draft-ietf-6man-rfc4941bis-05.txt   draft-ietf-6man-rfc4941bis-06.txt 
IPv6 Maintenance (6man) Working Group F. Gont IPv6 Maintenance (6man) Working Group F. Gont
Internet-Draft SI6 Networks / UTN-FRH Internet-Draft SI6 Networks / UTN-FRH
Obsoletes: rfc4941 (if approved) S. Krishnan Obsoletes: rfc4941 (if approved) S. Krishnan
Intended status: Standards Track Ericsson Research Intended status: Standards Track Ericsson Research
Expires: June 12, 2020 T. Narten Expires: August 12, 2020 T. Narten
IBM Corporation IBM Corporation
R. Draves R. Draves
Microsoft Research Microsoft Research
December 10, 2019 February 9, 2020
Privacy Extensions for Stateless Address Autoconfiguration in IPv6 Privacy Extensions for Stateless Address Autoconfiguration in IPv6
draft-ietf-6man-rfc4941bis-05 draft-ietf-6man-rfc4941bis-06
Abstract Abstract
Nodes use IPv6 stateless address autoconfiguration to generate Nodes use IPv6 stateless address autoconfiguration to generate
addresses using a combination of locally available information and addresses using a combination of locally available information and
information advertised by routers. Addresses are formed by combining information advertised by routers. Addresses are formed by combining
network prefixes with an interface identifier. This document network prefixes with an interface identifier. This document
describes an extension that causes nodes to generate global scope describes an extension that causes nodes to generate global scope
addresses with randomized interface identifiers that change over addresses with randomized interface identifiers that change over
time. Changing global scope addresses over time makes it more time. Changing global scope addresses over time makes it more
difficult for eavesdroppers and other information collectors to difficult for eavesdroppers and other information collectors to
identify when different addresses used in different transactions identify when different addresses used in different transactions
actually correspond to the same node. This document formally correspond to the same node. This document obsoletes RFC4941.
obsoletes RFC4941.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 12, 2020. This Internet-Draft will expire on August 12, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Problem Statement . . . . . . . . . . . . . . . . . . . . 3 1.2. Problem Statement . . . . . . . . . . . . . . . . . . . . 4
2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Extended Use of the Same Identifier . . . . . . . . . . . 4 2.1. Extended Use of the Same Identifier . . . . . . . . . . . 4
2.2. Possible Approaches . . . . . . . . . . . . . . . . . . . 6 2.2. Possible Approaches . . . . . . . . . . . . . . . . . . . 6
3. Protocol Description . . . . . . . . . . . . . . . . . . . . 6 3. Protocol Description . . . . . . . . . . . . . . . . . . . . 6
3.1. Assumptions . . . . . . . . . . . . . . . . . . . . . . . 7 3.1. Design Guidelines . . . . . . . . . . . . . . . . . . . . 6
3.2. Generation of Randomized Interface Identifiers . . . . . 8 3.2. Assumptions . . . . . . . . . . . . . . . . . . . . . . . 7
3.2.1. Simple Randomized Interface Identifiers . . . . . . . 8 3.3. Generation of Randomized Interface Identifiers . . . . . 8
3.2.2. Hash-based Generation of Randomized Interface 3.3.1. Simple Randomized Interface Identifiers . . . . . . . 8
3.3.2. Hash-based Generation of Randomized Interface
Identifiers . . . . . . . . . . . . . . . . . . . . . 9 Identifiers . . . . . . . . . . . . . . . . . . . . . 9
3.3. Generating Temporary Addresses . . . . . . . . . . . . . 10 3.4. Generating Temporary Addresses . . . . . . . . . . . . . 10
3.4. Expiration of Temporary Addresses . . . . . . . . . . . . 12 3.5. Expiration of Temporary Addresses . . . . . . . . . . . . 12
3.5. Regeneration of Temporary Addresses . . . . . . . . . . . 12 3.6. Regeneration of Temporary Addresses . . . . . . . . . . . 12
3.6. Deployment Considerations . . . . . . . . . . . . . . . . 13 3.7. Implementation Considerations . . . . . . . . . . . . . . 14
4. Implications of Changing Interface Identifiers . . . . . . . 14 3.8. Defined Constants . . . . . . . . . . . . . . . . . . . . 14
5. Defined Constants . . . . . . . . . . . . . . . . . . . . . . 15 4. Implications of Changing Interface Identifiers . . . . . . . 15
6. Future Work . . . . . . . . . . . . . . . . . . . . . . . . . 15 5. Significant Changes from RFC4941 . . . . . . . . . . . . . . 16
6. Future Work . . . . . . . . . . . . . . . . . . . . . . . . . 16
7. Security Considerations . . . . . . . . . . . . . . . . . . . 16 7. Security Considerations . . . . . . . . . . . . . . . . . . . 16
8. Significant Changes from RFC4941 . . . . . . . . . . . . . . 16 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 9.1. Normative References . . . . . . . . . . . . . . . . . . 17
10.1. Normative References . . . . . . . . . . . . . . . . . . 17 9.2. Informative References . . . . . . . . . . . . . . . . . 19
10.2. Informative References . . . . . . . . . . . . . . . . . 18 Appendix A. Changes from RFC4941 [to be removed by the RFC-
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 Editor before publication . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
1. Introduction 1. Introduction
Stateless address autoconfiguration [RFC4862] defines how an IPv6 Stateless address autoconfiguration (SLAAC) [RFC4862] defines how an
node generates addresses without the need for a Dynamic Host IPv6 node generates addresses without the need for a Dynamic Host
Configuration Protocol for IPv6 (DHCPv6) server. The security and Configuration Protocol for IPv6 (DHCPv6) server. The security and
privacy implications of such addresses have been discussed in great privacy implications of such addresses have been discussed in great
detail in [RFC7721],[RFC7217], and RFC7707. This document specifies detail in [RFC7721],[RFC7217], and RFC7707. This document specifies
an extension for SLAAC to generate temporary addresses, such that the an extension for SLAAC to generate temporary addresses, such that the
aforementioned issues are mitigated. aforementioned issues are mitigated. This is a revision of RFC4941,
and formally obsoletes RFC4941. Section 5 describes the changes from
[RFC4941].
The default address selection for IPv6 has been specified in The default address selection for IPv6 has been specified in
[RFC6724]. We note that the determination as to whether to use [RFC6724]. The determination as to whether to use stable versus
stable versus temporary addresses can in some cases only be made by temporary addresses can in some cases only be made by an application.
an application. For example, some applications may always want to For example, some applications may always want to use temporary
use temporary addresses, while others may want to use them only in addresses, while others may want to use them only in some
some circumstances or not at all. An API such as that specified in circumstances or not at all. An API such as that specified in
[RFC5014] can enable individual applications to indicate with [RFC5014] can enable individual applications to indicate a preference
sufficient granularity their needs with regards to the use of for the use of temporary addresses.
temporary addresses.
Section 2 provides background information on the issue. Section 3 Section 2 provides background information on the issue. Section 3
describes a procedure for generating temporary interface identifiers describes a procedure for generating temporary interface identifiers
and global scope addresses. Section 4 discusses implications of and global scope addresses. Section 4 discusses implications of
changing interface identifiers. changing interface identifiers. Section 5 describes the changes from
[RFC4941].
1.1. Terminology 1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
The terms "public address", "stable address", "temporary address", The terms "public address", "stable address", "temporary address",
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interpreted as specified in [RFC7721]. interpreted as specified in [RFC7721].
The term "global scope addresses" is used in this document to The term "global scope addresses" is used in this document to
collectively refer to "Global unicast addresses" as defined in collectively refer to "Global unicast addresses" as defined in
[RFC4291] and "Unique local addresses" as defined in [RFC4193], and [RFC4291] and "Unique local addresses" as defined in [RFC4193], and
not to "globally reachable" as defined in [RFC8190]. not to "globally reachable" as defined in [RFC8190].
1.2. Problem Statement 1.2. Problem Statement
Addresses generated using stateless address autoconfiguration Addresses generated using stateless address autoconfiguration
[RFC4862] contain an embedded interface identifier, which remains [RFC4862] contain an embedded interface identifier, which may remain
stable over time. Anytime a fixed identifier is used in multiple stable over time. Anytime a fixed identifier is used in multiple
contexts, it becomes possible to correlate seemingly unrelated contexts, it becomes possible to correlate seemingly unrelated
activity using this identifier. activity using this identifier.
The correlation can be performed by The correlation can be performed by
o An attacker who is in the path between the node in question and o An attacker who is in the path between the node in question and
the peer(s) to which it is communicating, and who can view the the peer(s) to which it is communicating, and who can view the
IPv6 addresses present in the datagrams. IPv6 addresses present in the datagrams.
o An attacker who can access the communication logs of the peers o An attacker who can access the communication logs of the peers
with which the node has communicated. with which the node has communicated.
Since the identifier is embedded within the IPv6 address, which is a Since the identifier is embedded within the IPv6 address, it cannot
fundamental requirement of communication, it cannot be easily hidden. be hidden. This document proposes a solution to this issue by
This document proposes a solution to this issue by generating generating interface identifiers that vary over time.
interface identifiers that vary over time.
Note that an attacker, who is on path, may be able to perform Note that an attacker, who is on path, may be able to perform
significant correlation based on significant correlation on unencrypted packets based on
o The payload contents of the packets on the wire o The payload contents of the packets on the wire
o The characteristics of the packets such as packet size and timing o The characteristics of the packets such as packet size and timing
Use of temporary addresses will not prevent such payload-based Use of temporary addresses will not prevent such payload-based
correlation, which can only be addressed by widespread deployment of correlation, which can only be addressed by widespread deployment of
encryption as advocated in [RFC7624]. encryption as advocated in [RFC7624]. Nor will it prevent an on-link
observer (e.g. the node's default router) to track all the node's
addresses.
2. Background 2. Background
This section discusses the problem in more detail, provides context This section discusses the problem in more detail, and provides
for evaluating the significance of the concerns in specific context for evaluating the significance of the concerns in specific
environments and makes comparisons with existing practices. environments and makes comparisons with existing practices.
2.1. Extended Use of the Same Identifier 2.1. Extended Use of the Same Identifier
The use of a non-changing interface identifier to form addresses is a The use of a non-changing interface identifier to form addresses is a
specific instance of the more general case where a constant specific instance of the more general case where a constant
identifier is reused over an extended period of time and in multiple identifier is reused over an extended period of time and in multiple
independent activities. Any time the same identifier is used in independent activities. Any time the same identifier is used in
multiple contexts, it becomes possible for that identifier to be used multiple contexts, it becomes possible for that identifier to be used
to correlate seemingly unrelated activity. For example, a network to correlate seemingly unrelated activity. For example, a network
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that changing an address regularly in such environments would be that changing an address regularly in such environments would be
desirable to lessen privacy concerns, it should be noted that the desirable to lessen privacy concerns, it should be noted that the
network prefix portion of an address also serves as a constant network prefix portion of an address also serves as a constant
identifier. All nodes at, say, a home, would have the same network identifier. All nodes at, say, a home, would have the same network
prefix, which identifies the topological location of those nodes. prefix, which identifies the topological location of those nodes.
This has implications for privacy, though not at the same granularity This has implications for privacy, though not at the same granularity
as the concern that this document addresses. Specifically, all nodes as the concern that this document addresses. Specifically, all nodes
within a home could be grouped together for the purposes of within a home could be grouped together for the purposes of
collecting information. If the network contains a very small number collecting information. If the network contains a very small number
of nodes, say, just one, changing just the interface identifier will of nodes, say, just one, changing just the interface identifier will
not enhance privacy at all, since the prefix serves as a constant not enhance privacy, since the prefix serves as a constant
identifier. identifier.
One of the requirements for correlating seemingly unrelated One of the requirements for correlating seemingly unrelated
activities is the use (and reuse) of an identifier that is activities is the use (and reuse) of an identifier that is
recognizable over time within different contexts. IP addresses recognizable over time within different contexts. IP addresses
provide one obvious example, but there are more. Many nodes also provide one obvious example, but there are more. Many nodes also
have DNS names associated with their addresses, in which case the DNS have DNS names associated with their addresses, in which case the DNS
name serves as a similar identifier. Although the DNS name name serves as a similar identifier. Although the DNS name
associated with an address is more work to obtain (it may require a associated with an address is more work to obtain (it may require a
DNS query), the information is often readily available. In such DNS query), the information is often readily available. In such
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The use of a constant identifier within an address is of special The use of a constant identifier within an address is of special
concern because addresses are a fundamental requirement of concern because addresses are a fundamental requirement of
communication and cannot easily be hidden from eavesdroppers and communication and cannot easily be hidden from eavesdroppers and
other parties. Even when higher layers encrypt their payloads, other parties. Even when higher layers encrypt their payloads,
addresses in packet headers appear in the clear. Consequently, if a addresses in packet headers appear in the clear. Consequently, if a
mobile host (e.g., laptop) accessed the network from several mobile host (e.g., laptop) accessed the network from several
different locations, an eavesdropper might be able to track the different locations, an eavesdropper might be able to track the
movement of that mobile host from place to place, even if the upper movement of that mobile host from place to place, even if the upper
layer payloads were encrypted. layer payloads were encrypted.
Using temporary address alone may not be sufficient to prevent all
forms of tracking. It is however quite clear that some usage of
temporary addresses is necessary to improve user privacy.
The security and privacy implications of IPv6 addresses are discussed The security and privacy implications of IPv6 addresses are discussed
in detail in [RFC7721], [RFC7707], and [RFC7217]. in detail in [RFC7721], [RFC7707], and [RFC7217].
2.2. Possible Approaches Using temporary addresses alone is not sufficient to prevent all
forms of tracking. It is however clear that temporary addresses are
useful to improve user privacy.
One way to avoid having a stable non-changing address is to use 2.2. Possible Approaches
DHCPv6 [RFC8415] for obtaining addresses. Section 12 of [RFC8415]
discusses the use of DHCPv6 for the assignment and management of
"temporary addresses", which are never renewed and provide the same
property of temporary addresses described in this document with
regards to the privacy concern.
Another approach, compatible with the stateless address One approach, compatible with the stateless address autoconfiguration
autoconfiguration architecture, would be to change the interface architecture, would be to change the interface identifier portion of
identifier portion of an address over time. Changing the interface an address over time. Changing the interface identifier can make it
identifier can make it more difficult to look at the IP addresses in more difficult to look at the IP addresses in independent
independent transactions and identify which ones actually correspond transactions and identify which ones actually correspond to the same
to the same node, both in the case where the routing prefix portion node, both in the case where the routing prefix portion of an address
of an address changes and when it does not. changes and when it does not.
Many machines function as both clients and servers. In such cases, Many machines function as both clients and servers. In such cases,
the machine would need a DNS name for its use as a server. Whether the machine would need a DNS name for its use as a server. Whether
the address stays fixed or changes has little privacy implication the address stays fixed or changes has little privacy implication
since the DNS name remains constant and serves as a constant since the DNS name remains constant and serves as a constant
identifier. When acting as a client (e.g., initiating identifier. When acting as a client (e.g., initiating
communication), however, such a machine may want to vary the communication), however, such a machine may want to vary the
addresses it uses. In such environments, one may need multiple addresses it uses. In such environments, one may need multiple
addresses: a stable address registered in the DNS, that is used to addresses: a stable address registered in the DNS, that is used to
accept incoming connection requests from other machines, and a accept incoming connection requests from other machines, and a
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to employ only temporary addresses for public communication. to employ only temporary addresses for public communication.
To make it difficult to make educated guesses as to whether two To make it difficult to make educated guesses as to whether two
different interface identifiers belong to the same node, the different interface identifiers belong to the same node, the
algorithm for generating alternate identifiers must include input algorithm for generating alternate identifiers must include input
that has an unpredictable component from the perspective of the that has an unpredictable component from the perspective of the
outside entities that are collecting information. outside entities that are collecting information.
3. Protocol Description 3. Protocol Description
The goal of this section is to define procedures that can generate The following subsections define the procedures for the generation of
IPv6 addresses with the following properties: IPv6 temporary addresses.
1. Temporary addresses can be employed for initiating outgoing 3.1. Design Guidelines
sessions.
Temporary addresses observe the following properties:
1. Temporary addresses are typically employed for initiating
outgoing sessions.
2. Temporary addresses are used for a short period of time 2. Temporary addresses are used for a short period of time
(typically hours to days) and are subsequently deprecated. (typically hours to days) and are subsequently deprecated.
Deprecated addresses can continue to be used for established
Deprecated addresses can continue to be used for already connections, but are not used to initiate new connections.
established connections, but are not used to initiate new
connections.
3. New temporary addresses are generated periodically to replace 3. New temporary addresses are generated periodically to replace
temporary addresses that expire. temporary addresses that expire.
4. Temporary addresses must have a limited lifetime (limited "valid 4. Temporary addresses must have a limited lifetime (limited "valid
lifetime" and "preferred lifetime" from [RFC4862]), that should lifetime" and "preferred lifetime" from [RFC4862]), that should
be statistically different for different addresses. The lifetime be statistically different for different addresses. The lifetime
of an address should be further reduced when privacy-meaningful of an address should be further reduced when privacy-meaningful
events (such as a node attaching to a different network, or the events (such as a node attaching to a different network, or the
regeneration of a new randomized MAC address) takes place. regeneration of a new randomized MAC address) takes place.
5. By default, one address is generated for each prefix advertised 5. By default, one address is generated for each prefix advertised
for stateless address autoconfiguration. The resulting Interface by stateless address autoconfiguration. The resulting Interface
Identifiers must be statistically different when addresses are Identifiers must be statistically different when addresses are
configured for different prefixes. That is, when temporary configured for different prefixes. That is, when temporary
addresses are generated for different autoconfiguration prefixes addresses are generated for different autoconfiguration prefixes
for the same network interface, the resulting Interface for the same network interface, the resulting Interface
Identifiers must be statistically different. This means that, Identifiers must be statistically different. This means that,
given two addresses that employ different prefixes, it must be given two addresses that employ different prefixes, it must be
difficult for an outside entity to tell whether the addresses difficult for an outside entity to tell whether the addresses
correspond to the same network interface or even whether they correspond to the same network interface or even whether they
have been generated by the same host. have been generated by the same host.
6. It must be difficult for an outside entity to predict the 6. It must be difficult for an outside entity to predict the
Interface Identifiers that will be employed for temporary Interface Identifiers that will be employed for temporary
addresses, even with knowledge of the algorithm/method employed addresses, even with knowledge of the algorithm/method employed
to generate them and/or knowledge of the Interface Identifiers to generate them and/or knowledge of the Interface Identifiers
previously employed for other temporary addresses. These previously employed for other temporary addresses. These
Interface Identifiers must be semantically opaque [RFC7136] and Interface Identifiers must be semantically opaque [RFC7136] and
must not follow any specific patterns. must not follow any specific patterns.
3.1. Assumptions 3.2. Assumptions
The following algorithm assumes that for a given temporary address, The following algorithm assumes that for a given temporary address,
an implementation can determine the prefix from which it was an implementation can determine the prefix from which it was
generated. When a temporary address is deprecated, a new temporary generated. When a temporary address is deprecated, a new temporary
address is generated. The specific valid and preferred lifetimes for address is generated. The specific valid and preferred lifetimes for
the new address are dependent on the corresponding lifetime values the new address are dependent on the corresponding lifetime values
set for the prefix from which it was generated. set for the prefix from which it was generated.
Finally, this document assumes that when a node initiates outgoing Finally, this document assumes that when a node initiates outgoing
communication, temporary addresses can be given preference over communication, temporary addresses can be given preference over
stable addresses (if available), when the device is configured to do stable addresses (if available), when the device is configured to do
so. [RFC6724] mandates implementations to provide a mechanism, which so. [RFC6724] mandates implementations to provide a mechanism, which
allows an application to configure its preference for temporary allows an application to configure its preference for temporary
addresses over stable addresses. It also allows for an addresses over stable addresses. It also allows for an
implementation to prefer temporary addresses by default, so that the implementation to prefer temporary addresses by default, so that the
connections initiated by the node can use temporary addresses without connections initiated by the node can use temporary addresses without
requiring application-specific enablement. This document also requiring application-specific enablement. This document also
assumes that an API will exist that allows individual applications to assumes that an API will exist that allows individual applications to
indicate whether they prefer to use temporary or stable addresses and indicate whether they prefer to use temporary or stable addresses and
override the system defaults. override the system defaults (see e.g. [RFC5014]).
3.2. Generation of Randomized Interface Identifiers 3.3. Generation of Randomized Interface Identifiers
The following subsections specify some possible algorithms for The following subsections specify example algorithms for generating
generating temporary interface identifiers that follow the guidelines temporary interface identifiers that follow the guidelines in
in Section 3 of this document. The algorithm specified in Section 3.1 of this document. The algorithm specified in
Section 3.2.1 benefits from a Pseudo-Random Number Generator (PRNG) Section 3.3.1 benefits from a Pseudo-Random Number Generator (PRNG)
available on the system. On the other hand, the algorithm specified available on the system. The algorithm specified in Section 3.3.2
in Section 3.2.2 allows for code reuse by nodes that implement allows for code reuse by nodes that implement [RFC7217].
[RFC7217].
3.2.1. Simple Randomized Interface Identifiers 3.3.1. Simple Randomized Interface Identifiers
One possible approach would be to select a pseudorandom number of the One approach is to select a pseudorandom number of the appropriate
appropriate length. A node employing this algorithm should generate length. A node employing this algorithm should generate IIDs as
IIDs as follows: follows:
1. Obtain a random number (see [RFC4086] for randomness requirements 1. Obtain a random number (see [RFC4086] for randomness requirements
for security) for security).
2. The Interface Identifier is obtained by taking as many bits from 2. The Interface Identifier is obtained by taking as many bits from
the aforementioned random number (obtained in the previous step) the random number obtained in the previous step as necessary.
as necessary. Note: there are no special bits in an Interface Note: there are no special bits in an Interface Identifier
Identifier [RFC7136]. [RFC7136].
We note that [RFC4291] requires that the Interface IDs of all We note that [RFC4291] requires that the Interface IDs of all
unicast addresses (except those that start with the binary unicast addresses (except those that start with the binary
value 000) be 64 bits long. However, the method discussed in value 000) be 64 bits long. However, the method discussed in
this document could be employed for generating Interface IDs this document could be employed for generating Interface IDs
of any arbitrary length, albeit at the expense of reduced of any arbitrary length, albeit at the expense of reduced
entropy (when employing Interface IDs smaller than 64 bits). entropy (when employing Interface IDs smaller than 64 bits).
The privacy implications of the IID length are discussed in
[RFC7421].
3. The resulting Interface Identifier SHOULD be compared against the 3. The resulting Interface Identifier SHOULD be compared against the
reserved IPv6 Interface Identifiers [RFC5453] [IANA-RESERVED-IID] reserved IPv6 Interface Identifiers [RFC5453] [IANA-RESERVED-IID]
and against those Interface Identifiers already employed in an and against those Interface Identifiers already employed in an
address of the same network interface and the same network address of the same network interface and the same network
prefix. In the event that an unacceptable identifier has been prefix. In the event that an unacceptable identifier has been
generated, a new interface identifier should be generated, by generated, a new interface identifier should be generated, by
repeating the algorithm from the first step. repeating the algorithm from the first step.
3.2.2. Hash-based Generation of Randomized Interface Identifiers 3.3.2. Hash-based Generation of Randomized Interface Identifiers
The algorithm in [RFC7217] can be augmented for the generation of The algorithm in [RFC7217] can be augmented for the generation of
temporary addresses. The benefit of this would be that a node could temporary addresses. The benefit of this would be that a node could
employ a single algorithm for generating stable and temporary employ a single algorithm for generating stable and temporary
addresses, by employing appropriate parameters. addresses, by employing appropriate parameters.
Nodes would employ the following algorithm for generating the Nodes would employ the following algorithm for generating the
temporary IID: temporary IID:
1. Compute a random identifier with the expression: 1. Compute a random identifier with the expression:
RID = F(Prefix, MAC_Address, Network_ID, Time, DAD_Counter, RID = F(Prefix, Net_Iface, Network_ID, Time, DAD_Counter,
secret_key) secret_key)
Where: Where:
RID: RID:
Random Identifier Random Identifier
F(): F():
A pseudorandom function (PRF) that MUST NOT be computable from A pseudorandom function (PRF) that MUST NOT be computable from
the outside (without knowledge of the secret key). F() MUST the outside (without knowledge of the secret key). F() MUST
also be difficult to reverse, such that it resists attempts to also be difficult to reverse, such that it resists attempts to
obtain the secret_key, even when given samples of the output obtain the secret_key, even when given samples of the output
of F() and knowledge or control of the other input parameters. of F() and knowledge or control of the other input parameters.
F() SHOULD produce an output of at least 64 bits. F() could F() SHOULD produce an output of at least 64 bits. F() could
be implemented as a cryptographic hash of the concatenation of be implemented as a cryptographic hash of the concatenation of
each of the function parameters. SHA-1 [FIPS-SHS] and SHA-256 each of the function parameters. SHA-256 [FIPS-SHS] is one
are two possible options for F(). Note: MD5 [RFC1321] is possible option for F(). Note: MD5 [RFC1321] is considered
considered unacceptable for F() [RFC6151]. unacceptable for F() [RFC6151].
Prefix: Prefix:
The prefix to be used for SLAAC, as learned from an ICMPv6 The prefix to be used for SLAAC, as learned from an ICMPv6
Router Advertisement message. Router Advertisement message.
MAC_Address: Net_Iface:
The MAC address corresponding to the underlying network The MAC address corresponding to the underlying network
interface card. Employing the MAC address in this expression interface card, in the case the link uses IEEE802 link-layer
(in replacement of the Net_Iface parameter of the expression identifiers. Employing the MAC address for this parameter
in RFC7217) means that the re-generation of a randomized MAC (over the other suggested options in RFC7217) means that the
address will result in a different temporary address. re-generation of a randomized MAC address will result in a
different temporary address.
Network_ID: Network_ID:
Some network-specific data that identifies the subnet to which Some network-specific data that identifies the subnet to which
this interface is attached -- for example, the IEEE 802.11 this interface is attached -- for example, the IEEE 802.11
Service Set Identifier (SSID) corresponding to the network to Service Set Identifier (SSID) corresponding to the network to
which this interface is associated. Additionally, Simple DNA which this interface is associated. Additionally, Simple DNA
[RFC6059] describes ideas that could be leveraged to generate [RFC6059] describes ideas that could be leveraged to generate
a Network_ID parameter. This parameter is SHOULD be employed a Network_ID parameter. This parameter is SHOULD be employed
if some form of "Network_ID" is available. if some form of "Network_ID" is available.
Time: Time:
An implementation-dependent representation of time. One An implementation-dependent representation of time. One
possible example is the representation in UNIX-like systems possible example is the representation in UNIX-like systems
[OPEN-GROUP], that measure time in terms of the number of [OPEN-GROUP], that measure time in terms of the number of
seconds elapsed since the Epoch (00:00:00 Coordinated seconds elapsed since the Epoch (00:00:00 Coordinated
Universal Time (UTC), 1 January 1970). Universal Time (UTC), 1 January 1970). The addition of the
"Time" argument results in (statistically) different interface
identifiers over time.
DAD_Counter: DAD_Counter:
A counter that is employed to resolve Duplicate Address A counter that is employed to resolve Duplicate Address
Detection (DAD) conflicts. Detection (DAD) conflicts.
secret_key: secret_key:
A secret key that is not known by the attacker. The secret A secret key that is not known by the attacker. The secret
key SHOULD be of at least 128 bits. It MUST be initialized to key SHOULD be of at least 128 bits. It MUST be initialized to
a pseudo-random number (see [RFC4086] for randomness a pseudo-random number (see [RFC4086] for randomness
requirements for security) when the operating system is requirements for security) when the operating system is
skipping to change at page 10, line 38 skipping to change at page 10, line 45
bits from the RID value (computed in the previous step) as bits from the RID value (computed in the previous step) as
necessary, starting from the least significant bit. The necessary, starting from the least significant bit. The
resulting Interface Identifier SHOULD be compared against the resulting Interface Identifier SHOULD be compared against the
reserved IPv6 Interface Identifiers [RFC5453] [IANA-RESERVED-IID] reserved IPv6 Interface Identifiers [RFC5453] [IANA-RESERVED-IID]
and against those Interface Identifiers already employed in an and against those Interface Identifiers already employed in an
address of the same network interface and the same network address of the same network interface and the same network
prefix. In the event that an unacceptable identifier has been prefix. In the event that an unacceptable identifier has been
generated, the value DAD_Counter should be incremented by 1, and generated, the value DAD_Counter should be incremented by 1, and
the algorithm should be restarted from the first step. the algorithm should be restarted from the first step.
3.3. Generating Temporary Addresses 3.4. Generating Temporary Addresses
[RFC4862] describes the steps for generating a link-local address [RFC4862] describes the steps for generating a link-local address
when an interface becomes enabled as well as the steps for generating when an interface becomes enabled as well as the steps for generating
addresses for other scopes. This document extends [RFC4862] as addresses for other scopes. This document extends [RFC4862] as
follows. When processing a Router Advertisement with a Prefix follows. When processing a Router Advertisement with a Prefix
Information option carrying a global scope prefix for the purposes of Information option carrying a prefix for the purposes of address
address autoconfiguration (i.e., the A bit is set), the node MUST autoconfiguration (i.e., the A bit is set), the node MUST perform the
perform the following steps: following steps:
1. Process the Prefix Information Option as defined in [RFC4862], 1. Process the Prefix Information Option as defined in [RFC4862],
adjusting the lifetimes of existing temporary addresses. If a adjusting the lifetimes of existing temporary addresses. If a
received option may extend the lifetimes of temporary addresses, received option may extend the lifetimes of temporary addresses,
with the overall constraint that no temporary addresses should with the overall constraint that no temporary addresses should
ever remain "valid" or "preferred" for a time longer than ever remain "valid" or "preferred" for a time longer than
(TEMP_VALID_LIFETIME) or (TEMP_PREFERRED_LIFETIME - (TEMP_VALID_LIFETIME) or (TEMP_PREFERRED_LIFETIME -
DESYNC_FACTOR) respectively. The configuration variables DESYNC_FACTOR) respectively. The configuration variables
TEMP_VALID_LIFETIME and TEMP_PREFERRED_LIFETIME correspond to TEMP_VALID_LIFETIME and TEMP_PREFERRED_LIFETIME correspond to
approximate target lifetimes for temporary addresses. approximate target lifetimes for temporary addresses.
skipping to change at page 11, line 42 skipping to change at page 11, line 50
* Its Preferred Lifetime is the lower of the Preferred Lifetime * Its Preferred Lifetime is the lower of the Preferred Lifetime
of the prefix and TEMP_PREFERRED_LIFETIME - DESYNC_FACTOR. of the prefix and TEMP_PREFERRED_LIFETIME - DESYNC_FACTOR.
5. A temporary address is created only if this calculated Preferred 5. A temporary address is created only if this calculated Preferred
Lifetime is greater than REGEN_ADVANCE time units. In Lifetime is greater than REGEN_ADVANCE time units. In
particular, an implementation MUST NOT create a temporary address particular, an implementation MUST NOT create a temporary address
with a zero Preferred Lifetime. with a zero Preferred Lifetime.
6. New temporary addresses MUST be created by appending a randomized 6. New temporary addresses MUST be created by appending a randomized
interface identifier (generates as described in Section 3.2 of interface identifier (generates as described in Section 3.3 of
this document) to the prefix that was received. this document) to the prefix that was received.
7. The node MUST perform duplicate address detection (DAD) on the 7. The node MUST perform duplicate address detection (DAD) on the
generated temporary address. If DAD indicates the address is generated temporary address. If DAD indicates the address is
already in use, the node MUST generate a new randomized interface already in use, the node MUST generate a new randomized interface
identifier, and repeat the previous steps as appropriate up to identifier, and repeat the previous steps as appropriate up to
TEMP_IDGEN_RETRIES times. If after TEMP_IDGEN_RETRIES TEMP_IDGEN_RETRIES times. If after TEMP_IDGEN_RETRIES
consecutive attempts no non-unique address was generated, the consecutive attempts no non-unique address was generated, the
node MUST log a system error and MUST NOT attempt to generate node MUST log a system error and MUST NOT attempt to generate
temporary addresses for that interface. Note that DAD MUST be temporary addresses for that interface. This allows hosts to
performed on every unicast address generated from this randomized recover from ocassional DAD failures, or otherwhise log the
interface identifier. recurrent address collissions.
3.4. Expiration of Temporary Addresses 3.5. Expiration of Temporary Addresses
When a temporary address becomes deprecated, a new one MUST be When a temporary address becomes deprecated, a new one MUST be
generated. This is done by repeating the actions described in generated. This is done by repeating the actions described in
Section 3.3, starting at step 4). Note that, except for the Section 3.4, starting at step 4). Note that, except for the
transient period when a temporary address is being regenerated, in transient period when a temporary address is being regenerated, in
normal operation at most one temporary address per prefix should be normal operation at most one temporary address per prefix should be
in a non-deprecated state at any given time on a given interface. in a non-deprecated state at any given time on a given interface.
Note that if a temporary address becomes deprecated as result of Note that if a temporary address becomes deprecated as result of
processing a Prefix Information Option with a zero Preferred processing a Prefix Information Option with a zero Preferred
Lifetime, then a new temporary address MUST NOT be generated. To Lifetime, then a new temporary address MUST NOT be generated. To
ensure that a preferred temporary address is always available, a new ensure that a preferred temporary address is always available, a new
temporary address SHOULD be regenerated slightly before its temporary address SHOULD be regenerated slightly before its
predecessor is deprecated. This is to allow sufficient time to avoid predecessor is deprecated. This is to allow sufficient time to avoid
race conditions in the case where generating a new temporary address race conditions in the case where generating a new temporary address
is not instantaneous, such as when duplicate address detection must is not instantaneous, such as when duplicate address detection must
be run. The node SHOULD start the address regeneration process be run. The node SHOULD start the address regeneration process
REGEN_ADVANCE time units before a temporary address would actually be REGEN_ADVANCE time units before a temporary address would actually be
deprecated. deprecated.
As an optional optimization, an implementation MAY remove a As an optional optimization, an implementation MAY remove a
deprecated temporary address that is not in use by applications or deprecated temporary address that is not in use by applications or
upper layers as detailed in Section 6. upper layers as detailed in Section 6.
3.5. Regeneration of Temporary Addresses 3.6. Regeneration of Temporary Addresses
The frequency at which temporary addresses change depends on how a The frequency at which temporary addresses change depends on how a
device is being used (e.g., how frequently it initiates new device is being used (e.g., how frequently it initiates new
communication) and the concerns of the end user. The most egregious communication) and the concerns of the end user. The most egregious
privacy concerns appear to involve addresses used for long periods of privacy concerns appear to involve addresses used for long periods of
time (weeks to months to years). The more frequently an address time (weeks to months to years). The more frequently an address
changes, the less feasible collecting or coordinating information changes, the less feasible collecting or coordinating information
keyed on interface identifiers becomes. Moreover, the cost of keyed on interface identifiers becomes. Moreover, the cost of
collecting information and attempting to correlate it based on collecting information and attempting to correlate it based on
interface identifiers will only be justified if enough addresses interface identifiers will only be justified if enough addresses
skipping to change at page 13, line 30 skipping to change at page 13, line 38
SHOULD provide end users with the ability to change the frequency at SHOULD provide end users with the ability to change the frequency at
which addresses are regenerated. The default value is given in which addresses are regenerated. The default value is given in
TEMP_PREFERRED_LIFETIME and is one day. In addition, the exact time TEMP_PREFERRED_LIFETIME and is one day. In addition, the exact time
at which to invalidate a temporary address depends on how at which to invalidate a temporary address depends on how
applications are used by end users. Thus, the suggested default applications are used by end users. Thus, the suggested default
value of one week (TEMP_VALID_LIFETIME) may not be appropriate in all value of one week (TEMP_VALID_LIFETIME) may not be appropriate in all
environments. Implementations SHOULD provide end users with the environments. Implementations SHOULD provide end users with the
ability to override both of these default values. ability to override both of these default values.
Finally, when an interface connects to a new (different) link, a new Finally, when an interface connects to a new (different) link, a new
set of temporary addresses MUST be generated immediately. If a set of temporary addresses MUST be generated immediately for use on
device moves from one ethernet to another, generating a new set of the new link. If a device moves from one link to another, generating
temporary addresses ensures that the device uses different randomized a new set of temporary addresses ensures that the device uses
interface identifiers for the temporary addresses associated with the different randomized interface identifiers for the temporary
two links, making it more difficult to correlate addresses from the addresses associated with the two links, making it more difficult to
two different links as being from the same node. The node MAY follow correlate addresses from the two different links as being from the
any process available to it, to determine that the link change has same node. The node MAY follow any process available to it, to
occurred. One such process is described by "Simple Procedures for determine that the link change has occurred. One such process is
Detecting Network Attachment in IPv6" [RFC6059]. Detecting link described by "Simple Procedures for Detecting Network Attachment in
changes would prevent link down/up events from causing temporary IPv6" [RFC6059]. Detecting link changes would prevent link down/up
addresses to be (unnecessarily) regenerated. events from causing temporary addresses to be (unnecessarily)
regenerated.
3.6. Deployment Considerations 3.7. Implementation Considerations
Devices implementing this specification MUST provide a way for the Devices implementing this specification MUST provide a way for the
end user to explicitly enable or disable the use of temporary end user to explicitly enable or disable the use of temporary
addresses. In addition, a site might wish to disable the use of addresses. In addition, a site might wish to disable the use of
temporary addresses in order to simplify network debugging and temporary addresses in order to simplify network debugging and
operations. Consequently, implementations SHOULD provide a way for operations. Consequently, implementations SHOULD provide a way for
trusted system administrators to enable or disable the use of trusted system administrators to enable or disable the use of
temporary addresses. temporary addresses.
Additionally, sites might wish to selectively enable or disable the Additionally, sites might wish to selectively enable or disable the
use of temporary addresses for some prefixes. For example, a site use of temporary addresses for some prefixes. For example, a site
might wish to disable temporary address generation for "Unique local" might wish to disable temporary address generation for "Unique local"
[RFC4193] prefixes while still generating temporary addresses for all [RFC4193] prefixes while still generating temporary addresses for all
other global prefixes. Another site might wish to enable temporary other global prefixes. Another site might wish to enable temporary
address generation only for the prefixes 2001::/16 and 2002::/16 address generation only for the prefixes 2001:db8:1::/48 and
while disabling it for all other prefixes. To support this behavior, 2001:db8:2::/48 while disabling it for all other prefixes. To
implementations SHOULD provide a way to enable and disable generation support this behavior, implementations SHOULD provide a way to enable
of temporary addresses for specific prefix subranges. This per- and disable generation of temporary addresses for specific prefix
prefix setting SHOULD override the global settings on the node with subranges. This per-prefix setting SHOULD override the global
respect to the specified prefix subranges. Note that the per-prefix settings on the node with respect to the specified prefix subranges.
setting can be applied at any granularity, and not necessarily on a Note that the per-prefix setting can be applied at any granularity,
per subnet basis. and not necessarily on a per subnet basis.
The use of temporary addresses may cause unexpected difficulties with Use of the extensions defined in this document may complicate
some applications. As described below, some servers refuse to accept debugging and other operational troubleshooting activities.
communications from clients for which they cannot map the IP address Consequently, it may be site policy that temporary addresses should
into a DNS name. In addition, some applications may not behave not be used. Consequently, implementations MUST provide a method for
robustly if temporary addresses are used and an address expires the end user or trusted administrator to override the use of
before the application has terminated, or if it opens multiple temporary addresses.
sessions, but expects them to all use the same addresses.
If a very small number of nodes (say, only one) use a given prefix 3.8. Defined Constants
for extended periods of time, just changing the interface identifier
part of the address may not be sufficient to ensure privacy, since Constants defined in this document include:
the prefix acts as a constant identifier. The procedures described
in this document are most effective when the prefix is reasonably non TEMP_VALID_LIFETIME -- Default value: 1 week. Users should be able
static or is used by a fairly large number of nodes. to override the default value.
TEMP_PREFERRED_LIFETIME -- Default value: 1 day. Users should be
able to override the default value.
REGEN_ADVANCE -- 5 seconds
MAX_DESYNC_FACTOR -- 10 minutes. Upper bound on DESYNC_FACTOR.
DESYNC_FACTOR -- A random value within the range 0 -
MAX_DESYNC_FACTOR. It is computed once at system start (rather than
each time it is used) and must never be greater than
(TEMP_PREFERRED_LIFETIME - REGEN_ADVANCE).
TEMP_IDGEN_RETRIES -- Default value: 3
4. Implications of Changing Interface Identifiers 4. Implications of Changing Interface Identifiers
The desires of protecting individual privacy versus the desire to The desires of protecting individual privacy versus the desire to
effectively maintain and debug a network can conflict with each effectively maintain and debug a network can conflict with each
other. Having clients use addresses that change over time will make other. Having clients use addresses that change over time will make
it more difficult to track down and isolate operational problems. it more difficult to track down and isolate operational problems.
For example, when looking at packet traces, it could become more For example, when looking at packet traces, it could become more
difficult to determine whether one is seeing behavior caused by a difficult to determine whether one is seeing behavior caused by a
single errant machine, or by a number of them. single errant machine, or by a number of them.
Some servers refuse to grant access to clients for which no DNS name Network deployments are currently recommended to provide multiple
exists. That is, they perform a DNS PTR query to determine the DNS IPv6 addresses from each prefix to general-purpose hosts [RFC7934].
name, and may then also perform an AAAA query on the returned name to However, in some scenarios, use of a large number of IPv6 addresses
verify that the returned DNS name maps back into the address being may have negative implications on network devices that need to
used. Consequently, clients not properly registered in the DNS may maintain entries for each IPv6 address in some data structures (e.g.,
be unable to access some services. As noted earlier, however, a [RFC7039]). Additionally, concurrent active use of multiple IPv6
addresses will increase neighbour discovery traffic if Neighbour
Caches in network devices are not large enough to store all addresses
on the link. This can impact performance and energy efficiency on
networks on which multicast is expensive (e.g.
[I-D.ietf-mboned-ieee802-mcast-problems]).
The use of temporary addresses may cause unexpected difficulties with
some applications. For example, some servers refuse to accept
communications from clients for which they cannot map the IP address
into a DNS name. That is, they perform a DNS PTR query to determine
the DNS name, and may then also perform an AAAA query on the returned
name to verify that the returned DNS name maps back into the address
being used. Consequently, clients not properly registered in the DNS
may be unable to access some services. As noted earlier, however, a
node's DNS name (if non-changing) serves as a constant identifier. node's DNS name (if non-changing) serves as a constant identifier.
The wide deployment of the extension described in this document could The wide deployment of the extension described in this document could
challenge the practice of inverse-DNS-based "authentication," which challenge the practice of inverse-DNS-based "authentication," which
has little validity, though it is widely implemented. In order to has little validity, though it is widely implemented. In order to
meet server challenges, nodes could register temporary addresses in meet server challenges, nodes could register temporary addresses in
the DNS using random names (for example, a string version of the the DNS using random names (for example, a string version of the
random address itself). random address itself).
Use of the extensions defined in this document may complicate In addition, some applications may not behave robustly if temporary
debugging and other operational troubleshooting activities. addresses are used and an address expires before the application has
Consequently, it may be site policy that temporary addresses should terminated, or if it opens multiple sessions, but expects them to all
not be used. Consequently, implementations MUST provide a method for use the same addresses.
the end user or trusted administrator to override the use of
temporary addresses.
5. Defined Constants
Constants defined in this document include: 5. Significant Changes from RFC4941
TEMP_VALID_LIFETIME -- Default value: 1 week. Users should be able This section summarizes the changes in this document relative to RFC
to override the default value. 4941 that an implementer of RFC 4941 should be aware of.
TEMP_PREFERRED_LIFETIME -- Default value: 1 day. Users should be Broadly speaking, this document introduces the following changes:
able to override the default value.
REGEN_ADVANCE -- 5 seconds o Addresses a number of flaws in the algorithm for generating
temporary addresses (see [RAID2015] and [RFC7721]).
MAX_DESYNC_FACTOR -- 10 minutes. Upper bound on DESYNC_FACTOR. o Allows hosts to employ only temporary addresses (i.e.
configuration of stable addresses is no longer implied or
required).
DESYNC_FACTOR -- A random value within the range 0 - o Suggests that temporary addresses be enabled by default (in line
MAX_DESYNC_FACTOR. It is computed once at system start (rather than with [RFC7258]).
each time it is used) and must never be greater than
(TEMP_PREFERRED_LIFETIME - REGEN_ADVANCE).
TEMP_IDGEN_RETRIES -- Default value: 3 o Addresses all errata submitted for [RFC4941].
6. Future Work 6. Future Work
An implementation might want to keep track of which addresses are An implementation might want to keep track of which addresses are
being used by upper layers so as to be able to remove a deprecated being used by upper layers so as to be able to remove a deprecated
temporary address from internal data structures once no upper layer temporary address from internal data structures once no upper layer
protocols are using it (but not before). This is in contrast to protocols are using it (but not before). This is in contrast to
current approaches where addresses are removed from an interface when current approaches where addresses are removed from an interface when
they become invalid [RFC4862], independent of whether or not upper they become invalid [RFC4862], independent of whether or not upper
layer protocols are still using them. For TCP connections, such layer protocols are still using them. For TCP connections, such
information is available in control blocks. For UDP-based information is available in control blocks. For UDP-based
applications, it may be the case that only the applications have applications, it may be the case that only the applications have
knowledge about what addresses are actually in use. Consequently, an knowledge about what addresses are actually in use. Consequently, an
implementation generally will need to use heuristics in deciding when implementation generally will need to use heuristics in deciding when
an address is no longer in use. an address is no longer in use.
Recommendations on DNS practices to avoid the problem described in 7. Security Considerations
Section 4 when reverse DNS lookups fail may be needed. [RFC4472]
contains a more detailed discussion of the DNS-related issues. If a very small number of nodes (say, only one) use a given prefix
for extended periods of time, just changing the interface identifier
part of the address may not be sufficient to address-based network
activity correlation, since the prefix acts as a constant identifier.
The procedures described in this document are most effective when the
prefix is reasonably non static or is used by a fairly large number
of nodes.
While this document discusses ways of obscuring a user's IP address, While this document discusses ways of obscuring a user's IP address,
the method described is believed to be ineffective against the method described is believed to be ineffective against
sophisticated forms of traffic analysis. To increase effectiveness, sophisticated forms of traffic analysis. To increase effectiveness,
one may need to consider use of more advanced techniques, such as one may need to consider the use of more advanced techniques, such as
Onion Routing [ONION]. Onion Routing [ONION].
7. Security Considerations
Ingress filtering has been and is being deployed as a means of Ingress filtering has been and is being deployed as a means of
preventing the use of spoofed source addresses in Distributed Denial preventing the use of spoofed source addresses in Distributed Denial
of Service (DDoS) attacks. In a network with a large number of of Service (DDoS) attacks. In a network with a large number of
nodes, new temporary addresses are created at a fairly high rate. nodes, new temporary addresses are created at a fairly high rate.
This might make it difficult for ingress filtering mechanisms to This might make it difficult for ingress filtering mechanisms to
distinguish between legitimately changing temporary addresses and distinguish between legitimately changing temporary addresses and
spoofed source addresses, which are "in-prefix" (using a spoofed source addresses, which are "in-prefix" (using a
topologically correct prefix and non-existent interface ID). This topologically correct prefix and non-existent interface ID). This
can be addressed by using access control mechanisms on a per-address can be addressed by using access control mechanisms on a per-address
basis on the network egress point. basis on the network egress point.
8. Significant Changes from RFC4941 8. Acknowledgments
This section summarizes the changes in this document relative to RFC
4941 that an implementer of RFC 4941 should be aware of.
1. Discussion of IEEE-based IIDs has been removed, since the current
recommendation ([RFC8064]) is to employ [RFC7217]).
2. The document employs the terminology from [RFC7721].
3. Sections 2.2 and 2.3 of [RFC4941] have been removed since the
topic has been discussed in more detail in e.g. [RFC7721].
4. The algorithm specified in Section 3.2.1 and 3.2.2 of [RFC4941]
was replaced by two possible alternative algorithms.
5. Generation of stable addresses is not implied or required by this
document.
6. Temporary addresses are *not* disabled by default.
7. Section 3.2.3 from [RFC4941] was removed, based on the
explanation of that very section of RFC4941.
8. All the verified errata for [RFC4941] has been incorporated.
9. Acknowledgments
The authors would like to thank (in alphabetical order) Brian The authors would like to thank (in alphabetical order) Fred Baker,
Carpenter, Tim Chown, Lorenzo Colitti, David Farmer, Tom Herbert, Bob Brian Carpenter, Tim Chown, Lorenzo Colitti, David Farmer, Tom
Hinden, Christian Huitema, Dave Plonka, Michael Richardson, Mark Herbert, Bob Hinden, Christian Huitema, Erik Kline, Gyan Mishra, Dave
Smith, Johanna Ullrich, and Timothy Winters, for providing valuable Plonka, Michael Richardson, Mark Smith, Pascal Thubert, Ole Troan,
comments on earlier versions of this document. Johanna Ullrich, and Timothy Winters, for providing valuable comments
on earlier versions of this document.
This document incoporates errata submitted for [RFC4941] by (in This document incorporates errata submitted for [RFC4941] by Jiri
alphabetical order) Jiri Bohac and Alfred Hoenes. Bohac and Alfred Hoenes.
This document is based on [RFC4941] (a revision of RFC3041). Suresh This document is based on [RFC4941] (a revision of RFC3041). Suresh
Krishnan was the sole author of RFC4941. He would like to Krishnan was the sole author of RFC4941. He would like to
acknowledge the contributions of the ipv6 working group and, in acknowledge the contributions of the IPv6 working group and, in
particular, Jari Arkko, Pekka Nikander, Pekka Savola, Francis Dupont, particular, Jari Arkko, Pekka Nikander, Pekka Savola, Francis Dupont,
Brian Haberman, Tatuya Jinmei, and Margaret Wasserman for their Brian Haberman, Tatuya Jinmei, and Margaret Wasserman for their
detailed comments. detailed comments.
Rich Draves and Thomas Narten were the authors of RFC 3041. They Rich Draves and Thomas Narten were the authors of RFC 3041. They
would like to acknowledge the contributions of the ipv6 working group would like to acknowledge the contributions of the IPv6 working group
and, in particular, Ran Atkinson, Matt Crawford, Steve Deering, and, in particular, Ran Atkinson, Matt Crawford, Steve Deering,
Allison Mankin, and Peter Bieringer. Allison Mankin, and Peter Bieringer.
10. References 9. References
10.1. Normative References 9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker, [RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC 4086, "Randomness Requirements for Security", BCP 106, RFC 4086,
DOI 10.17487/RFC4086, June 2005, DOI 10.17487/RFC4086, June 2005,
<https://www.rfc-editor.org/info/rfc4086>. <https://www.rfc-editor.org/info/rfc4086>.
skipping to change at page 18, line 48 skipping to change at page 19, line 14
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8190] Bonica, R., Cotton, M., Haberman, B., and L. Vegoda, [RFC8190] Bonica, R., Cotton, M., Haberman, B., and L. Vegoda,
"Updates to the Special-Purpose IP Address Registries", "Updates to the Special-Purpose IP Address Registries",
BCP 153, RFC 8190, DOI 10.17487/RFC8190, June 2017, BCP 153, RFC 8190, DOI 10.17487/RFC8190, June 2017,
<https://www.rfc-editor.org/info/rfc8190>. <https://www.rfc-editor.org/info/rfc8190>.
10.2. Informative References 9.2. Informative References
[FIPS-SHS] [FIPS-SHS]
NIST, "Secure Hash Standard (SHS)", FIPS NIST, "Secure Hash Standard (SHS)", FIPS
Publication 180-4, March 2012, Publication 180-4, August 2015,
<http://csrc.nist.gov/publications/fips/fips180-4/fips- <https://nvlpubs.nist.gov/nistpubs/FIPS/
180-4.pdf>. NIST.FIPS.180-4.pdf>.
[I-D.ietf-mboned-ieee802-mcast-problems]
Perkins, C., McBride, M., Stanley, D., Kumari, W., and J.
Zuniga, "Multicast Considerations over IEEE 802 Wireless
Media", draft-ietf-mboned-ieee802-mcast-problems-11 (work
in progress), December 2019.
[IANA-RESERVED-IID] [IANA-RESERVED-IID]
IANA, "Reserved IPv6 Interface Identifiers", IANA, "Reserved IPv6 Interface Identifiers",
<http://www.iana.org/assignments/ipv6-interface-ids>. <http://www.iana.org/assignments/ipv6-interface-ids>.
[ONION] Reed, MGR., Syverson, PFS., and DMG. Goldschlag, "Proxies [ONION] Reed, MGR., Syverson, PFS., and DMG. Goldschlag, "Proxies
for Anonymous Routing", Proceedings of the 12th Annual for Anonymous Routing", Proceedings of the 12th Annual
Computer Security Applications Conference, San Diego, CA, Computer Security Applications Conference, San Diego, CA,
December 1996. December 1996.
[OPEN-GROUP] [OPEN-GROUP]
The Open Group, "The Open Group Base Specifications Issue The Open Group, "The Open Group Base Specifications Issue
7 / IEEE Std 1003.1-2008, 2016 Edition", 7 / IEEE Std 1003.1-2008, 2016 Edition",
Section 4.16 Seconds Since the Epoch, 2016, Section 4.16 Seconds Since the Epoch, 2016,
<http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/ <http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/
contents.html>. contents.html>.
[RAID2015]
Ullrich, J. and E. Weippl, "Privacy is Not an Option:
Attacking the IPv6 Privacy Extension", International
Symposium on Recent Advances in Intrusion Detection
(RAID), 2015, <https://www.sba-research.org/wp-
content/uploads/publications/Ullrich2015Privacy.pdf>.
[RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, [RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
DOI 10.17487/RFC1321, April 1992, DOI 10.17487/RFC1321, April 1992,
<https://www.rfc-editor.org/info/rfc1321>. <https://www.rfc-editor.org/info/rfc1321>.
[RFC4472] Durand, A., Ihren, J., and P. Savola, "Operational [RFC4472] Durand, A., Ihren, J., and P. Savola, "Operational
Considerations and Issues with IPv6 DNS", RFC 4472, Considerations and Issues with IPv6 DNS", RFC 4472,
DOI 10.17487/RFC4472, April 2006, DOI 10.17487/RFC4472, April 2006,
<https://www.rfc-editor.org/info/rfc4472>. <https://www.rfc-editor.org/info/rfc4472>.
[RFC5014] Nordmark, E., Chakrabarti, S., and J. Laganier, "IPv6 [RFC5014] Nordmark, E., Chakrabarti, S., and J. Laganier, "IPv6
skipping to change at page 20, line 9 skipping to change at page 20, line 33
[RFC6151] Turner, S. and L. Chen, "Updated Security Considerations [RFC6151] Turner, S. and L. Chen, "Updated Security Considerations
for the MD5 Message-Digest and the HMAC-MD5 Algorithms", for the MD5 Message-Digest and the HMAC-MD5 Algorithms",
RFC 6151, DOI 10.17487/RFC6151, March 2011, RFC 6151, DOI 10.17487/RFC6151, March 2011,
<https://www.rfc-editor.org/info/rfc6151>. <https://www.rfc-editor.org/info/rfc6151>.
[RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265, [RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265,
DOI 10.17487/RFC6265, April 2011, DOI 10.17487/RFC6265, April 2011,
<https://www.rfc-editor.org/info/rfc6265>. <https://www.rfc-editor.org/info/rfc6265>.
[RFC7039] Wu, J., Bi, J., Bagnulo, M., Baker, F., and C. Vogt, Ed.,
"Source Address Validation Improvement (SAVI) Framework",
RFC 7039, DOI 10.17487/RFC7039, October 2013,
<https://www.rfc-editor.org/info/rfc7039>.
[RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
2014, <https://www.rfc-editor.org/info/rfc7258>.
[RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S.,
Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit
Boundary in IPv6 Addressing", RFC 7421,
DOI 10.17487/RFC7421, January 2015,
<https://www.rfc-editor.org/info/rfc7421>.
[RFC7624] Barnes, R., Schneier, B., Jennings, C., Hardie, T., [RFC7624] Barnes, R., Schneier, B., Jennings, C., Hardie, T.,
Trammell, B., Huitema, C., and D. Borkmann, Trammell, B., Huitema, C., and D. Borkmann,
"Confidentiality in the Face of Pervasive Surveillance: A "Confidentiality in the Face of Pervasive Surveillance: A
Threat Model and Problem Statement", RFC 7624, Threat Model and Problem Statement", RFC 7624,
DOI 10.17487/RFC7624, August 2015, DOI 10.17487/RFC7624, August 2015,
<https://www.rfc-editor.org/info/rfc7624>. <https://www.rfc-editor.org/info/rfc7624>.
[RFC7707] Gont, F. and T. Chown, "Network Reconnaissance in IPv6 [RFC7707] Gont, F. and T. Chown, "Network Reconnaissance in IPv6
Networks", RFC 7707, DOI 10.17487/RFC7707, March 2016, Networks", RFC 7707, DOI 10.17487/RFC7707, March 2016,
<https://www.rfc-editor.org/info/rfc7707>. <https://www.rfc-editor.org/info/rfc7707>.
[RFC7721] Cooper, A., Gont, F., and D. Thaler, "Security and Privacy [RFC7721] Cooper, A., Gont, F., and D. Thaler, "Security and Privacy
Considerations for IPv6 Address Generation Mechanisms", Considerations for IPv6 Address Generation Mechanisms",
RFC 7721, DOI 10.17487/RFC7721, March 2016, RFC 7721, DOI 10.17487/RFC7721, March 2016,
<https://www.rfc-editor.org/info/rfc7721>. <https://www.rfc-editor.org/info/rfc7721>.
[RFC7934] Colitti, L., Cerf, V., Cheshire, S., and D. Schinazi,
"Host Address Availability Recommendations", BCP 204,
RFC 7934, DOI 10.17487/RFC7934, July 2016,
<https://www.rfc-editor.org/info/rfc7934>.
[RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A.,
Richardson, M., Jiang, S., Lemon, T., and T. Winters, Richardson, M., Jiang, S., Lemon, T., and T. Winters,
"Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
RFC 8415, DOI 10.17487/RFC8415, November 2018, RFC 8415, DOI 10.17487/RFC8415, November 2018,
<https://www.rfc-editor.org/info/rfc8415>. <https://www.rfc-editor.org/info/rfc8415>.
Appendix A. Changes from RFC4941 [to be removed by the RFC-Editor
before publication
The following changes have been introduced by this document:
1. Discussion of IIDs based on IEEE identifiers has been removed,
since the current recommendation ([RFC8064]) is to employ
[RFC7217]).
2. The document employs the terminology from [RFC7721].
3. Sections 2.2 and 2.3 of [RFC4941] have been removed since the
topic has been discussed in more detail in e.g. [RFC7721].
4. The algorithm specified in Section 3.2.1 and 3.2.2 of [RFC4941]
was replaced by two possible alternative algorithms.
5. Generation of stable addresses is not implied or required by this
document.
6. Temporary addresses are enabled by default, in the light of
[RFC7258].
7. Section 3.2.3 from [RFC4941] was removed, based on the
explanation of that very section of RFC4941.
8. All the verified errata for [RFC4941] has been incorporated.
Authors' Addresses Authors' Addresses
Fernando Gont Fernando Gont
SI6 Networks / UTN-FRH SI6 Networks / UTN-FRH
Evaristo Carriego 2644 Evaristo Carriego 2644
Haedo, Provincia de Buenos Aires 1706 Haedo, Provincia de Buenos Aires 1706
Argentina Argentina
Phone: +54 11 4650 8472 Phone: +54 11 4650 8472
Email: fgont@si6networks.com Email: fgont@si6networks.com
 End of changes. 81 change blocks. 
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