DNS-Based Service Discovery (DNS-SD) Privacy and Security RequirementsPrivate Octopus Inc.Friday Harbor98250WAUnited States of Americahuitema@huitema.nethttp://privateoctopus.com/University of Luxembourg6, avenue de la FonteEsch-sur-Alzette4364Luxembourgdaniel.kaiser@uni.luhttps://secan-lab.uni.lu/Multicast DNSmDNSDNS-SD (DNS-based Service Discovery) normally discloses information about
devices offering and requesting services. This information includes
hostnames, network parameters, and possibly a further description of the
corresponding service instance. Especially when mobile devices engage in
DNS-based Service Discovery at a public hotspot, serious privacy problems
arise. We analyze the requirements of a privacy-respecting discovery
service.Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are candidates for any level of Internet
Standard; see Section 2 of RFC 7841.
Information about the current status of this document, any
errata, and how to provide feedback on it may be obtained at
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Table of Contents
. Introduction
. Threat Model
. Threat Analysis
. Service Discovery Scenarios
. Private Client and Public Server
. Private Client and Private Server
. Wearable Client and Server
. DNS-SD Privacy Considerations
. Information Made Available Via DNS-SD Resource Records
. Privacy Implication of Publishing Service Instance Names
. Privacy Implication of Publishing Node Names
. Privacy Implication of Publishing Service Attributes
. Device Fingerprinting
. Privacy Implication of Discovering Services
. Security Considerations
. Authenticity, Integrity, and Freshness
. Confidentiality
. Resistance to Dictionary Attacks
. Resistance to Denial-of-Service Attacks
. Resistance to Sender Impersonation
. Sender Deniability
. Operational Considerations
. Power Management
. Protocol Efficiency
. Secure Initialization and Trust Models
. External Dependencies
. Requirements for a DNS-SD Privacy Extension
. Private Client Requirements
. Private Server Requirements
. Security and Operation
. IANA Considerations
. References
. Normative References
. Informative References
Acknowledgments
Authors' Addresses
IntroductionDNS-Based Service Discovery (DNS-SD) over Multicast DNS (mDNS) enables zero-configuration service discovery in local
networks. It is very convenient for users, but it requires the public
exposure of the offering and requesting identities along with
information about the offered and requested services. Parts of the
published information can seriously breach the user's privacy. These
privacy issues and potential solutions are discussed in , , and . While the
multicast nature of mDNS makes these risks obvious, most risks derive
from the observability of transactions. These risks also need to be
mitigated when using server-based variants of DNS-SD.There are cases when nodes connected to a network want to provide or
consume services without exposing their identities to the other parties
connected to the same network. Consider, for example, a traveler wanting
to upload pictures from a phone to a laptop when both are connected to
the Wi-Fi network of an Internet cafe, or two travelers who want to
share files between their laptops when waiting for their plane in an
airport lounge.We expect that these exchanges will start with a discovery procedure
using DNS-SD over mDNS. One of the devices will publish the availability
of a service, such as a picture library or a file store in our
examples. The user of the other device will discover this service and
then connect to it.When analyzing these scenarios in , we find that the DNS-SD messages leak identifying
information, such as the Service Instance Name, the hostname, or service
properties. We use the following definitions:
Identity
In this document, the term "identity" refers to the identity of
the entity (legal person) operating a device.
Disclosing an Identity
In this document, "disclosing an identity" means showing the
identity of operating entities to devices external to the discovery
process, e.g., devices on the same network link that are listening to
the network traffic but are not actually involved in the discovery
process. This document focuses on identity disclosure by data conveyed
via messages on the service discovery protocol layer. Still, identity
leaks on deeper layers, e.g., the IP layer, are mentioned.
Disclosing Information
In this document, "disclosing information" is also focused on
disclosure of data conveyed via messages on the service discovery
protocol layer, including both identity-revealing information and
other still potentially sensitive data.
Threat ModelThis document considers the following attacker types sorted by
increasing power. All these attackers can either be passive (they just
listen to network traffic they have access to) or active (they
additionally can craft and send malicious packets).
external
An external attacker is not on the same network link as victim
devices engaging in service discovery; thus, the external attacker is
in a different multicast domain.
on-link
An on-link attacker is on the same network link as victim devices
engaging in service discovery; thus, the on-link attacker is in the
same multicast domain. This attacker can also mount all attacks an
external attacker can mount.
MITM
A Man-in-the-Middle (MITM) attacker either controls (parts of) a
network link or can trick two parties to send traffic via the
attacker; thus, the MITM attacker has access to unicast traffic
between devices engaging in service discovery. This attacker can also
mount all attacks an on-link attacker can mount.
Threat AnalysisIn this section, we analyze how the attackers described in the
previous section might threaten the privacy of entities operating
devices engaging in service discovery. We focus on attacks leveraging
data transmitted in service discovery protocol messages.Service Discovery ScenariosIn this section, we review common service discovery scenarios and
discuss privacy threats and their privacy requirements. In all three
of these common scenarios, the attacker is of the type passive
on-link.Private Client and Public ServerPerhaps the simplest private discovery scenario involves a single
client connecting to a public server through a public network. A
common example would be a traveler using a publicly available
printer in a business center, in a hotel, or at an airport.
( Taking notes:
( David is printing
( a document.
~~~~~~~~~~~
o
___ o ___
/ \ _|___|_
| | client server |* *|
\_/ __ \_/
| / / Discovery +----------+ |
/|\ /_/ <-----------> | +----+ | /|\
/ | \__/ +--| |--+ / | \
/ | |____/ / | \
/ | / | \
/ \ / \
/ \ / \
/ \ / \
/ \ / \
/ \ / \
David Adversary
In that scenario, the server is public and wants to be
discovered, but the client is private. The adversary will be
listening to the network traffic, trying to identify the visitors'
devices and their activity. Identifying devices leads to identifying
people, either for surveillance of these individuals in the physical
world or as a preliminary step for a targeted cyber attack.The requirement in that scenario is that the discovery activity
should not disclose the identity of the client.Private Client and Private ServerThe second private discovery scenario involves a private client
connecting to a private server. A common example would be two people
engaging in a collaborative application in a public place, such as
an airport's lounge.
( Taking notes:
( David is meeting
( with Stuart.
~~~~~~~~~~~
o
___ ___ o ___
/ \ / \ _|___|_
| | server client | | |* *|
\_/ __ __ \_/ \_/
| / / Discovery \ \ | |
/|\ /_/ <-----------> \_\ /|\ /|\
/ | \__/ \__/ | \ / | \
/ | | \ / | \
/ | | \ / | \
/ \ / \ / \
/ \ / \ / \
/ \ / \ / \
/ \ / \ / \
/ \ / \ / \
David Stuart Adversary
In that scenario, the collaborative application on one of the
devices will act as a server, and the application on the other
device will act as a client. The server wants to be discovered by
the client but has no desire to be discovered by anyone else. The
adversary will be listening to network traffic, attempting to
discover the identity of devices as in the first scenario and also
attempting to discover the patterns of traffic, as these patterns
reveal the business and social interactions between the owners of
the devices.The requirement in that scenario is that the discovery activity
should not disclose the identity of either the client or the server
nor reveal the business and social interactions between the owners
of the devices.Wearable Client and ServerThe third private discovery scenario involves wearable devices. A
typical example would be the watch on someone's wrist connecting to
the phone in their pocket.
( Taking notes:
( David is here. His watch is
( talking to his phone.
~~~~~~~~~~~
o
___ o ___
/ \ _|___|_
| | client |* *|
\_/ \_/
| _/ |
/|\ // /|\
/ | \__/ ^ / | \
/ |__ | Discovery / | \
/ |\ \ v / | \
/ \\_\ / \
/ \ server / \
/ \ / \
/ \ / \
/ \ / \
David Adversary
This third scenario is in many ways similar to the second
scenario. It involves two devices, one acting as server and the
other acting as client, and it leads to the same requirement of the
discovery traffic not disclosing the identity of either the client
or the server. The main difference is that the devices are managed
by a single owner, which can lead to different methods for
establishing secure relations between the devices. There is also an
added emphasis on hiding the type of devices that the person
wears.In addition to tracking the identity of the owner of the devices,
the adversary is interested in the characteristics of the devices,
such as type, brand, and model. Identifying the type of device can
lead to further attacks, from theft to device-specific hacking. The
combination of devices worn by the same person will also provide a
"fingerprint" of the person, risking identification.This scenario also represents the general case of bringing
private Internet-of-Things (IoT) devices into public places. A
wearable IoT device might
act as a DNS-SD/mDNS client, which allows attackers to infer
information about devices' owners. While the attacker might be a
person, as in the example figure, this could also be abused for
large-scale data collection installing stationary
IoT-device-tracking
servers in frequented public places.The issues described in , such as identifying people or using the
information for targeted attacks, apply here too.DNS-SD Privacy ConsiderationsWhile the discovery process illustrated in the scenarios in most likely would be based on
as a means for making
service information available, this document considers all kinds of
means for making DNS-SD resource records available. These means
comprise of but are not limited to mDNS , DNS servers (, , and ), the use of Service Registration
Protocol (SRP) , and multi-link networks.The discovery scenarios in illustrate three separate abstract privacy
requirements that vary based on the use case. These are not limited to
mDNS.
Client identity privacy: Client identities are not leaked during
service discovery or use.
Multi-entity, mutual client and server identity privacy: Neither
client nor server identities are leaked during service discovery or
use.
Single-entity, mutual client and server identity privacy:
Identities of clients and servers owned and managed by the same
legal person are not leaked during service discovery or use.
In this section, we describe aspects of DNS-SD that make these
requirements difficult to achieve in practice. While it is intended to
be thorough, it is not possible to be exhaustive.Client identity privacy, if not addressed properly, can be thwarted
by a passive attacker (see ). The type of passive attacker necessary depends on
the means of making service information available. Information
conveyed via multicast messages can be obtained by an on-link
attacker. Unicast messages are harder to access,
but if the transmission is not encrypted they could still be accessed by
an attacker with access to network routers or bridges. Using multi-link service discovery
solutions , external
attackers have to be taken into consideration as well, e.g., when
relaying multicast messages to other links.Server identity privacy can be thwarted by a passive attacker in
the same way as client identity privacy. Additionally, active
attackers querying for information have to be taken into consideration
as well. This is mainly relevant for unicast-based discovery, where
listening to discovery traffic requires a MITM attacker; however, an
external active attacker might be able to learn the server identity by
just querying for service information, e.g., via DNS.Information Made Available Via DNS-SD Resource RecordsDNS-Based Service Discovery (DNS-SD) is defined in . It allows nodes to publish the
availability of an instance of a service by inserting specific
records in the DNS (, , and ) or by publishing these records locally using
multicast DNS (mDNS) . Available services are described using three
types of records:
PTR Record
Associates a service type in the domain with an "instance"
name of this service type.
SRV Record
Provides the node name, port number, priority and weight
associated with the service instance, in conformance with .
TXT Record
Provides a set of attribute-value pairs describing specific
properties of the service instance.
Privacy Implication of Publishing Service Instance NamesIn the first phase of discovery, clients obtain all PTR records
associated with a service type in a given naming domain. Each PTR
record contains a Service Instance Name defined in
:
Service Instance Name = <Instance> . <Service> . <Domain>
The <Instance> portion of the Service Instance Name is
meant to convey enough information for users of discovery clients to
easily select the desired service instance. Nodes that use DNS-SD
over mDNS in a mobile
environment will rely on the specificity of the instance name to
identify the desired service instance. In our example of users
wanting to upload pictures to a laptop in an Internet cafe, the list
of available service instances may look like:
Alice's Images . _imageStore._tcp . local
Alice's Mobile Phone . _presence._tcp . local
Alice's Notebook . _presence._tcp . local
Bob's Notebook . _presence._tcp . local
Carol's Notebook . _presence._tcp . local
Alice will see the list on her phone and understand intuitively
that she should pick the first item. The discovery will "just
work". (Note that our examples of service names conform to the
specification in but may require some character escaping when
entered in conventional DNS software.)However, DNS-SD/mDNS will reveal to anybody that Alice is
currently visiting the Internet cafe. It further discloses the fact
that she uses two devices, shares an image store, and uses a chat
application supporting the _presence protocol on both of her
devices. She might currently chat with Bob or Carol, as they are
also using a _presence supporting chat application. This information
is not just available to devices actively browsing for and offering
services but to anybody passively listening to the network traffic,
i.e., a passive on-link attacker.There is, of course, also no authentication requirement to claim
a particular instance name, so an active attacker can provide
resources that claim to be Alice's but are not.Privacy Implication of Publishing Node NamesThe SRV records contain the DNS name of the node publishing the
service. Typical implementations construct this DNS name by
concatenating the "hostname" of the node with the name of the local
domain. The privacy implications of this practice are reviewed in
. Depending on naming
practices, the hostname is either a strong identifier of the
device or, at a minimum, a partial identifier. It enables tracking of
both the device and, by extension, the device's owner.Privacy Implication of Publishing Service AttributesThe TXT record's attribute-value pairs contain information on the
characteristics of the corresponding service instance. This in turn
reveals information about the devices that publish services. The
amount of information varies widely with the particular service and
its implementation:
Some attributes, such as the paper size available in a
printer, are the same on many devices and thus only provide
limited information to a tracker.
Attributes that have free-form values, such as the name of a
directory, may reveal much more information.
Combinations of individual attributes have more information power
than specific attributes and can potentially be used for
"fingerprinting" a specific device.Information contained in TXT records not only breaches privacy by
making devices trackable but might directly contain private
information about the user. For instance, the _presence service
reveals the "chat status" to everyone in the same network. Users
might not be aware of that.Further, TXT records often contain version information about
services, allowing potential attackers to identify devices running
exploit-prone versions of a certain service.Device FingerprintingThe combination of information published in DNS-SD has the
potential to provide a "fingerprint" of a specific device. Such
information includes:
A list of services published by the device, which can be
retrieved because the SRV records will point to the same
hostname.
Specific attributes describing these services.
Port numbers used by the services.
Priority and weight attributes in the SRV records.
This combination of services and attributes will often be
sufficient to identify the version of the software running on a
device. If a device publishes many services with rich sets of
attributes, the combination may be sufficient to identify the
specific device and track its owner.An argument is sometimes made that devices providing services can
be identified by observing the local traffic and that trying to
hide the presence of the service is futile. However, there are good
reasons for the discovery service layer to avoid unnecessary
exposure:
Providing privacy at the discovery layer is of the essence for
enabling automatically configured privacy-preserving network
applications. Application layer protocols are not forced to
leverage the offered privacy, but if device tracking is not
prevented at the deeper layers, including the service discovery
layer, obfuscating a certain service's protocol at the application
layer is futile.
Further, in the case of mDNS-based discovery, even if the
application layer does not protect privacy, services are typically
provided via unicast, which requires a MITM attacker, whereas
identifying services based on multicast discovery messages just
requires an on-link attacker.
The same argument can be extended to say that the pattern of
services offered by a device allows for fingerprinting the
device. This may or may not be true, since we can expect that
services will be designed or updated to avoid leaking
fingerprints. In any case, the design of the discovery service
should avoid making a bad situation worse and should, as much as
possible, avoid providing new fingerprinting information.Privacy Implication of Discovering ServicesThe consumers of services engage in discovery and in doing so
reveal some information, such as the list of services they are
interested in and the domains in which they are looking for the
services. When the clients select specific instances of services,
they reveal their preference for these instances. This can be benign
if the service type is very common, but it could be more problematic
for sensitive services, such as some private messaging services.One way to protect clients would be to somehow encrypt the
requested service types. Of course, just as we noted in , traffic analysis can
often reveal the service.Security ConsiderationsFor each of the operations described above, we must also consider
security threats we are concerned about.Authenticity, Integrity, and FreshnessCan devices (both servers and clients) trust the information they
receive? Has it been modified in flight by an adversary? Can
devices trust the source of the information? Is the source of
information fresh, i.e., not replayed? Freshness may or may not be
required depending on whether the discovery process is meant to be
online. In some cases, publishing discovery information to a shared
directory or registry, rather than to each online recipient through
a broadcast channel, may suffice.ConfidentialityConfidentiality is about restricting information access to only
authorized individuals. Ideally, this should only be the appropriate
trusted parties, though it can be challenging to define who are "the
appropriate trusted parties." In some use cases, this may mean that
only mutually authenticated and trusting clients and servers can
read messages sent for one another. The process of service discovery
in particular is often used to discover new entities that the device
did not previously know about. It may be tricky to work out how a
device can have an established trust relationship with a new entity
it has never previously communicated with.Resistance to Dictionary AttacksIt can be tempting to use (publicly computable) hash functions to
obscure sensitive identifiers. This transforms a sensitive unique
identifier, such as an email address, into a "scrambled" but still
unique identifier. Unfortunately, simple solutions may be vulnerable
to offline dictionary attacks.Resistance to Denial-of-Service AttacksIn any protocol where the receiver of messages has to perform
cryptographic operations on those messages, there is a risk of a
brute-force flooding attack causing the receiver to expend excessive
amounts of CPU time and, where applicable, battery power just
processing and discarding those messages.Also, amplification attacks have to be taken into
consideration. Messages with larger payloads should only be sent as
an answer to a query sent by a verified client.Resistance to Sender ImpersonationSender impersonation is an attack wherein messages, such as
service offers, are forged by entities who do not possess the
corresponding secret key material. These attacks may be used to
learn the identity of a communicating party, actively or
passively.Sender DeniabilityDeniability of sender activity, e.g., of broadcasting a discovery
request, may be desirable or necessary in some use cases. This
property ensures that eavesdroppers cannot prove senders issued a
specific message destined for one or more peers. Operational ConsiderationsPower ManagementMany modern devices, especially battery-powered devices, use
power management techniques to conserve energy. One such technique
is for a device to transfer information about itself to a proxy,
which will act on behalf of the device for some functions while the
device itself goes to sleep to reduce power consumption. When the
proxy determines that some action is required, which only the device
itself can perform, the proxy may have some way to wake the device,
as described for example in .In many cases, the device may not trust the network proxy
sufficiently to share all its confidential key material with the
proxy. This poses challenges for combining private discovery that
relies on per-query cryptographic operations with energy-saving
techniques that rely on having (somewhat untrusted) network proxies
answer queries on behalf of sleeping devices.Protocol EfficiencyCreating a discovery protocol that has the desired security
properties may result in a design that is not efficient. To perform
the necessary operations, the protocol may need to send and receive a
large number of network packets or require an inordinate amount of
multicast transmissions. This may consume an unreasonable amount of
network capacity, particularly problematic when it is a shared
wireless spectrum. Further, it may cause an unnecessary level of
power consumption, which is particularly problematic on battery
devices and may result in the discovery process being slow.It is a difficult challenge to design a discovery protocol that
has the property of obscuring the details of what it is doing from
unauthorized observers while also managing to perform
efficiently.Secure Initialization and Trust ModelsOne of the challenges implicit in the preceding discussions is
that whenever we discuss "trusted entities" versus "untrusted
entities", there needs to be some way that trust is initially
established to convert an "untrusted entity" into a "trusted
entity".The purpose of this document is not to define the specific way in
which trust can be established. Protocol designers may rely on a
number of existing technologies, including PKI, Trust On First Use
(TOFU), or the use of a short passphrase or PIN with cryptographic
algorithms, such as Secure Remote Password (SRP) or a
Password-Authenticated Key
Exchange like J-PAKE using a Schnorr Non-interactive
Zero-Knowledge Proof .Protocol designers should consider a specific usability pitfall
when trust is established immediately prior to performing
discovery. Users will have a tendency to "click OK" in order to
achieve their task. This implicit vulnerability is avoided if the
trust establishment requires more significant participation of the
user, such as entering a password or PIN.External DependenciesTrust establishment may depend on external parties. Optionally,
this might involve synchronous communication. Systems that have
such a dependency may be attacked by interfering with communication
to external dependencies. Where possible, such dependencies should
be minimized. Local trust models are best for secure initialization
in the presence of active attackers.Requirements for a DNS-SD Privacy ExtensionGiven the considerations discussed in the previous sections, we state
requirements for privacy preserving DNS-SD in the following
subsections.Defining a solution according to these requirements is intended to
lead to a solution that does not transmit privacy-violating DNS-SD
messages and further does not open pathways to new attacks against the
operation of DNS-SD.However, while this document gives advice on which privacy protecting
mechanisms should be used on deeper-layer network protocols and on how
to actually connect to services in a privacy-preserving way, stating
corresponding requirements is out of the scope of this document. To
mitigate attacks against privacy on lower layers, both servers and
clients must use privacy options available at lower layers and, for
example, avoid publishing static IPv4 or IPv6 addresses or static IEEE
802 Media Access Control (MAC) addresses. For services advertised on a
single network link,
link-local IP addresses should be used; see and for
IPv4 and IPv6, respectively. Static servers advertising services
globally via DNS can hide their IP addresses from unauthorized clients
using the split mode topology shown in Encrypted Server Name Indication
. Hiding static MAC addresses can be achieved via MAC
address randomization (see ).Private Client RequirementsFor all three scenarios described in , client privacy requires DNS-SD messages to:
Avoid disclosure of the client's identity, either directly or
via inference, to nodes other than select servers.
Avoid exposure of linkable identifiers that allow tracing client devices.
Avoid disclosure of the client's interest in specific service
instances or service types to nodes other than select servers.
When listing and resolving services via current DNS-SD deployments,
clients typically disclose their interest in specific services types
and specific instances of these types, respectively.In addition to the exposure and disclosure risks noted above,
protocols and implementations will have to consider fingerprinting
attacks (see ) that
could retrieve similar information.Private Server RequirementsServers like the "printer" discussed in are public, but
the servers discussed in Sections and
are, by essence, private.
Server privacy requires DNS-SD messages
to:
Avoid disclosure of the server's identity, either directly or
via inference, to nodes other than authorized clients. In
particular, servers must avoid publishing static identifiers, such as
hostnames or service names. When those fields are required by the
protocol, servers should publish randomized values. (See for a discussion of hostnames.)
Avoid exposure of linkable identifiers that allow tracing servers.
Avoid disclosure to unauthorized clients of Service Instance
Names or service types of offered services.
Avoid disclosure to unauthorized clients of information about
the services they offer.
Avoid disclosure of static IPv4 or IPv6 addresses.
When offering services via current DNS-SD deployments, servers
typically disclose their hostnames (SRV, A/AAAA), instance names of
offered services (PTR, SRV), and information about services
(TXT). Heeding these requirements protects a server's privacy on the
DNS-SD level.The current DNS-SD user interfaces present the list of discovered
service names to the users and let them pick a service from the
list. Using random identifiers for service names renders that UI flow
unusable. Privacy-respecting discovery protocols will have to solve
this issue, for example, by presenting authenticated or decrypted
service names instead of the randomized values.Security and OperationIn order to be secure and feasible, a DNS-SD privacy extension
needs to consider security and operational requirements including:
Avoiding significant CPU overhead on nodes or significantly
higher network load. Such overhead or load would make nodes
vulnerable to denial-of-service attacks. Further, it would increase
power consumption, which is damaging for IoT devices.
Avoiding designs in which a small message can trigger a large
amount of traffic towards an unverified address, as this could be
exploited in amplification attacks.
IANA ConsiderationsThis document has no IANA actions.ReferencesNormative ReferencesMulticast DNSAs networked devices become smaller, more portable, and more ubiquitous, the ability to operate with less configured infrastructure is increasingly important. In particular, the ability to look up DNS resource record data types (including, but not limited to, host names) in the absence of a conventional managed DNS server is useful.Multicast DNS (mDNS) provides the ability to perform DNS-like operations on the local link in the absence of any conventional Unicast DNS server. In addition, Multicast DNS designates a portion of the DNS namespace to be free for local use, without the need to pay any annual fee, and without the need to set up delegations or otherwise configure a conventional DNS server to answer for those names.The primary benefits of Multicast DNS names are that (i) they require little or no administration or configuration to set them up, (ii) they work when no infrastructure is present, and (iii) they work during infrastructure failures.DNS-Based Service DiscoveryThis document specifies how DNS resource records are named and structured to facilitate service discovery. Given a type of service that a client is looking for, and a domain in which the client is looking for that service, this mechanism allows clients to discover a list of named instances of that desired service, using standard DNS queries. This mechanism is referred to as DNS-based Service Discovery, or DNS-SD.Informative ReferencesTLS Encrypted Client HelloRTFM, Inc.FastlyCloudflareCloudflare This document describes a mechanism in Transport Layer Security (TLS)
for encrypting a ClientHello message under a server public key.
Work in ProgressEfficient Privacy-Preserving Configurationless Service Discovery Supporting Multi-Link NetworksAdding Privacy to Multicast DNS Service DiscoveryEfficient Privacy Preserving Multicast DNS Service DiscoveryDomain Administrators Operations GuideThis RFC provides guidelines for domain administrators in operating a domain server and maintaining their portion of the hierarchical database. Familiarity with the domain system is assumed (see RFCs 1031, 1032, 1034, and 1035).Domain names - concepts and facilitiesThis RFC is the revised basic definition of The Domain Name System. It obsoletes RFC-882. This memo describes the domain style names and their used for host address look up and electronic mail forwarding. It discusses the clients and servers in the domain name system and the protocol used between them.Domain names - implementation and specificationThis RFC is the revised specification of the protocol and format used in the implementation of the Domain Name System. It obsoletes RFC-883. This memo documents the details of the domain name client - server communication.A DNS RR for specifying the location of services (DNS SRV)This document describes a DNS RR which specifies the location of the server(s) for a specific protocol and domain. [STANDARDS-TRACK]Dynamic Configuration of IPv4 Link-Local AddressesTo participate in wide-area IP networking, a host needs to be configured with IP addresses for its interfaces, either manually by the user or automatically from a source on the network such as a Dynamic Host Configuration Protocol (DHCP) server. Unfortunately, such address configuration information may not always be available. It is therefore beneficial for a host to be able to depend on a useful subset of IP networking functions even when no address configuration is available. This document describes how a host may automatically configure an interface with an IPv4 address within the 169.254/16 prefix that is valid for communication with other devices connected to the same physical (or logical) link.IPv4 Link-Local addresses are not suitable for communication with devices not directly connected to the same physical (or logical) link, and are only used where stable, routable addresses are not available (such as on ad hoc or isolated networks). This document does not recommend that IPv4 Link-Local addresses and routable addresses be configured simultaneously on the same interface. [STANDARDS-TRACK]IP Version 6 Addressing ArchitectureThis specification defines the addressing architecture of the IP Version 6 (IPv6) protocol. The document includes the IPv6 addressing model, text representations of IPv6 addresses, definition of IPv6 unicast addresses, anycast addresses, and multicast addresses, and an IPv6 node's required addresses.This document obsoletes RFC 3513, "IP Version 6 Addressing Architecture". [STANDARDS-TRACK]Using the Secure Remote Password (SRP) Protocol for TLS AuthenticationThis memo presents a technique for using the Secure Remote Password protocol as an authentication method for the Transport Layer Security protocol. This memo provides information for the Internet community.Requirements for Scalable DNS-Based Service Discovery (DNS-SD) / Multicast DNS (mDNS) ExtensionsDNS-based Service Discovery (DNS-SD) over Multicast DNS (mDNS) is widely used today for discovery and resolution of services and names on a local link, but there are use cases to extend DNS-SD/mDNS to enable service discovery beyond the local link. This document provides a problem statement and a list of requirements for scalable DNS-SD.Anonymity Profiles for DHCP ClientsSome DHCP options carry unique identifiers. These identifiers can enable device tracking even if the device administrator takes care of randomizing other potential identifications like link-layer addresses or IPv6 addresses. The anonymity profiles are designed for clients that wish to remain anonymous to the visited network. The profiles provide guidelines on the composition of DHCP or DHCPv6 messages, designed to minimize disclosure of identifying information.Current Hostname Practice Considered HarmfulGiving a hostname to your computer and publishing it as you roam from one network to another is the Internet's equivalent of walking around with a name tag affixed to your lapel. This current practice can significantly compromise your privacy, and something should change in order to mitigate these privacy threats.There are several possible remedies, such as fixing a variety of protocols or avoiding disclosing a hostname at all. This document describes some of the protocols that reveal hostnames today and sketches another possible remedy, which is to replace static hostnames by frequently changing randomized values.Schnorr Non-interactive Zero-Knowledge ProofThis document describes the Schnorr non-interactive zero-knowledge (NIZK) proof, a non-interactive variant of the three-pass Schnorr identification scheme. The Schnorr NIZK proof allows one to prove the knowledge of a discrete logarithm without leaking any information about its value. It can serve as a useful building block for many cryptographic protocols to ensure that participants follow the protocol specification honestly. This document specifies the Schnorr NIZK proof in both the finite field and the elliptic curve settings.J-PAKE: Password-Authenticated Key Exchange by JugglingThis document specifies a Password-Authenticated Key Exchange by Juggling (J-PAKE) protocol. This protocol allows the establishment of a secure end-to-end communication channel between two remote parties over an insecure network solely based on a shared password, without requiring a Public Key Infrastructure (PKI) or any trusted third party.Understanding Sleep Proxy ServiceService Registration Protocol for DNS-Based Service DiscoveryApple Inc.Apple Inc. The Service Registration Protocol for DNS-Based Service Discovery
uses the standard DNS Update mechanism to enable DNS-Based Service
Discovery using only unicast packets. This makes it possible to
deploy DNS Service Discovery without multicast, which greatly
improves scalability and improves performance on networks where
multicast service is not an optimal choice, particularly 802.11
(Wi-Fi) and 802.15.4 (IoT) networks. DNS-SD Service registration
uses public keys and SIG(0) to allow services to defend their
registrations against attack.
Work in ProgressAcknowledgmentsThis document incorporates many contributions from and . Thanks to for extensive
review and suggestions on the organization of the threat model. Thanks
to for an extensive review. Thanks to
, ,
, and
for their comments during IESG review.Authors' AddressesPrivate Octopus Inc.Friday Harbor98250WAUnited States of Americahuitema@huitema.nethttp://privateoctopus.com/University of Luxembourg6, avenue de la FonteEsch-sur-Alzette4364Luxembourgdaniel.kaiser@uni.luhttps://secan-lab.uni.lu/