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
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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
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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
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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
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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
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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.
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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
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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).
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