 421 agreement FP7-318627 mPlane. Support does not imply endorsement. 423 7. IANA Considerations 425 This memo includes no request to IANA. 427 8. Security Considerations 429 This document deals with privacy-related considerations of broadcast- 430 and multicast-based protocols. It contains advice for designers of 431 such protocols to minimize the leakage of privacy-sensitive 432 information. The intent of the advice is to make sure that 433 identities will remain anonymous and user tracking will be made 434 difficult. 436 It should be noted that certain applications could make use of 437 existing mechanisms to protect multicast traffic such as the ones 438 defined in [RFC5374]. Examples of such applications can be found in 439 Appendix A. of [RFC5374]. Given the required infrastructure and 440 assumptions about these applications and the security infrastructure, 441 many applications will not be able to make use of such mechanisms. 443 9. References 445 9.1. Normative References 447 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 448 Requirement Levels", BCP 14, RFC 2119, March 1997. 450 9.2. Informative References 452 [I-D.huitema-6man-random-addresses] 453 Huitema, C., "Implications of Randomized Link Layers 454 Addresses for IPv6 Address Assignment", draft-huitema- 455 6man-random-addresses-03 (work in progress), March 2016. 457 [I-D.ietf-dnssd-privacy] 458 Huitema, C. and D. Kaiser, "Privacy Extensions for DNS- 459 SD", draft-ietf-dnssd-privacy-00 (work in progress), 460 October 2016. 462 [I-D.ietf-v6ops-reducing-ra-energy-consumption] 463 Yourtchenko, A. and L. Colitti, "Reducing energy 464 consumption of Router Advertisements", draft-ietf-v6ops- 465 reducing-ra-energy-consumption-03 (work in progress), 466 November 2015. 468 [I-D.perkins-intarea-multicast-ieee802] 469 Perkins, C., Stanley, D., Kumari, W., and J. Zuniga, 470 "Multicast Considerations over IEEE 802 Wireless Media", 471 draft-perkins-intarea-multicast-ieee802-03 (work in 472 progress), July 2017. 474 [RFC0919] Mogul, J., "Broadcasting Internet Datagrams", STD 5, RFC 475 919, DOI 10.17487/RFC0919, October 1984, 476 . 478 [RFC1812] Baker, F., Ed., "Requirements for IP Version 4 Routers", 479 RFC 1812, DOI 10.17487/RFC1812, June 1995, 480 . 482 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 483 2131, DOI 10.17487/RFC2131, March 1997, 484 . 486 [RFC2644] Senie, D., "Changing the Default for Directed Broadcasts 487 in Routers", BCP 34, RFC 2644, DOI 10.17487/RFC2644, 488 August 1999, . 490 [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, 491 C., and M. Carney, "Dynamic Host Configuration Protocol 492 for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July 493 2003, . 495 [RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D., 496 Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. 497 Wood, "Advice for Internet Subnetwork Designers", BCP 89, 498 RFC 3819, DOI 10.17487/RFC3819, July 2004, 499 . 501 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 502 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 503 2006, . 505 [RFC4795] Aboba, B., Thaler, D., and L. Esibov, "Link-local 506 Multicast Name Resolution (LLMNR)", RFC 4795, DOI 507 10.17487/RFC4795, January 2007, 508 . 510 [RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy 511 Extensions for Stateless Address Autoconfiguration in 512 IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007, 513 . 515 [RFC5374] Weis, B., Gross, G., and D. Ignjatic, "Multicast 516 Extensions to the Security Architecture for the Internet 517 Protocol", RFC 5374, DOI 10.17487/RFC5374, November 2008, 518 . 520 [RFC5771] Cotton, M., Vegoda, L., and D. Meyer, "IANA Guidelines for 521 IPv4 Multicast Address Assignments", BCP 51, RFC 5771, DOI 522 10.17487/RFC5771, March 2010, 523 . 525 [RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762, 526 DOI 10.17487/RFC6762, February 2013, 527 . 529 [RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J., 530 Morris, J., Hansen, M., and R. Smith, "Privacy 531 Considerations for Internet Protocols", RFC 6973, DOI 532 10.17487/RFC6973, July 2013, 533 . 535 [RFC7721] Cooper, A., Gont, F., and D. Thaler, "Security and Privacy 536 Considerations for IPv6 Address Generation Mechanisms", 537 RFC 7721, DOI 10.17487/RFC7721, March 2016, 538 . 540 [RFC7819] Jiang, S., Krishnan, S., and T. Mrugalski, "Privacy 541 Considerations for DHCP", RFC 7819, DOI 10.17487/RFC7819, 542 April 2016, . 544 [RFC8117] Huitema, C., Thaler, D., and R. Winter, "Current Hostname 545 Practice Considered Harmful", RFC 8117, DOI 10.17487/ 546 RFC8117, March 2017, . 549 [TRAC2016] 550 Faath, M., Weisshaar, F., and R. Winter, "How Broadcast 551 Data Reveals Your Identity and Social Graph", 7th 552 International Workshop on TRaffic Analysis and 553 Characterization IEEE TRAC 2016, September 2016. 555 Authors' Addresses 557 Rolf Winter 558 University of Applied Sciences Augsburg 559 Augsburg 560 DE 562 Email: rolf.winter@hs-augsburg.de 563 Michael Faath 564 Conntac GmbH 565 Augsburg 566 DE 568 Email: faath@conntac.net 570 Fabian Weisshaar 571 University of Applied Sciences Augsburg 572 Augsburg 573 DE 575 Email: fabian.weisshaar@hs-augsburg.de