draft-ietf-6man-stable-privacy-addresses-13.txt		draft-ietf-6man-stable-privacy-addresses-14.txt
	IPv6 maintenance Working Group (6man) F. Gont		IPv6 maintenance Working Group (6man) F. Gont
	Internet-Draft SI6 Networks / UTN-FRH		Internet-Draft SI6 Networks / UTN-FRH
	Intended status: Standards Track September 3, 2013		Intended status: Standards Track October 11, 2013
	Expires: March 7, 2014		Expires: April 14, 2014
	A Method for Generating Semantically Opaque Interface Identifiers with		A Method for Generating Semantically Opaque Interface Identifiers with
	IPv6 Stateless Address Autoconfiguration (SLAAC)		IPv6 Stateless Address Autoconfiguration (SLAAC)
	draft-ietf-6man-stable-privacy-addresses-13		draft-ietf-6man-stable-privacy-addresses-14
	Abstract		Abstract
	This document specifies a method for generating IPv6 Interface		This document specifies a method for generating IPv6 Interface
	Identifiers to be used with IPv6 Stateless Address Autoconfiguration		Identifiers to be used with IPv6 Stateless Address Autoconfiguration
	(SLAAC), such that addresses configured using this method are stable		(SLAAC), such that addresses configured using this method are stable
	within each subnet, but the Interface Identifier changes when hosts		within each subnet, but the Interface Identifier changes when hosts
	move from one network to another. This method is meant to be an		move from one network to another. This method is meant to be an
	alternative to generating Interface Identifiers based on hardware		alternative to generating Interface Identifiers based on hardware
	address (e.g., using IEEE identifiers), such that the benefits of		addresses (e.g., IEEE LAN MAC addresses), such that the benefits of
	stable addresses can be achieved without sacrificing the privacy of		stable addresses can be achieved without sacrificing the privacy of
	users. The method specified in this document applies to all prefixes		users. The method specified in this document applies to all prefixes
	a host may be employing, including link-local, global, and unique-		a host may be employing, including link-local, global, and unique-
	local addresses.		local addresses.
	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 http://datatracker.ietf.org/drafts/current/.		Drafts is at http://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 March 7, 2014.		This Internet-Draft will expire on April 14, 2014.
	Copyright Notice		Copyright Notice
	Copyright (c) 2013 IETF Trust and the persons identified as the		Copyright (c) 2013 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
	2. Design goals . . . . . . . . . . . . . . . . . . . . . . . . . 7		2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
	3. Algorithm specification . . . . . . . . . . . . . . . . . . . 9		3. Relationship to Other standards . . . . . . . . . . . . . . . 7
	4. Resolving Duplicate Address Detection (DAD) conflicts . . . . 14		4. Design goals . . . . . . . . . . . . . . . . . . . . . . . . . 8
	5. Specified Constants . . . . . . . . . . . . . . . . . . . . . 15		5. Algorithm specification . . . . . . . . . . . . . . . . . . . 10
	6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16		6. Resolving Duplicate Address Detection (DAD) conflicts . . . . 15
	7. Security Considerations . . . . . . . . . . . . . . . . . . . 17		7. Specified Constants . . . . . . . . . . . . . . . . . . . . . 16
	8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19		8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20		9. Security Considerations . . . . . . . . . . . . . . . . . . . 18
	9.1. Normative References . . . . . . . . . . . . . . . . . . . 20		10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 20
	9.2. Informative References . . . . . . . . . . . . . . . . . . 21		11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
	Appendix A. Possible sources for the Net_Iface parameter . . . . 23		11.1. Normative References . . . . . . . . . . . . . . . . . . 21
	A.1. Interface Index . . . . . . . . . . . . . . . . . . . . . 23		11.2. Informative References . . . . . . . . . . . . . . . . . 21
	A.2. Interface Name . . . . . . . . . . . . . . . . . . . . . . 23		Appendix A. Possible sources for the Net_Iface parameter . . . . 24
	A.3. Link-layer Addresses . . . . . . . . . . . . . . . . . . . 23		A.1. Interface Index . . . . . . . . . . . . . . . . . . . . . 24
	A.4. Logical Network Service Identity . . . . . . . . . . . . . 24		A.2. Interface Name . . . . . . . . . . . . . . . . . . . . . 24
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 25		A.3. Link-layer Addresses . . . . . . . . . . . . . . . . . . 24
			A.4. Logical Network Service Identity . . . . . . . . . . . . 25
			Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 26
	1. Introduction		1. Introduction
	[RFC4862] specifies Stateless Address Autoconfiguration (SLAAC) for		[RFC4862] specifies Stateless Address Autoconfiguration (SLAAC) for
	IPv6 [RFC2460], which typically results in hosts configuring one or		IPv6 [RFC2460], which typically results in hosts configuring one or
	more "stable" addresses composed of a network prefix advertised by a		more "stable" addresses composed of a network prefix advertised by a
	local router, and an Interface Identifier (IID) that typically embeds		local router, and an Interface Identifier (IID) that typically embeds
	a hardware address (e.g., using IEEE identifiers) [RFC4291].		a hardware address (e.g., an IEEE LAN MAC address) [RFC4291].
			Cryptographically Generated Addresses (CGAs) [RFC3972] are yet
	Cryptographically Generated Addresses (CGAs) [RFC3972] are yet		another method for generating Interface Identifiers, which bind a
	another method for generating Interface Identifiers, which bind a		public signature key to an IPv6 address in the SEcure Neighbor
	public signature key to an IPv6 address in the SEcure Neighbor		Discovery (SEND) [RFC3971] protocol.
	Discovery (SEND) [RFC3971] protocol.
	Generally, the traditional SLAAC addresses are thought to simplify		Generally, the traditional SLAAC addresses are thought to simplify
	network management, since they simplify Access Control Lists (ACLs)		network management, since they simplify Access Control Lists (ACLs)
	and logging. However, they have a number of drawbacks:		and logging. However, they have a number of drawbacks:
	o since the resulting Interface Identifiers do not vary over time,		o since the resulting Interface Identifiers do not vary over time,
	they allow correlation of node activities within the same network,		they allow correlation of node activities within the same network,
	thus negatively affecting the privacy of users.		thus negatively affecting the privacy of users (see
			[I-D.cooper-6man-ipv6-address-generation-privacy] and
			[IAB-PRIVACY]).
	o since the resulting Interface Identifiers are constant across		o since the resulting Interface Identifiers are constant across
	networks, the resulting IPv6 addresses can be leveraged to track		networks, the resulting IPv6 addresses can be leveraged to track
	and correlate the activity of a node across multiple networks		and correlate the activity of a node across multiple networks
	(e.g. track and correlate the activities of a typical client		(e.g. track and correlate the activities of a typical client
	connecting to the public Internet from different locations), thus		connecting to the public Internet from different locations), thus
	negatively affecting the privacy of users.		negatively affecting the privacy of users.
	o since embedding the underlying link-layer address in the Interface		o since embedding the underlying link-layer address in the Interface
	Identifier will result in specific address patterns, such patterns		Identifier will result in specific address patterns, such patterns
	may be leveraged by attackers to reduce the search space when		may be leveraged by attackers to reduce the search space when
	performing address scanning attacks. For example, the IPv6		performing address scanning attacks
	addresses of all nodes manufactured by the same vendor (at a given		[I-D.ietf-opsec-ipv6-host-scanning]. For example, the IPv6
	time frame) will likely contain the same IEEE Organizationally		addresses of all nodes manufactured by the same vendor (within a
	Unique Identifier (OUI) in the Interface Identifier.		given time frame) will likely contain the same IEEE
			Organizationally Unique Identifier (OUI) in the Interface
			Identifier.
	o embedding the underlying link-layer address in the Interface		o embedding the underlying hardware address in the Interface
	Identifier leaks device-specific information that could be		Identifier leaks device-specific information that could be
	leveraged to launch device-specific attacks.		leveraged to launch device-specific attacks.
	o embedding the underlying link-layer address in the Interface		o embedding the underlying link-layer address in the Interface
	Identifier means that replacement of the underlying interface		Identifier means that replacement of the underlying interface
	hardware will result in a change of the IPv6 address(es) assigned		hardware will result in a change of the IPv6 address(es) assigned
	to that interface.		to that interface.
	[I-D.cooper-6man-ipv6-address-generation-privacy] provides additional		[I-D.cooper-6man-ipv6-address-generation-privacy] provides additional
	details regarding how these vulnerabilities could be exploited, and		details regarding how these vulnerabilities could be exploited, and
	the extent to which the method discussed in this document mitigates		the extent to which the method discussed in this document mitigates
	them.		them.
	The "Privacy Extensions for Stateless Address Autoconfiguration in		The "Privacy Extensions for Stateless Address Autoconfiguration in
	IPv6" [RFC4941] (henceforth referred to as "temporary addresses")		IPv6" [RFC4941] (henceforth referred to as "temporary addresses")
	were introduced to complicate the task of eavesdroppers and other		were introduced to complicate the task of eavesdroppers and other
	information collectors (e.g. IPv6 addresses in web server logs or		information collectors (e.g., IPv6 addresses in web server logs or
	email headers, etc.) to correlate the activities of a node, and		email headers, etc.) to correlate the activities of a node, and
	basically result in temporary (and random) Interface Identifiers.		basically result in temporary (and random) Interface Identifiers.
	These temporary addresses are generated in addition to the		These temporary addresses are generated in addition to the
	traditional IPv6 addresses based on IEEE identifiers, with the		traditional IPv6 addresses based on IEEE LAC MAC addresses, with the
	"temporary addresses" being employed for "outgoing communications",		"temporary addresses" being employed for "outgoing communications",
	and the traditional SLAAC addresses being employed for "server"		and the traditional SLAAC addresses being employed for "server"
	functions (i.e., receiving incoming connections).		functions (i.e., receiving incoming connections).
	It should be noted that temporary addresses can be challenging in		It should be noted that temporary addresses can be challenging in a
	a number of areas. For example, from a network-management point		number of areas. For example, from a network-management point of
	of view, they tend to increase the complexity of event logging,		view, they tend to increase the complexity of event logging, trouble-
	trouble-shooting, enforcement of access controls and quality of		shooting, enforcement of access controls and quality of service, etc.
	service, etc. As a result, some organizations disable the use of		As a result, some organizations disable the use of temporary
	temporary addresses even at the expense of reduced privacy		addresses even at the expense of reduced privacy [Broersma].
	[Broersma]. Temporary addresses may also result in increased		Temporary addresses may also result in increased implementation
	implementation complexity, which might not be possible or		complexity, which might not be possible or desirable in some
	desirable in some implementations (e.g., some embedded devices).		implementations (e.g., some embedded devices).
	In scenarios in which temporary addresses are deliberately not		In scenarios in which temporary addresses are deliberately not used
	used (possibly for any of the aforementioned reasons), all a host		(possibly for any of the aforementioned reasons), all a host is left
	is left with is the stable addresses that have been generated		with is the stable addresses that have typically been generated from
	using e.g. IEEE identifiers. In such scenarios, it may still be		the underlying hardware addresses. In such scenarios, it may still
	desirable to have addresses that mitigate address scanning		be desirable to have addresses that mitigate address scanning
	attacks, and that at the very least do not reveal the node's		attacks, and that at the very least do not reveal the node's identity
	identity when roaming from one network to another -- without		when roaming from one network to another -- without complicating the
	complicating the operation of the corresponding networks.		operation of the corresponding networks.
	However, even with "temporary addresses" in place, a number of issues		However, even with "temporary addresses" in place, a number of issues
	remain to be mitigated. Namely,		remain to be mitigated. Namely,
	o since "temporary addresses" [RFC4941] do not eliminate the use of		o since "temporary addresses" [RFC4941] do not eliminate the use of
	fixed identifiers for server-like functions, they only partially		fixed identifiers for server-like functions, they only partially
	mitigate host-tracking and activity correlation across networks		mitigate host-tracking and activity correlation across networks
	(see [I-D.cooper-6man-ipv6-address-generation-privacy] for some		(see [I-D.cooper-6man-ipv6-address-generation-privacy] for some
	example attacks that are still possible with temporary addresses).		example attacks that are still possible with temporary addresses).
	o since "temporary addresses" [RFC4941] do not replace the		o since "temporary addresses" [RFC4941] do not replace the
	traditional SLAAC addresses, an attacker can still leverage		traditional SLAAC addresses, an attacker can still leverage
	patterns in those addresses to greatly reduce the search space for		patterns in SLAAC addresses to greatly reduce the search space for
	"alive" nodes [Gont-DEEPSEC2011] [CPNI-IPv6]		"alive" nodes [Gont-DEEPSEC2011] [CPNI-IPv6]
	[I-D.ietf-opsec-ipv6-host-scanning].		[I-D.ietf-opsec-ipv6-host-scanning].
	Hence, there is a motivation to improve the properties of "stable"		Hence, there is a motivation to improve the properties of "stable"
	addresses regardless of whether temporary addresses are employed or		addresses regardless of whether temporary addresses are employed or
	not.		not.
	We note that attackers can employ a plethora of probing techniques
	[I-D.ietf-opsec-ipv6-host-scanning] to exploit the aforementioned
	issues. Some of them (such as the use of ICMPv6 Echo Request and
	ICMPv6 Echo Response packets) could mitigated by a personal firewall
	at the target host. For other vectors, such listening to ICMPv6
	"Destination Unreachable, Address Unreachable" (Type 1, Code 3) error
	messages referring to the target addresses
	[I-D.ietf-opsec-ipv6-host-scanning], there is nothing a host can do
	(e.g., a personal firewall at the target host would not be able to
	mitigate this probing technique).
	This document specifies a method to generate Interface Identifiers		This document specifies a method to generate Interface Identifiers
	that are stable/constant for each network interface within each		that are stable/constant for each network interface within each
	subnet, but that change as hosts move from one network to another,		subnet, but that change as hosts move from one network to another,
	thus keeping the "stability" properties of the Interface Identifiers		thus keeping the "stability" properties of the Interface Identifiers
	specified in [RFC4291], while still mitigating address-scanning		specified in [RFC4291], while still mitigating address-scanning
	attacks and preventing correlation of the activities of a node as it		attacks and preventing correlation of the activities of a node as it
	moves from one network to another.		moves from one network to another.
	The method specified in this document is a orthogonal to the use of		2. Terminology
			The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
			"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
			document are to be interpreted as described in RFC 2119 [RFC2119].
			3. Relationship to Other standards
			The method specified in this document is orthogonal to the use of
	"temporary" addresses [RFC4941], since it is meant to improve the		"temporary" addresses [RFC4941], since it is meant to improve the
	security and privacy properties of the stable addresses that are		security and privacy properties of the stable addresses that are
	employed along with the aforementioned "temporary" addresses. In		employed along with the aforementioned "temporary" addresses. In
	scenarios in which "temporary addresses" are employed, implementation		scenarios in which "temporary addresses" are employed, implementation
	of the mechanism described in this document (in replacement of stable		of the mechanism described in this document (in replacement of stable
	addresses based on e.g. IEEE identifiers) would mitigate address-		addresses based on e.g., IEEE LAN MAC addresses) will mitigate
	scanning attacks and also mitigate the remaining vectors for		address-scanning attacks and also mitigate the remaining vectors for
	correlating host activities based on the node's constant (i.e. stable		correlating host activities based on the node's constant (i.e. stable
	across networks) Interface Identifiers. On the other hand, for nodes		across networks) Interface Identifiers. On the other hand, for nodes
	that currently disable "temporary addresses" [RFC4941] for some of		that currently disable "temporary addresses" [RFC4941],
	the reasons described earlier in this document, implementation of		implementation of this mechanism would mitigate the host-tracking and
	this mechanism will result in stable privacy-enhanced addresses which		address scanning issues discussed in Section 1.
	address some of the concerns related to addresses that embed IEEE
	identifiers [RFC4291], and which mitigate IPv6 address-scanning
	attacks.
	We note that this method is incrementally deployable, since it does
	not pose any interoperability implications when deployed on networks
	where other nodes do not implement or employ it. Additionally, we
	note that this document does not update or modify IPv6 StateLess
	Address Auto-Configuration (SLAAC) [RFC4862] itself, but rather only
	specifies an alternative algorithm to generate Interface Identifiers.
	Therefore, the usual address lifetime properties (as specified in the
	corresponding Prefix Information Options) apply when IPv6 addresses
	are generated as a result of employing the algorithm specified in
	this document with SLAAC [RFC4862]. Additionally, from the point of
	view of renumbering, we note that these addresses behave like the
	traditional IPv6 addresses (that embed a hardware address) resulting
	from SLAAC [RFC4862].
	While the method specified in this document is meant to be used with		While the method specified in this document is meant to be used with
	SLAAC, this does not preclude the same algorithm from being used with		SLAAC, this does not preclude this algorithm from being used with
	other address configuration mechanisms, such as DHCPv6 [RFC3315] or		other address configuration mechanisms, such as DHCPv6 [RFC3315] or
	manual address configuration.		manual address configuration.
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		4. Design goals
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in RFC 2119 [RFC2119].
	2. Design goals
	This document specifies a method for selecting Interface Identifiers		This document specifies a method for generating Interface Identifiers
	to be used with IPv6 SLAAC, with the following goals:		to be used with IPv6 SLAAC, with the following goals:
	o The resulting Interface Identifiers remain constant/stable for		o The resulting Interface Identifiers remain constant/stable for
	each prefix used with SLAAC within each subnet. That is, the		each prefix used with SLAAC within each subnet. That is, the
	algorithm generates the same Interface Identifier when configuring		algorithm generates the same Interface Identifier when configuring
	an address (for the same interface) belonging to the same prefix		an address (for the same interface) belonging to the same prefix
	within the same subnet.		within the same subnet.
	o The resulting Interface Identifiers do change when addresses are		o The resulting Interface Identifiers do change when addresses are
	configured for different prefixes. That is, if different		configured for different prefixes. That is, if different
	skipping to change at page 7, line 30		skipping to change at page 8, line 30
	must be (statistically) different. This means that, given two		must be (statistically) different. This means that, given two
	addresses produced by the method specified in this document, it		addresses produced by the method specified in this document, it
	must be difficult for an attacker tell whether the addresses have		must be difficult for an attacker tell whether the addresses have
	been generated/used by the same node.		been generated/used by the same node.
	o It must be difficult for an outsider to predict the Interface		o It must be difficult for an outsider to predict the Interface
	Identifiers that will be generated by the algorithm, even with		Identifiers that will be generated by the algorithm, even with
	knowledge of the Interface Identifiers generated for configuring		knowledge of the Interface Identifiers generated for configuring
	other addresses.		other addresses.
	o Depending on the specific implementation approach (see Section 3		o Depending on the specific implementation approach (see Section 5
	and Appendix A), the resulting Interface Identifiers may be		and Appendix A), the resulting Interface Identifiers may be
	independent of the underlying hardware (e.g. link-layer address).		independent of the underlying hardware (e.g. IEEE LAN MAC
	This means that e.g. replacing a Network Interface Card (NIC) will		address). This means that e.g. replacing a Network Interface Card
	not have the (generally undesirable) effect of changing the IPv6		(NIC) or adding links dynamically to a Link Aggregation Group
	addresses used for that network interface.		(LAG) will not have the (generally undesirable) effect of changing
			the IPv6 addresses used for that network interface.
	o The method specified in this document is meant to be an		o The method specified in this document is meant to be an
	alternative to producing IPv6 addresses based on e.g. IEEE		alternative to producing IPv6 addresses based hardware addresses
	identifiers (as specified in [RFC2464]). It is meant to be		(e.g. IEEE LAN MAC addresses, as specified in [RFC2464]). That
	employed for all of the stable (i.e. non-temporary) IPv6 addresses		is, this document does not formally obsolete or deprecate any of
	configured with SLAAC for a given interface, including global,		the existing algorithms to generate Interface Identifiers. It is
	link-local, and unique-local IPv6 addresses.		meant to be employed for all of the stable (i.e. non-temporary)
			IPv6 addresses configured with SLAAC for a given interface,
			including global, link-local, and unique-local IPv6 addresses.
	We note that of use of the algorithm specified in this document is		We note that this method is incrementally deployable, since it does
	(to a large extent) orthogonal to the use of "temporary addresses"		not pose any interoperability implications when deployed on networks
	[RFC4941]. When employed along with "temporary addresses", the		where other nodes do not implement or employ it. Additionally, we
	method specified in this document will mitigate address-scanning		note that this document does not update or modify IPv6 StateLess
	attacks and correlation of node activities across networks (see		Address Auto-Configuration (SLAAC) [RFC4862] itself, but rather only
	[I-D.cooper-6man-ipv6-address-generation-privacy] and [IAB-PRIVACY]).		specifies an alternative algorithm to generate Interface Identifiers.
	On the other hand, hosts that do not implement/use "temporary
	addresses" but employ the method specified in this document would, at
	the very least, mitigate the host-tracking and address scanning
	issues discussed in the previous section.
	3. Algorithm specification		Therefore, the usual address lifetime properties (as specified in the
			corresponding Prefix Information Options) apply when IPv6 addresses
			are generated as a result of employing the algorithm specified in
			this document with SLAAC [RFC4862]. Additionally, from the point of
			view of renumbering, we note that these addresses behave like the
			traditional IPv6 addresses (that embed a hardware address) resulting
			from SLAAC [RFC4862].
			5. Algorithm specification
	IPv6 implementations conforming to this specification MUST generate		IPv6 implementations conforming to this specification MUST generate
	Interface Identifiers using the algorithm specified in this section		Interface Identifiers using the algorithm specified in this section
	in replacement of any other algorithms used for generating "stable"		in replacement of any other algorithms used for generating "stable"
	addresses with SLAAC (such as those specified in [RFC2464]).		addresses with SLAAC (such as those specified in [RFC2464],
	However, implementations conforming to this specification MAY employ		[RFC2467], and [RFC2470]). However, implementations conforming to
	the algorithm specified in [RFC4941] to generate temporary addresses		this specification MAY employ the algorithm specified in [RFC4941] to
	in addition to the addresses generated with the algorithm specified		generate temporary addresses in addition to the addresses generated
	in this document. The method specified in this document MUST be		with the algorithm specified in this document. The method specified
	employed for generating the Interface Identifiers with SLAAC for all		in this document MUST be employed for generating the Interface
	the stable addresses of a given interface, including IPv6 global,		Identifiers with SLAAC for all the stable addresses, including IPv6
	link-local, and unique-local addresses.		global, link-local, and unique-local addresses.
	This means that this document does not formally obsolete or
	deprecate any of the existing algorithms to generate Interface
	Identifiers (e.g. such as that specified in [RFC2464]). However,
	those IPv6 implementations that employ this specification MUST
	generate all of their "stable" addresses as specified in this
	document.
	Implementations conforming to this specification SHOULD provide the		Implementations conforming to this specification SHOULD provide the
	means for a system administrator to enable or disable the use of this		means for a system administrator to enable or disable the use of this
	algorithm for generating Interface Identifiers.		algorithm for generating Interface Identifiers.
	Unless otherwise noted, all of the parameters included in the		Unless otherwise noted, all of the parameters included in the
	expression below MUST be included when generating an Interface		expression below MUST be included when generating an Interface
	Identifier.		Identifier.
	1. Compute a random (but stable) identifier with the expression:		1. Compute a random (but stable) identifier with the expression:
	RID = F(Prefix, Net_Iface, Network_ID, DAD_Counter, secret_key)		RID = F(Prefix, Net_Iface, Network_ID, DAD_Counter, secret_key)
	Where:		Where:
	RID:		RID:
	Random (but stable) Interface Identifier		Random (but stable) Identifier
	F():		F():
	A pseudorandom function (PRF) that is not computable from the		A pseudorandom function (PRF) that MUST NOT be computable from
	outside (without knowledge of the secret key), which should		the outside (without knowledge of the secret key). F() MUST
	produce an output of at least 64 bits.The PRF could be		also be difficult to reverse, such that it resists attempts to
	implemented as a cryptographic hash of the concatenation of		obtain the secret_key, even when given samples of the output
			of F() and knowledge or control of the other input parameters.
			F() SHOULD produce an output of at least 64 bits. F() could
			be implemented as a cryptographic hash of the concatenation of
	each of the function parameters.		each of the function parameters.
	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, or the link-local IPv6 unicast		Router Advertisement message, or the link-local IPv6 unicast
	prefix.		prefix [RFC4291].
	Net_Iface:		Net_Iface:
	An implementation-dependent stable identifier associated with		An implementation-dependent stable identifier associated with
	the network interface for which the RID is being generated.		the network interface for which the RID is being generated.
	An implementation MAY provide a configuration option to select		An implementation MAY provide a configuration option to select
	the source of the identifier to be used for the Net_Iface		the source of the identifier to be used for the Net_Iface
	parameter. A discussion of possible sources for this value		parameter. A discussion of possible sources for this value
	(along with the corresponding trade-offs) can be found in		(along with the corresponding trade-offs) can be found in
	Appendix A.		Appendix A.
	skipping to change at page 10, line 34		skipping to change at page 11, line 29
	OPTIONAL.		OPTIONAL.
	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. It MUST be initialized to 0, and		Detection (DAD) conflicts. It MUST be initialized to 0, and
	incremented by 1 for each new tentative address that is		incremented by 1 for each new tentative address that is
	configured as a result of a DAD conflict. Implementations		configured as a result of a DAD conflict. Implementations
	that record DAD_Counter in non-volatile memory for each		that record DAD_Counter in non-volatile memory for each
	{Prefix, Net_Iface, Network_ID} tuple MUST initialize		{Prefix, Net_Iface, Network_ID} tuple MUST initialize
	DAD_Counter to the recorded value if such an entry exists in		DAD_Counter to the recorded value if such an entry exists in
	non-volatile memory). See Section 4 for additional details.		non-volatile memory. See Section 6 for additional details.
	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 MUST be initialized at operating system installation time		key MUST be initialized to a pseudo-random number (see
	to a pseudo-random number (see [RFC4086] for randomness		[RFC4086] for randomness requirements for security) at
	requirements for security). An implementation MAY provide the		operating system installation time or when the IPv6 protocol
	means for the the system administrator to change or display		stack is initialized for the first time. An implementation
	the secret key.		MAY provide the means for the the system administrator to
			change or display the secret key.
	2. The Interface Identifier is finally obtained by taking as many		2. The Interface Identifier is finally obtained by taking as many
	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.		necessary, starting from the least significant bit.
	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-bit long. However, the method discussed in		value 000) be 64-bit 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 resulting Interface Identifier should be compared against the		The resulting Interface Identifier SHOULD be compared against the
	Subnet-Router Anycast [RFC4291] and the Reserved Subnet Anycast		Subnet-Router Anycast [RFC4291] and the Reserved Subnet Anycast
	Addresses [RFC2526], and against those Interface Identifiers		Addresses [RFC2526], and against those Interface Identifiers
	already employed in an address of the same network interface and		already employed in an address of the same network interface and
	the same network prefix. In the event that an unacceptable		the same network prefix. In the event that an unacceptable
	identifier has been generated, this situation should be handled		identifier has been generated, this situation SHOULD be handled
	in the same way as the case of duplicate addresses (see		in the same way as the case of duplicate addresses (see
	Section 4).		Section 6).
	This document does not require the use of any specific PRF for the		This document does not require the use of any specific PRF for the
	function F() above, since the choice of such PRF is usually a trade-		function F() above, since the choice of such PRF is usually a trade-
	off between a number of properties (processing requirements, ease of		off between a number of properties (processing requirements, ease of
	implementation, possible intellectual property rights, etc.), and		implementation, possible intellectual property rights, etc.), and
	since the best possible choice for F() might be different for		since the best possible choice for F() might be different for
	different types of devices (e.g. embedded systems vs. regular		different types of devices (e.g. embedded systems vs. regular
	servers) and might possibly change over time.		servers) and might possibly change over time.
	Note that the result of F() in the algorithm above is no more secure		Note that the result of F() in the algorithm above is no more secure
	skipping to change at page 11, line 42		skipping to change at page 12, line 38
	enabled/used automatically, without user intervention.		enabled/used automatically, without user intervention.
	Including the SLAAC prefix in the PRF computation causes the		Including the SLAAC prefix in the PRF computation causes the
	Interface Identifier to vary across each prefix (link-local, global,		Interface Identifier to vary across each prefix (link-local, global,
	etc.) employed by the node and, as consequently, also across		etc.) employed by the node and, as consequently, also across
	networks. This mitigates the correlation of activities of multi-		networks. This mitigates the correlation of activities of multi-
	homed nodes (since each of the corresponding addresses will employ a		homed nodes (since each of the corresponding addresses will employ a
	different Interface ID), host-tracking (since the network prefix will		different Interface ID), host-tracking (since the network prefix will
	change as the node moves from one network to another), and any other		change as the node moves from one network to another), and any other
	attacks that benefit from predictable Interface Identifiers (such as		attacks that benefit from predictable Interface Identifiers (such as
	address scanning attacks).		IPv6 address scanning attacks).
	The Net_Iface is a value that identifies the network interface for		The Net_Iface is a value that identifies the network interface for
	which an IPv6 address is being generated. The following properties		which an IPv6 address is being generated. The following properties
	are required for the Net_Iface parameter:		are required for the Net_Iface parameter:
	o it MUST be constant across system bootstrap sequences and other		o it MUST be constant across system bootstrap sequences and other
	network events (e.g., bringing another interface up or down)		network events (e.g., bringing another interface up or down)
	o it MUST be different for each network interface simultaneously in		o it MUST be different for each network interface simultaneously in
	use		use
	skipping to change at page 12, line 27		skipping to change at page 13, line 21
	that are attached to the underlying network interface card (NIC),		that are attached to the underlying network interface card (NIC),
	such that a removable NIC always gets the same IPv6 address,		such that a removable NIC always gets the same IPv6 address,
	irrespective of the system communications port to which it is		irrespective of the system communications port to which it is
	attached. On the other hand, a server-oriented operating system		attached. On the other hand, a server-oriented operating system
	might prefer Net_Iface identifiers that are attached to system slots/		might prefer Net_Iface identifiers that are attached to system slots/
	ports, such that replacement of a network interface card does not		ports, such that replacement of a network interface card does not
	result in an IPv6 address change. Appendix A discusses possible		result in an IPv6 address change. Appendix A discusses possible
	sources for the Net_Iface, along with their pros and cons.		sources for the Net_Iface, along with their pros and cons.
	Including the optional Network_ID parameter when computing the RID		Including the optional Network_ID parameter when computing the RID
	value above would cause the algorithm to produce a different		value above causes the algorithm to produce a different Interface
	Interface Identifier when connecting to different networks, even when		Identifier when connecting to different networks, even when
	configuring addresses belonging to the same prefix. This means that		configuring addresses belonging to the same prefix. This means that
	a host would employ a different Interface Identifier as it moves from		a host would employ a different Interface Identifier as it moves from
	one network to another even for IPv6 link-local addresses or Unique		one network to another even for IPv6 link-local addresses or Unique
	Local Addresses (ULAs). In those scenarios where the Network_ID is		Local Addresses (ULAs). In those scenarios where the Network_ID is
	unknown to the attacker, including this parameter might help mitigate		unknown to the attacker, including this parameter might help mitigate
	attacks where a victim node connects to the same subnet as the		attacks where a victim node connects to the same subnet as the
	attacker, and the attacker tries to learn the Interface Identifier		attacker, and the attacker tries to learn the Interface Identifier
	used by the victim node for a remote network (see Section 7 for		used by the victim node for a remote network (see Section 9 for
	further details).		further details).
	The DAD_Counter parameter provides the means to intentionally cause		The DAD_Counter parameter provides the means to intentionally cause
	this algorithm produce a different IPv6 addresses (all other		this algorithm to produce a different IPv6 addresses (all other
	parameters being the same). This could be necessary to resolve		parameters being the same). This could be necessary to resolve
	Duplicate Address Detection (DAD) conflicts, as discussed in detail		Duplicate Address Detection (DAD) conflicts, as discussed in detail
	in Section 4.		in Section 6.
	Finally, we note that all of the bits in the resulting Interface IDs		Finally, we note that all of the bits in the resulting Interface IDs
	are treated as "opaque" bits. For example, the universal/local bit		are treated as "opaque" bits. For example, the universal/local bit
	of Modified EUI-64 format identifiers is treated as any other bit of		of Modified EUI-64 format identifiers is treated as any other bit of
	such identifier. In theory, this might result in Duplicate Address		such identifier. In theory, this might result in Duplicate Address
	Detection (DAD) failures that would otherwise not be encountered.		Detection (DAD) failures that would otherwise not be encountered.
	However, this is not deemed as a real issue, because of the following		However, this is not deemed as a real issue, because of the following
	considerations:		considerations:
	o The interface IDs of all addresses (except those of addresses that		o The interface IDs of all addresses (except those of addresses that
	that start with the binary value 000) are 64-bit long. Since the		that start with the binary value 000) are 64-bit long. Since the
	method specified in this document results in random Interface IDs,		method specified in this document results in random Interface IDs,
	the probability of DAD failures is very small.		the probability of DAD failures is very small.
	o Real world data indicates that MAC address reuse is far more		o Real world data indicates that MAC address reuse is far more
	common than assumed [HDMoore]. This means that even IPv6		common than assumed [HDMoore]. This means that even IPv6
	addresses that employ (allegedly) unique identifiers (such as IEEE		addresses that employ (allegedly) unique identifiers (such as IEEE
	identifiers) might result in DAD failures, and hence		LAN MAC addresses) might result in DAD failures, and hence
	implementations should be prepared to gracefully handle such		implementations should be prepared to gracefully handle such
	occurrences.		occurrences.
	o Since some popular and widely-deployed operating systems (such as		o Since some popular and widely-deployed operating systems (such as
	Microsoft Windows) do not employ unique hardware identifiers for		Microsoft Windows) do not employ unique hardware addresses for the
	the Interface IDs of their stable addresses, reliance on such		Interface IDs of their stable addresses, reliance on such unique
	unique identifiers is more reduced in the deployed world (fewer		identifiers is more reduced in the deployed world (fewer deployed
	deployed systems rely on them for the avoidance of address		systems rely on them for the avoidance of address collisions).
	collisions).
	4. Resolving Duplicate Address Detection (DAD) conflicts		6. Resolving Duplicate Address Detection (DAD) conflicts
	If as a result of performing Duplicate Address Detection (DAD)		If as a result of performing Duplicate Address Detection (DAD)
	[RFC4862] a host finds that the tentative address generated with the		[RFC4862] a host finds that the tentative address generated with the
	algorithm specified in Section 3 is a duplicate address, it SHOULD		algorithm specified in Section 5 is a duplicate address, it SHOULD
	resolve the address conflict by trying a new tentative address as		resolve the address conflict by trying a new tentative address as
	follows:		follows:
	o DAD_Counter is incremented by 1.		o DAD_Counter is incremented by 1.
	o A new Interface Identifier is generated with the algorithm		o A new Interface Identifier is generated with the algorithm
	specified in Section 3, using the incremented DAD_Counter value.		specified in Section 5, using the incremented DAD_Counter value.
			Hosts SHOULD introduce a random delay between 0 and IDGEN_DELAY
			seconds (see Section 7) before trying a new tentative address, to
			avoid lock-step behavior of multiple hosts.
	This procedure may be repeated a number of times until the address		This procedure may be repeated a number of times until the address
	conflict is resolved. Hosts SHOULD try at least IDGEN_RETRIES (see		conflict is resolved. Hosts SHOULD try at least IDGEN_RETRIES (see
	Section 5) tentative addresses if DAD fails for successive generated		Section 7) tentative addresses if DAD fails for successive generated
	addresses, in the hopes of resolving the address conflict. We also		addresses, in the hopes of resolving the address conflict. We also
	note that hosts MUST limit the number of tentative addresses that are		note that hosts MUST limit the number of tentative addresses that are
	tried (rather than indefinitely try a new tentative address until the		tried (rather than indefinitely try a new tentative address until the
	conflict is resolved).		conflict is resolved).
	In those (unlikely) scenarios in which duplicate addresses are		In those unlikely scenarios in which duplicate addresses are detected
	detected and in which the order in which the conflicting nodes		and in which the order in which the conflicting nodes configure their
	configure their addresses may vary (e.g., because they may be		addresses may vary (e.g., because they may be bootstrapped in
	bootstrapped in different order), the algorithm specified in this		different order), the algorithm specified in this section for
	section for resolving DAD conflicts could lead to addresses that are		resolving DAD conflicts could lead to addresses that are not stable
	not stable within the same subnet. In order to mitigate this		within the same subnet. In order to mitigate this potential problem,
	potential problem, nodes MAY record the DAD_Counter value employed		nodes MAY record the DAD_Counter value employed for a specific
	for a specific {Prefix, Net_Iface, Network_ID} tuple in non-volatile		{Prefix, Net_Iface, Network_ID} tuple in non-volatile memory, such
	memory, such that the same DAD_Counter value is employed when		that the same DAD_Counter value is employed when configuring an
	configuring an address for the same Prefix and subnet at any other		address for the same Prefix and subnet at any other point in time.
	point in time.		We note that the use of non-volatile memory is OPTIONAL, and hosts
			that do not implement this feature are still compliant to this
			protocol specification.
	In the event that a DAD conflict cannot be solved (possibly after		In the event that a DAD conflict cannot be solved (possibly after
	trying a number of different addresses), address configuration would		trying a number of different addresses), address configuration would
	fail. In those scenarios, nodes MUST NOT automatically fall back to		fail. In those scenarios, nodes MUST NOT automatically fall back to
	employing other algorithms for generating Interface Identifiers.		employing other algorithms for generating Interface Identifiers.
	5. Specified Constants		7. Specified Constants
	This document specifies the following constant:		This document specifies the following constant:
	IDGEN_RETRIES:		IDGEN_RETRIES:
	defaults to 3.		defaults to 3.
	6. IANA Considerations		IDGEN_DELAY:
			defaults to 1 second.
			8. IANA Considerations
	There are no IANA registries within this document. The RFC-Editor		There are no IANA registries within this document. The RFC-Editor
	can remove this section before publication of this document as an		can remove this section before publication of this document as an
	RFC.		RFC.
	7. Security Considerations		9. Security Considerations
	This document specifies an algorithm for generating Interface		This document specifies an algorithm for generating Interface
	Identifiers to be used with IPv6 Stateless Address Autoconfiguration		Identifiers to be used with IPv6 Stateless Address Autoconfiguration
	(SLAAC), as an alternative to e.g. Interface Identifiers that embed		(SLAAC), as an alternative to e.g. Interface Identifiers that embed
	IEEE identifiers (such as those specified in [RFC2464]). When		hardware addresses (such as those specified in [RFC2464], [RFC2467],
	compared to such identifiers, the identifiers specified in this		and [RFC2470]). When compared to such identifiers, the identifiers
	document have a number of advantages:		specified in this document have a number of advantages:
	o They prevent trivial host-tracking, since when a host moves from		o They prevent trivial host-tracking, since when a host moves from
	one network to another the network prefix used for		one network to another the network prefix used for
	autoconfiguration and/or the Network ID (e.g., IEEE 802.11 SSID)		autoconfiguration and/or the Network ID (e.g., IEEE 802.11 SSID)
	will typically change, and hence the resulting Interface		will typically change, and hence the resulting Interface
	Identifier will also change (see		Identifier will also change (see
	[I-D.cooper-6man-ipv6-address-generation-privacy]).		[I-D.cooper-6man-ipv6-address-generation-privacy]).
	o They mitigate address-scanning techniques which leverage		o They mitigate address-scanning techniques which leverage
	predictable Interface Identifiers (e.g., known Organizationally		predictable Interface Identifiers (e.g., known Organizationally
	Unique Identifiers) [I-D.ietf-opsec-ipv6-host-scanning].		Unique Identifiers) [I-D.ietf-opsec-ipv6-host-scanning].
	o They may result in IPv6 addresses that are independent of the		o They may result in IPv6 addresses that are independent of the
	underlying hardware (i.e. the resulting IPv6 addresses do not		underlying hardware (i.e. the resulting IPv6 addresses do not
	change if a network interface card is replaced) if an appropriate		change if a network interface card is replaced) if an appropriate
	source for Net_Iface (Section 3) is employed.		source for Net_Iface (Section 5) is employed.
	o They prevent the information leakage produced by embedding		o They prevent the information leakage produced by embedding
	hardware addresses in the Interface Identifier (which could be		hardware addresses in the Interface Identifier (which could be
	exploited to launch device-specific attacks).		exploited to launch device-specific attacks).
	o Since the method specified in this document will result in		o Since the method specified in this document will result in
	different Interface Identifiers for each configured address,		different Interface Identifiers for each configured address,
	knowledge/leakage of the Interface Identifier employed for one		knowledge/leakage of the Interface Identifier employed for one
	stable address of will not negatively affect the security/privacy		stable address will not negatively affect the security/privacy of
	of other stable addresses configured for other prefixes (whether		other stable addresses configured for other prefixes (whether at
	at the same time or at some other point in time).		the same time or at some other point in time).
			We note that while some probing techniques (such as the use of ICMPv6
			Echo Request and ICMPv6 Echo Response packets) could be mitigated by
			a personal firewall at the target host, for other probing vectors,
			such as listening to ICMPv6 "Destination Unreachable, Address
			Unreachable" (Type 1, Code 3) error messages referring to the target
			addresses [I-D.ietf-opsec-ipv6-host-scanning], there is nothing a
			host can do (e.g., a personal firewall at the target host would not
			be able to mitigate this probing technique). Hence, the method
			specified in this document is still of value for nodes that employ
			personal firewalls.
	In scenarios in which an attacker can connect to the same subnet as a		In scenarios in which an attacker can connect to the same subnet as a
	victim node, the attacker might be able to learn the Interface		victim node, the attacker might be able to learn the Interface
	Identifier employed by the victim node for an arbitrary prefix, by		Identifier employed by the victim node for an arbitrary prefix, by
	simply sending a forged Router Advertisement [RFC4861] for that		simply sending a forged Router Advertisement [RFC4861] for that
	prefix, and subsequently learning the corresponding address		prefix, and subsequently learning the corresponding address
	configured by the victim node (either listening to the Duplicate		configured by the victim node (either listening to the Duplicate
	Address Detection packets, or to any other traffic that employs the		Address Detection packets, or to any other traffic that employs the
	newly configured address). We note that a number of factors might		newly configured address). We note that a number of factors might
	limit the ability of an attacker to successfully perform such an		limit the ability of an attacker to successfully perform such an
	attack:		attack:
	o First-Hop security mechanisms such as RA-Guard [RFC6105]		o First-Hop security mechanisms such as RA-Guard [RFC6105]
	[I-D.ietf-v6ops-ra-guard-implementation] could prevent the forged		[I-D.ietf-v6ops-ra-guard-implementation] could prevent the forged
	Router Advertisement from reaching the victim node		Router Advertisement from reaching the victim node
	o If the victim implementation includes the (optional) Network_ID		o If the victim implementation includes the (optional) Network_ID
	parameter for computing F() (see Section 3), and the Network_ID		parameter for computing F() (see Section 5), and the Network_ID
	employed by the victim for a remote network is unknown to the		employed by the victim for a remote network is unknown to the
	attacker, the Interface Identifier learned by the attacker would		attacker, the Interface Identifier learned by the attacker would
	differ from the one used by the victim when connecting to the		differ from the one used by the victim when connecting to the
	legitimate network.		legitimate network.
	In any case, we note that at the point in which this kind of attack		In any case, we note that at the point in which this kind of attack
	becomes a concern, a host should consider employing Secure Neighbor		becomes a concern, a host should consider employing Secure Neighbor
	Discovery (SEND) [RFC3971] to prevent an attacker from illegitimately		Discovery (SEND) [RFC3971] to prevent an attacker from illegitimately
	claiming authority for a network prefix.		claiming authority for a network prefix.
	skipping to change at page 18, line 34		skipping to change at page 19, line 43
	as those specified in [RFC4941]). Clearly, temporary addresses may		as those specified in [RFC4941]). Clearly, temporary addresses may
	help to mitigate the correlation of activities of a node within the		help to mitigate the correlation of activities of a node within the
	same network, and may also reduce the attack exposure window (since		same network, and may also reduce the attack exposure window (since
	temporary addresses are short-lived when compared to the addresses		temporary addresses are short-lived when compared to the addresses
	generated with the method specified in this document). We note that		generated with the method specified in this document). We note that
	implementation of this algorithm would still benefit those hosts		implementation of this algorithm would still benefit those hosts
	employing "temporary addresses", since it would mitigate host-		employing "temporary addresses", since it would mitigate host-
	tracking vectors still present when such addresses are used (see		tracking vectors still present when such addresses are used (see
	[I-D.cooper-6man-ipv6-address-generation-privacy]), and would also		[I-D.cooper-6man-ipv6-address-generation-privacy]), and would also
	mitigate address-scanning techniques that leverage patterns in IPv6		mitigate address-scanning techniques that leverage patterns in IPv6
	addresses that embed IEEE identifiers.		addresses that embed IEEE LAN MAC addresses. Finally, we note that
			the method described in this document addresses some of the privacy
	Finally, we note that the method described in this document addresses		concerns arising from the use of IPv6 addresses that embed IEEE LAN
	some of the privacy concerns arising from the use of IPv6 addresses		MAC addresses, without the use of temporary addresses, thus possibly
	that embed IEEE identifiers, without the use of temporary addresses,		offering an interesting trade-off for those scenarios in which the
	thus possibly offering an interesting trade-off for those scenarios		use of temporary addresses is not feasible.
	in which the use of temporary addresses is not feasible.
	8. Acknowledgements		10. Acknowledgements
	The algorithm specified in this document has been inspired by Steven		The algorithm specified in this document has been inspired by Steven
	Bellovin's work ([RFC1948]) in the area of TCP sequence numbers.		Bellovin's work ([RFC1948]) in the area of TCP sequence numbers.
	The author would like to thank (in alphabetical order) Mikael		The author would like to thank (in alphabetical order) Mikael
	Abrahamsson, Ran Atkinson, Karl Auer, Steven Bellovin, Matthias		Abrahamsson, Ran Atkinson, Karl Auer, Steven Bellovin, Matthias
	Bethke, Ben Campbell, Brian Carpenter, Tassos Chatzithomaoglou, Tim		Bethke, Ben Campbell, Brian Carpenter, Tassos Chatzithomaoglou, Tim
	Chown, Alissa Cooper, Dominik Elsbroek, Brian Haberman, Bob Hinden,		Chown, Alissa Cooper, Dominik Elsbroek, Eric Gray, Brian Haberman,
	Christian Huitema, Ray Hunter, Jouni Korhonen, Eliot Lear, Jong-Hyouk		Bob Hinden, Christian Huitema, Ray Hunter, Jouni Korhonen, Eliot
	Lee, Andrew McGregor, Tom Petch, Michael Richardson, Mark Smith, Dave		Lear, Jong-Hyouk Lee, Andrew McGregor, Tom Petch, Michael Richardson,
	Thaler, Ole Troan, James Woodyatt, and He Xuan, for providing		Mark Smith, Dave Thaler, Ole Troan, James Woodyatt, and He Xuan, for
	valuable comments on earlier versions of this document.		providing valuable comments on earlier versions of this document.
	This document is based on the technical report "Security Assessment		This document is based on the technical report "Security Assessment
	of the Internet Protocol version 6 (IPv6)" [CPNI-IPv6] authored by		of the Internet Protocol version 6 (IPv6)" [CPNI-IPv6] authored by
	Fernando Gont on behalf of the UK Centre for the Protection of		Fernando Gont on behalf of the UK Centre for the Protection of
	National Infrastructure (CPNI).		National Infrastructure (CPNI).
	Fernando Gont would like to thank CPNI (http://www.cpni.gov.uk) for		The author would like to thank CPNI (http://www.cpni.gov.uk) for
	their continued support.		their continued support.
	9. References		11. References
	9.1. Normative References		11.1. Normative References
	[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6		[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
	(IPv6) Specification", RFC 2460, December 1998.		(IPv6) Specification", RFC 2460, December 1998.
	[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, March 1997.		Requirement Levels", BCP 14, RFC 2119, March 1997.
	[RFC2526] Johnson, D. and S. Deering, "Reserved IPv6 Subnet Anycast		[RFC2526] Johnson, D. and S. Deering, "Reserved IPv6 Subnet Anycast
	Addresses", RFC 2526, March 1999.		Addresses", RFC 2526, March 1999.
	[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,		[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
	and M. Carney, "Dynamic Host Configuration Protocol for		and M. Carney, "Dynamic Host Configuration Protocol for
	IPv6 (DHCPv6)", RFC 3315, July 2003.		IPv6 (DHCPv6)", RFC 3315, July 2003.
	[RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W.
	Stevens, "Basic Socket Interface Extensions for IPv6",
	RFC 3493, February 2003.
	[RFC3542] Stevens, W., Thomas, M., Nordmark, E., and T. Jinmei,
	"Advanced Sockets Application Program Interface (API) for
	IPv6", RFC 3542, May 2003.
	[RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure		[RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure
	Neighbor Discovery (SEND)", RFC 3971, March 2005.		Neighbor Discovery (SEND)", RFC 3971, March 2005.
	[RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)",		[RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)",
	RFC 3972, March 2005.		RFC 3972, March 2005.
	[RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness		[RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness
	Requirements for Security", BCP 106, RFC 4086, June 2005.		Requirements for Security", BCP 106, RFC 4086, June 2005.
	[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally		[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
	skipping to change at page 21, line 9		skipping to change at page 21, line 49
	"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,		"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
	September 2007.		September 2007.
	[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless		[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
	Address Autoconfiguration", RFC 4862, September 2007.		Address Autoconfiguration", RFC 4862, September 2007.
	[RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy		[RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy
	Extensions for Stateless Address Autoconfiguration in		Extensions for Stateless Address Autoconfiguration in
	IPv6", RFC 4941, September 2007.		IPv6", RFC 4941, September 2007.
	[RFC6105] Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C., and J.		11.2. Informative References
	Mohacsi, "IPv6 Router Advertisement Guard", RFC 6105,
	February 2011.
	9.2. Informative References
	[RFC1948] Bellovin, S., "Defending Against Sequence Number Attacks",		[RFC1948] Bellovin, S., "Defending Against Sequence Number Attacks",
	RFC 1948, May 1996.		RFC 1948, May 1996.
	[RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet		[RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet
	Networks", RFC 2464, December 1998.		Networks", RFC 2464, December 1998.
			[RFC2467] Crawford, M., "Transmission of IPv6 Packets over FDDI
			Networks", RFC 2467, December 1998.
			[RFC2470] Crawford, M., Narten, T., and S. Thomas, "Transmission of
			IPv6 Packets over Token Ring Networks", RFC 2470,
			December 1998.
			[RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W.
			Stevens, "Basic Socket Interface Extensions for IPv6",
			RFC 3493, February 2003.
			[RFC3542] Stevens, W., Thomas, M., Nordmark, E., and T. Jinmei,
			"Advanced Sockets Application Program Interface (API) for
			IPv6", RFC 3542, May 2003.
			[RFC6105] Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C., and J.
			Mohacsi, "IPv6 Router Advertisement Guard", RFC 6105,
			February 2011.
	[I-D.ietf-opsec-ipv6-host-scanning]		[I-D.ietf-opsec-ipv6-host-scanning]
	Gont, F. and T. Chown, "Network Reconnaissance in IPv6		Gont, F. and T. Chown, "Network Reconnaissance in IPv6
	Networks", draft-ietf-opsec-ipv6-host-scanning-02 (work in		Networks", draft-ietf-opsec-ipv6-host-scanning-02 (work in
	progress), July 2013.		progress), July 2013.
	[I-D.ietf-v6ops-ra-guard-implementation]		[I-D.ietf-v6ops-ra-guard-implementation]
	Gont, F., "Implementation Advice for IPv6 Router		Gont, F., "Implementation Advice for IPv6 Router
	Advertisement Guard (RA-Guard)",		Advertisement Guard (RA-Guard)",
	draft-ietf-v6ops-ra-guard-implementation-07 (work in		draft-ietf-v6ops-ra-guard-implementation-07 (work in
	progress), November 2012.		progress), November 2012.
	skipping to change at page 21, line 49		skipping to change at page 23, line 6
	September 25-29, 2012,		September 25-29, 2012,
	<https://speakerdeck.com/hdm/derbycon-2012-the-wild-west>.		<https://speakerdeck.com/hdm/derbycon-2012-the-wild-west>.
	[Gont-DEEPSEC2011]		[Gont-DEEPSEC2011]
	Gont, "Results of a Security Assessment of the Internet		Gont, "Results of a Security Assessment of the Internet
	Protocol version 6 (IPv6)", DEEPSEC 2011 Conference,		Protocol version 6 (IPv6)", DEEPSEC 2011 Conference,
	Vienna, Austria, November 2011, <http://		Vienna, Austria, November 2011, <http://
	www.si6networks.com/presentations/deepsec2011/		www.si6networks.com/presentations/deepsec2011/
	fgont-deepsec2011-ipv6-security.pdf>.		fgont-deepsec2011-ipv6-security.pdf>.
	[Gont-BRUCON2012]
	Gont, "Recent Advances in IPv6 Security", BRUCON 2012
	Conference, Ghent, Belgium, September 2012, <http://
	www.si6networks.com/presentations/brucon2012/
	fgont-brucon2012-recent-advances-in-ipv6-security.pdf>.
	[Broersma]		[Broersma]
	Broersma, R., "IPv6 Everywhere: Living with a Fully IPv6-		Broersma, R., "IPv6 Everywhere: Living with a Fully IPv6-
	enabled environment", Australian IPv6 Summit 2010,		enabled environment", Australian IPv6 Summit 2010,
	Melbourne, VIC Australia, October 2010, <http://		Melbourne, VIC Australia, October 2010, <http://
	www.ipv6.org.au/10ipv6summit/talks/Ron_Broersma.pdf>.		www.ipv6.org.au/10ipv6summit/talks/Ron_Broersma.pdf>.
	[IAB-PRIVACY]		[IAB-PRIVACY]
	IAB, "Privacy and IPv6 Addresses", July 2011, <http://		IAB, "Privacy and IPv6 Addresses", July 2011, <http://
	www.iab.org/wp-content/IAB-uploads/2011/07/		www.iab.org/wp-content/IAB-uploads/2011/07/
	IPv6-addresses-privacy-review.txt>.		IPv6-addresses-privacy-review.txt>.
	[CPNI-IPv6]		[CPNI-IPv6]
	Gont, F., "Security Assessment of the Internet Protocol		Gont, F., "Security Assessment of the Internet Protocol
	version 6 (IPv6)", UK Centre for the Protection of		version 6 (IPv6)", UK Centre for the Protection of
	National Infrastructure, (available on request).		National Infrastructure, (available on request).
	Appendix A. Possible sources for the Net_Iface parameter		Appendix A. Possible sources for the Net_Iface parameter
	The following subsections describe a number of possible sources for		The following subsections describe a number of possible sources for
	the Net_Iface parameter employed by the F() function in Section 3.		the Net_Iface parameter employed by the F() function in Section 5.
	The choice of a specific source for this value represents a number of		The choice of a specific source for this value represents a number of
	trade-offs, which may vary from one implementation to another.		trade-offs, which may vary from one implementation to another.
	A.1. Interface Index		A.1. Interface Index
	The Interface Index [RFC3493] [RFC3542] of an interface uniquely		The Interface Index [RFC3493] [RFC3542] of an interface uniquely
	identifies an interface within a node. However, these identifiers		identifies an interface within a node. However, these identifiers
	might or might not have the stability properties required for the		might or might not have the stability properties required for the
	Net_Iface value employed by this method. For example, the Interface		Net_Iface value employed by this method. For example, the Interface
	Index might change upon removal or installation of a network		Index might change upon removal or installation of a network
	skipping to change at page 24, line 4		skipping to change at page 25, line 4
	(for example, consider Universal Serial Bus-based network interface		(for example, consider Universal Serial Bus-based network interface
	cards which might be added or removed once the system has been		cards which might be added or removed once the system has been
	bootstrapped).		bootstrapped).
	A.3. Link-layer Addresses		A.3. Link-layer Addresses
	Link-layer addresses typically provide for unique identifiers for		Link-layer addresses typically provide for unique identifiers for
	network interfaces; although, for obvious reasons, they generally		network interfaces; although, for obvious reasons, they generally
	change when a network interface card is replaced. In scenarios where		change when a network interface card is replaced. In scenarios where
	neither Interface Indexes nor Interface Names have the stability		neither Interface Indexes nor Interface Names have the stability
	properties specified in Section 3 for Net_Iface, an implementation		properties specified in Section 5 for Net_Iface, an implementation
	might want to employ the link-layer address of the interface for the		might want to employ the link-layer address of the interface for the
	Net_Iface parameter, albeit at the expense of making the		Net_Iface parameter, albeit at the expense of making the
	corresponding IPv6 addresses dependent on the underlying network		corresponding IPv6 addresses dependent on the underlying network
	interface card (i.e., the corresponding IPv6 address would typically		interface card (i.e., the corresponding IPv6 address would typically
	change upon replacement of the underlying network interface card).		change upon replacement of the underlying network interface card).
	A.4. Logical Network Service Identity		A.4. Logical Network Service Identity
	Host operating systems with a conception of logical network service		Host operating systems with a conception of logical network service
	identity, distinct from network interface identity or index, may keep		identity, distinct from network interface identity or index, may keep
End of changes. 66 change blocks.
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