draft-ietf-ipsecme-qr-ikev2-10.txt		draft-ietf-ipsecme-qr-ikev2-11.txt
	Internet Engineering Task Force S. Fluhrer		Internet Engineering Task Force S. Fluhrer
	Internet-Draft D. McGrew		Internet-Draft P. Kampanakis
	Intended status: Standards Track P. Kampanakis		Intended status: Standards Track D. McGrew
	Expires: June 29, 2020 Cisco Systems		Expires: July 17, 2020 Cisco Systems
	V. Smyslov		V. Smyslov
	ELVIS-PLUS		ELVIS-PLUS
	December 27, 2019		January 14, 2020
	Mixing Preshared Keys in IKEv2 for Post-quantum Resistance		Mixing Preshared Keys in IKEv2 for Post-quantum Security
	draft-ietf-ipsecme-qr-ikev2-10		draft-ietf-ipsecme-qr-ikev2-11
	Abstract		Abstract
	The possibility of quantum computers poses a serious challenge to		The possibility of quantum computers poses a serious challenge to
	cryptographic algorithms deployed widely today. IKEv2 is one example		cryptographic algorithms deployed widely today. IKEv2 is one example
	of a cryptosystem that could be broken; someone storing VPN		of a cryptosystem that could be broken; someone storing VPN
	communications today could decrypt them at a later time when a		communications today could decrypt them at a later time when a
	quantum computer is available. It is anticipated that IKEv2 will be		quantum computer is available. It is anticipated that IKEv2 will be
	extended to support quantum-secure key exchange algorithms; however		extended to support quantum-secure key exchange algorithms; however
	that is not likely to happen in the near term. To address this		that is not likely to happen in the near term. To address this
	skipping to change at page 1, line 42 ¶		skipping to change at page 1, line 42 ¶
	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 29, 2020.		This Internet-Draft will expire on July 17, 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.
	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
	(https://trustee.ietf.org/license-info) in effect on the date of		(https://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
	skipping to change at page 2, line 33 ¶		skipping to change at page 2, line 33 ¶
	5. PPK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12		5. PPK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
	5.1. PPK_ID format . . . . . . . . . . . . . . . . . . . . . . 12		5.1. PPK_ID format . . . . . . . . . . . . . . . . . . . . . . 12
	5.2. Operational Considerations . . . . . . . . . . . . . . . 13		5.2. Operational Considerations . . . . . . . . . . . . . . . 13
	5.2.1. PPK Distribution . . . . . . . . . . . . . . . . . . 13		5.2.1. PPK Distribution . . . . . . . . . . . . . . . . . . 13
	5.2.2. Group PPK . . . . . . . . . . . . . . . . . . . . . . 13		5.2.2. Group PPK . . . . . . . . . . . . . . . . . . . . . . 13
	5.2.3. PPK-only Authentication . . . . . . . . . . . . . . . 14		5.2.3. PPK-only Authentication . . . . . . . . . . . . . . . 14
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 14		6. Security Considerations . . . . . . . . . . . . . . . . . . . 14
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16		7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
	8. References . . . . . . . . . . . . . . . . . . . . . . . . . 17		8. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
	8.1. Normative References . . . . . . . . . . . . . . . . . . 17		8.1. Normative References . . . . . . . . . . . . . . . . . . 17
	8.2. Informational References . . . . . . . . . . . . . . . . 17		8.2. Informational References . . . . . . . . . . . . . . . . 18
	Appendix A. Discussion and Rationale . . . . . . . . . . . . . . 18		Appendix A. Discussion and Rationale . . . . . . . . . . . . . . 19
	Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 19		Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 20
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20
	1. Introduction		1. Introduction
	Recent achievements in developing quantum computers demonstrate that		Recent achievements in developing quantum computers demonstrate that
	it is probably feasible to build a cryptographically significant one.		it is probably feasible to build a cryptographically significant one.
	If such a computer is implemented, many of the cryptographic		If such a computer is implemented, many of the cryptographic
	algorithms and protocols currently in use would be insecure. A		algorithms and protocols currently in use would be insecure. A
	quantum computer would be able to solve DH and ECDH problems in		quantum computer would be able to solve DH and ECDH problems in
	polynomial time [I-D.hoffman-c2pq], and this would imply that the		polynomial time [I-D.hoffman-c2pq], and this would imply that the
	security of existing IKEv2 [RFC7296] systems would be compromised.		security of existing IKEv2 [RFC7296] systems would be compromised.
	IKEv1 [RFC2409], when used with strong preshared keys, is not		IKEv1 [RFC2409], when used with strong preshared keys, is not
	vulnerable to quantum attacks, because those keys are one of the		vulnerable to quantum attacks, because those keys are one of the
	inputs to the key derivation function. If the preshared key has		inputs to the key derivation function. If the preshared key has
	sufficient entropy and the PRF, encryption and authentication		sufficient entropy and the PRF, encryption and authentication
	transforms are quantum-secure, then the resulting system is believed		transforms are quantum-secure, then the resulting system is believed
	to be quantum resistant, that is, invulnerable to an attacker with a		to be quantum-secure, that is, secure against classical attackers of
	quantum computer.		today or future attackers with a quantum computer.
	This document describes a way to extend IKEv2 to have a similar		This document describes a way to extend IKEv2 to have a similar
	property; assuming that the two end systems share a long secret key,		property; assuming that the two end systems share a long secret key,
	then the resulting exchange is quantum resistant. By bringing post-		then the resulting exchange is quantum-secure. By bringing post-
	quantum security to IKEv2, this note removes the need to use an		quantum security to IKEv2, this document removes the need to use an
	obsolete version of the Internet Key Exchange in order to achieve		obsolete version of the Internet Key Exchange in order to achieve
	that security goal.		that security goal.
	The general idea is that we add an additional secret that is shared		The general idea is that we add an additional secret that is shared
	between the initiator and the responder; this secret is in addition		between the initiator and the responder; this secret is in addition
	to the authentication method that is already provided within IKEv2.		to the authentication method that is already provided within IKEv2.
	We stir this secret into the SK_d value, which is used to generate		We stir this secret into the SK_d value, which is used to generate
	the key material (KEYMAT) and the SKEYSEED for the child SAs; this		the key material (KEYMAT) and the SKEYSEED for the child SAs; this
	secret provides quantum resistance to the IPsec SAs (and any child		secret provides quantum resistance to the IPsec SAs (and any child
	IKE SAs). We also stir the secret into the SK_pi, SK_pr values; this		IKE SAs). We also stir the secret into the SK_pi, SK_pr values; this
	allows both sides to detect a secret mismatch cleanly.		allows both sides to detect a secret mismatch cleanly.
	It was considered important to minimize the changes to IKEv2. The		It was considered important to minimize the changes to IKEv2. The
	existing mechanisms to do authentication and key exchange remain in		existing mechanisms to do authentication and key exchange remain in
	place (that is, we continue to do (EC)DH, and potentially PKI		place (that is, we continue to do (EC)DH, and potentially PKI
	authentication if configured). This document does not replace the		authentication if configured). This document does not replace the
	authentication checks that the protocol does; instead, it is done as		authentication checks that the protocol does; instead, they are
	a parallel check.		strengthened by using an additional secret key.
	1.1. Changes		1.1. Changes
	RFC EDITOR PLEASE DELETE THIS SECTION.		RFC EDITOR PLEASE DELETE THIS SECTION.
	Changes in this draft in each version iterations.		Changes in this draft in each version iterations.
			draft-ietf-ipsecme-qr-ikev2-11
			o Updates the IANA section based on Eric V.'s IESG Review.
			o Updates based on IESG Reviews (Alissa, Adam, Barry, Alexey, Mijra,
			Roman, Martin.
	draft-ietf-ipsecme-qr-ikev2-10		draft-ietf-ipsecme-qr-ikev2-10
	o Addresses issues raised during IETF LC.		o Addresses issues raised during IETF LC.
	draft-ietf-ipsecme-qr-ikev2-09		draft-ietf-ipsecme-qr-ikev2-09
	o Addresses issues raised in AD review.		o Addresses issues raised in AD review.
	draft-ietf-ipsecme-qr-ikev2-08		draft-ietf-ipsecme-qr-ikev2-08
	o Editorial changes.		o Editorial changes.
	draft-ietf-ipsecme-qr-ikev2-07		draft-ietf-ipsecme-qr-ikev2-07
	o Editorial changes.		o Editorial changes.
			draft-ietf-ipsecme-qr-ikev2-06
	o Editorial changes.		o Editorial changes.
	draft-ietf-ipsecme-qr-ikev2-05		draft-ietf-ipsecme-qr-ikev2-05
	o Addressed comments received during WGLC.		o Addressed comments received during WGLC.
	draft-ietf-ipsecme-qr-ikev2-04		draft-ietf-ipsecme-qr-ikev2-04
	o Using Group PPK is clarified based on comment from Quynh Dang.		o Using Group PPK is clarified based on comment from Quynh Dang.
	skipping to change at page 4, line 46 ¶		skipping to change at page 5, line 5 ¶
	o Nits and minor fixes.		o Nits and minor fixes.
	o prf is replaced with prf+ for the SK_d and SK_pi/r calculations.		o prf is replaced with prf+ for the SK_d and SK_pi/r calculations.
	o Clarified using PPK in case of EAP authentication.		o Clarified using PPK in case of EAP authentication.
	o PPK_SUPPORT notification is changed to USE_PPK to better reflect		o PPK_SUPPORT notification is changed to USE_PPK to better reflect
	its purpose.		its purpose.
	draft-ietf-ipsecme-qr-ikev2-00
	o Migrated from draft-fluhrer-qr-ikev2-05 to draft-ietf-ipsecme-qr-		o Migrated from draft-fluhrer-qr-ikev2-05 to draft-ietf-ipsecme-qr-
	ikev2-00 that is a WG item.		ikev2-00 that is a WG item.
			draft-fluhrer-qr-ikev2-05
	o Nits and editorial fixes.		o Nits and editorial fixes.
	o Made PPK_ID format and PPK Distributions subsection of the PPK		o Made PPK_ID format and PPK Distributions subsection of the PPK
	section. Also added an Operational Considerations section.		section. Also added an Operational Considerations section.
	o Added comment about Child SA rekey in the Security Considerations		o Added comment about Child SA rekey in the Security Considerations
	section.		section.
	o Added NO_PPK_AUTH to solve the cases where a PPK_ID is not		o Added NO_PPK_AUTH to solve the cases where a PPK_ID is not
	configured for a responder.		configured for a responder.
	skipping to change at page 6, line 42 ¶		skipping to change at page 6, line 47 ¶
	not used for any key derivation, and thus doesn't protect against		not used for any key derivation, and thus doesn't protect against
	quantum computers). The PPK specific configuration that is assumed		quantum computers). The PPK specific configuration that is assumed
	to be on each node consists of the following tuple:		to be on each node consists of the following tuple:
	Peer, PPK, PPK_ID, mandatory_or_not		Peer, PPK, PPK_ID, mandatory_or_not
	3. Exchanges		3. Exchanges
	If the initiator is configured to use a post-quantum preshared key		If the initiator is configured to use a post-quantum preshared key
	with the responder (whether or not the use of the PPK is mandatory),		with the responder (whether or not the use of the PPK is mandatory),
	then it will include a notification USE_PPK in the IKE_SA_INIT		then it MUST include a notification USE_PPK in the IKE_SA_INIT
	request message as follows:		request message as follows:
	Initiator Responder		Initiator Responder
	------------------------------------------------------------------		------------------------------------------------------------------
	HDR, SAi1, KEi, Ni, N(USE_PPK) --->		HDR, SAi1, KEi, Ni, N(USE_PPK) --->
	N(USE_PPK) is a status notification payload with the type 16435; it		N(USE_PPK) is a status notification payload with the type 16435; it
	has a protocol ID of 0, no SPI and no notification data associated		has a protocol ID of 0, no SPI and no notification data associated
	with it.		with it.
	If the initiator needs to resend this initial message with a cookie		If the initiator needs to resend this initial message with a COOKIE
	(because the responder response included a COOKIE notification), then		notification, then the resend would include the USE_PPK notification
	the resend would include the USE_PPK notification if the original		if the original message did (see Section 2.6 of [RFC7296]).
	message did.
	If the responder does not support this specification or does not have		If the responder does not support this specification or does not have
	any PPK configured, then it ignores the received notification (as		any PPK configured, then it ignores the received notification (as
	defined in [RFC7296] for unknown status notifications) and continues		defined in [RFC7296] for unknown status notifications) and continues
	with the IKEv2 protocol as normal. Otherwise the responder replies		with the IKEv2 protocol as normal. Otherwise the responder replies
	with the IKE_SA_INIT message including a USE_PPK notification in the		with the IKE_SA_INIT message including a USE_PPK notification in the
	response:		response:
	Initiator Responder		Initiator Responder
	------------------------------------------------------------------		------------------------------------------------------------------
	<--- HDR, SAr1, KEr, Nr, [CERTREQ,] N(USE_PPK)		<--- HDR, SAr1, KEr, Nr, [CERTREQ,] N(USE_PPK)
	When the initiator receives this reply, it checks whether the		When the initiator receives this reply, it checks whether the
	responder included the USE_PPK notification. If the responder did		responder included the USE_PPK notification. If the responder did
	not and the flag mandatory_or_not indicates that using PPKs is		not and the flag mandatory_or_not indicates that using PPKs is
	mandatory for communication with this responder, then the initiator		mandatory for communication with this responder, then the initiator
	MUST abort the exchange. This situation may happen in case of		MUST abort the exchange. This situation may happen in case of
	misconfiguration, when the initiator believes it has a mandatory to		misconfiguration, when the initiator believes it has a mandatory-to-
	use PPK for the responder, while the responder either doesn't support		use PPK for the responder, while the responder either doesn't support
	PPKs at all or doesn't have any PPK configured for the initiator.		PPKs at all or doesn't have any PPK configured for the initiator.
	See Section 6 for discussion of the possible impacts of this		See Section 6 for discussion of the possible impacts of this
	situation.		situation.
	If the responder did not include the USE_PPK notification and using a		If the responder did not include the USE_PPK notification and using a
	PPK for this particular responder is optional, then the initiator		PPK for this particular responder is optional, then the initiator
	continues with the IKEv2 protocol as normal, without using PPKs.		continues with the IKEv2 protocol as normal, without using PPKs.
	If the responder did include the USE_PPK notification, then the		If the responder did include the USE_PPK notification, then the
	initiator selects a PPK, along with its identifier PPK_ID. Then, it		initiator selects a PPK, along with its identifier PPK_ID. Then, it
	computes this modification of the standard IKEv2 key derivation:		computes this modification of the standard IKEv2 key derivation from
			Section 2.14 of [RFC7296]:
	SKEYSEED = prf(Ni | Nr, g^ir)		SKEYSEED = prf(Ni | Nr, g^ir)
	{SK_d' | SK_ai | SK_ar | SK_ei | SK_er | SK_pi' | SK_pr' )		{SK_d' | SK_ai | SK_ar | SK_ei | SK_er | SK_pi' | SK_pr' )
	= prf+ (SKEYSEED, Ni | Nr | SPIi | SPIr }		= prf+ (SKEYSEED, Ni | Nr | SPIi | SPIr }
	SK_d = prf+ (PPK, SK_d')		SK_d = prf+ (PPK, SK_d')
	SK_pi = prf+ (PPK, SK_pi')		SK_pi = prf+ (PPK, SK_pi')
	SK_pr = prf+ (PPK, SK_pr')		SK_pr = prf+ (PPK, SK_pr')
	That is, we use the standard IKEv2 key derivation process except that		That is, we use the standard IKEv2 key derivation process except that
	the three subkeys SK_d, SK_pi, SK_pr are run through the prf+ again,		the three resulting subkeys SK_d, SK_pi, SK_pr (marked with primes in
	this time using the PPK as the key. Using prf+ construction ensures		the formula above) are then run through the prf+ again, this time
	that it is always possible to get the resulting keys of the same size		using the PPK as the key. The result is the unprimed versions of
	as the initial ones, even if the underlying PRF has output size		these keys which are then used as inputs to subsequent steps of the
	different from its key size. Note, that at the time this document		IKEv2 exchange.
	was written, all PRFs defined for use in IKEv2 [IKEV2-IANA-PRFS] had
	output size equal to the (preferred) key size. For such PRFs only		Using a prf+ construction ensures that it is always possible to get
	the first iteration of prf+ is needed:		the resulting keys of the same size as the initial ones, even if the
			underlying PRF has output size different from its key size. Note,
			that at the time of this writing, all PRFs defined for use in IKEv2
			[IKEV2-IANA-PRFS] had output size equal to the (preferred) key size.
			For such PRFs only the first iteration of prf+ is needed:
	SK_d = prf (PPK, SK_d' | 0x01)		SK_d = prf (PPK, SK_d' | 0x01)
	SK_pi = prf (PPK, SK_pi' | 0x01)		SK_pi = prf (PPK, SK_pi' | 0x01)
	SK_pr = prf (PPK, SK_pr' | 0x01)		SK_pr = prf (PPK, SK_pr' | 0x01)
	Note that the PPK is used in SK_d, SK_pi and SK_pr calculation only		Note that the PPK is used in SK_d, SK_pi and SK_pr calculation only
	during the initial IKE SA setup. It MUST NOT be used when these		during the initial IKE SA setup. It MUST NOT be used when these
	subkeys are calculated as result of IKE SA rekey, resumption or other		subkeys are calculated as result of IKE SA rekey, resumption or other
	similar operation.		similar operation.
	skipping to change at page 8, line 38 ¶		skipping to change at page 9, line 7 ¶
	protocol ID of 0, no SPI and a notification data that consists of the		protocol ID of 0, no SPI and a notification data that consists of the
	identifier PPK_ID.		identifier PPK_ID.
	A situation may happen when the responder has some PPKs, but doesn't		A situation may happen when the responder has some PPKs, but doesn't
	have a PPK with the PPK_ID received from the initiator. In this case		have a PPK with the PPK_ID received from the initiator. In this case
	the responder cannot continue with PPK (in particular, it cannot		the responder cannot continue with PPK (in particular, it cannot
	authenticate the initiator), but the responder could be able to		authenticate the initiator), but the responder could be able to
	continue with normal IKEv2 protocol if the initiator provided its		continue with normal IKEv2 protocol if the initiator provided its
	authentication data computed as in normal IKEv2, without using PPKs.		authentication data computed as in normal IKEv2, without using PPKs.
	For this purpose, if using PPKs for communication with this responder		For this purpose, if using PPKs for communication with this responder
	is optional for the initiator, then the initiator MAY include a		is optional for the initiator (based on the mandatory_or_not flag),
	notification NO_PPK_AUTH in the above message.		then the initiator MUST include a NO_PPK_AUTH notification in the
			above message. This notification informs the responder that PPK is
			optional and allows for authenticating the initiator without using
			PPK.
	NO_PPK_AUTH is a status notification with the type 16437; it has a		NO_PPK_AUTH is a status notification with the type 16437; it has a
	protocol ID of 0 and no SPI. The Notification Data field contains		protocol ID of 0 and no SPI. The Notification Data field contains
	the initiator's authentication data computed using SK_pi', which has		the initiator's authentication data computed using SK_pi', which has
	been computed without using PPKs. This is the same data that would		been computed without using PPKs. This is the same data that would
	normally be placed in the Authentication Data field of an AUTH		normally be placed in the Authentication Data field of an AUTH
	payload. Since the Auth Method field is not present in the		payload. Since the Auth Method field is not present in the
	notification, the authentication method used for computing the		notification, the authentication method used for computing the
	authentication data MUST be the same as method indicated in the AUTH		authentication data MUST be the same as method indicated in the AUTH
	payload. Note that if the initiator decides to include the		payload. Note that if the initiator decides to include the
	NO_PPK_AUTH notification, the initiator needs to perform		NO_PPK_AUTH notification, the initiator needs to perform
	authentication data computation twice, which may consume computation		authentication data computation twice, which may consume computation
	power (e.g. if digital signatures are involved).		power (e.g., if digital signatures are involved).
	When the responder receives this encrypted exchange, it first		When the responder receives this encrypted exchange, it first
	computes the values:		computes the values:
	SKEYSEED = prf(Ni | Nr, g^ir)		SKEYSEED = prf(Ni | Nr, g^ir)
	{SK_d' | SK_ai | SK_ar | SK_ei | SK_er | SK_pi' | SK_pr' }		{SK_d' | SK_ai | SK_ar | SK_ei | SK_er | SK_pi' | SK_pr' }
	= prf+ (SKEYSEED, Ni | Nr | SPIi | SPIr )		= prf+ (SKEYSEED, Ni | Nr | SPIi | SPIr )
	The responder then uses the SK_ei/SK_ai values to decrypt/check the		The responder then uses the SK_ei/SK_ai values to decrypt/check the
	message and then scans through the payloads for the PPK_ID attached		message and then scans through the payloads for the PPK_ID attached
	skipping to change at page 12, line 12 ¶		skipping to change at page 12, line 30 ¶
	both peers have been upgraded, but the responder isn't yet configured		both peers have been upgraded, but the responder isn't yet configured
	with the PPK for the initiator, then the responder could do standard		with the PPK for the initiator, then the responder could do standard
	IKEv2 protocol if the initiator sent NO_PPK_AUTH notification. If		IKEv2 protocol if the initiator sent NO_PPK_AUTH notification. If
	both the responder and initiator have been upgraded and properly		both the responder and initiator have been upgraded and properly
	configured, they will both realize it, and the Child SAs will be		configured, they will both realize it, and the Child SAs will be
	quantum-secure.		quantum-secure.
	As an optional second step, after all nodes have been upgraded, then		As an optional second step, after all nodes have been upgraded, then
	the administrator should then go back through the nodes, and mark the		the administrator should then go back through the nodes, and mark the
	use of PPK as mandatory. This will not affect the strength against a		use of PPK as mandatory. This will not affect the strength against a
	passive attacker; it would mean that an attacker with a quantum		passive attacker, but it would mean that an active attacker with a
	computer (which is sufficiently fast to be able to break the (EC)DH		quantum computer (which is sufficiently fast to be able to break the
	in real time) would not be able to perform a downgrade attack.		(EC)DH in real-time) would not be able to perform a downgrade attack.
	5. PPK		5. PPK
	5.1. PPK_ID format		5.1. PPK_ID format
	This standard requires that both the initiator and the responder have		This standard requires that both the initiator and the responder have
	a secret PPK value, with the responder selecting the PPK based on the		a secret PPK value, with the responder selecting the PPK based on the
	PPK_ID that the initiator sends. In this standard, both the		PPK_ID that the initiator sends. In this standard, both the
	initiator and the responder are configured with fixed PPK and PPK_ID		initiator and the responder are configured with fixed PPK and PPK_ID
	values, and do the look up based on PPK_ID value. It is anticipated		values, and do the look up based on PPK_ID value. It is anticipated
	that later standards will extend this technique to allow dynamically		that later specifications will extend this technique to allow
	changing PPK values. To facilitate such an extension, we specify		dynamically changing PPK values. To facilitate such an extension, we
	that the PPK_ID the initiator sends will have its first octet be the		specify that the PPK_ID the initiator sends will have its first octet
	PPK_ID Type value. This document defines two values for PPK_ID Type:		be the PPK_ID Type value. This document defines two values for
			PPK_ID Type:
	o PPK_ID_OPAQUE (1) - for this type the format of the PPK_ID (and		o PPK_ID_OPAQUE (1) - for this type the format of the PPK_ID (and
	the PPK itself) is not specified by this document; it is assumed		the PPK itself) is not specified by this document; it is assumed
	to be mutually intelligible by both by initiator and the		to be mutually intelligible by both by initiator and the
	responder. This PPK_ID type is intended for those implementations		responder. This PPK_ID type is intended for those implementations
	that choose not to disclose the type of PPK to active attackers.		that choose not to disclose the type of PPK to active attackers.
	o PPK_ID_FIXED (2) - in this case the format of the PPK_ID and the		o PPK_ID_FIXED (2) - in this case the format of the PPK_ID and the
	PPK are fixed octet strings; the remaining bytes of the PPK_ID are		PPK are fixed octet strings; the remaining bytes of the PPK_ID are
	a configured value. We assume that there is a fixed mapping		a configured value. We assume that there is a fixed mapping
	between PPK_ID and PPK, which is configured locally to both the		between PPK_ID and PPK, which is configured locally to both the
	initiator and the responder. The responder can use the PPK_ID to		initiator and the responder. The responder can use the PPK_ID to
	look up the corresponding PPK value. Not all implementations are		look up the corresponding PPK value. Not all implementations are
	able to configure arbitrary octet strings; to improve the		able to configure arbitrary octet strings; to improve the
	potential interoperability, it is recommended that, in the		potential interoperability, it is recommended that, in the
	PPK_ID_FIXED case, both the PPK and the PPK_ID strings be limited		PPK_ID_FIXED case, both the PPK and the PPK_ID strings be limited
	to the base64 character set, namely the 64 characters 0-9, A-Z,		to the Base64 character set [RFC4648].
	a-z, + and /.
	The PPK_ID type value 0 is reserved; values 3-127 are reserved for
	IANA; values 128-255 are for private use among mutually consenting
	parties.
	5.2. Operational Considerations		5.2. Operational Considerations
	The need to maintain several independent sets of security credentials		The need to maintain several independent sets of security credentials
	can significantly complicate a security administrator's job, and can		can significantly complicate a security administrator's job, and can
	potentially slow down widespread adoption of this specification. It		potentially slow down widespread adoption of this specification. It
	is anticipated, that administrators will try to simplify their job by		is anticipated, that administrators will try to simplify their job by
	decreasing the number of credentials they need to maintain. This		decreasing the number of credentials they need to maintain. This
	section describes some of the considerations for PPK management.		section describes some of the considerations for PPK management.
	skipping to change at page 14, line 21 ¶		skipping to change at page 14, line 31 ¶
	Combining group PPK and PPK-only authentication is NOT RECOMMENDED,		Combining group PPK and PPK-only authentication is NOT RECOMMENDED,
	since in this case any member of the group can impersonate any other		since in this case any member of the group can impersonate any other
	member even without help of quantum computers.		member even without help of quantum computers.
	PPK-only authentication can be achieved in IKEv2 if the NULL		PPK-only authentication can be achieved in IKEv2 if the NULL
	Authentication method [RFC7619] is employed. Without PPK the NULL		Authentication method [RFC7619] is employed. Without PPK the NULL
	Authentication method provides no authentication of the peers,		Authentication method provides no authentication of the peers,
	however since a PPK is stirred into the SK_pi and the SK_pr, the		however since a PPK is stirred into the SK_pi and the SK_pr, the
	peers become authenticated if a PPK is in use. Using PPKs MUST be		peers become authenticated if a PPK is in use. Using PPKs MUST be
	mandatory for the peers if they advertise support for PPK in		mandatory for the peers if they advertise support for PPK in
	IKE_SA_INIT and use NULL Authentication. Addtionally, since the		IKE_SA_INIT and use NULL Authentication. Additionally, since the
	peers are authenticated via PPK, the ID Type in the IDi/IDr payloads		peers are authenticated via PPK, the ID Type in the IDi/IDr payloads
	SHOULD NOT be ID_NULL, despite using the NULL Authentication method.		SHOULD NOT be ID_NULL, despite using the NULL Authentication method.
	6. Security Considerations		6. Security Considerations
	Quantum computers are able to perform Grover's algorithm [GROVER];		Quantum computers are able to perform Grover's algorithm [GROVER];
	that effectively halves the size of a symmetric key. Because of		that effectively halves the size of a symmetric key. Because of
	this, the user SHOULD ensure that the post-quantum preshared key used		this, the user SHOULD ensure that the post-quantum preshared key used
	has at least 256 bits of entropy, in order to provide 128 bits of		has at least 256 bits of entropy, in order to provide 128 bits of
	post-quantum security. That provides security equivalent to Level 5		post-quantum security. That provides security equivalent to Level 5
	as defined in the NIST PQ Project Call For Proposals [NISTPQCFP].		as defined in the NIST PQ Project Call For Proposals [NISTPQCFP].
	With this protocol, the computed SK_d is a function of the PPK.		With this protocol, the computed SK_d is a function of the PPK.
	Assuming that the PPK has sufficient entropy (for example, at least		Assuming that the PPK has sufficient entropy (for example, at least
	2^256 possible values), then even if an attacker was able to recover		2^256 possible values), then even if an attacker was able to recover
	the rest of the inputs to the PRF function, it would be infeasible to		the rest of the inputs to the PRF function, it would be infeasible to
	use Grover's algorithm with a quantum computer to recover the SK_d		use Grover's algorithm with a quantum computer to recover the SK_d
	value. Similarly, all keys that are a function of SK_d, which		value. Similarly, all keys that are a function of SK_d, which
	include all Child SAs keys and all keys for subsequent IKE SAs		include all Child SAs keys and all keys for subsequent IKE SAs
	(created when the initial IKE SA is rekeyed), are also quantum		(created when the initial IKE SA is rekeyed), are also quantum-secure
	resistant (assuming that the PPK was of high enough entropy, and that		(assuming that the PPK was of high enough entropy, and that all the
	all the subkeys are sufficiently long).		subkeys are sufficiently long).
	An attacker with a quantum computer that can decrypt the initial IKE		An attacker with a quantum computer that can decrypt the initial IKE
	SA has access to all the information exchanged over it, such as		SA has access to all the information exchanged over it, such as
	identities of the peers, configuration parameters and all negotiated		identities of the peers, configuration parameters and all negotiated
	IPsec SAs information (including traffic selectors), with the		IPsec SAs information (including traffic selectors), with the
	exception of the cryptographic keys used by the IPsec SAs which are		exception of the cryptographic keys used by the IPsec SAs which are
	protected by the PPK.		protected by the PPK.
	Deployments that treat this information as sensitive or that send		Deployments that treat this information as sensitive or that send
	other sensitive data (like cryptographic keys) over IKE SA MUST rekey		other sensitive data (like cryptographic keys) over IKE SA MUST rekey
	the IKE SA before the sensitive information is sent to ensure this		the IKE SA before the sensitive information is sent to ensure this
	information is protected by the PPK. It is possible to create a		information is protected by the PPK. It is possible to create a
	childless IKE SA as specified in [RFC6023]. This prevents Child SA		childless IKE SA as specified in [RFC6023]. This prevents Child SA
	configuration information from being transmited in the original IKE		configuration information from being transmitted in the original IKE
	SA that is not protected by a PPK. Some information related to IKE		SA that is not protected by a PPK. Some information related to IKE
	SA, that is sent in the IKE_AUTH exchange, such as peer identities,		SA, that is sent in the IKE_AUTH exchange, such as peer identities,
	feature notifications, Vendor ID's etc. cannot be hidden from the		feature notifications, Vendor ID's etc. cannot be hidden from the
	attack described above, even if the additional IKE SA rekey is		attack described above, even if the additional IKE SA rekey is
	performed.		performed.
	In addition, the policy SHOULD be set to negotiate only quantum-		In addition, the policy SHOULD be set to negotiate only quantum-
	resistant symmetric algorithms; while this RFC doesn't claim to give		secure symmetric algorithms; while this RFC doesn't claim to give
	advice as to what algorithms are secure (as that may change based on		advice as to what algorithms are secure (as that may change based on
	future cryptographical results), below is a list of defined IKEv2 and		future cryptographical results), below is a list of defined IKEv2 and
	IPsec algorithms that should not be used, as they are known to		IPsec algorithms that should not be used, as they are known to
	provide less than 128 bits of post-quantum security		provide less than 128 bits of post-quantum security
	o Any IKEv2 Encryption algorithm, PRF or Integrity algorithm with		o Any IKEv2 Encryption algorithm, PRF or Integrity algorithm with
	key size less than 256 bits.		key size less than 256 bits.
	o Any ESP Transform with key size less than 256 bits.		o Any ESP Transform with key size less than 256 bits.
	skipping to change at page 15, line 41 ¶		skipping to change at page 15, line 50 ¶
	128-bit key internally.		128-bit key internally.
	Section 3 requires the initiator to abort the initial exchange if		Section 3 requires the initiator to abort the initial exchange if
	using PPKs is mandatory for it, but the responder does not include		using PPKs is mandatory for it, but the responder does not include
	the USE_PPK notification in the response. In this situation, when		the USE_PPK notification in the response. In this situation, when
	the initiator aborts negotiation it leaves a half-open IKE SA on the		the initiator aborts negotiation it leaves a half-open IKE SA on the
	responder (because IKE_SA_INIT completes successfully from the		responder (because IKE_SA_INIT completes successfully from the
	responder's point of view). This half-open SA will eventually expire		responder's point of view). This half-open SA will eventually expire
	and be deleted, but if the initiator continues its attempts to create		and be deleted, but if the initiator continues its attempts to create
	IKE SA with a high enough rate, then the responder may consider it as		IKE SA with a high enough rate, then the responder may consider it as
	a Denial-of-Service attack and take protection measures (see		a Denial-of-Service (DoS) attack and take protection measures (see
	[RFC8019] for more detail). In this situation, it is RECOMMENDED		[RFC8019] for more detail). In this situation, it is RECOMMENDED
	that the initiator caches the negative result of the negotiation for		that the initiator caches the negative result of the negotiation and
	some time and doesn't make attempts to create it again for some time,		doesn't make attempts to create it again for some time. This period
	because this is a result of misconfiguration and probably some re-		of time may vary, but it is believed that waiting for at least few
	configuration of the peers is needed.		minutes will not cause the responder to treat it as DoS attack.
			Note, that this situation would most likely be a result of
			misconfiguration and some re-configuration of the peers would
			probably be needed.
	If using PPKs is optional for both peers and they authenticate		If using PPKs is optional for both peers and they authenticate
	themselves using digital signatures, then an attacker in between,		themselves using digital signatures, then an attacker in between,
	equipped with a quantum computer capable of breaking public key		equipped with a quantum computer capable of breaking public key
	operations in real time, is able to mount downgrade attack by		operations in real time, is able to mount downgrade attack by
	removing USE_PPK notification from the IKE_SA_INIT and forging		removing USE_PPK notification from the IKE_SA_INIT and forging
	digital signatures in the subsequent exchange. If using PPKs is		digital signatures in the subsequent exchange. If using PPKs is
	mandatory for at least one of the peers or PSK is used for		mandatory for at least one of the peers or PSK is used for
	authentication, then the attack will be detected and the SA won't be		authentication, then the attack will be detected and the SA won't be
	created.		created.
	skipping to change at page 16, line 19 ¶		skipping to change at page 16, line 32 ¶
	If using PPKs is mandatory for the initiator, then an attacker able		If using PPKs is mandatory for the initiator, then an attacker able
	to eavesdrop and to inject packets into the network can prevent		to eavesdrop and to inject packets into the network can prevent
	creating an IKE SA by mounting the following attack. The attacker		creating an IKE SA by mounting the following attack. The attacker
	intercepts the initial request containing the USE_PPK notification		intercepts the initial request containing the USE_PPK notification
	and injects a forged response containing no USE_PPK. If the attacker		and injects a forged response containing no USE_PPK. If the attacker
	manages to inject this packet before the responder sends a genuine		manages to inject this packet before the responder sends a genuine
	response, then the initiator would abort the exchange. To thwart		response, then the initiator would abort the exchange. To thwart
	this kind of attack it is RECOMMENDED, that if using PPKs is		this kind of attack it is RECOMMENDED, that if using PPKs is
	mandatory for the initiator and the received response doesn't contain		mandatory for the initiator and the received response doesn't contain
	the USE_PPK notification, then the initiator doesn't abort the		the USE_PPK notification, then the initiator doesn't abort the
	exchange immediately, but instead waits some time for more responses		exchange immediately. Instead it waits for more response messages
	(possibly retransmitting the request). If all the received responses		retransmitting the request as if no responses were received at all,
	contain no USE_PPK, then the exchange is aborted.		until either the received message contains the USE_PPK or the
			exchange times out (see section 2.4 of [RFC7296] for more details
			about retransmission timers in IKEv2). If neither of the received
			responses contains USE_PPK, then the exchange is aborted.
	If using PPK is optional for both peers, then in case of		If using PPK is optional for both peers, then in case of
	misconfiguration (e.g. mismatched PPK_ID) the IKE SA will be created		misconfiguration (e.g., mismatched PPK_ID) the IKE SA will be created
	without protection against quantum computers. It is advised that if		without protection against quantum computers. It is advised that if
	PPK was configured, but was not used for a particular IKE SA, then		PPK was configured, but was not used for a particular IKE SA, then
	implementations SHOULD audit this event.		implementations SHOULD audit this event.
	7. IANA Considerations		7. IANA Considerations
	This document defines three new Notify Message Types in the "Notify		This document defines three new Notify Message Types in the "Notify
	Message Types - Status Types" registry:		Message Types - Status Types" registry
			(https://www.iana.org/assignments/ikev2-parameters/
			ikev2-parameters.xhtml#ikev2-parameters-16):
	16435 USE_PPK [THIS RFC]		16435 USE_PPK [THIS RFC]
	16436 PPK_IDENTITY [THIS RFC]		16436 PPK_IDENTITY [THIS RFC]
	16437 NO_PPK_AUTH [THIS RFC]		16437 NO_PPK_AUTH [THIS RFC]
	This document also creates a new IANA registry "IKEv2 Post-quantum		This document also creates a new IANA registry "IKEv2 Post-quantum
	Preshared Key ID Types" in IKEv2 IANA registry		Preshared Key ID Types" in IKEv2 IANA registry
	(https://www.iana.org/assignments/ikev2-parameters/) for the PPK_ID		(https://www.iana.org/assignments/ikev2-parameters/) for the PPK_ID
	types. The initial values of the new registry are:		types used in the PPK_IDENTITY notification defined in this
			specification. The initial values of the new registry are:
	PPK_ID Type Value Reference		PPK_ID Type Value Reference
	----------- ----- ---------		----------- ----- ---------
	Reserved 0 [THIS RFC]		Reserved 0 [THIS RFC]
	PPK_ID_OPAQUE 1 [THIS RFC]		PPK_ID_OPAQUE 1 [THIS RFC]
	PPK_ID_FIXED 2 [THIS RFC]		PPK_ID_FIXED 2 [THIS RFC]
	Unassigned 3-127 [THIS RFC]		Unassigned 3-127 [THIS RFC]
	Reserved for private use 128-255 [THIS RFC]		Private Use 128-255 [THIS RFC]
	Changes and additions to this registry are by Expert Review
	[RFC8126].		The PPK_ID type value 0 is reserved; values 3-127 are to be assigned
			by IANA; values 128-255 are for private use among mutually consenting
			parties. To register new PPK_IDs in the unassigned range, a Type
			name, a Value between 3 and 127 and a Reference specification need to
			be defined. Changes and additions to the unassigned range of this
			registry are by the Expert Review Policy [RFC8126]. Changes and
			additions to the private use range of this registry are by the
			Private Use Policy [RFC8126].
	8. References		8. References
	8.1. Normative References		8.1. 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>.
	skipping to change at page 17, line 44 ¶		skipping to change at page 18, line 24 ¶
	progress), November 2019.		progress), November 2019.
	[IKEV2-IANA-PRFS]		[IKEV2-IANA-PRFS]
	"Internet Key Exchange Version 2 (IKEv2) Parameters,		"Internet Key Exchange Version 2 (IKEv2) Parameters,
	Transform Type 2 - Pseudorandom Function Transform IDs",		Transform Type 2 - Pseudorandom Function Transform IDs",
	<https://www.iana.org/assignments/ikev2-parameters/		<https://www.iana.org/assignments/ikev2-parameters/
	ikev2-parameters.xhtml#ikev2-parameters-6>.		ikev2-parameters.xhtml#ikev2-parameters-6>.
	[NISTPQCFP]		[NISTPQCFP]
	NIST, "NIST Post-Quantum Cryptography Call for Proposals",		NIST, "NIST Post-Quantum Cryptography Call for Proposals",
	2016.		2016, <https://csrc.nist.gov/CSRC/media/Projects/Post-
			Quantum-Cryptography/documents/call-for-proposals-final-
			dec-2016.pdf>.
	[RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange		[RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange
	(IKE)", RFC 2409, DOI 10.17487/RFC2409, November 1998,		(IKE)", RFC 2409, DOI 10.17487/RFC2409, November 1998,
	<https://www.rfc-editor.org/info/rfc2409>.		<https://www.rfc-editor.org/info/rfc2409>.
			[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
			Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
			<https://www.rfc-editor.org/info/rfc4648>.
	[RFC6023] Nir, Y., Tschofenig, H., Deng, H., and R. Singh, "A		[RFC6023] Nir, Y., Tschofenig, H., Deng, H., and R. Singh, "A
	Childless Initiation of the Internet Key Exchange Version		Childless Initiation of the Internet Key Exchange Version
	2 (IKEv2) Security Association (SA)", RFC 6023,		2 (IKEv2) Security Association (SA)", RFC 6023,
	DOI 10.17487/RFC6023, October 2010,		DOI 10.17487/RFC6023, October 2010,
	<https://www.rfc-editor.org/info/rfc6023>.		<https://www.rfc-editor.org/info/rfc6023>.
	[RFC6030] Hoyer, P., Pei, M., and S. Machani, "Portable Symmetric		[RFC6030] Hoyer, P., Pei, M., and S. Machani, "Portable Symmetric
	Key Container (PSKC)", RFC 6030, DOI 10.17487/RFC6030,		Key Container (PSKC)", RFC 6030, DOI 10.17487/RFC6030,
	October 2010, <https://www.rfc-editor.org/info/rfc6030>.		October 2010, <https://www.rfc-editor.org/info/rfc6030>.
	skipping to change at page 19, line 10 ¶		skipping to change at page 19, line 44 ¶
	Another goal of this protocol is to minimize the number of changes		Another goal of this protocol is to minimize the number of changes
	within the IKEv2 protocol, and in particular, within the cryptography		within the IKEv2 protocol, and in particular, within the cryptography
	of IKEv2. By limiting our changes to notifications, and only		of IKEv2. By limiting our changes to notifications, and only
	adjusting the SK_d, SK_pi, SK_pr, it is hoped that this would be		adjusting the SK_d, SK_pi, SK_pr, it is hoped that this would be
	implementable, even on systems that perform most of the IKEv2		implementable, even on systems that perform most of the IKEv2
	processing in hardware.		processing in hardware.
	A third goal was to be friendly to incremental deployment in		A third goal was to be friendly to incremental deployment in
	operational networks, for which we might not want to have a global		operational networks, for which we might not want to have a global
	shared key, or quantum resistant IKEv2 is rolled out incrementally.		shared key, or quantum-secure IKEv2 is rolled out incrementally.
	This is why we specifically try to allow the PPK to be dependent on		This is why we specifically try to allow the PPK to be dependent on
	the peer, and why we allow the PPK to be configured as optional.		the peer, and why we allow the PPK to be configured as optional.
	A fourth goal was to avoid violating any of the security properties		A fourth goal was to avoid violating any of the security properties
	provided by IKEv2.		provided by IKEv2.
	Appendix B. Acknowledgements		Appendix B. Acknowledgements
	We would like to thank Tero Kivinen, Paul Wouters, Graham Bartlett,		We would like to thank Tero Kivinen, Paul Wouters, Graham Bartlett,
	Tommy Pauly, Quynh Dang and the rest of the IPSecME Working Group for		Tommy Pauly, Quynh Dang and the rest of the IPSecME Working Group for
	their feedback and suggestions for the scheme.		their feedback and suggestions for the scheme.
	Authors' Addresses		Authors' Addresses
	Scott Fluhrer		Scott Fluhrer
	Cisco Systems		Cisco Systems
	Email: sfluhrer@cisco.com		Email: sfluhrer@cisco.com
	David McGrew		Panos Kampanakis
	Cisco Systems		Cisco Systems
	Email: mcgrew@cisco.com		Email: pkampana@cisco.com
	Panos Kampanakis		David McGrew
	Cisco Systems		Cisco Systems
	Email: pkampana@cisco.com		Email: mcgrew@cisco.com
	Valery Smyslov		Valery Smyslov
	ELVIS-PLUS		ELVIS-PLUS
	Phone: +7 495 276 0211		Phone: +7 495 276 0211
	Email: svan@elvis.ru		Email: svan@elvis.ru
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