draft-ietf-uta-tls-bcp-09.txt		draft-ietf-uta-tls-bcp-10.txt
	UTA Y. Sheffer		UTA Y. Sheffer
	Internet-Draft Porticor		Internet-Draft Intuit
	Intended status: Best Current Practice R. Holz		Intended status: Best Current Practice R. Holz
	Expires: August 15, 2015 TUM		Expires: August 24, 2015 TUM
	P. Saint-Andre		P. Saint-Andre
	&yet		&yet
	February 11, 2015		February 20, 2015
	Recommendations for Secure Use of TLS and DTLS		Recommendations for Secure Use of TLS and DTLS
	draft-ietf-uta-tls-bcp-09		draft-ietf-uta-tls-bcp-10
	Abstract		Abstract
	Transport Layer Security (TLS) and Datagram Transport Layer Security		Transport Layer Security (TLS) and Datagram Transport Layer Security
	(DTLS) are widely used to protect data exchanged over application		(DTLS) are widely used to protect data exchanged over application
	protocols such as HTTP, SMTP, IMAP, POP, SIP, and XMPP. Over the		protocols such as HTTP, SMTP, IMAP, POP, SIP, and XMPP. Over the
	last few years, several serious attacks on TLS have emerged,		last few years, several serious attacks on TLS have emerged,
	including attacks on its most commonly used cipher suites and modes		including attacks on its most commonly used cipher suites and their
	of operation. This document provides recommendations for improving		modes of operation. This document provides recommendations for
	the security of deployed services that use TLS and DTLS. The		improving the security of deployed services that use TLS and DTLS.
	recommendations are applicable to the majority of use cases.		The recommendations are applicable to the majority of use cases.
	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 August 15, 2015.		This Internet-Draft will expire on August 24, 2015.
	Copyright Notice		Copyright Notice
	Copyright (c) 2015 IETF Trust and the persons identified as the		Copyright (c) 2015 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
	skipping to change at page 2, line 23		skipping to change at page 2, line 23
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
	2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4		2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
	3. General Recommendations . . . . . . . . . . . . . . . . . . . 4		3. General Recommendations . . . . . . . . . . . . . . . . . . . 4
	3.1. Protocol Versions . . . . . . . . . . . . . . . . . . . . 4		3.1. Protocol Versions . . . . . . . . . . . . . . . . . . . . 4
	3.1.1. SSL/TLS Protocol Versions . . . . . . . . . . . . . . 4		3.1.1. SSL/TLS Protocol Versions . . . . . . . . . . . . . . 4
	3.1.2. DTLS Protocol Versions . . . . . . . . . . . . . . . 5		3.1.2. DTLS Protocol Versions . . . . . . . . . . . . . . . 5
	3.1.3. Fallback to Lower Versions . . . . . . . . . . . . . 6		3.1.3. Fallback to Lower Versions . . . . . . . . . . . . . 6
	3.2. Strict TLS . . . . . . . . . . . . . . . . . . . . . . . 6		3.2. Strict TLS . . . . . . . . . . . . . . . . . . . . . . . 6
	3.3. Compression . . . . . . . . . . . . . . . . . . . . . . . 7		3.3. Compression . . . . . . . . . . . . . . . . . . . . . . . 7
	3.4. TLS Session Resumption . . . . . . . . . . . . . . . . . 7		3.4. TLS Session Resumption . . . . . . . . . . . . . . . . . 7
	3.5. TLS Renegotiation . . . . . . . . . . . . . . . . . . . . 7		3.5. TLS Renegotiation . . . . . . . . . . . . . . . . . . . . 8
	3.6. Server Name Indication . . . . . . . . . . . . . . . . . 8		3.6. Server Name Indication . . . . . . . . . . . . . . . . . 8
	4. Recommendations: Cipher Suites . . . . . . . . . . . . . . . 8		4. Recommendations: Cipher Suites . . . . . . . . . . . . . . . 8
	4.1. General Guidelines . . . . . . . . . . . . . . . . . . . 8		4.1. General Guidelines . . . . . . . . . . . . . . . . . . . 8
	4.2. Recommended Cipher Suites . . . . . . . . . . . . . . . . 10		4.2. Recommended Cipher Suites . . . . . . . . . . . . . . . . 10
	4.2.1. Implementation Details . . . . . . . . . . . . . . . 10		4.2.1. Implementation Details . . . . . . . . . . . . . . . 11
	4.3. Public Key Length . . . . . . . . . . . . . . . . . . . . 11		4.3. Public Key Length . . . . . . . . . . . . . . . . . . . . 11
	4.4. Modular vs. Elliptic Curve DH Cipher Suites . . . . . . . 12		4.4. Modular vs. Elliptic Curve DH Cipher Suites . . . . . . . 12
	4.5. Truncated HMAC . . . . . . . . . . . . . . . . . . . . . 13		4.5. Truncated HMAC . . . . . . . . . . . . . . . . . . . . . 13
	5. Applicability Statement . . . . . . . . . . . . . . . . . . . 13		5. Applicability Statement . . . . . . . . . . . . . . . . . . . 13
	5.1. Security Services . . . . . . . . . . . . . . . . . . . . 13		5.1. Security Services . . . . . . . . . . . . . . . . . . . . 14
	5.2. Unauthenticated TLS and Opportunistic Security . . . . . 14		5.2. Unauthenticated TLS and Opportunistic Security . . . . . 15
	6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15		6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
	7. Security Considerations . . . . . . . . . . . . . . . . . . . 15		7. Security Considerations . . . . . . . . . . . . . . . . . . . 16
	7.1. Host Name Validation . . . . . . . . . . . . . . . . . . 15		7.1. Host Name Validation . . . . . . . . . . . . . . . . . . 16
	7.2. AES-GCM . . . . . . . . . . . . . . . . . . . . . . . . . 16		7.2. AES-GCM . . . . . . . . . . . . . . . . . . . . . . . . . 17
	7.3. Forward Secrecy . . . . . . . . . . . . . . . . . . . . . 16		7.3. Forward Secrecy . . . . . . . . . . . . . . . . . . . . . 17
	7.4. Diffie-Hellman Exponent Reuse . . . . . . . . . . . . . . 17		7.4. Diffie-Hellman Exponent Reuse . . . . . . . . . . . . . . 18
	7.5. Certificate Revocation . . . . . . . . . . . . . . . . . 18		7.5. Certificate Revocation . . . . . . . . . . . . . . . . . 18
	8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19		8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . 19		9. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
	9.1. Normative References . . . . . . . . . . . . . . . . . . 19		9.1. Normative References . . . . . . . . . . . . . . . . . . 20
	9.2. Informative References . . . . . . . . . . . . . . . . . 20		9.2. Informative References . . . . . . . . . . . . . . . . . 21
	Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 24		Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 25
	A.1. draft-ietf-uta-tls-bcp-08 . . . . . . . . . . . . . . . . 24		A.1. draft-ietf-uta-tls-bcp-08 . . . . . . . . . . . . . . . . 25
	A.2. draft-ietf-uta-tls-bcp-07 . . . . . . . . . . . . . . . . 24		A.2. draft-ietf-uta-tls-bcp-07 . . . . . . . . . . . . . . . . 25
	A.3. draft-ietf-uta-tls-bcp-06 . . . . . . . . . . . . . . . . 24		A.3. draft-ietf-uta-tls-bcp-06 . . . . . . . . . . . . . . . . 25
	A.4. draft-ietf-uta-tls-bcp-05 . . . . . . . . . . . . . . . . 24		A.4. draft-ietf-uta-tls-bcp-05 . . . . . . . . . . . . . . . . 25
	A.5. draft-ietf-uta-tls-bcp-04 . . . . . . . . . . . . . . . . 24		A.5. draft-ietf-uta-tls-bcp-04 . . . . . . . . . . . . . . . . 26
	A.6. draft-ietf-uta-tls-bcp-03 . . . . . . . . . . . . . . . . 24		A.6. draft-ietf-uta-tls-bcp-03 . . . . . . . . . . . . . . . . 26
	A.7. draft-ietf-uta-tls-bcp-02 . . . . . . . . . . . . . . . . 25		A.7. draft-ietf-uta-tls-bcp-02 . . . . . . . . . . . . . . . . 26
	A.8. draft-ietf-tls-bcp-01 . . . . . . . . . . . . . . . . . . 25		A.8. draft-ietf-tls-bcp-01 . . . . . . . . . . . . . . . . . . 26
	A.9. draft-ietf-tls-bcp-00 . . . . . . . . . . . . . . . . . . 25		A.9. draft-ietf-tls-bcp-00 . . . . . . . . . . . . . . . . . . 27
	A.10. draft-sheffer-tls-bcp-02 . . . . . . . . . . . . . . . . 25		A.10. draft-sheffer-tls-bcp-02 . . . . . . . . . . . . . . . . 27
	A.11. draft-sheffer-tls-bcp-01 . . . . . . . . . . . . . . . . 26		A.11. draft-sheffer-tls-bcp-01 . . . . . . . . . . . . . . . . 27
	A.12. draft-sheffer-tls-bcp-00 . . . . . . . . . . . . . . . . 26		A.12. draft-sheffer-tls-bcp-00 . . . . . . . . . . . . . . . . 27
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28
	1. Introduction		1. Introduction
	Transport Layer Security (TLS) [RFC5246] and Datagram Transport		Transport Layer Security (TLS) [RFC5246] and Datagram Transport
	Security Layer (DTLS) [RFC6347] are widely used to protect data		Security Layer (DTLS) [RFC6347] are widely used to protect data
	exchanged over application protocols such as HTTP, SMTP, IMAP, POP,		exchanged over application protocols such as HTTP, SMTP, IMAP, POP,
	SIP, and XMPP. Over the last few years, several serious attacks on		SIP, and XMPP. Over the last few years, several serious attacks on
	TLS have emerged, including attacks on its most commonly used cipher		TLS have emerged, including attacks on its most commonly used cipher
	suites and modes of operation. For instance, both the AES-CBC		suites and their modes of operation. For instance, both the AES-CBC
	[RFC3602] and RC4 [I-D.ietf-tls-prohibiting-rc4] encryption		[RFC3602] and RC4 [RFC7465] encryption algorithms, which together
	algorithms, which together are the most widely deployed ciphers, have		have been the most widely deployed ciphers, have been attacked in the
	been attacked in the context of TLS. A companion document [RFC7457]		context of TLS. A companion document [RFC7457] provides detailed
	provides detailed information about these attacks.		information about these attacks and will help the reader understand
			the rationale behind the recommendations provided here.
	Because of these attacks, those who implement and deploy TLS and DTLS		Because of these attacks, those who implement and deploy TLS and DTLS
	need updated guidance on how TLS can be used securely. This document		need updated guidance on how TLS can be used securely. This document
	provides guidance for deployed services as well as for software		provides guidance for deployed services as well as for software
	implementations, assuming the implementer expects his or her code to		implementations, assuming the implementer expects his or her code to
	be deployed in environments defined in the following section. In		be deployed in environments defined in Section 5. In fact, this
	fact, this document calls for the deployment of algorithms that are		document calls for the deployment of algorithms that are widely
	widely implemented but not yet widely deployed. Concerning		implemented but not yet widely deployed. Concerning deployment, this
	deployment, this document targets a wide audience, namely all		document targets a wide audience, namely all deployers who wish to
	deployers who wish to add authentication (be it one-way only or		add authentication (be it one-way only or mutual), confidentiality,
	mutual), confidentiality, and data integrity protection to their		and data integrity protection to their communications.
	communications.
	The recommendations herein take into consideration the security of		The recommendations herein take into consideration the security of
	various mechanisms, their technical maturity and interoperability,		various mechanisms, their technical maturity and interoperability,
	and their prevalence in implementations at the time of writing.		and their prevalence in implementations at the time of writing.
	Unless it is explicitly called out that a recommendation applies to		Unless it is explicitly called out that a recommendation applies to
	TLS alone or to DTLS alone, each recommendation applies to both TLS		TLS alone or to DTLS alone, each recommendation applies to both TLS
	and DTLS.		and DTLS.
	It is expected that the TLS 1.3 specification will resolve many of		It is expected that the TLS 1.3 specification will resolve many of
	the vulnerabilities listed in this document. A system that deploys		the vulnerabilities listed in this document. A system that deploys
	TLS 1.3 will have fewer vulnerabilities than TLS 1.2 or below. This		TLS 1.3 should have fewer vulnerabilities than TLS 1.2 or below.
	document is likely to be updated after TLS 1.3 gets noticeable		This document is likely to be updated after TLS 1.3 gets noticeable
	deployment.		deployment.
	These are minimum recommendations for the use of TLS in the vast		These are minimum recommendations for the use of TLS in the vast
	majority of implementation and deployment scenarios, with the		majority of implementation and deployment scenarios, with the
	exception of unauthenticated TLS (see Section 5). Other		exception of unauthenticated TLS (see Section 5). Other
	specifications that reference this document can have stricter		specifications that reference this document can have stricter
	requirements related to one or more aspects of the protocol, based on		requirements related to one or more aspects of the protocol, based on
	their particular circumstances (e.g., for use with a particular		their particular circumstances (e.g., for use with a particular
	application protocol); when that is the case, implementers are		application protocol); when that is the case, implementers are
	advised to adhere to those stricter requirements. Furthermore, this		advised to adhere to those stricter requirements. Furthermore, this
	skipping to change at page 5, line 10		skipping to change at page 5, line 10
	Rationale: Today, SSLv2 is considered insecure [RFC6176].		Rationale: Today, SSLv2 is considered insecure [RFC6176].
	o Implementations MUST NOT negotiate SSL version 3.		o Implementations MUST NOT negotiate SSL version 3.
	Rationale: SSLv3 [RFC6101] was an improvement over SSLv2 and		Rationale: SSLv3 [RFC6101] was an improvement over SSLv2 and
	plugged some significant security holes, but did not support		plugged some significant security holes, but did not support
	strong cipher suites. SSLv3 does not support TLS extensions, some		strong cipher suites. SSLv3 does not support TLS extensions, some
	of which (e.g., renegotiation_info) are security-critical. In		of which (e.g., renegotiation_info) are security-critical. In
	addition, with the emergence of the POODLE attack [POODLE], SSLv3		addition, with the emergence of the POODLE attack [POODLE], SSLv3
	is now widely recognized as fundamentally insecure.		is now widely recognized as fundamentally insecure. See
			[I-D.ietf-tls-sslv3-diediedie] for further details.
	o Implementations SHOULD NOT negotiate TLS version 1.0 [RFC2246].		o Implementations SHOULD NOT negotiate TLS version 1.0 [RFC2246]
			unless no higher version is available in the negotiation.
	Rationale: TLS 1.0 (published in 1999) does not support many		Rationale: TLS 1.0 (published in 1999) does not support many
	modern, strong cipher suites. In addition, TLS 1.0 lacks a per-		modern, strong cipher suites. In addition, TLS 1.0 lacks a per-
	record IV for CBC-based cipher suites and does not warn against		record IV for CBC-based cipher suites and does not warn against
	common padding errors.		common padding errors.
	o Implementations SHOULD NOT negotiate TLS version 1.1 [RFC4346].		o Implementations SHOULD NOT negotiate TLS version 1.1 [RFC4346]
			unless no higher version is available in the negotiation.
	Rationale: TLS 1.1 (published in 2006) is a security improvement		Rationale: TLS 1.1 (published in 2006) is a security improvement
	over TLS 1.0, but still does not support certain stronger cipher		over TLS 1.0, but still does not support certain stronger cipher
	suites.		suites.
	o Implementations MUST support TLS 1.2 [RFC5246] and MUST prefer to		o Implementations MUST support TLS 1.2 [RFC5246] and MUST prefer to
	negotiate TLS version 1.2 over earlier versions of TLS.		negotiate TLS version 1.2 over earlier versions of TLS.
	Rationale: Several stronger cipher suites are available only with		Rationale: Several stronger cipher suites are available only with
	TLS 1.2 (published in 2008). In fact, the cipher suites		TLS 1.2 (published in 2008). In fact, the cipher suites
	skipping to change at page 5, line 50		skipping to change at page 6, line 5
	1.1 was published. The following are the recommendations with		1.1 was published. The following are the recommendations with
	respect to DTLS:		respect to DTLS:
	o Implementations SHOULD NOT negotiate DTLS version 1.0 [RFC4347].		o Implementations SHOULD NOT negotiate DTLS version 1.0 [RFC4347].
	Version 1.0 of DTLS correlates to version 1.1 of TLS (see above).		Version 1.0 of DTLS correlates to version 1.1 of TLS (see above).
	o Implementations MUST support, and prefer to negotiate, DTLS		o Implementations MUST support, and prefer to negotiate, DTLS
	version 1.2 [RFC6347].		version 1.2 [RFC6347].
	Version 1.2 of DTLS correlates to Version 1.2 of TLS 1.2 (see		Version 1.2 of DTLS correlates to Version 1.2 of TLS (see above).
	above). (There is no Version 1.1 of DTLS.)		(There is no Version 1.1 of DTLS.)
	3.1.3. Fallback to Lower Versions		3.1.3. Fallback to Lower Versions
	Clients that "fall back" to lower versions of the protocol after the		Clients that "fall back" to lower versions of the protocol after the
	server rejects higher versions of the protocol MUST NOT fall back to		server rejects higher versions of the protocol MUST NOT fall back to
	SSLv3 or earlier.		SSLv3 or earlier.
	Rationale: Some client implementations revert to lower versions of		Rationale: Some client implementations revert to lower versions of
	TLS or even to SSLv3 if the server rejected higher versions of the		TLS or even to SSLv3 if the server rejected higher versions of the
	protocol. This fallback can be forced by a man in the middle (MITM)		protocol. This fallback can be forced by a man in the middle (MITM)
	attacker. TLS 1.0 and SSLv3 are significantly less secure than TLS		attacker. TLS 1.0 and SSLv3 are significantly less secure than TLS
	1.2, the version recommended by this document. While TLS 1.0-only		1.2, the version recommended by this document. While TLS 1.0-only
	servers are still quite common, IP scans show that SSLv3-only servers		servers are still quite common, IP scans show that SSLv3-only servers
	amount to only about 3% of the current Web server population. (At		amount to only about 3% of the current Web server population. (At
	the time of this writing, an explicit method for preventing downgrade		the time of this writing, an explicit method for preventing downgrade
	attacks is being defined in [I-D.ietf-tls-downgrade-scsv].)		attacks is being defined in [I-D.ietf-tls-downgrade-scsv].)
	3.2. Strict TLS		3.2. Strict TLS
	To prevent SSL Stripping:		The following recommendations are provided to help prevent SSL
			Stripping (the attack is summarized in Section 2.1 of [RFC7457]):
	o In cases where an application protocol allows implementations or		o In cases where an application protocol allows implementations or
	deployments a choice between strict TLS configuration and dynamic		deployments a choice between strict TLS configuration and dynamic
	upgrade from unencrypted to TLS-protected traffic (such as		upgrade from unencrypted to TLS-protected traffic (such as
	STARTTLS), clients and servers SHOULD prefer strict TLS		STARTTLS), clients and servers SHOULD prefer strict TLS
	configuration.		configuration.
	o Application protocols typically provide a way for the server to		o Application protocols typically provide a way for the server to
	offer TLS during an initial protocol exchange, and sometimes also		offer TLS during an initial protocol exchange, and sometimes also
	provide a way for the server to advertise support for TLS (e.g.,		provide a way for the server to advertise support for TLS (e.g.,
	through a flag indicating that TLS is required); unfortunately,		through a flag indicating that TLS is required); unfortunately,
	these indications are sent before the communication channel is		these indications are sent before the communication channel is
	encrypted. A client SHOULD attempt to negotiate TLS even if these		encrypted. A client SHOULD attempt to negotiate TLS even if these
	indications are not communicated by the server.		indications are not communicated by the server.
	o HTTP client and server implementations MUST support the HTTP		o HTTP client and server implementations MUST support the HTTP
	Strict Transport Security (HSTS) header [RFC6797], in order to		Strict Transport Security (HSTS) header [RFC6797], in order to
	allow Web servers to advertise that they are willing to accept		allow Web servers to advertise that they are willing to accept
	TLS-only clients.		TLS-only clients.
	o When applicable, Web servers SHOULD use HSTS to indicate that they		o Web servers SHOULD use HSTS to indicate that they are willing to
	are willing to accept TLS-only clients.		accept TLS-only clients, unless they are deployed in such a way
			that using HSTS would in fact weaken overall security (e.g., it
			can be problematic to use HSTS with self-signed certificates, as
			described in Section 11.3 of [RFC6797]).
	Rationale: Combining unprotected and TLS-protected communication		Rationale: Combining unprotected and TLS-protected communication
	opens the way to SSL Stripping and similar attacks, since an initial		opens the way to SSL Stripping and similar attacks, since an initial
	part of the communication is not integrity protected and therefore		part of the communication is not integrity protected and therefore
	can be manipulated by an attacker whose goal is to keep the		can be manipulated by an attacker whose goal is to keep the
	communication in the clear.		communication in the clear.
	3.3. Compression		3.3. Compression
	Implementations and deployments SHOULD disable TLS-level compression		In order to help prevent compression-related attacks (summarized in
	([RFC5246], Section 6.2.2).		Section 2.6 of [RFC7457]), implementations and deployments SHOULD
			disable TLS-level compression ([RFC5246], Section 6.2.2), unless the
			application protocol in question has been shown not to be open to
			such attacks.
	Rationale: TLS compression has been subject to security attacks, such		Rationale: TLS compression has been subject to security attacks, such
	as the CRIME attack.		as the CRIME attack.
	Implementers should note that compression at higher protocol levels		Implementers should note that compression at higher protocol levels
	can allow an active attacker to extract cleartext information from		can allow an active attacker to extract cleartext information from
	the connection. The BREACH attack is one such case. These issues		the connection. The BREACH attack is one such case. These issues
	can only be mitigated outside of TLS and are thus out of scope of the		can only be mitigated outside of TLS and are thus out of scope of the
	current document. See Section 2.6 of [RFC7457] for further details.		current document. See Section 2.6 of [RFC7457] for further details.
	skipping to change at page 7, line 51		skipping to change at page 8, line 11
	the TLS endpoint (either client or server) and its secrets from		the TLS endpoint (either client or server) and its secrets from
	reading either past or future communication. The tickets must be		reading either past or future communication. The tickets must be
	managed so as not to negate this security property.		managed so as not to negate this security property.
	3.5. TLS Renegotiation		3.5. TLS Renegotiation
	Where handshake renegotiation is implemented, both clients and		Where handshake renegotiation is implemented, both clients and
	servers MUST implement the renegotiation_info extension, as defined		servers MUST implement the renegotiation_info extension, as defined
	in [RFC5746].		in [RFC5746].
	To counter the Triple Handshake attack, the recommended		The most secure option for countering the Triple Handshake attack is
	countermeasures from [triple-handshake] are adopted: TLS clients		to refuse any change of certificates during renegotiation. In
	SHOULD apply the same validation policy for all certificates received		addition, TLS clients SHOULD apply the same validation policy for all
	over a connection, bind the master secret to the full handshake, and		certificates received over a connection. The [triple-handshake]
	bind the abbreviated session resumption handshake to the original		document suggests several other possible countermeasures, such as
	full handshake. In some usages, the most secure option might be to		binding the master secret to the full handshake (see
	refuse any change of certificates during renegotiation.		[I-D.ietf-tls-session-hash]) and binding the abbreviated session
			resumption handshake to the original full handshake. Although the
			latter two techniques are still under development and thus do not
			qualify as current practices, those who implement and deploy TLS are
			advised to watch for further development of appropriate
			countermeasures.
	3.6. Server Name Indication		3.6. Server Name Indication
	TLS implementations MUST support the Server Name Indication (SNI)		TLS implementations MUST support the Server Name Indication (SNI)
	extension for those higher level protocols which would benefit from		extension defined in Section 3 of [RFC6066] for those higher level
	it, including HTTPS. However, unlike implementation, the use of SNI		protocols which would benefit from it, including HTTPS. However,
	in particular circumstances is a matter of local policy.		unlike implementation, the use of SNI in particular circumstances is
			a matter of local policy.
	Rationale: SNI supports deployment of multiple TLS-protected virtual		Rationale: SNI supports deployment of multiple TLS-protected virtual
	servers on a single address, and therefore enables fine-grained		servers on a single address, and therefore enables fine-grained
	security for these virtual servers, by allowing each one to have its		security for these virtual servers, by allowing each one to have its
	own certificate.		own certificate.
	4. Recommendations: Cipher Suites		4. Recommendations: Cipher Suites
	TLS and its implementations provide considerable flexibility in the		TLS and its implementations provide considerable flexibility in the
	selection of cipher suites. Unfortunately, some available cipher		selection of cipher suites. Unfortunately, some available cipher
	skipping to change at page 9, line 10		skipping to change at page 9, line 24
	provide no confidentiality services. Any entity in the network		provide no confidentiality services. Any entity in the network
	with access to the connection can view the plaintext of contents		with access to the connection can view the plaintext of contents
	being exchanged by the client and server. (Nevertheless, this		being exchanged by the client and server. (Nevertheless, this
	document does not discourage software from implementing NULL		document does not discourage software from implementing NULL
	cipher suites, since they can be useful for testing and		cipher suites, since they can be useful for testing and
	debugging.)		debugging.)
	o Implementations MUST NOT negotiate RC4 cipher suites.		o Implementations MUST NOT negotiate RC4 cipher suites.
	Rationale: The RC4 stream cipher has a variety of cryptographic		Rationale: The RC4 stream cipher has a variety of cryptographic
	weaknesses, as documented in [I-D.ietf-tls-prohibiting-rc4]. Note		weaknesses, as documented in [RFC7465]. Note that DTLS
	that DTLS specifically forbids the use of RC4 already.		specifically forbids the use of RC4 already.
	o Implementations MUST NOT negotiate cipher suites offering less		o Implementations MUST NOT negotiate cipher suites offering less
	than 112 bits of security, including the so-called "export-level"		than 112 bits of security, including so-called "export-level"
	encryption (which provide 40 or 56 bits of security).		encryption (which provide 40 or 56 bits of security).
	Rationale: Based on [RFC3766], at least 112 bits of security is		Rationale: Based on [RFC3766], at least 112 bits of security is
	needed. 40-bit and 56-bit security are considered insecure today.		needed. 40-bit and 56-bit security are considered insecure today.
	TLS 1.1 and 1.2 never negotiate 40-bit or 56-bit export ciphers.		TLS 1.1 and 1.2 never negotiate 40-bit or 56-bit export ciphers.
	o Implementations SHOULD NOT negotiate cipher suites that use		o Implementations SHOULD NOT negotiate cipher suites that use
	algorithms offering less than 128 bits of security.		algorithms offering less than 128 bits of security.
	Rationale: Cipher suites that offer between 112-bits and 128-bits		Rationale: Cipher suites that offer between 112-bits and 128-bits
	of security are not considered weak at this time, however it is		of security are not considered weak at this time, however it is
	expected that their useful lifespan is short enough to justify		expected that their useful lifespan is short enough to justify
	supporting stronger cipher suites at this time. 128-bit ciphers		supporting stronger cipher suites at this time. 128-bit ciphers
	are expected to remain secure for at least several years, and		are expected to remain secure for at least several years, and
	256-bit ciphers "until the next fundamental technology		256-bit ciphers until the next fundamental technology
	breakthrough". Note that, because of so-called "meet-in-the-		breakthrough. Note that, because of so-called "meet-in-the-
	middle" attacks [Multiple-Encryption] some legacy cipher suites		middle" attacks [Multiple-Encryption] some legacy cipher suites
	(e.g., 168-bit 3DES) have an effective key length which is smaller		(e.g., 168-bit 3DES) have an effective key length which is smaller
	than their nominal key length (112 bits in the case of 3DES).		than their nominal key length (112 bits in the case of 3DES).
	Such cipher suites should be evaluated according to their		Such cipher suites should be evaluated according to their
	effective key length.		effective key length.
	o Implementations MUST support, and SHOULD prefer to negotiate,		o Implementations SHOULD NOT negotiate cipher suites based on RSA
	cipher suites offering forward secrecy, such as those in the		key transport, a.k.a. "static RSA".
	Ephemeral Diffie-Hellman and Elliptic Curve Ephemeral Diffie-
	Hellman ("DHE" and "ECDHE") families.		Rationale: These cipher suites, which have assigned values
			starting with the string "TLS_RSA_WITH_*", have several drawbacks,
			especially the fact that they do not support forward secrecy.
			o Implementations MUST support and prefer to negotiate, cipher
			suites offering forward secrecy, such as those in the Ephemeral
			Diffie-Hellman and Elliptic Curve Ephemeral Diffie-Hellman ("DHE"
			and "ECDHE") families.
	Rationale: Forward secrecy (sometimes called "perfect forward		Rationale: Forward secrecy (sometimes called "perfect forward
	secrecy") prevents the recovery of information that was encrypted		secrecy") prevents the recovery of information that was encrypted
	with older session keys, thus limiting the amount of time during		with older session keys, thus limiting the amount of time during
	which attacks can be successful. See Section 7.3 for a detailed		which attacks can be successful. See Section 7.3 for a detailed
	discussion.		discussion.
	4.2. Recommended Cipher Suites		4.2. Recommended Cipher Suites
	Given the foregoing considerations, implementation and deployment of		Given the foregoing considerations, implementation and deployment of
	skipping to change at page 10, line 22		skipping to change at page 10, line 40
	o TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256		o TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
	o TLS_DHE_RSA_WITH_AES_256_GCM_SHA384		o TLS_DHE_RSA_WITH_AES_256_GCM_SHA384
	o TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384		o TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
	These cipher suites are supported only in TLS 1.2 because they are		These cipher suites are supported only in TLS 1.2 because they are
	authenticated encryption (AEAD) algorithms [RFC5116].		authenticated encryption (AEAD) algorithms [RFC5116].
	Typically, in order to prefer these suites, the order of suites needs		Typically, in order to prefer these suites, the order of suites needs
	to be explicitly configured in server software. It would be ideal if		to be explicitly configured in server software (see [BETTERCRYPTO]
	server software implementations were to prefer these suites by		for helpful deployment guidelines, but note that its recommendations
			differ from the current document in some details). It would be ideal
			if server software implementations were to prefer these suites by
	default.		default.
	Some devices have hardware support for AES-CCM but not AES-GCM, so		Some devices have hardware support for AES-CCM but not AES-GCM, so
	they are unable to follow the foregoing recommendations regarding		they are unable to follow the foregoing recommendations regarding
	cipher suites. There are even devices that do not support public key		cipher suites. There are even devices that do not support public key
	cryptography at all, but they are out of scope entirely.		cryptography at all, but they are out of scope entirely.
	4.2.1. Implementation Details		4.2.1. Implementation Details
	Clients SHOULD include TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 as the		Clients SHOULD include TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 as the
	first proposal to any server, unless they have prior knowledge that		first proposal to any server, unless they have prior knowledge that
	the server cannot respond to a TLS 1.2 client_hello message.		the server cannot respond to a TLS 1.2 client_hello message.
	Servers SHOULD prefer this cipher suite over weaker cipher suites		Servers MUST prefer this cipher suite over weaker cipher suites
	whenever it is proposed, even if it is not the first proposal.		whenever it is proposed, even if it is not the first proposal.
	Clients are of course free to offer stronger cipher suites, e.g.,		Clients are of course free to offer stronger cipher suites, e.g.,
	using AES-256; when they do, the server SHOULD prefer the stronger		using AES-256; when they do, the server SHOULD prefer the stronger
	cipher suite unless there are compelling reasons (e.g., seriously		cipher suite unless there are compelling reasons (e.g., seriously
	degraded performance) to choose otherwise.		degraded performance) to choose otherwise.
	This document does not change the mandatory-to-implement TLS cipher		This document does not change the mandatory-to-implement TLS cipher
	suite(s) prescribed by TLS or application protocols using TLS. To		suite(s) prescribed by TLS. To maximize interoperability, RFC 5246
	maximize interoperability, RFC 5246 mandates implementation of the		mandates implementation of the TLS_RSA_WITH_AES_128_CBC_SHA cipher
	TLS_RSA_WITH_AES_128_CBC_SHA cipher suite, which is significantly		suite, which is significantly weaker than the cipher suites
	weaker than the cipher suites recommended here (the GCM mode does not		recommended here (the GCM mode does not suffer from the same
	suffer from the same weakness, caused by the order of MAC-then-		weakness, caused by the order of MAC-then-Encrypt in TLS
	Encrypt in TLS [Krawczyk2001], since it uses an Authenticated		[Krawczyk2001], since it uses an Authenticated Encryption with
	Encryption with Associated Data (AEAD) mode of operation).		Associated Data (AEAD) mode of operation). Implementers should
			consider the interoperability gain against the loss in security when
	Implementers should consider the interoperability gain against the		deploying the TLS_RSA_WITH_AES_128_CBC_SHA cipher suite. Other
	loss in security when deploying that cipher suite. Other application		application protocols specify other cipher suites as mandatory to
	protocols specify other cipher suites as mandatory to implement		implement (MTI).
	(MTI).
	Note that some profiles of TLS 1.2 use different cipher suites. For		Note that some profiles of TLS 1.2 use different cipher suites. For
	example, [RFC6460] defines a profile that uses the		example, [RFC6460] defines a profile that uses the
	TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 and		TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 and
	TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 cipher suites.		TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 cipher suites.
	[RFC4492] allows clients and servers to negotiate ECDH parameters		[RFC4492] allows clients and servers to negotiate ECDH parameters
	(curves). Both clients and servers SHOULD include the "Supported		(curves). Both clients and servers SHOULD include the "Supported
	Elliptic Curves" extension [RFC4492]. For interoperability, clients		Elliptic Curves" extension [RFC4492]. For interoperability, clients
	and servers SHOULD support the NIST P-256 (secp256r1) curve		and servers SHOULD support the NIST P-256 (secp256r1) curve
	skipping to change at page 12, line 20		skipping to change at page 12, line 41
	TLS 1.2.		TLS 1.2.
	4.4. Modular vs. Elliptic Curve DH Cipher Suites		4.4. Modular vs. Elliptic Curve DH Cipher Suites
	Not all TLS implementations support both modular and elliptic curve		Not all TLS implementations support both modular and elliptic curve
	Diffie-Hellman groups, as required by Section 4.2. Some		Diffie-Hellman groups, as required by Section 4.2. Some
	implementations are severely limited in the length of DH values.		implementations are severely limited in the length of DH values.
	When such implementations need to be accommodated, the following are		When such implementations need to be accommodated, the following are
	RECOMMENDED (in priority order):		RECOMMENDED (in priority order):
	1. Elliptic Curve DHE with negotiated parameters [RFC5289]		1. Elliptic Curve DHE with appropriately negotiated parameters
			(e.g., the curve to be used) and a MAC algorithm stronger than
			HMAC-SHA1 [RFC5289]
	2. TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 [RFC5288], with 2048-bit		2. TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 [RFC5288], with 2048-bit
	Diffie-Hellman parameters		Diffie-Hellman parameters
	3. TLS_DHE_RSA_WITH_AES_128_GCM_SHA256, with 1024-bit parameters.		3. TLS_DHE_RSA_WITH_AES_128_GCM_SHA256, with 1024-bit parameters.
	Rationale: Although Elliptic Curve Cryptography is widely deployed		Rationale: Although Elliptic Curve Cryptography is widely deployed
	there are some communities where its uptake has been limited for		there are some communities where its uptake has been limited for
	several reasons, including its complexity compared to modular		several reasons, including its complexity compared to modular
	arithmetic and longstanding perceptions of IPR concerns (which, for		arithmetic and longstanding perceptions of IPR concerns (which, for
	skipping to change at page 13, line 22		skipping to change at page 13, line 44
	Implementations MUST NOT use the Truncated HMAC extension, defined in		Implementations MUST NOT use the Truncated HMAC extension, defined in
	Section 7 of [RFC6066].		Section 7 of [RFC6066].
	Rationale: the extension does not apply to the AEAD cipher suites		Rationale: the extension does not apply to the AEAD cipher suites
	recommended above. However it does apply to most other TLS cipher		recommended above. However it does apply to most other TLS cipher
	suites. Its use has been shown to be insecure in [PatersonRS11].		suites. Its use has been shown to be insecure in [PatersonRS11].
	5. Applicability Statement		5. Applicability Statement
	The deployment recommendations of this document address the operators		The recommendations of this document primarily apply to the
	of application layer services that are most commonly used on the		implementation and deployment of application protocols that are most
	Internet, including, but not limited to:		commonly used with TLS and DTLS on the Internet today. Examples
			include, but are not limited to:
	o Operators of web services that wish to protect HTTP with TLS.		o Web software and services that wish to protect HTTP traffic with
			TLS.
	o Operators of email services who wish to protect the application-		o Email software and services that wish to protect IMAP, POP3, or
	layer protocols with TLS (e.g., IMAP, POP3 or SMTP).		SMTP traffic with TLS.
	o Operators of instant-messaging services who wish to protect their		o Instant-messaging software and services that wish to protect XMPP
	application-layer protocols with TLS (e.g., XMPP or IRC).		or IRC traffic with TLS.
			o Realtime media software and services that wish to protect SRTP
			traffic with DTLS.
			This document does not modify the implementation and deployment
			recommendations (e.g., mandatory-to-implement cipher suites)
			prescribed by existing application protocols that employ TLS or DTLS.
			If the community that uses such an application protocol wishes to
			modernize its usage of TLS or DTLS to be consistent with the best
			practices recommended here, it needs to explicitly update the
			existing application protocol definition (one example is
			[I-D.ietf-uta-xmpp], which updates [RFC6120]).
			Designers of new application protocols developed through the Internet
			Standards Process are expected to conform to the best practices
			recommended here, unless they provide documentation of compelling
			reasons that would prevent such conformance (e.g., widespread
			deployment on constrained devices that lack support for the necessary
			algorithms).
	5.1. Security Services		5.1. Security Services
	This document provides recommendations for an audience that wishes to		This document provides recommendations for an audience that wishes to
	secure their communication with TLS to achieve the following:		secure their communication with TLS to achieve the following:
	o Confidentiality: all application-layer communication is encrypted		o Confidentiality: all application-layer communication is encrypted
	with the goal that no party should be able to decrypt it except		with the goal that no party should be able to decrypt it except
	the intended receiver.		the intended receiver.
	skipping to change at page 18, line 11		skipping to change at page 18, line 52
	known attacks. These tests are not standardized in TLS at the		known attacks. These tests are not standardized in TLS at the
	time of writing. See [RFC6989] for recipient tests required of		time of writing. See [RFC6989] for recipient tests required of
	IKEv2 implementations that reuse DH exponents.		IKEv2 implementations that reuse DH exponents.
	7.5. Certificate Revocation		7.5. Certificate Revocation
	The following considerations and recommendations represent the		The following considerations and recommendations represent the
	current state of the art regarding certificate revocation, even		current state of the art regarding certificate revocation, even
	though no complete and efficient solution exists for the problem of		though no complete and efficient solution exists for the problem of
	checking the revocation status of common public key certificates		checking the revocation status of common public key certificates
	(a.k.a. PKIX certificates, [RFC5280]):		[RFC5280]:
	o Although Certificate Revocation Lists (CRLs) are the most widely		o Although Certificate Revocation Lists (CRLs) are the most widely
	supported mechanism for distributing revocation information, they		supported mechanism for distributing revocation information, they
	have known scaling challenges that limit their usefulness (despite		have known scaling challenges that limit their usefulness (despite
	workarounds such as partitioned CRLS and delta CRLs).		workarounds such as partitioned CRLS and delta CRLs).
	o Proprietary mechanisms that embed revocation lists in the Web		o Proprietary mechanisms that embed revocation lists in the Web
	browser's configuration database cannot scale beyond a small		browser's configuration database cannot scale beyond a small
	number of the most heavily used Web servers.		number of the most heavily used Web servers.
	skipping to change at page 18, line 44		skipping to change at page 19, line 36
	o OCSP stapling as defined in [RFC6066] does not extend to		o OCSP stapling as defined in [RFC6066] does not extend to
	intermediate certificates used in a certificate chain. Although		intermediate certificates used in a certificate chain. Although
	[RFC6961] addresses this shortcoming, it is a recent addition		[RFC6961] addresses this shortcoming, it is a recent addition
	without much deployment.		without much deployment.
	o Both CRLs and OSCP depend on relatively reliable connectivity to		o Both CRLs and OSCP depend on relatively reliable connectivity to
	the Internet, which might not be available to certain kinds of		the Internet, which might not be available to certain kinds of
	nodes (such as newly provisioned devices that need to establish a		nodes (such as newly provisioned devices that need to establish a
	secure connection in order to boot up for the first time).		secure connection in order to boot up for the first time).
	With regard to PKIX certificates, servers SHOULD support the		With regard to common public key certificates, servers SHOULD support
	following as a best practice given the current state of the art and		the following as a best practice given the current state of the art
	as a foundation for a possible future solution:		and as a foundation for a possible future solution:
	1. OCSP [RFC6960]		1. OCSP [RFC6960]
	2. Both the status_request extension defined in [RFC6066] and the		2. Both the status_request extension defined in [RFC6066] and the
	status_request_v2 extension defined in [RFC6961] (this might		status_request_v2 extension defined in [RFC6961] (this might
	enable interoperability with the widest range of clients)		enable interoperability with the widest range of clients)
	3. The OCSP stapling extension defined in [RFC6961]		3. The OCSP stapling extension defined in [RFC6961]
	The foregoing considerations do not apply to scenarios where the		The considerations in this section do not apply to scenarios where
	DANE-TLSA resource record [RFC6698] is used to signal to a client		the DANE-TLSA resource record [RFC6698] is used to signal to a client
	which certificate a server considers valid and good to use for TLS		which certificate a server considers valid and good to use for TLS
	connections.		connections.
	8. Acknowledgments		8. Acknowledgments
	Thanks to RJ Atkinson, Uri Blumenthal, Viktor Dukhovni, Stephen		Thanks to RJ Atkinson, Uri Blumenthal, Viktor Dukhovni, Stephen
	Farrell, Daniel Kahn Gillmor, Paul Hoffman, Simon Josefsson, Watson		Farrell, Daniel Kahn Gillmor, Paul Hoffman, Simon Josefsson, Watson
	Ladd, Orit Levin, Ilari Liusvaara, Johannes Merkle, Bodo Moeller,		Ladd, Orit Levin, Ilari Liusvaara, Johannes Merkle, Bodo Moeller,
	Yoav Nir, Massimiliano Pala, Kenny Paterson, Patrick Pelletier, Tom		Yoav Nir, Massimiliano Pala, Kenny Paterson, Patrick Pelletier, Tom
	Ritter, Joe St. Sauver, Joe Salowey, Rich Salz, Brian Smith, Sean		Ritter, Joe St. Sauver, Joe Salowey, Rich Salz, Brian Smith, Sean
	skipping to change at page 19, line 30		skipping to change at page 20, line 23
	improvements. Thanks also to Brian Smith, who has provided a great		improvements. Thanks also to Brian Smith, who has provided a great
	resource in his "Proposal to Change the Default TLS Ciphersuites		resource in his "Proposal to Change the Default TLS Ciphersuites
	Offered by Browsers" [Smith2013]. Finally, thanks to all others who		Offered by Browsers" [Smith2013]. Finally, thanks to all others who
	commented on the TLS, UTA, and other discussion lists but who are not		commented on the TLS, UTA, and other discussion lists but who are not
	mentioned here by name.		mentioned here by name.
	Robert Sparks and Dave Waltermire provided helpful reviews on behalf		Robert Sparks and Dave Waltermire provided helpful reviews on behalf
	of the General Area Review Team and the Security Directorate,		of the General Area Review Team and the Security Directorate,
	respectively.		respectively.
			During IESG review, Richard Barnes, Alissa Cooper, Spencer Dawkins,
			Stephen Farrell, Barry Leiba, Kathleen Moriarty, and Pete Resnick
			provided comments that led to further improvements.
	The authors gratefully acknowledge the assistance of Leif Johansson		The authors gratefully acknowledge the assistance of Leif Johansson
	and Orit Levin as the working group chairs and Pete Resnick as the		and Orit Levin as the working group chairs and Pete Resnick as the
	sponsoring Area Director.		sponsoring Area Director.
	9. References		9. References
	9.1. Normative References		9.1. Normative References
	[I-D.ietf-tls-prohibiting-rc4]
	Popov, A., "Prohibiting RC4 Cipher Suites", draft-ietf-
	tls-prohibiting-rc4-01 (work in progress), October 2014.
	[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.
	[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.		[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
	[RFC3766] Orman, H. and P. Hoffman, "Determining Strengths For		[RFC3766] Orman, H. and P. Hoffman, "Determining Strengths For
	Public Keys Used For Exchanging Symmetric Keys", BCP 86,		Public Keys Used For Exchanging Symmetric Keys", BCP 86,
	RFC 3766, April 2004.		RFC 3766, April 2004.
	[RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B.		[RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B.
	Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites		Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites
	for Transport Layer Security (TLS)", RFC 4492, May 2006.		for Transport Layer Security (TLS)", RFC 4492, May 2006.
			[RFC4949] Shirey, R., "Internet Security Glossary, Version 2", RFC
			4949, August 2007.
	[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security		[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
	(TLS) Protocol Version 1.2", RFC 5246, August 2008.		(TLS) Protocol Version 1.2", RFC 5246, August 2008.
	[RFC5288] Salowey, J., Choudhury, A., and D. McGrew, "AES Galois		[RFC5288] Salowey, J., Choudhury, A., and D. McGrew, "AES Galois
	Counter Mode (GCM) Cipher Suites for TLS", RFC 5288,		Counter Mode (GCM) Cipher Suites for TLS", RFC 5288,
	August 2008.		August 2008.
	[RFC5289] Rescorla, E., "TLS Elliptic Curve Cipher Suites with		[RFC5289] Rescorla, E., "TLS Elliptic Curve Cipher Suites with
	SHA-256/384 and AES Galois Counter Mode (GCM)", RFC 5289,		SHA-256/384 and AES Galois Counter Mode (GCM)", RFC 5289,
	August 2008.		August 2008.
	[RFC5746] Rescorla, E., Ray, M., Dispensa, S., and N. Oskov,		[RFC5746] Rescorla, E., Ray, M., Dispensa, S., and N. Oskov,
	"Transport Layer Security (TLS) Renegotiation Indication		"Transport Layer Security (TLS) Renegotiation Indication
	Extension", RFC 5746, February 2010.		Extension", RFC 5746, February 2010.
			[RFC6066] Eastlake, D., "Transport Layer Security (TLS) Extensions:
			Extension Definitions", RFC 6066, January 2011.
	[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and		[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
	Verification of Domain-Based Application Service Identity		Verification of Domain-Based Application Service Identity
	within Internet Public Key Infrastructure Using X.509		within Internet Public Key Infrastructure Using X.509
	(PKIX) Certificates in the Context of Transport Layer		(PKIX) Certificates in the Context of Transport Layer
	Security (TLS)", RFC 6125, March 2011.		Security (TLS)", RFC 6125, March 2011.
	[RFC6176] Turner, S. and T. Polk, "Prohibiting Secure Sockets Layer		[RFC6176] Turner, S. and T. Polk, "Prohibiting Secure Sockets Layer
	(SSL) Version 2.0", RFC 6176, March 2011.		(SSL) Version 2.0", RFC 6176, March 2011.
	[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer		[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
	Security Version 1.2", RFC 6347, January 2012.		Security Version 1.2", RFC 6347, January 2012.
			[RFC7465] Popov, A., "Prohibiting RC4 Cipher Suites", RFC 7465,
			February 2015.
	9.2. Informative References		9.2. Informative References
			[BETTERCRYPTO]
			bettercrypto.org, , "Applied Crypto Hardening", 2015,
			<https://bettercrypto.org/static/applied-crypto-
			hardening.pdf>.
	[CAB-Baseline]		[CAB-Baseline]
	CA/Browser Forum, , "Baseline Requirements for the		CA/Browser Forum, , "Baseline Requirements for the
	Issuance and Management of Publicly-Trusted Certificates		Issuance and Management of Publicly-Trusted Certificates
	Version 1.1.6", 2013, <https://www.cabforum.org/		Version 1.1.6", 2013, <https://www.cabforum.org/
	documents.html>.		documents.html>.
	[DegabrieleP07]		[DegabrieleP07]
	Degabriele, J. and K. Paterson, "Attacking the IPsec		Degabriele, J. and K. Paterson, "Attacking the IPsec
	standards in encryption-only configurations", 2007,		standards in encryption-only configurations", 2007,
	<http://dx.doi.org/10.1109/SP.2007.8>.		<http://dx.doi.org/10.1109/SP.2007.8>.
	skipping to change at page 21, line 28		skipping to change at page 22, line 33
	Based Authentication of Named Entities (DANE) TLSA Records		Based Authentication of Named Entities (DANE) TLSA Records
	with SRV Records", draft-ietf-dane-srv-06 (work in		with SRV Records", draft-ietf-dane-srv-06 (work in
	progress), June 2014.		progress), June 2014.
	[I-D.ietf-tls-downgrade-scsv]		[I-D.ietf-tls-downgrade-scsv]
	Moeller, B. and A. Langley, "TLS Fallback Signaling Cipher		Moeller, B. and A. Langley, "TLS Fallback Signaling Cipher
	Suite Value (SCSV) for Preventing Protocol Downgrade		Suite Value (SCSV) for Preventing Protocol Downgrade
	Attacks", draft-ietf-tls-downgrade-scsv-02 (work in		Attacks", draft-ietf-tls-downgrade-scsv-02 (work in
	progress), November 2014.		progress), November 2014.
			[I-D.ietf-tls-session-hash]
			Bhargavan, K., Delignat-Lavaud, A., Pironti, A., Langley,
			A., and M. Ray, "Transport Layer Security (TLS) Session
			Hash and Extended Master Secret Extension", draft-ietf-
			tls-session-hash-03 (work in progress), November 2014.
			[I-D.ietf-tls-sslv3-diediedie]
			Barnes, R., Thomson, M., Pironti, A., and A. Langley,
			"Deprecating Secure Sockets Layer Version 3.0", draft-
			ietf-tls-sslv3-diediedie-00 (work in progress), December
			2014.
			[I-D.ietf-uta-xmpp]
			Saint-Andre, P. and a. alkemade, "Use of Transport Layer
			Security (TLS) in the Extensible Messaging and Presence
			Protocol (XMPP)", draft-ietf-uta-xmpp-05 (work in
			progress), January 2015.
	[Kleinjung2010]		[Kleinjung2010]
	Kleinjung, T., "Factorization of a 768-Bit RSA Modulus",		Kleinjung, T., "Factorization of a 768-Bit RSA Modulus",
	CRYPTO 10, 2010, <https://eprint.iacr.org/2010/006.pdf>.		CRYPTO 10, 2010, <https://eprint.iacr.org/2010/006.pdf>.
	[Krawczyk2001]		[Krawczyk2001]
	Krawczyk, H., "The order of encryption and authentication		Krawczyk, H., "The order of encryption and authentication
	for protecting communications (Or: how secure is SSL?)",		for protecting communications (Or: how secure is SSL?)",
	CRYPTO 01, 2001, <https://eprint.iacr.org/2001/045.pdf>.		CRYPTO 01, 2001, <https://eprint.iacr.org/2001/045.pdf>.
	[Multiple-Encryption]		[Multiple-Encryption]
	skipping to change at page 22, line 24		skipping to change at page 23, line 49
	[RFC3602] Frankel, S., Glenn, R., and S. Kelly, "The AES-CBC Cipher		[RFC3602] Frankel, S., Glenn, R., and S. Kelly, "The AES-CBC Cipher
	Algorithm and Its Use with IPsec", RFC 3602, September		Algorithm and Its Use with IPsec", RFC 3602, September
	2003.		2003.
	[RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security		[RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security
	(TLS) Protocol Version 1.1", RFC 4346, April 2006.		(TLS) Protocol Version 1.1", RFC 4346, April 2006.
	[RFC4347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer		[RFC4347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
	Security", RFC 4347, April 2006.		Security", RFC 4347, April 2006.
	[RFC4949] Shirey, R., "Internet Security Glossary, Version 2", RFC
	4949, August 2007.
	[RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig,		[RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig,
	"Transport Layer Security (TLS) Session Resumption without		"Transport Layer Security (TLS) Session Resumption without
	Server-Side State", RFC 5077, January 2008.		Server-Side State", RFC 5077, January 2008.
	[RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated		[RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated
	Encryption", RFC 5116, January 2008.		Encryption", RFC 5116, January 2008.
	[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,		[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
	Housley, R., and W. Polk, "Internet X.509 Public Key		Housley, R., and W. Polk, "Internet X.509 Public Key
	Infrastructure Certificate and Certificate Revocation List		Infrastructure Certificate and Certificate Revocation List
	(CRL) Profile", RFC 5280, May 2008.		(CRL) Profile", RFC 5280, May 2008.
	[RFC6066] Eastlake, D., "Transport Layer Security (TLS) Extensions:
	Extension Definitions", RFC 6066, January 2011.
	[RFC6090] McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic		[RFC6090] McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic
	Curve Cryptography Algorithms", RFC 6090, February 2011.		Curve Cryptography Algorithms", RFC 6090, February 2011.
	[RFC6101] Freier, A., Karlton, P., and P. Kocher, "The Secure		[RFC6101] Freier, A., Karlton, P., and P. Kocher, "The Secure
	Sockets Layer (SSL) Protocol Version 3.0", RFC 6101,		Sockets Layer (SSL) Protocol Version 3.0", RFC 6101,
	August 2011.		August 2011.
			[RFC6120] Saint-Andre, P., "Extensible Messaging and Presence
			Protocol (XMPP): Core", RFC 6120, March 2011.
	[RFC6460] Salter, M. and R. Housley, "Suite B Profile for Transport		[RFC6460] Salter, M. and R. Housley, "Suite B Profile for Transport
	Layer Security (TLS)", RFC 6460, January 2012.		Layer Security (TLS)", RFC 6460, January 2012.
	[RFC6698] Hoffman, P. and J. Schlyter, "The DNS-Based Authentication		[RFC6698] Hoffman, P. and J. Schlyter, "The DNS-Based Authentication
	of Named Entities (DANE) Transport Layer Security (TLS)		of Named Entities (DANE) Transport Layer Security (TLS)
	Protocol: TLSA", RFC 6698, August 2012.		Protocol: TLSA", RFC 6698, August 2012.
	[RFC6797] Hodges, J., Jackson, C., and A. Barth, "HTTP Strict		[RFC6797] Hodges, J., Jackson, C., and A. Barth, "HTTP Strict
	Transport Security (HSTS)", RFC 6797, November 2012.		Transport Security (HSTS)", RFC 6797, November 2012.
	skipping to change at page 26, line 34		skipping to change at page 28, line 8
	o Discussion of the regular TLS mandatory cipher suite.		o Discussion of the regular TLS mandatory cipher suite.
	A.12. draft-sheffer-tls-bcp-00		A.12. draft-sheffer-tls-bcp-00
	o Initial version.		o Initial version.
	Authors' Addresses		Authors' Addresses
	Yaron Sheffer		Yaron Sheffer
	Porticor		Intuit
	29 HaHarash St.		4 HaHarash St.
	Hod HaSharon 4501303		Hod HaSharon 4524075
	Israel		Israel
	Email: yaronf.ietf@gmail.com		Email: yaronf.ietf@gmail.com
	Ralph Holz		Ralph Holz
	Technische Universitaet Muenchen		Technische Universitaet Muenchen
	Boltzmannstr. 3		Boltzmannstr. 3
	Garching 85748		Garching 85748
	Germany		Germany
End of changes. 48 change blocks.
	123 lines changed or deleted		199 lines changed or added
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