Internet Draft Steve Dusse, draft-dusse-smime-cert-00.txt RSA Data Security March 25, 1997 Paul Hoffman, Expires September 25, 1997 Internet Mail Consortium Blake Ramsdell, Deming Internet Security Laurence Lundblade, Qualcomm Lisa Repka, Netscape S/MIME Certificate Handling Status of this memo This document is an Internet-Draft. 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." To learn the current status of any Internet-Draft, please check the "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). 1. Overview S/MIME (Secure/Multipurpose Internet Mail Extensions), described in [SMIME-MSG], provides a standard way to send and receive secure MIME messages. In order to validate the keys of a message sent to it, an S/MIME agent needs to certify that the key is valid. This draft describes the mechanisms S/MIME uses to create and validate keys using certificates. This specification is compatible with PKCS #7 in that it uses the data types defined by PKCS #7. It also inherits all the varieties of architectures for certificate-based key management supported by PKCS #7. Note that the method S/MIME messages make certificate requests is defined in [SMIME-MSG]. In order to handle S/MIME certificates, an agent has to follow specifications in this draft, as well as some of the specifications listed in the following pre-standards works: - "PKCS #1: RSA Encryption Standard", [PKCS-1]. - "PKCS #7: Cryptographic Message Syntax Standard", [PKCS-7] - "PKCS #9: Selected Attribute Types", [PKCS-9]. - "PKCS #10: Certification Request Syntax Standard", [PKCS-10]. 1.1 Definitions For the purposes of this draft, the following definitions apply. ASN.1: Abstract Syntax Notation One, as defined in CCITT X.208. BER: Basic Encoding Rules for ASN.1, as defined in CCITT X.209. Certificate: A type that binds an entity's distinguished name to a public key with a digital signature. This type is defined in CCITT X.509. This type also contains the distinguished name of the certificate issuer (the signer), an issuer-specific serial number, the issuer's signature algorithm identifier, and a validity period. CertificateRevocationList (CRL): A type that contains information about certificates whose validity an issuer has prematurely revoked. The information consists of an issuer name, the time of issue, the next scheduled time of issue, and a list of certificate serial numbers and their associated revocation times. The CRL is signed by the issuer. The type intended by this standard is the one defined in [KEYM]. DER: Distinguished Encoding Rules for ASN.1, as defined in CCITT X.509, Section 8.7. 1.2 Compatibility with Pre-standards S/MIME Appendix C contains importnat information about how standards-based S/MIME agents should act in order to have the greatest interoperability with pre-standards S/MIME. 2. PKCS #7 Options The PKCS #7 message format allows for a wide variety of options in content and algorithm support. This section puts forth a number of support requirements and recommendations in order to achieve a base level of interoperability among all S/MIME implementations. Most of the PKCS #7 format for S/MIME messages is defined in [SMIME-MSG]. 2.1 CertificateRevocationLists Receiving agents MUST support for the Certificate Revocation List (CRL) format defined in [KEYM]. It is anticipated that there will be a transition to the use of the X.509 v2 CRL format. However, because insufficient profiling has taken place to make this the default, agents SHOULD support for the X.509 v2 CRL format in incoming messages. If sending agents include CRLs in outgoing messages, the CRL format defined in [KEYM] SHOULD be used. 2.2 ExtendedCertificateOrCertificate Receiving agents MUST support X.509 v1 and X.509 v2 certificates, and SHOULD support X.509 v3 certificates. It is expected that, when the specification for X.509 v3 certificates is finished, this S/MIME specification will be altered to require X.509 v3 certificates. Sending agents that include certificates on outgoing messages SHOULD use the same type and version that was decided during the certification request/fulfillment process. 2.2.1 Historical Note About PKCS #7 Certificates The PKCS #7 message format supports a choice of certificate two formats for public key content types: X.509 and PKCS #6 Extended Certificates. The PKCS #6 format is not in widespread use. In addition, proposed revisions of X.509 certificates address much of the same functionality and flexibility as was intended in the PKCS #6. Thus, sending and receiving agents MUST NOT use PKCS #6 extended certificates. 2.3 ExtendedCertificateAndCertificates Receiving agents MUST be able to handle an arbitrary number of certificates of arbitrary relationship to the message sender and to each other in arbitrary order. In many cases, the certificates included in a signed message may represent a chain of certification from the sender to a particular root. There may be, however, situations where the certificates in a signed message may be unrelated and included for convenience. Sending agents SHOULD include any certificates for the user's public key(s) and associated issuer certificates. This increases the likelihood that the intended recipient can establish trust in the originator's public key(s). This is especially important when sending a message to recipients that may not have access to the sender's public key through any other means or when sending a signed message to a new recipient. The inclusion of certificates in outgoing messages can be omitted S/MIME objects are sent within a group of correspondents that has established access to each other's certificates by some other means such as a shared directory or manual certificate distribution. 3. Distinguished Names in Certificates 3.1 Using Distinguished Names for Internet Mail The format of an X.509 certificate includes fields for the subject name and issuer name. (The X.509 v1 certificate syntax is reproduced in Appendix A to PKCS #6). The subject name identifies the owner of a particular public key/private key pair while the issuer name is meant to identify the entity that "certified" the subject (that is, who signed the subject's certificate). The subject name and issuer name are defined by X.509 as Distinguished Names. Distinguished Names are defined by a CCITT standard X.501. A Distinguished Name is broken into one or more Relative Distinguished Names. Each Relative Distinguished Name is comprised of one or more Attribute-Value Assertions. Each Attribute-Value Assertion consists of a Attribute Identifier and its corresponding value information, such as CountryName=US. Distinguished Names were intended to identify entities in the X.500 directory tree. Each Relative Distinguished Name can be thought of as a node in the tree which is described by some collection of Attribute-Value Assertions. The entire Distinguished Name is some collection of nodes in the tree that traverse a path from the root of the tree to some end node which represents a particular entity. The goal of the directory was to provide an infrastructure to uniquely name every communications entity everywhere. However, adoption of a global X.500 directory infrastructure has been slower than expected. Consequently, there is no requirement for X.500 directory service provision in the S/MIME environment, although such provision would almost undoubtedly be of great value in facilitating key management for S/MIME. The use of Distinguished Names in accordance with the X.500 directory is not very widespread. By contrast, Internet mail addresses, as described in RFC 822, are used almost exclusively in the Internet environment to identify originators and recipients of messages. However, Internet mail addresses bear no resemblance to X.500 Distinguished Names (except, perhaps, that they are both hierarchical in nature). Some method is needed to map Internet mail addresses to entities that hold public keys. Some people have suggested that the X.509 certificate format should be abandoned in favor of other binding mechanisms. Instead, S/MIME keeps the X.509 certificate and Distinguished Name mechanisms while tailoring the content of the naming information to suit the Internet mail environment. At a minimum, either the Distinguished Name used to identify an Internet mail entity MUST include an Internet mail address, or some other mechanism MUST be implemented in the user agent to provide for mapping Distinguished Names to Internet mail address. If a mapping mechanism is used, the mapping database MUST be protected from tampering to defend against malicious insertion of non-trusted certificates, CRLs, and chains. The creation and use of a Distinguished Name which includes only an Internet mail address as the subject name in an X.509 certificate SHOULD be used for initial deployment of S/MIME. Such a construct, however, does not conform to the CCITT standards for Distinguished Names and should be used only as a transitional strategy. In many environments, the eventual addition of classical Distinguished Name attributes to the Internet mail address will be of value, such as for inter-organization commerce. The decision of what kind of Distinguished Name a user should construct will likely be influenced by the environment in which S/MIME is used as well as by whatever requirements are levied by the user's certifier or certification service provider. 3.2 Required Name Attributes Receiving agents MUST support parsing and display of zero, one, or more instances of each of the following set of name attributes within the Distinguished Names in certificates. Sending agents SHOULD include the Internet mail address during Distinguished Name creation. Guidelines for the inclusion, omission, and ordering of the remaining name attributes during the creation of a distinguished name will most likely be dictated by the policies associated with the certification service which will certify the corresponding name and public key. Name Attribute Description CountryName X.520 StateOrProvinceName X.520 Locality X.520 CommonName X.520 Title X.520 Organization X.520 OrganizationalUnit X.520 StreetAddress X.520 Postal Code X.520 Phone Number X.520 e-mailAddress PKCS #9 4. Certificate Processing A receiving agent MUST provide some certificate retrieval mechanism in order to gain access to certificates for recipients of digital envelopes. There are many ways to implement certificate retrieval mechanisms. X.500 directory service is an excellent example of a certificate retrieval-only mechanism that is compatible with classic X.500 Distinguished Names. Another method under consideration by the IETF is to provide certificate retrieval services as part of the existing Domain Name System (DNS). Until such mechanisms are widely used, their utility may be limited by the small number of correspondent's certificates that can be retrieved. At a minimum, for initial S/MIME deployment, a user agent could automatically generate a message to an intended recipient requesting that recipient's certificate in a signed return message. Receiving and sending agents SHOULD also provide a mechanism to allow a user to "store and protect" certificates for correspondents in such a way so as to guarantee their later retrieval. In many environments, it may be desirable to link the certificate retrieval/storage mechanisms together in some sort of certificate database. In its simplest form, a certificate database would be local to a particular user and would function in a similar way as a "address book" that stores a user's frequent correspondents. In this way, the certificate retrieval mechanism would be limited to the certificates that a user has stored (presumably from incoming messages). A comprehensive certificate retrieval/storage solution may combine two or more mechanisms to allow the greatest flexibility and utility to the user. For instance, a secure Internet mail agent may resort to checking a centralized certificate retrieval mechanism for a certificate if it can not be found in a user's local certificate storage/retrieval database. Receiving and sending agents SHOULD provide a mechanism for the import and export of certificates, using a PKCS #7 certs-only message. This allows for import and export of full certificate chains as opposed to just a single certificate. This is described in [SMIME-MSG]. 4.1 Certificate Revocation Lists A receiving agent SHOULD have access to some certificate-revocation list (CRL) retrieval mechanism in order to gain access to certificate-revocation information when validating certificate chains. A receiving or sending agent SHOULD also provide a mechanism to allow a user to "store" incoming certificate-revocation information for correspondents in such a way so as to guarantee its later retrieval, however, it is always better to get the latest information from the CA than to get information stored away from incoming messages. Receiving and sending agents SHOULD retrieve and utilize CRL information every time a certificate is verified as part of a certificate chain validation even if the certificate was already verified in the past. However, in many instances (such as off-line verification) access to the latest CRL information may be difficult or impossible. The use of CRL information, therefore, should be dictated by the value of the information that is protected. The value of the CRL information in a particular context is beyond the scope of this draft but may be governed by the policies associated with particular certificate hierarchies. 4.2 Certificate Chain Validation In creating a user agent for secure messaging, certificate, CRL, and certificate chain validation SHOULD be highly automated while still acting in the best interests of the user. Certificate, CRL, and chain validation MUST be performed when validating a correspondent's public key. This is necessary when a) verifying a signature from a correspondent and, b) creating a digital envelope with the correspondent as the intended recipient. Certificates and CRLs are made available to the chain validation procedure in two ways: a) incoming messages, and b) certificate and CRL retrieval mechanisms. Certificates and CRLs in incoming messages 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 (although in most cases they will be related to the sender). Incoming certificates and CRLs SHOULD be cached for use in chain validation and optionally stored for later use. This temporary certificate and CRL cache SHOULD be used to augment any other certificate and CRL retrieval mechanisms for chain validation on incoming signed messages. 4.3 Certificate and CRL Signing Algorithms Certificates and Certificate-Revocation Lists (CRLs) are signed by the certificate issuer. A receiving agent MUST be capable of verifying the signatures on certificates and CRLs made with the md2WithRSAEncryption, md5WithRSAEncryption and sha-1WithRSAEncryption signature algorithms with key sizes from 512 bits to 2048 bits. 4.4 X.509 Version 3 Certificate Extensions The X.509 v3 standard describes an extensible framework in which the basic certificate information can be extended and how such extensions can be used to control the process of issuing and validating certificates. Because the v3 standard is relatively new, there are ongoing efforts to identify and create extensions which have value in particular certification environments. As such, there is still a fair amount of profiling work to be done before there is widespread agreement on which v3 extensions will be used. Further, there are active efforts underway to issue X.509 v3 certificates for business purposes. This draft identifies the smallest set of certificate extensions which have the greatest value in the S/MIME environment. The basicConstraints, keyUsage, and certificatePolicies extensions are defined in the X.509 v3 draft; Amendment 1 to ISO/IEC 9594- 8:1995. Sending and receiving agents MUST correctly handle and display the v3 Basic Constraints Certificate Extension, the Key Usage Certificate Extension, and the Certificate Policy Certificate Extension when they appear in end-user certificates. Some mechanism SHOULD exist to handle and display the defined v3 certificate extensions when they appear in intermediate or CA certificates. In the S/MIME environment, CAs which issue v3 certificates SHOULD include only the extensions listed in the subsections of this section. For these extensions, the criticality flag SHOULD be set to False unless the proper handling and display of the corresponding extension is deemed critical to the correct interpretation of the associated certificate. Also, in an S/MIME environment, when additional v3 extensions are included in a certificate, the corresponding criticality flags SHOULD be set to False. 4.4.1 Basic Constraints Certificate Extension The basic constraints extension serves to delimit the role and position of an issuing authority or end-user certificate plays in a chain of certificates. For example, certificates issued to CAs and subordinate CAs contain a basic constraint extension that identifies them as issuing authority certificates. End-user subscriber certificates contain an extension that constrains the certificate from being an issuing authority certificate. 4.4.2 Key Usage Certificate Extension The key usage extension serves to limit the technical purposes for which a public key listed in a valid certificate may be used. Issuing authority certificates may contain a key usage extension that restricts the key to signing certificates, certificate revocation lists and other data. For example, a certification authority may create subordinate issuer certs which contain a keyUsage extension which specifies that the corresponding public key can be used to sign end user certs and sign CRLs. 4.4.3 Certificate Policy Certificate Extension The certificate policy extension limits a certificate to the practices required by relying parties. 5. Generating Keys and Certification Requests 5.1 Binding Names and Keys An S/MIME agent or some related administrative utility or function MUST be capable of generating a certification request given a user's public key and associated name information. In most cases, the user's public key/private key pair will be generated simultaneously. However, there are cases where the keying information may be generated by an external process (such as when a key pair is generated on a cryptographic token or by a "key recovery" service). There SHOULD never exist multiple valid (that is, non-expired and non-revoked) certificates for the same key pair bound to different Distinguished Names. Otherwise, a security flaw exists where an attacker can substitute one valid certificate for another in such a way that can not be detected by a message recipient. If a users wishes to change their name (or create an alternate name), the user agent SHOULD generate a new key pair. If the user wishes to reuse an existing key pair with a new or alternate name, the user SHOULD first have any valid certificates for the existing public key revoked. In general, it is possible for a user to request certification for the same name and key from multiple certification authorities. This SHOULD not be done, however, because the policies of different certification authorities may vary and this may create confusion among a user's correspondents as to which policy was used to certify the user. In general, it is possible for a user to request certification for the same name with multiple key pairs from the same or different certification authorities. Although this may be somewhat confusing, this is acceptable for end-user certificates because the use of the Issuer Name/Serial Number pair in the PKCS #7 automatically disambiguates each user certificate. The use of the same name with different key pairs SHOULD not be done, however, for issuer keys, since certificate chain processing would be made more difficult by the task of having to "try" each different issuer key when validating a certificate created by that issuer. 5.2 Using PKCS #10 for Certification Requests PKCS #10 is a flexible and extensible message format for representing the results of cryptographic operations on some data. The choice of naming information is largely dictated by the policies and procedures associated with the intended certification service. In addition to key and naming information, the PKCS #10 format supports the inclusion of optional attributes, signed by the entity requesting certification. This allows for information to be conveyed in a certification request which may be useful to the request process, but not necessarily part of the Distinguished Name being certified. Certification authorities MUST support parsing and display of zero or one instance of each of the following set of certification- request attributes on incoming messages. Inclusion of the following attributes during the creation and submission of a certification-request will most likely be dictated by the policies associated with the certification service which will certify the corresponding name and public key. Attribute Description postalAddress X.520 challengePassword PKCS #9 unstructuredAddress PKCS #9 unstructuredName PKCS #9 Receiving agents MUST support the identification of an RSA key with the rsa OID defined in X.509 and the rsaEncryption OID. Certification authorities MUST also support the verification of signatures on certificate requests made with sha-1WithRSAEncryption, md5WithRSAEncryption, and MD2WithRSAEncryption signature algorithms.. For the creation and submission of certification-requests, RSA keys SHOULD be identified with the rsaEncryption OID and signed with the sha-1WithRSAEncryption signature algorithm. 5.3 Fulfilling a Certification Request Certification authorities SHOULD use the sha-1WithRSAEncryption signature algorithms when signing certificates. 5.4 Using PKCS #7 for Fulfilled Certificate Response [PKCS-7] supports a degenerate case of the SignedData content type where there are no signers on the content (and hence, the content value is "irrelevant"). This degenerate case is used to convey certificate and CRL information. Certification authorities MUST use this format for returning certificate information resulting from the successful fulfillment of a certification request. At a minimum, the fulfilled certificate response MUST include the actual subject certificate (corresponding to the information in the certification request). The response SHOULD include other certificates which link the issuer to higher level certification authorities and corresponding certificate-revocation lists. Unrelated certificates and revocation information is also acceptable. Receiving agents MUST parse this degenerate PKCS #7 message type and handle the certificates and CRLs according to the requirements and recommendations in Section 4. 6. Security Considerations All of the security issues faced by any cryptographic application must be faced by a S/MIME agent. Among these issues are protecting the user's private key, preventing various attacks, and helping the user avoid mistakes such as inadvertently encrypting a message for the wrong recipient. The entire list of security considerations is beyond the scope of this document, but some significant concerns are listed here. An implementor may choose not to present data which has been digitally signed if the signature verification fails. The reasoning is that if the signature fails, the data very likely has been tampered with and should be considered untrustworthy. This is consistent with the fact that the signed data within an application/pkcs7-mime entity cannot be seen by viewing the "raw" MIME message, since it is base64 encoded (unless is it sent clear signed). The message must be processed and the signature verified before the data is presented. If the implementor does choose to present the data even if the signature verification fails, it is advisable to strongly warn the user. A MIME agent which supports application/pkcs7-mime inherits the certificate-based key management supported by PKCS #7. In particular, a typical agent must be able to process certificates and CRLs which may be included inside a SignedData or SignedAndEnvelopedData type. The agent may also include auxiliary services to allow the user to generate keys, submit and process certification requests and to request updated CRLs. Appendix A - Object Identifiers & Syntax Sections A.1 through A.4 are adopted from [SMIME-MSG]. A.5 Name Attributes emailAddress OBJECT IDENTIFIER ::= {iso(1) member-body(2) US(840) rsadsi(113549) pkcs(1) pkcs-9(9) 1} CountryName OBJECT IDENTIFIER ::= {joint-iso-ccitt(2) ds(5) attributeType(4) 6} StateOrProvinceName OBJECT IDENTIFIER ::= {joint-iso-ccitt(2) ds(5) attributeType(4) 8} locality OBJECT IDENTIFIER ::= {joint-iso-ccitt(2) ds(5) attributeType(4) 7} CommonName OBJECT IDENTIFIER ::= {joint-iso-ccitt(2) ds(5) attributeType(4) 3} Title OBJECT IDENTIFIER ::= {joint-iso-ccitt(2) ds(5) attributeType(4) 12} Organization OBJECT IDENTIFIER ::= {joint-iso-ccitt(2) ds(5) attributeType(4) 10} OrganizationalUnit OBJECT IDENTIFIER ::= {joint-iso-ccitt(2) ds(5) attributeType(4) 11} StreetAddress OBJECT IDENTIFIER ::= {joint-iso-ccitt(2) ds(5) attributeType(4) 9} Postal Code OBJECT IDENTIFIER ::= {joint-iso-ccitt(2) ds(5) attributeType(4) 17} Phone Number OBJECT IDENTIFIER ::= {joint-iso-ccitt(2) ds(5) attributeType(4) 20} A.6 Certification Request Attributes postalAddress OBJECT IDENTIFIER ::= {joint-iso-ccitt(2) ds(5) attributeType(4) 16} challengePassword OBJECT IDENTIFIER ::= {iso(1) member-body(2) US(840) rsadsi(113549) pkcs(1) pkcs-9(9) 7} unstructuredName OBJECT IDENTIFIER ::= {iso(1) member-body(2) US(840) rsadsi(113549) pkcs(1) pkcs-9(9) 2} unstructuredAddress OBJECT IDENTIFIER ::= {iso(1) member-body(2) US(840) rsadsi(113549) pkcs(1) pkcs-9(9) 8} A.7 X.509 V3 Certificate Extensions basicConstraints OBJECT IDENTIFIER ::= {joint-iso-ccitt(2) ds(5) 29 19 } The ASN.1 definition of basicConstraints certificate extension is: basicConstraints basicConstraints EXTENSION ::= { SYNTAX BasicConstraintsSyntax IDENTIFIED BY { id-ce 19 } } BasicConstraintsSyntax ::= SEQUENCE { cA BOOLEAN DEFAULT FALSE, pathLenConstraint INTEGER (0..MAX) OPTIONAL } keyUsage OBJECT IDENTIFIER ::= {joint-iso-ccitt(2) ds(5) 29 15 } The ASN.1 definition of keyUsage certificate extension is: keyUsage EXTENSION ::= { SYNTAX KeyUsage IDENTIFIED BY { id-ce 15 }} KeyUsage ::= BIT STRING { digitalSignature (0), nonRepudiation (1), keyEncipherment (2), dataEncipherment (3), keyAgreement (4), keyCertSign (5), cRLSign (6)} certificatePolicies OBJECT IDENTIFIER ::= {joint-iso-ccitt(2) ds(5) 29 32} The ASN.1 definition of certificatePolicies certificate extension is: certificatePolicies EXTENSION ::= { SYNTAX CertificatePoliciesSyntax IDENTIFIED BY { id-ce 32 }} CertificatePoliciesSyntax ::= SEQUENCE SIZE (1..MAX) OF PolicyInformation PolicyInformation ::= SEQUENCE { policyIdentifier CertPolicyId, policyQualifiers SEQUENCE SIZE (1..MAX) OF PolicyQualifierInfo OPTIONAL } CertPolicyId ::= OBJECT IDENTIFIER PolicyQualifierInfo ::= SEQUENCE { policyQualifierId CERT-POLICY-QUALIFIER.&id ({SupportedPolicyQualifiers}), qualifier CERT-POLICY-QUALIFIER.&Qualifier ({SupportedPolicyQualifiers}{@policyQualifierId}) OPTIONAL } SupportedPolicyQualifiers CERT-POLICY-QUALIFIER ::= {...} CERT-POLICY-QUALIFIER ::= CLASS { &id OBJECT IDENTIFIER UNIQUE, &Qualifier OPTIONAL } WITH SYNTAX { POLICY-QUALIFIER-ID &id [QUALIFIER-TYPE &Qualifier] } B. References [KEYM] "PEM key management", RFC 1422 [PEM] "Privacy-Enhanced Mail (PEM) basics", RFC 1421 [PKCS-1], "PKCS #1: RSA Encryption Standard", submission of draft pending [PKCS-7], "PKCS #7: Cryptographic Message Syntax Standard", submission of draft pending [PKCS-9], "PKCS #9: Selected Attribute Types", submission of draft pending [PKCS-10], "PKCS #10: Certification Request Syntax Standard", submission of draft pending [SMIME-MSG] "S/MIME Message Specification", Internet Draft draft-dusse-smime-msg-xx. C. Compatibility with Pre-standards S/MIME S/MIME was originally developed by RSA Data Security, Inc. Many developers implemented S/MIME agents before the standard was turned over to the IETF. All S/MIME receiving agents SHOULD make every attempt to interoperate with pre-standards S/MIME sending agents. C.1 Pre-standards MIME Types Pre-standard S/MIME agents used the following MIME types: application/x-pkcs7-mime application/x-pkcs7-signature application/x-pkcs10 In each case, the "x-" subtypes correspond to the subtypes described in this document without the "x-". D. Revision History This draft is a combination of an earlier draft, draft-dusse-mime-msg-spec-00, which specified the format for S/MIME messages, and the "S/MIME Implementation Guide, Interoperability Profiles, Version 2", a document from RSA Data Security. This draft includes changes to the wording, but not the intent, of both documents. Part of the "Implementation Guide" document was split out into a draft that describes S/MIME certification issues. E. Open Issues Make the draft more definitive by: - removing X.509 v2 - making X.509 v3 required instead of recommended - removing section 2.2 recommendation that sending agents use same type and version. Whether or not the PKCS-nn documents will be IETF RFCs or simply be referenced as external documents. References to the encryption and hash algorithms. Use of the S/MIME trademark. F. Trademarks RSA Data Security, Inc., owns the US trademark for the name "S/MIME" and for a logo associated with that name. RSA Data Security, Inc., is currently in discussions with the IETF about the use of the name "S/MIME" for interoperable message security. The name "S/MIME" may or may not be used in future versions of this draft. G. Acknowledgements Significant contributions to the content of this draft were made by many people, including: Jeff Thompson Jeff Weinstein H. Authors' addresses Steve Dusse RSA Data Security, Inc. 100 Marine Parkway, #500 Redwood City, CA 94065 USA (415) 595-8782 spock@rsa.com Paul Hoffman Internet Mail Consortium 127 Segre Place Santa Cruz, CA 95060 (408) 426-9827 phoffman@imc.org Blake Ramsdell Deming Internet Security 13122 NE 20th St., Suite C Bellevue, WA 98005 (206) 882-8861 blaker@deming.com Laurence Lundblade QUALCOMM Incorporated Eudora Division 6455 Lusk Boulevard San Diego, California 92121-2779 (800) 238-3672 lgl@qualcomm.com Lisa Repka Netscape Communications Corporation 501 East Middlefield Road Mountain View, CA 94043 (415) 254-1900 repka@netscape.com