rfc3850.txt		draft-ietf-smime-3850bis-08.txt
			S/MIME WG Blake Ramsdell, Brute Squad Labs
			Internet Draft Sean Turner, IECA
			Intended Status: Standard Track October 2, 2008
			Obsoletes: 3850 (once approved)
			Expires: April 2, 2009
	Network Working Group B. Ramsdell, Editor		Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.2
	Request for Comments: 3850 Sendmail, Inc.
	Category: Standards Track
	Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1
	Certificate Handling		Certificate Handling
			draft-ietf-smime-3850bis-08.txt
	Status of this Memo		Status of this Memo
	This document specifies an Internet standards track protocol for the		By submitting this Internet-Draft, each author represents that any
	Internet community, and requests discussion and suggestions for		applicable patent or other IPR claims of which he or she is aware
	improvements. Please refer to the current edition of the "Internet		have been or will be disclosed, and any of which he or she becomes
	Official Protocol Standards" (STD 1) for the standardization state		aware will be disclosed, in accordance with Section 6 of BCP 79.
	and status of this protocol. Distribution of this memo is unlimited.
			Internet-Drafts are working documents of the Internet Engineering
			Task Force (IETF), its areas, and its working groups. Note that
			other groups may also distribute working documents as Internet-
			Drafts.
			Internet-Drafts are draft documents valid for a maximum of six months
			and may be updated, replaced, or obsoleted by other documents at any
			time. It is inappropriate to use Internet-Drafts as reference
			material or to cite them other than as "work in progress."
			The list of current Internet-Drafts can be accessed at
			http://www.ietf.org/ietf/1id-abstracts.txt
			The list of Internet-Draft Shadow Directories can be accessed at
			http://www.ietf.org/shadow.html
			This Internet-Draft will expire on April 2, 2008.
	Copyright Notice		Copyright Notice
	Copyright (C) The Internet Society (2004).		Copyright (C) The IETF Trust (2008).
	Abstract		Abstract
	This document specifies conventions for X.509 certificate usage by		This document specifies conventions for X.509 certificate usage by
	Secure/Multipurpose Internet Mail Extensions (S/MIME) agents. S/MIME		Secure/Multipurpose Internet Mail Extensions (S/MIME) agents. S/MIME
	provides a method to send and receive secure MIME messages, and		provides a method to send and receive secure MIME messages, and
	certificates are an integral part of S/MIME agent processing. S/MIME		certificates are an integral part of S/MIME agent processing. S/MIME
	agents validate certificates as described in RFC 3280, the Internet		agents validate certificates as described in RFC 5280, the Internet
	X.509 Public Key Infrastructure Certificate and CRL Profile. S/MIME		X.509 Public Key Infrastructure Certificate and CRL Profile. S/MIME
	agents must meet the certificate processing requirements in this		agents must meet the certificate processing requirements in this
	document as well as those in RFC 3280.		document as well as those in RFC 5280. This document obsoletes RFC
			3850.
			Discussion
			This draft is being discussed on the 'ietf-smime' mailing list. To
			subscribe, send a message to ietf-smime-request@imc.org with the
			single word subscribe in the body of the message. There is a Web site
			for the mailing list at <http://www.imc.org/ietf-smime/>.
	Table of Contents		Table of Contents
	1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction...................................................2
	1.1. Definitions. . . . . . . . . . . . . . . . . . . . . . . 2		1.1. Definitions...............................................3
	1.2. Compatibility with Prior Practice of S/MIME. . . . . . . 3		1.2. Conventions used in this document.........................4
	1.3. Terminology. . . . . . . . . . . . . . . . . . . . . . . 3		1.3. Compatibility with Prior Practice S/MIME..................4
	1.4. Changes Since S/MIME v3 (RFC 2632) . . . . . . . . . . . 3		1.4. Changes From S/MIME v3 to S/MIME v3.1.....................4
	2. CMS Options. . . . . . . . . . . . . . . . . . . . . . . . . . 4		1.5. Changes Since S/MIME v3.1.................................5
	2.1 . CertificateRevocationLists . . . . . . . . . . . . . . . 4		2. CMS Options....................................................6
	2.2. CertificateChoices . . . . . . . . . . . . . . . . . . . 4		2.1. Certificate Revocation Lists..............................6
	2.3. CertificateSet . . . . . . . . . . . . . . . . . . . . . 5		2.2. Certificate Choices.......................................6
	3. Using Distinguished Names for Internet Mail . . . . . . . . . . 6		2.2.1. Historical Note About CMS Certificates...............6
	4. Certificate Processing . . . . . . . . . . . . . . . . . . . . 7		2.3. CertificateSet............................................7
	4.1. Certificate Revocation Lists . . . . . . . . . . . . . . 8		3. Using Distinguished Names For Internet Mail....................8
	4.2. Certification Path Validation. . . . . . . . . . . . . . 8		4. Certificate Processing.........................................9
	4.3. Certificate and CRL Signing Algorithms . . . . . . . . . 9		4.1. Certificate Revocation Lists.............................10
	4.4. PKIX Certificate Extensions. . . . . . . . . . . . . . . 9		4.2. Certificate Path Validation..............................10
	5. Security Considerations. . . . . . . . . . . . . . . . . . . . 11		4.3. Certificate and CRL Signing Algorithms and Key Sizes.....11
	A. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13		4.4. PKIX Certificate Extensions..............................12
	A.1. Normative References . . . . . . . . . . . . . . . . . . 13		5. IANA Considerations...........................................14
	A.2. Informative References . . . . . . . . . . . . . . . . . 14		6. Security Considerations.......................................14
	B. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15		7. References....................................................16
	C. Editor's Address . . . . . . . . . . . . . . . . . . . . . . . 15		7.1. Normative References.....................................16
	Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 16		7.2. Informative References...................................18
			Appendix A. Moving S/MIME v2 Certificate Handling to Historic
			Status...............................................20
			Appendix B. Acknowledgements.....................................20
	1. Overview		1. Introduction
	S/MIME (Secure/Multipurpose Internet Mail Extensions), described in		S/MIME (Secure/Multipurpose Internet Mail Extensions), described in
	[SMIME-MSG], provides a method to send and receive secure MIME		[SMIME-MSG], provides a method to send and receive secure MIME
	messages. Before using a public key to provide security services,		messages. Before using a public key to provide security services,
	the S/MIME agent MUST verify that the public key is valid. S/MIME		the S/MIME agent MUST verify that the public key is valid. S/MIME
	agents MUST use PKIX certificates to validate public keys as		agents MUST use PKIX certificates to validate public keys as
	described in the Internet X.509 Public Key Infrastructure (PKIX)		described in the Internet X.509 Public Key Infrastructure (PKIX)
	Certificate and CRL Profile [KEYM]. S/MIME agents MUST meet the		Certificate and CRL Profile [KEYM]. S/MIME agents MUST meet the
	certificate processing requirements documented in this document in		certificate processing requirements documented in this document in
	addition to those stated in [KEYM].		addition to those stated in [KEYM].
	This specification is compatible with the Cryptographic Message		This specification is compatible with the Cryptographic Message
	Syntax [CMS] in that it uses the data types defined by CMS. It also		Syntax (CMS) RFC 3852 and RFC 4853 [CMS] in that it uses the data
	inherits all the varieties of architectures for certificate-based key		types defined by CMS. It also inherits all the varieties of
	management supported by CMS.		architectures for certificate-based key management supported by CMS.
	1.1. Definitions		1.1. Definitions
	For the purposes of this document, the following definitions apply.		For the purposes of this document, the following definitions apply.
	ASN.1: Abstract Syntax Notation One, as defined in ITU-T X.208		ASN.1: Abstract Syntax Notation One, as defined in ITU-T X.680
	[X.208-88].		[X.680].
	Attribute Certificate (AC): An X.509 AC is a separate structure from		Attribute Certificate (AC): An X.509 AC is a separate structure from
	a subject's public key X.509 Certificate. A subject may have		a subject's public key X.509 Certificate. A subject may have
	multiple X.509 ACs associated with each of its public key X.509		multiple X.509 ACs associated with each of its public key X.509
	Certificates. Each X.509 AC binds one or more Attributes with one of		Certificates. Each X.509 AC binds one or more Attributes with one of
	the subject's public key X.509 Certificates. The X.509 AC syntax is		the subject's public key X.509 Certificates. The X.509 AC syntax is
	defined in [ACAUTH].		defined in [ACAUTH].
	Certificate: A type that binds an entity's name to a public key with		Certificate: A type that binds an entity's name to a public key with
	a digital signature. This type is defined in the Internet X.509		a digital signature. This type is defined in the Internet X.509
	skipping to change at page 3, line 13		skipping to change at page 3, line 45
	also defined in that document.		also defined in that document.
	Certificate Revocation List (CRL): A type that contains information		Certificate Revocation List (CRL): A type that contains information
	about certificates whose validity an issuer has prematurely revoked.		about certificates whose validity an issuer has prematurely revoked.
	The information consists of an issuer name, the time of issue, the		The information consists of an issuer name, the time of issue, the
	next scheduled time of issue, a list of certificate serial numbers		next scheduled time of issue, a list of certificate serial numbers
	and their associated revocation times, and extensions as defined in		and their associated revocation times, and extensions as defined in
	[KEYM]. The CRL is signed by the issuer. The type intended by this		[KEYM]. The CRL is signed by the issuer. The type intended by this
	specification is the one defined in [KEYM].		specification is the one defined in [KEYM].
	Receiving agent: software that interprets and processes S/MIME CMS		Receiving agent: Software that interprets and processes S/MIME CMS
	objects, MIME body parts that contain CMS objects, or both.		objects, MIME body parts that contain CMS objects, or both.
	Sending agent: software that creates S/MIME CMS objects, MIME body		Sending agent: Software that creates S/MIME CMS objects, MIME body
	parts that contain CMS objects, or both.		parts that contain CMS objects, or both.
	S/MIME agent: user software that is a receiving agent, a sending		S/MIME agent: User software that is a receiving agent, a sending
	agent, or both.		agent, or both.
	1.2. Compatibility with Prior Practice of S/MIME		1.2. Conventions used in this document
	S/MIME version 3.1 agents should attempt to have the greatest
	interoperability possible with agents for prior versions of S/MIME.
	S/MIME version 2 is described in RFC 2311 through RFC 2315, inclusive
	and S/MIME version 3 is described in RFC 2630 through RFC 2634
	inclusive. RFC 2311 also has historical information about the
	development of S/MIME.
	1.3. Terminology
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in [MUSTSHOULD].		document are to be interpreted as described in [MUSTSHOULD].
	1.4. Changes Since S/MIME v3 (RFC 2632)		We define some additional terms here:
			SHOULD+ This term means the same as SHOULD. However, the authors
			expect that a requirement marked as SHOULD+ will be promoted at
			some future time to be a MUST.
			SHOULD- This term means the same as SHOULD. However, the authors
			expect that a requirement marked as SHOULD- will be demoted to a
			MAY in a future version of this document.
			MUST- This term means the same as MUST. However, the authors
			expect that this requirement will no longer be a MUST in a future
			document. Although its status will be determined at a later
			time, it is reasonable to expect that if a future revision of a
			document alters the status of a MUST- requirement, it will remain
			at least a SHOULD or a SHOULD-.
			1.3. Compatibility with Prior Practice S/MIME
			S/MIME version 3.2 agents should attempt to have the greatest
			interoperability possible with agents for prior versions of S/MIME.
			S/MIME version 2 is described in RFC 2311 through RFC 2315 inclusive
			[SMIMEv2], S/MIME version 3 is described in RFC 2630 through RFC 2634
			inclusive and RFC 5035 [SMIMEv3], and S/MIME version 3.1 is described
			in RFC 3850, RFC 3851, RFC 3852, RFC 2634, RFC4853, and RFC 5035
			[SMIMEv3.1]. RFC 2311 also has historical information about the
			development of S/MIME.
			1.4. Changes From S/MIME v3 To S/MIME v3.1
	Version 1 and Version 2 CRLs MUST be supported.		Version 1 and Version 2 CRLs MUST be supported.
	Multiple CA certificates with the same subject and public key, but		Multiple CA certificates with the same subject and public key, but
	with overlapping validity periods, MUST be supported.		with overlapping validity periods, MUST be supported.
	Version 2 attribute certificates SHOULD be supported, and version 1		Version 2 attribute certificates SHOULD be supported, and version 1
	attributes certificates MUST NOT be used.		attributes certificates MUST NOT be used.
	The use of the MD2 digest algorithm for certificate signatures is		The use of the MD2 digest algorithm for certificate signatures is
	skipping to change at page 4, line 14		skipping to change at page 5, line 21
	Receiving agents SHOULD display certificate information when		Receiving agents SHOULD display certificate information when
	displaying the results of signature verification.		displaying the results of signature verification.
	Receiving agents MUST NOT accept a signature made with a certificate		Receiving agents MUST NOT accept a signature made with a certificate
	that does not have the digitalSignature or nonRepudiation bit set.		that does not have the digitalSignature or nonRepudiation bit set.
	Clarifications for the interpretation of the key usage and extended		Clarifications for the interpretation of the key usage and extended
	key usage extensions.		key usage extensions.
			1.5. Changes Since S/MIME v3.1
			Conventions Used in This Document: Moved to section 1.2. Added
			definitions for SHOULD+, SHOULD-, and MUST-.
			Sec 1.1: Updated ASN.1 definition and reference.
			Sec 1.3: Added text about v3.1 RFCs.
			Sec 3: Updated note to indicate emailAddress IA5String upper bound is
			255 characters.
			Sec 4.2: Added text to indicate how S/MIME agents locate the correct
			user certificate.
			Sec 4.3: RSA with SHA-256 (PKCS #1 v1.5) added as MUST, DSA with SHA-
			256 added as SHOULD+, RSA with SHA-1, DSA with SHA-1, and RSA with
			MD5 changed to SHOULD-, and RSA-PSS with SHA-256 added as SHOULD+.
			Updated key sizes and changed pointer to PKIX RFCs.
			Sec 4.4.1: Aligned with PKIX on use of basic constraints extension in
			CA certificates. Clarified which extension is used to constrain EEs
			from using their keys to perform issuing authority operations.
			Sec 6: Updated security considerations.
			Sec 7: Moved references from Appendix B to section 7. Updated the
			references.
			Appendix A: Moved Appendix A to Appendix B. Added Appendix A to move
			S/MIME v2 Certificate Handling to Historic Status.
	2. CMS Options		2. CMS Options
	The CMS message format allows for a wide variety of options in		The CMS message format allows for a wide variety of options in
	content and algorithm support. This section puts forth a number of		content and algorithm support. This section puts forth a number of
	support requirements and recommendations in order to achieve a base		support requirements and recommendations in order to achieve a base
	level of interoperability among all S/MIME implementations. Most of		level of interoperability among all S/MIME implementations. Most of
	the CMS format for S/MIME messages is defined in [SMIME-MSG].		the CMS format for S/MIME messages is defined in [SMIME-MSG].
	2.1. CertificateRevocationLists		2.1. CertificateRevocationLists
	skipping to change at page 4, line 39		skipping to change at page 6, line 30
	All agents MUST be capable of performing revocation checks using CRLs		All agents MUST be capable of performing revocation checks using CRLs
	as specified in [KEYM]. All agents MUST perform revocation status		as specified in [KEYM]. All agents MUST perform revocation status
	checking in accordance with [KEYM]. Receiving agents MUST recognize		checking in accordance with [KEYM]. Receiving agents MUST recognize
	CRLs in received S/MIME messages.		CRLs in received S/MIME messages.
	Agents SHOULD store CRLs received in messages for use in processing		Agents SHOULD store CRLs received in messages for use in processing
	later messages.		later messages.
	2.2. CertificateChoices		2.2. CertificateChoices
	Receiving agents MUST support v1 X.509 and v3 X.509 identity		Receiving agents MUST support v1 X.509 and v3 X.509 certificates as
	certificates as profiled in [KEYM]. End entity certificates MAY		profiled in [KEYM]. End entity certificates MAY include an Internet
	include an Internet mail address, as described in section 3.		mail address, as described in section 3.
	Receiving agents SHOULD support X.509 version 2 attribute		Receiving agents SHOULD support X.509 version 2 attribute
	certificates. See [ACAUTH] for details about the profile for		certificates. See [ACAUTH] for details about the profile for
	attribute certificates.		attribute certificates.
	2.2.1. Historical Note About CMS Certificates		2.2.1. Historical Note About CMS Certificates
	The CMS message format supports a choice of certificate formats for		The CMS message format supports a choice of certificate formats for
	public key content types: PKIX, PKCS #6 Extended Certificates [PKCS6]		public key content types: PKIX, PKCS #6 Extended Certificates [PKCS6]
	and PKIX Attribute Certificates.		and PKIX Attribute Certificates.
	skipping to change at page 5, line 45		skipping to change at page 7, line 37
	certificate distribution. Receiving S/MIME agents SHOULD be able to		certificate distribution. Receiving S/MIME agents SHOULD be able to
	handle messages without certificates using a database or directory		handle messages without certificates using a database or directory
	lookup scheme.		lookup scheme.
	A sending agent SHOULD include at least one chain of certificates up		A sending agent SHOULD include at least one chain of certificates up
	to, but not including, a Certificate Authority (CA) that it believes		to, but not including, a Certificate Authority (CA) that it believes
	that the recipient may trust as authoritative. A receiving agent		that the recipient may trust as authoritative. A receiving agent
	MUST be able to handle an arbitrarily large number of certificates		MUST be able to handle an arbitrarily large number of certificates
	and chains.		and chains.
	Agents MAY send CA certificates, that is, certificates which can be		Agents MAY send CA certificates, that is, cross-certificates, self-
	considered the "root" of other chains, and which MAY be self-signed.		issued certificates, and self-signed certificates. Note that
	Note that receiving agents SHOULD NOT simply trust any self-signed		receiving agents SHOULD NOT simply trust any self-signed certificates
	certificates as valid CAs, but SHOULD use some other mechanism to		as valid CAs, but SHOULD use some other mechanism to determine if
	determine if this is a CA that should be trusted. Also note that		this is a CA that should be trusted. Also note that when
	when certificates contain DSA public keys the parameters may be		certificates contain DSA public keys the parameters may be located in
	located in the root certificate. This would require that the		the root certificate. This would require that the recipient possess
	recipient possess both the end-entity certificate as well as the root		both the end-entity certificate as well as the root certificate to
	certificate to perform a signature verification, and is a valid		perform a signature verification, and is a valid example of a case
	example of a case where transmitting the root certificate may be		where transmitting the root certificate may be required.
	required.
	Receiving agents MUST support chaining based on the distinguished		Receiving agents MUST support chaining based on the distinguished
	name fields. Other methods of building certificate chains MAY be		name fields. Other methods of building certificate chains MAY be
	supported.		supported.
	Receiving agents SHOULD support the decoding of X.509 attribute		Receiving agents SHOULD support the decoding of X.509 attribute
	certificates included in CMS objects. All other issues regarding the		certificates included in CMS objects. All other issues regarding the
	generation and use of X.509 attribute certificates are outside of the		generation and use of X.509 attribute certificates are outside of the
	scope of this specification. One specification that addresses		scope of this specification. One specification that addresses
	attribute certificate use is defined in [SECLABEL].		attribute certificate use is defined in [SECLABEL].
	3. Using Distinguished Names for Internet Mail		3. Using Distinguished Names For Internet Mail
	End-entity certificates MAY contain an Internet mail address as		End-entity certificates MAY contain an Internet mail address as
	described in [RFC-2822]. The address must be an "addr-spec" as		described in [IMF]. The address must be an "addr-spec" as defined in
	defined in Section 3.4.1 of that specification. The email address		Section 3.4.1 of that specification. The email address SHOULD be in
	SHOULD be in the subjectAltName extension, and SHOULD NOT be in the		the subjectAltName extension, and SHOULD NOT be in the subject
	subject distinguished name.		distinguished name.
	Receiving agents MUST recognize and accept certificates that contain		Receiving agents MUST recognize and accept certificates that contain
	no email address. Agents are allowed to provide an alternative		no email address. Agents are allowed to provide an alternative
	mechanism for associating an email address with a certificate that		mechanism for associating an email address with a certificate that
	does not contain an email address, such as through the use of the		does not contain an email address, such as through the use of the
	agent's address book, if available. Receiving agents MUST recognize		agent's address book, if available. Receiving agents MUST recognize
	email addresses in the subjectAltName field. Receiving agents MUST		email addresses in the subjectAltName field. Receiving agents MUST
	recognize email addresses in the Distinguished Name field in the PKCS		recognize email addresses in the Distinguished Name field in the PKCS
	#9 [PKCS9] emailAddress attribute:		#9 [PKCS9] emailAddress attribute:
	pkcs-9-at-emailAddress OBJECT IDENTIFIER ::=		pkcs-9-at-emailAddress OBJECT IDENTIFIER ::=
	{iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) 1 }		{iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) 1 }
	Note that this attribute MUST be encoded as IA5String.		Note that this attribute MUST be encoded as IA5String and has an
			upper bound of 255 characters.
	Sending agents SHOULD make the address in the From or Sender header		Sending agents SHOULD make the address in the From or Sender header
	in a mail message match an Internet mail address in the signer's		in a mail message match an Internet mail address in the signer's
	certificate. Receiving agents MUST check that the address in the		certificate. Receiving agents MUST check that the address in the
	From or Sender header of a mail message matches an Internet mail		From or Sender header of a mail message matches an Internet mail
	address, if present, in the signer's certificate, if mail addresses		address, if present, in the signer's certificate, if mail addresses
	are present in the certificate. A receiving agent SHOULD provide		are present in the certificate. A receiving agent SHOULD provide
	some explicit alternate processing of the message if this comparison		some explicit alternate processing of the message if this comparison
	fails, which may be to display a message that shows the recipient the		fails, which may be to display a message that shows the recipient the
	addresses in the certificate or other certificate details.		addresses in the certificate or other certificate details.
	A receiving agent SHOULD display a subject name or other certificate		A receiving agent SHOULD display a subject name or other certificate
	details when displaying an indication of successful or unsuccessful		details when displaying an indication of successful or unsuccessful
	signature verification.		signature verification.
	All subject and issuer names MUST be populated (i.e., not an empty		All subject and issuer names MUST be populated (i.e., not an empty
	SEQUENCE) in S/MIME-compliant X.509 identity certificates, except		SEQUENCE) in S/MIME-compliant X.509 certificates, except that the
	that the subject DN in a user's (i.e., end-entity) certificate MAY be		subject DN in a user's (i.e., end-entity) certificate MAY be an empty
	an empty SEQUENCE in which case the subjectAltName extension will		SEQUENCE in which case the subjectAltName extension will include the
	include the subject's identifier and MUST be marked as critical.		subject's identifier and MUST be marked as critical.
	4. Certificate Processing		4. Certificate Processing
	A receiving agent needs to provide some certificate retrieval		S/MIME agents need to provide some certificate retrieval mechanism in
	mechanism in order to gain access to certificates for recipients of		order to gain access to certificates for recipients of digital
	digital envelopes. There are many ways to implement certificate		envelopes. There are many ways to implement certificate retrieval
	retrieval mechanisms. X.500 directory service is an excellent		mechanisms. [X.500] directory service is an excellent example of a
	example of a certificate retrieval-only mechanism that is compatible		certificate retrieval-only mechanism that is compatible with classic
	with classic X.500 Distinguished Names. Another method under		X.500 Distinguished Names. Another method under consideration by the
	consideration by the IETF is to provide certificate retrieval		IETF is to provide certificate retrieval services as part of the
	services as part of the existing Domain Name System (DNS). Until		existing Domain Name System (DNS). Until such mechanisms are widely
	such mechanisms are widely used, their utility may be limited by the		used, their utility may be limited by the small number of the
	small number of correspondent's certificates that can be retrieved.		correspondent's certificates that can be retrieved. At a minimum, for
	At a minimum, for initial S/MIME deployment, a user agent could		initial S/MIME deployment, a user agent could automatically generate
	automatically generate a message to an intended recipient requesting		a message to an intended recipient requesting the recipient's
	that recipient's certificate in a signed return message.		certificate in a signed return message.
	Receiving and sending agents SHOULD also provide a mechanism to allow		Receiving and sending agents SHOULD also provide a mechanism to allow
	a user to "store and protect" certificates for correspondents in such		a user to "store and protect" certificates for correspondents in such
	a way so as to guarantee their later retrieval. In many		a way so as to guarantee their later retrieval. In many
	environments, it may be desirable to link the certificate		environments, it may be desirable to link the certificate
	retrieval/storage mechanisms together in some sort of certificate		retrieval/storage mechanisms together in some sort of certificate
	database. In its simplest form, a certificate database would be		database. In its simplest form, a certificate database would be
	local to a particular user and would function in a similar way as an		local to a particular user and would function in a similar way as an
	"address book" that stores a user's frequent correspondents. In this		"address book" that stores a user's frequent correspondents. In this
	way, the certificate retrieval mechanism would be limited to the		way, the certificate retrieval mechanism would be limited to the
	skipping to change at page 8, line 36		skipping to change at page 10, line 32
	dictated by the value of the information that is protected. The		dictated by the value of the information that is protected. The
	value of the CRL information in a particular context is beyond the		value of the CRL information in a particular context is beyond the
	scope of this specification but may be governed by the policies		scope of this specification but may be governed by the policies
	associated with particular certification paths.		associated with particular certification paths.
	All agents MUST be capable of performing revocation checks using CRLs		All agents MUST be capable of performing revocation checks using CRLs
	as specified in [KEYM]. All agents MUST perform revocation status		as specified in [KEYM]. All agents MUST perform revocation status
	checking in accordance with [KEYM]. Receiving agents MUST recognize		checking in accordance with [KEYM]. Receiving agents MUST recognize
	CRLs in received S/MIME messages.		CRLs in received S/MIME messages.
	4.2. Certification Path Validation		4.2. Certificate Path Validation
	In creating a user agent for secure messaging, certificate, CRL, and		In creating a user agent for secure messaging, certificate, CRL, and
	certification path validation SHOULD be highly automated while still		certification path validation SHOULD be highly automated while still
	acting in the best interests of the user. Certificate, CRL, and path		acting in the best interests of the user. Certificate, CRL, and path
	validation MUST be performed as per [KEYM] when validating a		validation MUST be performed as per [KEYM] when validating a
	correspondent's public key. This is necessary before using a public		correspondent's public key. This is necessary before using a public
	key to provide security services such as: verifying a signature;		key to provide security services such as: verifying a signature;
	encrypting a content-encryption key (ex: RSA); or forming a pairwise		encrypting a content-encryption key (ex: RSA); or forming a pairwise
	symmetric key (ex: Diffie-Hellman) to be used to encrypt or decrypt a		symmetric key (ex: Diffie-Hellman) to be used to encrypt or decrypt a
	content-encryption key.		content-encryption key.
	Certificates and CRLs are made available to the path validation		Certificates and CRLs are made available to the path validation
	procedure in two ways: a) incoming messages, and b) certificate and		procedure in two ways: a) incoming messages, and b) certificate and
	CRL retrieval mechanisms. Certificates and CRLs in incoming messages		CRL retrieval mechanisms. Certificates and CRLs in incoming messages
	are not required to be in any particular order nor are they required		are not required to be in any particular order nor are they required
	to be in any way related to the sender or recipient of the message		to be in any way related to the sender or recipient of the message
	(although in most cases they will be related to the sender).		(although in most cases they will be related to the sender). Incoming
	Incoming certificates and CRLs SHOULD be cached for use in path		certificates and CRLs SHOULD be cached for use in path validation and
	validation and optionally stored for later use. This temporary		optionally stored for later use. This temporary certificate and CRL
	certificate and CRL cache SHOULD be used to augment any other		cache SHOULD be used to augment any other certificate and CRL
	certificate and CRL retrieval mechanisms for path validation on		retrieval mechanisms for path validation on incoming signed messages.
	incoming signed messages.
	4.3. Certificate and CRL Signing Algorithms		When verifying a signature and the certificates are included in the
			message, if a signingCertificate attribute from RFC 2634 [ESS] or a
			signingCertificateV2 attribute from RFC 5035 [ESS] is found in an
			S/MIME message, it SHALL be used to identify the signer's
			certificate. Otherwise, the certificate is identified in an S/MIME
			message, either using the issuerAndSerialNumber which identifies the
			signer's certificate by the issuer's distinguished name and the
			certificate serial number, or the subjectKeyIdentifier which
			identifies the signer's certificate by a key identifier.
			When decrypting an encrypted message, if a
			SMIMEEncryptionKeyPreference attribute is found in an encapsulating
			SignedData, it SHALL be used to identify the originator's certificate
			found in OriginatorInfo. See [CMS] for the CMS fields that reference
			the originator's and recipient's certificates.
			4.3. Certificate and CRL Signing Algorithms and Key Sizes
	Certificates and Certificate Revocation Lists (CRLs) are signed by		Certificates and Certificate Revocation Lists (CRLs) are signed by
	the certificate issuer. A receiving agent MUST be capable of		the certificate issuer. Receiving agents:
	verifying the signatures on certificates and CRLs made with
	id-dsa-with-sha1 [CMSALG].
	A receiving agent MUST be capable of verifying the signatures on		- MUST support RSA with SHA-256
	certificates and CRLs made with md5WithRSAEncryption and
	sha1WithRSAEncryption signature algorithms with key sizes from 512
	bits to 2048 bits described in [CMSALG].
	Because of the security issues surrounding MD2 [RC95], and in light		- SHOULD+ support DSA with SHA-256
	of current use, md2WithRSAEncryption MAY be supported.
			- SHOULD+ support RSA-PSS with SHA-256
			- SHOULD- support RSA with SHA-1
			- SHOULD- support DSA with SHA-1
			- SHOULD- support RSA with MD5
			The following are the RSA key size requirements for S/MIME receiving
			agents during certificate and CRL signature verification:
			0 < key size < 512 : MAY (see Section 6)
			512 <= key size <= 4096 : MUST (see Section 6)
			4096 < key size : MAY (see Section 6)
			The following are the DSA key size requirements for S/MIME receiving
			agents during certificate and CRL signature verification:
			512 <= key size <= 1023 : MAY (see Section 6)
			1024 = key size : SHOULD- (see Section 6)
			For 512-bit RSA with SHA-1 see [KEYMALG] and [FIPS186-2] without
			Change Notice 1, for 512-bit RSA with SHA-256 see [RSAOAEP] and
			[FIPS186-2] without Change Notice 1, for 1024-bit through 3072-bit
			RSA with SHA-256 see [RSAOAEP] and [FIPS186-2] with Change Notice 1,
			and for 4096-bit RSA with SHA-256 see [RSAOAEP] and [PKCS1]. The
			first reference provides the signature algorithm's object identifier
			and the second provides the signature algorithm's definition.
			For 512-bit DSA with SHA-1 see [KEYMALG] and [FIPS186-2] without
			Change Notice 1, for 512-bit DSA with SHA-256 see [KEYMALG2] and
			[FIPS186-2] without Change Notice 1, for 1024-bit DSA with SHA-1 see
			[KEYMALG] and [FIPS186-2] with Change Notice 1, for 1024-bit DSA with
			SHA-256 see [KEYMALG2] and [FIPS186-3]. The first reference provides
			the signature algorithm's object identifier and the second provides
			the signature algorithm's definition.
			For 512-4096-bit RSA-PSS with SHA-256 see [RSAPSS].
	4.4. PKIX Certificate Extensions		4.4. PKIX Certificate Extensions
	PKIX describes an extensible framework in which the basic certificate		PKIX describes an extensible framework in which the basic certificate
	information can be extended and how such extensions can be used to		information can be extended and describes how such extensions can be
	control the process of issuing and validating certificates. The PKIX		used to control the process of issuing and validating certificates.
	Working Group has ongoing efforts to identify and create extensions		The PKIX Working Group has ongoing efforts to identify and create
	which have value in particular certification environments. Further,		extensions which have value in particular certification environments.
	there are active efforts underway to issue PKIX certificates for		Further, there are active efforts underway to issue PKIX certificates
	business purposes. This document identifies the minimum required set		for business purposes. This document identifies the minimum required
	of certificate extensions which have the greatest value in the S/MIME		set of certificate extensions which have the greatest value in the
	environment. The syntax and semantics of all the identified		S/MIME environment. The syntax and semantics of all the identified
	extensions are defined in [KEYM].		extensions are defined in [KEYM].
	Sending and receiving agents MUST correctly handle the basic		Sending and receiving agents MUST correctly handle the basic
	constraints, key usage, authority key identifier, subject key		constraints, key usage, authority key identifier, subject key
	identifier, and subject alternative names certificate extensions when		identifier, and subject alternative names certificate extensions when
	they appear in end-entity and CA certificates. Some mechanism SHOULD		they appear in end-entity and CA certificates. Some mechanism SHOULD
	exist to gracefully handle other certificate extensions when they		exist to gracefully handle other certificate extensions when they
	appear in end-entity or CA certificates.		appear in end-entity or CA certificates.
	Certificates issued for the S/MIME environment SHOULD NOT contain any		Certificates issued for the S/MIME environment SHOULD NOT contain any
	critical extensions (extensions that have the critical field set to		critical extensions (extensions that have the critical field set to
	TRUE) other than those listed here. These extensions SHOULD be		TRUE) other than those listed here. These extensions SHOULD be
	marked as non-critical unless the proper handling of the extension is		marked as non-critical unless the proper handling of the extension is
	deemed critical to the correct interpretation of the associated		deemed critical to the correct interpretation of the associated
	certificate. Other extensions may be included, but those extensions		certificate. Other extensions may be included, but those extensions
	SHOULD NOT be marked as critical.		SHOULD NOT be marked as critical.
	Interpretation and syntax for all extensions MUST follow [KEYM],		Interpretation and syntax for all extensions MUST follow [KEYM],
	unless otherwise specified here.		unless otherwise specified here.
	4.4.1. Basic Constraints Certificate Extension		4.4.1. Basic Constraints
	The basic constraints extension serves to delimit the role and		The basic constraints extension serves to delimit the role and
	position that an issuing authority or end-entity certificate plays in		position that an issuing authority or end-entity certificate plays in
	a certification path.		a certification path.
	For example, certificates issued to CAs and subordinate CAs contain a		For example, certificates issued to CAs and subordinate CAs contain a
	basic constraint extension that identifies them as issuing authority		basic constraint extension that identifies them as issuing authority
	certificates. End-entity certificates contain an extension that		certificates. End-entity certificates contain the key usage
	constrains the certificate from being an issuing authority		extension which restrains EEs from using the key to performing
	certificate.		issuing authority operations (see Section 4.4.2).
	Certificates SHOULD contain a basicConstraints extension in CA		As per [KEYM], Certificates MUST contain a basicConstraints extension
	certificates, and SHOULD NOT contain that extension in end entity		in CA certificates, and SHOULD NOT contain that extension in end
	certificates.		entity certificates.
	4.4.2. Key Usage Certificate Extension		4.4.2. Key Usage Certificate Extension
	The key usage extension serves to limit the technical purposes for		The key usage extension serves to limit the technical purposes for
	which a public key listed in a valid certificate may be used.		which a public key listed in a valid certificate may be used. Issuing
	Issuing authority certificates may contain a key usage extension that		authority certificates may contain a key usage extension that
	restricts the key to signing certificates, certificate revocation		restricts the key to signing certificates, certificate revocation
	lists and other data.		lists and other data.
	For example, a certification authority may create subordinate issuer		For example, a certification authority may create subordinate issuer
	certificates which contain a key usage extension which specifies that		certificates which contain a key usage extension which specifies that
	the corresponding public key can be used to sign end user		the corresponding public key can be used to sign end user
	certificates and sign CRLs.		certificates and sign CRLs.
	If a key usage extension is included in a PKIX certificate, then it		If a key usage extension is included in a PKIX certificate, then it
	MUST be marked as critical.		MUST be marked as critical.
	skipping to change at page 11, line 8		skipping to change at page 14, line 10
	extension without either the digitalSignature or nonRepudiation bit		extension without either the digitalSignature or nonRepudiation bit
	set. Sometimes S/MIME is used as a secure message transport for		set. Sometimes S/MIME is used as a secure message transport for
	applications beyond interpersonal messaging. In such cases, the		applications beyond interpersonal messaging. In such cases, the
	S/MIME-enabled application can specify additional requirements		S/MIME-enabled application can specify additional requirements
	concerning the digitalSignature or nonRepudiation bits within this		concerning the digitalSignature or nonRepudiation bits within this
	extension.		extension.
	If the key usage extension is not specified, receiving clients MUST		If the key usage extension is not specified, receiving clients MUST
	presume that the digitalSignature and nonRepudiation bits are set.		presume that the digitalSignature and nonRepudiation bits are set.
	4.4.3. Subject Alternative Name Extension		4.4.3. Subject Alternative Name
	The subject alternative name extension is used in S/MIME as the		The subject alternative name extension is used in S/MIME as the
	preferred means to convey the RFC-2822 email address(es) that		preferred means to convey the RFC-2822 email address(es) that
	correspond(s) to the entity for this certificate. Any RFC-2822 email		correspond(s) to the entity for this certificate. Any RFC-2822 email
	addresses present MUST be encoded using the rfc822Name CHOICE of the		addresses present MUST be encoded using the rfc822Name CHOICE of the
	GeneralName type. Since the SubjectAltName type is a SEQUENCE OF		GeneralName type. Since the SubjectAltName type is a SEQUENCE OF
	GeneralName, multiple RFC-2822 email addresses MAY be present.		GeneralName, multiple RFC-2822 email addresses MAY be present.
	4.4.4. Extended Key Usage Extension		4.4.4. Extended Key Usage Extension
	skipping to change at page 11, line 40		skipping to change at page 14, line 42
	signature, but no extended key usage extension then the certificate		signature, but no extended key usage extension then the certificate
	may also be used to sign but not encrypt S/MIME messages.		may also be used to sign but not encrypt S/MIME messages.
	If the extended key usage extension is present in the certificate		If the extended key usage extension is present in the certificate
	then interpersonal message S/MIME receiving agents MUST check that it		then interpersonal message S/MIME receiving agents MUST check that it
	contains either the emailProtection or the anyExtendedKeyUsage OID as		contains either the emailProtection or the anyExtendedKeyUsage OID as
	defined in [KEYM]. S/MIME uses other than interpersonal messaging		defined in [KEYM]. S/MIME uses other than interpersonal messaging
	MAY require the explicit presence of the extended key usage extension		MAY require the explicit presence of the extended key usage extension
	or other OIDs to be present in the extension or both.		or other OIDs to be present in the extension or both.
	5. Security Considerations		5. IANA Considerations
			None: All identifiers are already registered. Please remove this
			section prior to publication as an RFC.
			6. Security Considerations
	All of the security issues faced by any cryptographic application		All of the security issues faced by any cryptographic application
	must be faced by a S/MIME agent. Among these issues are protecting		must be faced by a S/MIME agent. Among these issues are protecting
	the user's private key, preventing various attacks, and helping the		the user's private key, preventing various attacks, and helping the
	user avoid mistakes such as inadvertently encrypting a message for		user avoid mistakes such as inadvertently encrypting a message for
	the wrong recipient. The entire list of security considerations is		the wrong recipient. The entire list of security considerations is
	beyond the scope of this document, but some significant concerns are		beyond the scope of this document, but some significant concerns are
	listed here.		listed here.
	When processing certificates, there are many situations where the		When processing certificates, there are many situations where the
	skipping to change at page 12, line 16		skipping to change at page 15, line 25
	that they are not important. The opposite is true: if a certificate		that they are not important. The opposite is true: if a certificate
	is not provably valid and associated with the message, the processing		is not provably valid and associated with the message, the processing
	software should take immediate and noticeable steps to inform the end		software should take immediate and noticeable steps to inform the end
	user about it.		user about it.
	Some of the many places where signature and certificate checking		Some of the many places where signature and certificate checking
	might fail include:		might fail include:
	- no Internet mail addresses in a certificate matches the sender of		- no Internet mail addresses in a certificate matches the sender of
	a message, if the certificate contains at least one mail address		a message, if the certificate contains at least one mail address
	- no certificate chain leads to a trusted CA		- no certificate chain leads to a trusted CA
	- no ability to check the CRL for a certificate		- no ability to check the CRL for a certificate
	- an invalid CRL was received		- an invalid CRL was received
	- the CRL being checked is expired		- the CRL being checked is expired
	- the certificate is expired		- the certificate is expired
	- the certificate has been revoked		- the certificate has been revoked
	There are certainly other instances where a certificate may be		There are certainly other instances where a certificate may be
	invalid, and it is the responsibility of the processing software to		invalid, and it is the responsibility of the processing software to
	check them all thoroughly, and to decide what to do if the check		check them all thoroughly, and to decide what to do if the check
	fails.		fails.
	At the Selected Areas in Cryptography '95 conference in May 1995,
	Rogier and Chauvaud presented an attack on MD2 that can nearly find
	collisions [RC95]. Collisions occur when one can find two different
	messages that generate the same message digest. A checksum operation
	in MD2 is the only remaining obstacle to the success of the attack.
	For this reason, the use of MD2 for new applications is discouraged.
	It is still reasonable to use MD2 to verify existing signatures, as
	the ability to find collisions in MD2 does not enable an attacker to
	find new messages having a previously computed hash value.
	It is possible for there to be multiple unexpired CRLs for a CA. If		It is possible for there to be multiple unexpired CRLs for a CA. If
	an agent is consulting CRLs for certificate validation, it SHOULD		an agent is consulting CRLs for certificate validation, it SHOULD
	make sure that the most recently issued CRL for that CA is consulted,		make sure that the most recently issued CRL for that CA is consulted,
	since an S/MIME message sender could deliberately include an older		since an S/MIME message sender could deliberately include an older
	unexpired CRL in an S/MIME message. This older CRL might not include		unexpired CRL in an S/MIME message. This older CRL might not include
	recent revoked certificates, which might lead an agent to accept a		recently revoked certificates, which might lead an agent to accept a
	certificate that has been revoked in a subsequent CRL.		certificate that has been revoked in a subsequent CRL.
	When determining the time for a certificate validity check, agents		When determining the time for a certificate validity check, agents
	have to be careful to use a reliable time. Unless it is from a		have to be careful to use a reliable time. Unless it is from a
	trusted agent, this time MUST NOT be the SigningTime attribute found		trusted agent, this time MUST NOT be the SigningTime attribute found
	in an S/MIME message. For most sending agents, the SigningTime		in an S/MIME message. For most sending agents, the SigningTime
	attribute could be deliberately set to direct the receiving agent to		attribute could be deliberately set to direct the receiving agent to
	check a CRL that could have out-of-date revocation status for a		check a CRL that could have out-of-date revocation status for a
	certificate, or cause an improper result when checking the Validity		certificate, or cause an improper result when checking the Validity
	field of a certificate.		field of a certificate.
	A. References		In addition to the Security Considerations identified in [KEYM],
			caution should be taken when processing certificates which have not
			first been validated to a trust anchor. Certificates could be
			manufactured by untrusted sources for the purpose of mounting denial
			of service or other attacks. For example, keys selected to require
			excessive cryptographic processing, or extensive lists of CDP and/or
			AIA addresses in the certificate, could be used to mount denial of
			service attacks. Similarly, attacker-specified CRL Distribution
			Point (CRLDP) and/or Authority Information Access (AIA) addresses
			could be included in fake certificates to allow the originator to
			detect receipt of the message even if signature verification fails.
	A.1. Normative References		The 4096-bit RSA key size requirement for certificate and CRL
			verification is larger than the 2048-bit RSA key sizes for message
			signature generation/verification or message encryption/decryption in
			[SMIME-MSG] because many Root CAs included in certificate stores have
			already issued Root certificates with 4096-bit key. The standard
			that defines comparable key sizes for DSA is not yet available. In
			particular, [FIPS186-2] without Change Notice 1 allowed DSA key sizes
			between 512 and 1024 bits and [FIPS186-2] with Change Notice 1 only
			allowed DSA key sizes of 1024 bits. A revision to support larger key
			sizes is being developed, and once it is available, implementors
			ought to support DSA key sizes comparable to the RSA key sizes
			recommended in this specification.
			Today, 512-bit RSA and DSA keys are considered by many experts to be
			cryptographically insecure.
			If an implementation is concerned about compliance with NIST key size
			recommendations, then see [SP800-57].
			7. References
			7.1. Normative References
	[ACAUTH] Farrell, S. and R. Housley, "An Internet Attribute		[ACAUTH] Farrell, S. and R. Housley, "An Internet Attribute
	Certificate Profile for Authorization", RFC 3281, April		Certificate Profile for Authorization", RFC 3281, April
	2002.		2002.
	[CMS] Housely, R., "Cryptographic Message Syntax (CMS)", RFC		[CMS] Housley, R., "Cryptographic Message Syntax (CMS)", RFC
	3852, July 2004.		3852, July 2004.
	[CMSALG] Housley, R., "Cryptographic Message Syntax (CMS)		Housley, R., "Cryptographic Message Syntax (CMS)
	Algorithms", RFC 3370, August 2002.		Multiple Signer Clarification", RFC 4853, April 2007.
	[KEYM] Housley, R., Polk, W., Ford, W., and D. Solo, "Internet		[ESS] Hoffman, P., "Enhanced Security Services for S/MIME",
	X.509 Public Key Infrastructure Certificate and		RFC 2634, June 1999.
	Certificate Revocation List (CRL) Profile", RFC 3280,
	April 2002.		Schaad, J., "ESS Update: Adding CertID Algorithm
			Agility", RFC 5035, August 2007.
			[FIPS186-2] National Institute of Standards and Technology (NIST),
			"Digital Signature Standard (DSS)", FIPS Publication
			186-3, January 2000. [With Change Notice 1]
			[FIPS186-3] National Institute of Standards and Technology (NIST),
			FIPS Publication 186-3: Digital Signature Standard,
			(draft) March 2006.
			[KEYM] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.
			Housley, R., and W. Polk, "Internet X.509 Public Key
			Infrastructure Certificate and Certificate Revocation
			List (CRL) Profile", RFC 5280, May 2008.
	[KEYMALG] Bassham, L., Polk, W., and R. Housley, "Algorithms and		[KEYMALG] Bassham, L., Polk, W., and R. Housley, "Algorithms and
	Identifiers for the Internet X.509 Public Key		Identifiers for the Internet X.509 Public Key
	Infrastructure Certificate and Certificate Revocation		Infrastructure Certificate and Certificate Revocation
	List (CRL) Profile", RFC 3279, April 2002.		List (CRL) Profile", RFC 3279, April 2002.
			[KEYMALG2] Dang, Q., Santesson, S., Moriarty, K., Brown, D., and
			T. Polk, "Internet X.509 Public Key Infrastructure:
			Additional Algorithms and Identifiers for DSA and
			ECDSA", draft-ietf-pkix-sha2-dsa-ecdsa, work-in-
			progress.
	[MUSTSHOULD] Bradner, S., "Key words for use in RFCs to Indicate		[MUSTSHOULD] 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.
			[PKCS1] Jonsson, J. and B. Kaliki, "Public-Key Cryptography
			Standards (PKCS) #1: RSA Cryptography Specifications
			Version 2.1", RFC 3447, February 2003.
	[PKCS9] Nystrom, M. and B. Kaliski, "PKCS #9: Selected Object		[PKCS9] Nystrom, M. and B. Kaliski, "PKCS #9: Selected Object
	Classes and Attribute Types Version 2.0", RFC 2985,		Classes and Attribute Types Version 2.0", RFC 2985,
	November 2000.		November 2000.
	[RFC-2822], Resnick, P., "Internet Message Format", RFC 2822, April		[IMF] Resnick, P., "Internet Message Format", RFC 5322,
	2001.		October 2008.
	[SMIME-MSG] Ramsdell, B., Ed., "S/MIME Version 3.1 Message		[RSAPSS] Schaad, J., "Use of RSASA-PSS Signature Algorithm in
	Specification", RFC 3851, July 2004.		Cryptographic Message Syntax (CMS)", RFC 4056, June
			2005.
	[x.208-88] ITU-T. Recommendation X.208: Specification of Abstract		[RSAOAEP] Schaad, J., Kaliski, B., and R. Housley, "Additional
	Syntax Notation One (ASN.1). 1988.		Algorithms and Identifiers for RSA Cryptography for use
			in the Internet X.509 Public Key Infrastructure
			Certificate and Certificate Revocation List (CRL)
			Profile", RFC 4055, June 2005.
	A.2. Informative References		[SMIME-MSG] Ramsdell, B., and S. Turner, "S/MIME Version 3.2
			Message Specification", draft-ietf-smime-3851bis-
			07.txt, work-in-progress.
	[CERTV2] Dusse, S., Hoffman, P., Ramsdell, B., and J. Weinstein,		[X.680] ITU-T Recommendation X.680 (2002) | ISO/IEC 8824-
	"S/MIME Version 2 Certificate Handling", RFC 2312, March		1:2002. Information Technology - Abstract Syntax
	1998.		Notation One (ASN.1): Specification of basic notation.
			7.2. Informative References
	[PKCS6] RSA Laboratories, "PKCS #6: Extended-Certificate Syntax		[PKCS6] RSA Laboratories, "PKCS #6: Extended-Certificate Syntax
	Standard", November 1993.		Standard", November 1993.
	[RC95] Rogier, N. and Chauvaud, P., "The compression function		[SECLABEL] Nicolls, W., "Implementing Company Classification
	of MD2 is not collision free," Presented at Selected		Policy with the S/MIME Security Label", RFC 3114, May
	Areas in Cryptography '95, May 1995.		2002.
	[SECLABEL] Nicolls, W., "Implementing Company Classification Policy		[SMIMEv2] Dusse, S., Hoffman, P., Ramsdell, B., Lundblade, L. and
	with the S/MIME Security Label", RFC 3114, May 2002.		L. Repka, "S/MIME Version 2 Message Specification", RFC
			2311, March 1998.
	[X.500] ITU-T Recommendation X.500 (1997) | ISO/IEC 9594-1:1997,		Dusse, S., Hoffman, P., Ramsdell, B., and J. Weinstein,
	Information technology - Open Systems Interconnection -		"S/MIME Version 2 Certificate Handling", RFC 2312,
	The Directory: Overview of concepts, models and		March 1998.
	services.
	[X.501] ITU-T Recommendation X.501 (1997) | ISO/IEC 9594-2:1997,		Kaliski, B., "PKCS #1: RSA Encryption Version 1.5", RFC
	Information technology - Open Systems Interconnection -		2313, March 1998.
	The Directory: Models.
	[X.509] ITU-T Recommendation X.509 (1997) | ISO/IEC 9594-8:1997,		Kaliski, B., "PKCS #10: Certificate Request Syntax
	Information technology - Open Systems Interconnection -		Version 1.5", RFC 2314, March 1998.
	The Directory: Authentication framework.
	[X.520] ITU-T Recommendation X.520 (1997) | ISO/IEC 9594-6:1997,		Kaliski, B., "PKCS #7: Certificate Message Syntax
	Information technology - Open Systems Interconnection -		Version 1.5", RFC 2315, March 1998.
	The Directory: Selected attribute types.
	B. Acknowledgements		[SMIMEv3] Housley, R., "Cryptographic Message Syntax", RFC 2630,
			June 1999.
			Rescorla, E., "Diffie-Hellman Key Agreement Method",
			RFC 2631, June 1999.
			Ramsdell, B., "S/MIME Version 3 Certificate Handling",
			RFC 2632, June 1999.
			Ramsdell, B., "S/MIME Version 3 Message Specification",
			RFC 2633, June 1999.
			Hoffman, P., "Enhanced Security Services for S/MIME",
			RFC 2634, June 1999.
			Schaad, J., "ESS Update: Adding CertID Algorithm
			Agility", RFC 5035, August 2007.
			[SMIMEv3.1] Housley, R., "Cryptographic Message Syntax", RFC 3852,
			July 2004.
			Housley, R., "Cryptographic Message Syntax (CMS)
			Multiple Signer Clarification", RFC 4853, April 2007.
			Ramsdell, B., "S/MIME Version 3.1 Certificate
			Handling", RFC 3850, July 2004.
			Ramsdell, B., "S/MIME Version 3.1 Message
			Specification", RFC 3851, July 2004.
			Hoffman, P., "Enhanced Security Services for S/MIME",
			RFC 2634, June 1999.
			Schaad, J., "ESS Update: Adding CertID Algorithm
			Agility", RFC 5035, August 2007.
			[SP800-57] National Institute of Standards and Technology (NIST),
			Special Publication 800-57: Recommendation for Key
			Management, August 2005.
			[X.500] ITU-T Recommendation X.500 (1997) | ISO/IEC 9594-
			1:1997, Information technology - Open Systems
			Interconnection - The Directory: Overview of concepts,
			models and services.
			Appendix A. Moving S/MIME v2 Certificate Handling to Historic Status
			The S/MIME v3 [SMIMEv3], v3.1 [SMIMEv3.1], and v3.2 (this document)
			are backwards compatible with the S/MIME v2 Certificate Handling
			Specification [SMIMEv2], with the exception of the algorithms
			(dropped RC2/40 requirement and added DSA and RSA-PSS requirements).
			Therefore, it is recommended that RFC 2312 [SMIMEv2] be moved to
			Historic status.
			Appendix B. Acknowledgements
	Many thanks go out to the other authors of the S/MIME v2 RFC: Steve		Many thanks go out to the other authors of the S/MIME v2 RFC: Steve
	Dusse, Paul Hoffman and Jeff Weinstein. Without v2, there wouldn't		Dusse, Paul Hoffman and Jeff Weinstein. Without v2, there wouldn't
	be a v3.		be a v3, v3.1 or v3.2.
	A number of the members of the S/MIME Working Group have also worked		A number of the members of the S/MIME Working Group have also worked
	very hard and contributed to this document. Any list of people is		very hard and contributed to this document. Any list of people is
	doomed to omission and for that I apologize. In alphabetical order,		doomed to omission and for that I apologize. In alphabetical order,
	the following people stand out in my mind due to the fact that they		the following people stand out in my mind due to the fact that they
	made direct contributions to this document.		made direct contributions to this document.
	Bill Flanigan		Bill Flanigan, Trevor Freeman, Elliott Ginsburg, Alfred Hoenes, Paul
	Trevor Freeman		Hoffman, Russ Housley, David P. Kemp, Michael Myers, John Pawling,
	Elliott Ginsburg		Denis Pinkas, and Jim Schaad.
	Paul Hoffman
	Russ Housley
	David P. Kemp
	Michael Myers
	John Pawling
	Denis Pinkas
	Jim Schaad
	C. Editor's Address		Author's Addresses
	Blake Ramsdell		Blake Ramsdell
	Sendmail, Inc.		Brute Squad Labs, Inc.
	704 228th Ave NE #775
	Sammamish, WA 98074
	EMail: blake@sendmail.com		Email: blaker@gmail.com
			Sean Turner
			IECA, Inc.
			3057 Nutley Street, Suite 106
			Fairfax, VA 22031
			USA
			Email: turners@ieca.com
	Full Copyright Statement		Full Copyright Statement
	Copyright (C) The Internet Society (2004). This document is subject		Copyright (C) The IETF Trust (2008).
	to the rights, licenses and restrictions contained in BCP 78, and
	except as set forth therein, the authors retain all their rights.		This document is subject to the rights, licenses and restrictions
			contained in BCP 78, and except as set forth therein, the authors
			retain all their rights.
	This document and the information contained herein are provided on an		This document and the information contained herein are provided on an
	"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS		"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
	OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET		OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
	ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,		THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
	INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE		OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
	INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED		THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
	WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.		WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
	Intellectual Property		Intellectual Property
	The IETF takes no position regarding the validity or scope of any		The IETF takes no position regarding the validity or scope of any
	Intellectual Property Rights or other rights that might be claimed to		Intellectual Property Rights or other rights that might be claimed to
	pertain to the implementation or use of the technology described in		pertain to the implementation or use of the technology described in
	this document or the extent to which any license under such rights		this document or the extent to which any license under such rights
	might or might not be available; nor does it represent that it has		might or might not be available; nor does it represent that it has
	made any independent effort to identify any such rights. Information		made any independent effort to identify any such rights. Information
	skipping to change at page 16, line 40		skipping to change at page 21, line 42
	Copies of IPR disclosures made to the IETF Secretariat and any		Copies of IPR disclosures made to the IETF Secretariat and any
	assurances of licenses to be made available, or the result of an		assurances of licenses to be made available, or the result of an
	attempt made to obtain a general license or permission for the use of		attempt made to obtain a general license or permission for the use of
	such proprietary rights by implementers or users of this		such proprietary rights by implementers or users of this
	specification can be obtained from the IETF on-line IPR repository at		specification can be obtained from the IETF on-line IPR repository at
	http://www.ietf.org/ipr.		http://www.ietf.org/ipr.
	The IETF invites any interested party to bring to its attention any		The IETF invites any interested party to bring to its attention any
	copyrights, patents or patent applications, or other proprietary		copyrights, patents or patent applications, or other proprietary
	rights that may cover technology that may be required to implement		rights that may cover technology that may be required to implement
	this standard. Please address the information to the IETF at ietf-		this standard. Please address the information to the IETF at
	ipr@ietf.org.		ietf-ipr@ietf.org.
	Acknowledgement		Acknowledgment
	Funding for the RFC Editor function is currently provided by the		Funding for the RFC Editor function is provided by the IETF
	Internet Society.		Administrative Support Activity (IASA).
End of changes. 74 change blocks.
	204 lines changed or deleted		448 lines changed or added
This html diff was produced by rfcdiff 1.32. The latest version is available from http://www.levkowetz.com/ietf/tools/rfcdiff/