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Network Working Group                                       Steve Crocker
INTERNET DRAFT                                                  Ned Freed
draft-ietf-pem-mime-05.txt
draft-ietf-pem-mime-06.txt                                     Jim Galvin
                                                             Sandy Murphy
                                                                June
                                                                July 1994


                     PEM Security Services and MIME



1.  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 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 one of the Internet Drafts Shadow
Directories on ds.internic.net (US East Coast), venera.isi.edu (US West
Coast), munnari.oz.au (Pacific Rim), or nic.nordu.net (Europe).

2.  Abstract

This document specifies how the services of MIME and PEM can be used in
a complementary fashion.  MIME, an acronym for "Multipurpose Internet
Mail Extensions", defines the format of the contents of Internet mail
messages and provides for multi-part textual and non-textual message
bodies.  PEM, an acronym for "Privacy Enhanced Mail", provides message
authentication/integrity and message encryption services for Internet
mail messages.

An Internet electronic mail message consists of two parts: the headers
and the body.  The headers form a collection of field/value pairs
structured according to RFC 822 RFC822 [1], whilst the body, if structured, is
defined according to MIME [2].  MIME does not provide for the
application of security services.







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PEM [3-6] specifies how to apply encryption and authentication/integrity
services to the contents of a textual electronic mail message but does
not provide message structuring or type labelling facilities.  This
document specifies how to use PEM with the multipart/signed and
multipart/encrypted MIME content types to provide
authentication/integrity and encryption services.  We refer to the
authentication/integrity service as a digital signature service.

This document specifies a number of changes to the message encryption
and signature procedures of PEM and broadens the name forms that may be
used to identify public keys.  Many of the changes represent a departure
in mechanism, not in effect.

3.  Introduction

This document updates the message encryption and signature procedures
defined by [3] and obsoletes the key certification and related services
defined by [6].  The changes to [3] include the separation of the
encryption and signature services, the removal of the limitation to
enhance only text-based messages, the removal of the transfer encoding
operation, the deprecation of the Content-Domain: and Proc-Type:
headers, and the separation of certificate and certificate revocation
list transmission from the security enhancements.  These changes
represent a departure in mechanism, not in effect, and are detailed in
Section ??. 10.

In addition, this document proposes specifies three technical changes: in [3] changes to PEM:
symmetric key management is deprecated, also in [3] is deprecated, the canonicalization
operation in [3] is generalized, and in [4] the allowable name forms for the
subjects
identification of certificates public keys is broadened to include arbitrary strings
and email addresses, and users may distribute their public keys directly
in lieu of certificates.

The key certification and related services document [6] is obsoleted by
the specification of two new MIME content types: application/key-request
and application/key-data.  These new content types are used to transmit
requests for key operations (retrieval, (storage, retrieval, certification,
revocation list retrieval, etc.)  and the responses to those requests.
These two content types are independent body parts and are not required
to be encapsulated in any other body part.  These changes represent a
departure in mechanism, not in effect, and are detailed in Section ??.

The relationship between MIME and PEM is described in terms 10.

In order to make use of two
functions: message composition and message delivery.

3.  Applying the PEM Security Services services, a user is required to MIME Body Parts

The next section describes the processing steps necessary have at
least one public/private key pair.  Prior to prepare a
MIME body part for the application of PEM security services.  The
succeeding two sections describe the content of the multipart/signed and
multipart/encrypted body parts resulting from this specification, the application of PEM
security services
public key was required to MIME body parts. be embodied in a certificate, an object that





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3.1.  PEM Processing Steps

The following three steps describe


binds a public key with a distinguished name, a name form that
identified the preparation owner of outbound PEM
messages.  These steps may the public key.  The embodiment was issued by a
certification authority, a role that was expected to be repeated trustworthy
insofar as necessary to prepare a message
for submission.

(1)  Local Form -- it verified the content identity of the message is prepared in owner prior to issuing the native
     format
certificate.  However, the deployment of certificates and the user's local environment

(2)  Canonical Form -- creation
of the content hierarchy of certification authorities has been problematic.

Instead, this specification bases the message PEM services on a public/private
key pair.  Each key pair is transformed required to belong to a
     canonical form for the digital signature service; no
     canonicalization user (where user is required for the encryption service

(3)  Security Form -- either of the signature
not limited to being a human, e.g., a process or encryption services may
     be applied

Each a role) which has a
name.  There are 3 name forms specified by this document.  For backward
compatibility (and forward compatibility if the X.500 Directory becomes
a ubiquitous service) one of these steps the name forms is described in detail below.  Their relationship to
message composition a distinguished name.  In
addition, email addresses and delivery arbitrary strings are allowed.

Since a user may have more than one key pair, a name form is described in Section ??.

3.1.1.  Step 1: Local Form
insufficient for uniquely identifying a key pair.  The message content is created in the native format of the user's local
environment.

3.1.2.  Step 2: Canonical Form

Prior to the application owner of the digital signature service, the content a key
pair must be in assign a canonical form.  No canonicalization is required for the
encryption service and therefore processing continues with the next
step.

Transforming the content key identifier to be signed into each key pair.  The combination of
a canonical name form is and a
necessary key identifier uniquely identifies a key pair and essential step in the digital signature process.  The
canonical form must satisfy the property that it each
key pair is uniquely identified by a name form and
unambiguously representable on both the originator and recipient's local
environment.  This key identifier
combination.  Throughout this document, this combination is required in order to ensure called an
identifier.  There are 6 identifiers specified by this document.

With a key pair for one's self and software that is both the
originator MIME and recipient have the same PEM
aware, an originating user may digitally sign arbitrary data with which and send it
to calculate one or more recipients.  With the
digital signature; public keys of the originator needs to be able to include recipients, a
user may encrypt the
digital signature value when transferring data so that only the body part, while intended recipients can
decrypt and read the
recipient needs it.  This specification separates these two
services so that an originator may apply either or both, in either
order.

The name forms and identifiers are described in detail in the next
section.  Succeeding sections specify how PEM and MIME are used together
and other ancillary details.

4.  Name Forms and Identifiers

Currently, [3] requires the use of certificates to be able identify the public
key (and corresponding private key) used to compare create a re-calculated value with PEM message.
Within certificates, [4] requires the
received value.  Further, use of distinguished names as
specified by the canonical form should satisfy X.500 Series of Recommendations.  However, the property
that it is representable on as many different host computers Internet
community has a great deal more experience with the use of electronic
mail addresses as
possible.  By satisfying this property, signed data may be forwarded by
recipients a name form and there is a desire to additional recipients, who will also be able to verify use
arbitrary strings to identify the
original signature.  This service owners of public keys.  Hence, there
is called forwardable authentication. a need to support name forms which do not conform to the expected





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The canonical form


usage of all content types distinguished names.

When processing PEM messages it is defined necessary to be 7bit.  The data able to be signed must be represented as 7bit.  Since the MIME standard
explicitly disallows nested encodings, the body parts enclosed in a
multipart content type, for example, must be encoded in a 7bit
representation.  Any valid MIME encoding may be selected.

The 7bit representation of uniquely
identify the data is transferred key pair used to create the recipient.  As
may be required by MIME, an appropriate Content-Transfer-Encoding:
header message.  A certificate is included with the data.  Upon receipt, a MIME implementation
would verify
uniquely identified by the signature combination of the data prior to decoding the data its issuer's distinguished
name and
displaying it to its serial number.  Thus, the recipient.

Representing all complex content types as 7bit transforms them into
text-based content types.  However, text-based content types present issuer name and serial number
uniquely identifies a
unique problem.  In particular, there are far too many broken message
transfer agents key pair.  Since a user may have more than one key
pair, a name form is insufficient for this purpose.  An identifier is
required that make arbitrary changes to text-based messages as
they are relayed, including adding, deleting, or changing TAB and SPACE
characters, consists of both a name form and line delimiters are altered by message transfer agent
protocols.  These changes will make it impossible for recipients key identifier, a value
assigned to
verify the signature on a message.

The application of the digital signature service requires that the same
line delimiter be used key pair by both the originator and the recipient.  This
document specifies that the two character sequence "<CR><LF>" must be
used as its owner.

In addition, users may distribute their public keys via mechanisms
outside the line delimiter.  Thus, scope of the canonicalization transformation PEM specification, for example, in a file via
FTP.  As a result, it is desirable to transform the local line delimiter be able to explicitly specify the two character sequence
"<CR><LF>".

The transformation to
public key used rather than an identifier of the universal line delimiter public key.  A
significant benefit of this mechanism is only required for the purposes ability to support
encrypted, anonymously signed mail.

The objective of computing the digital signature.  Thus, originators must
apply the universal line delimiter transformation before calculating the
digital signature but must transfer the data without the universal line
delimiter transformation.  Similarly, recipients must apply the
universal line delimiter transformation before calculating the digital
signature.

    NOTE: An originator can not transfer various Originator and Recipient fields specified
in [3] is to identify which public key has been used or is required.
This document simplifies the content set of fields by specifying exactly two:
Originator-ID: for originators and Recipient-ID: for recipients.  This
specification defines six (6) identifiers with which the
    universal line delimiter transformation intact because the
    transformation process is not idempotent.  In particular, SMTP
    servers public key used
may themselves convert be indicated in each of these fields.

In the universal line delimiter to a
    local line delimiter, prior to next section the message being delivered to 3 name forms are described in detail.  Following
that is the user.  Thus, a recipient has no way specification of knowing if the
    transformation 6 identifiers.

4.1.  Name Forms

There are 3 name forms specified by this document: email address,
distinguished names, and arbitrary strings.

4.1.1.  Email Addresses

The email address (grammar token <emailstr>) used must be a valid RFC822
address, which is present or not.  Thus, if defined in terms of the recipient
    applies two grammar tokens <addr-spec>
and <route-addr>.  The grammar for these two tokens is included in the transformation to
Appendix as a content in which it is already
    present, convenience; the resulting content may have definitive source for these tokens is
necessarily RFC822 [1].

    <emailstr>      ::= <addr-spec> / <route-addr>
                        ; an electronic mail address as defined by
                        ; these two line delimiters tokens from RFC822






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    present, which would cause


For example, the verification of string "galvin@tis.com" is an email address.

4.1.2.  Arbitrary Strings

The arbitrary string (grammar token <string>) must chosen from the signature to
    fail.


3.1.3.  Step 3: Security Form

Either us-
ascii character set and must have a length of at least 1.  It is
possible to encode the digital signature or encryption services is applied to actual string in such a
content.  The content to be protected way that only characters
from the us-ascii character set are generated, but there is prepared by a MIME
implementation and made available to a PEM implementation according no mechanism
for conveying to a
local convention.  The PEM implementation must produce two outputs: recipient the
data encoding that has been protected and the control information necessary to
verify or remove was used.

    <string>        ::= ; a non-null sequence of us-ascii characters

For example, the protection.  These outputs string

    Jim "the SAAG mailing list maintainer" Galvin

is an arbitrary string.

4.1.3.  Distinguished Names

The distinguished name (grammar token <dname>) must be made available
to the MIME implementation which will construct a multipart/signed or
multipart/encrypted content, constructed
according to the service requested.  The
multipart content replaces the content that was selected for protection.

3.2.  Use guidelines of multipart/signed Content Type

When this content type is used, the value of X.500 Directory.  For the required parameter
"protocol" is "pem" purposes of
conveying a distinguished name from an originator to a recipient, it
must be ASN.1 encoded and then printably encoded according to the value of base64
encoding defined by MIME.

    <dnamestr>      ::= <encbin>
                        ; a printably encoded, ASN.1 encoded
                        ; distinguished name


    ** EXAMPLE DISTINGUISHED NAME **


4.2.  Identifiers

There are 6 identifiers specified by this document: email address,
arbitrary string, distinguished name, PGP key identifier, the required parameter "hashalg" is
one of public key
itself, and the valid choices issuer name and serial number pair from [5], for example:

    Content-Type: multipart/signed; protocol="pem"; hashalg="md5";
      boundary="Signed Message"

    --Signed Message
    Content-Type: text/plain

    This is some example text.

    --Signed Message
    Content-Type: application/signature

    <pemsig>
    --Signed Message--


where a certificate.
All of these have approximately the <pemsig> token is defined same structure as follows. follows:

    TYPE, KEYID, STRING








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    <pemsig>             ::= <version> (1*<origasymflds>)

    <version>            ::= "Version:" "5" CRLF

    <origasymflds>       ::= <origid> <micinfo>

    <origid>             ::= "Originator-ID:" <id> CRLF


The token <id> TYPE field is defined in Section ??. a literal string, one for each of the possible
identifiers.

The only valid KEYID field is used to distinguish between the multiple public keys
that may be associated with the name form in the STRING field.  In 3 of
the identifiers its value for is arbitrary, chosen by the owner of the key
pair, except that it must be distinct from all the other KEYIDs used by
the owner.  Suggested values include a Content-Transfer-Encoding: header, if
included, portion (low-order 16 or 32 bits)
or all of the actual public key used.  In the other 3 identifiers the
value is "7bit".

3.3.  Use still chosen by the owner of multipart/encrypted Content Type

When this content type the public key and it must still
be unique, but its value is used, chosen from a more restricted alphabet.

The STRING field is the name form and has a different syntax according
to the value of the required parameter
"protocol" TYPE field.

The identifier used in each of the originator and recipient fields is "pem", for example:

    Content-Type: multipart/encrypted; protocol="pem";
      boundary="Encrypted Message"

    --Encrypted Message
    Content-Type: application/keys

    <pemkeys>

    --Encrypted Message
    Content-Type: application/octet-stream

    <encrypted data>
    --Encrypted Message--


where
described by the <pemkeys> following grammar.  The definition of the key
identifier token is defined as follows.

    <pemkeys> included here since it used by several of the
identifiers below.

    <id>            ::= <version> <dekinfo> 1*<recipasymflds>

    <version> <nameid> / <id-publickey> / <id-issuer>

    <nameid>        ::= "Version:" "5" CRLF

    <recipasymflds> <id-email> / <id-string> / <id-dname> / <id-pgp>

    <keyid>         ::= <recipid> <asymkeyinfo>

    <recipid> <encbin>
                        ; a printably encoded non-null sequence of octets

Each of the identifier name forms is described below.

4.2.1.  Email Address

The email address identifier has the following syntax.

    <id-email>      ::= "Recipient-ID:" <id> "EN"  "," <keyid> "," <emailstr> CRLF

    <asymkeyinfo>


4.2.2.  Arbitrary String

The arbitrary string identifier has the following syntax.

    <id-string>     ::= "Key-Info" ":" <ikalgid> "STR" "," <asymencdek> <keyid> "," <string> CRLF









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4.2.3.  Distinguished Name

The token <id> is defined in Section ??.

4.  Removing PEM Security Services from PEM Body Parts

Upon receipt of a multipart/signed or multipart/encrypted body part, the
PEM security services are removed by reversing the sequence of steps
specified in Section ??, modifying step 2 as follows.

(1)  All content types must have their line delimiters canonicalized
     prior to removing distinguished name identifier has the PEM security services.

(2)  Outer layers of PEM security services must be processed prior to
     processing inner layers following syntax.

    <id-dname>      ::= "DN"  "," <keyid> "," <dnamestr> CRLF


The actual form and syntax of PEM security services.  Processing
     includes a user choosing to display a content without removing the
     PEM security services.

5.  Definition of New Name Forms

    WARNING: This distinguished name is outside the first draft
scope of this section.  Although
    conceptually it represents specification.  RFC1422 specifies one possible form based
on a direction that will not change,
    while this document is an internet draft the details particular choice of the
    specification are subject to change at any time, without notice,
    owing to comments and implementation experience.  Implementors
    are encouraged to contact the authors a certification hierarchy for certificates.

4.2.4.  PGP Public Key

The PGP public key identifier has the current status.


Currently, [3] requires the use of certificates to specify following syntax.

    <id-pgp>        ::= "PGP2" ",0x" <pgp-keyid> "," <string> CRLF

    <pgp-keyid>     ::= ; a sequence from the following alphabet: {0-9, A-F}
                        ; which is either exactly six or eight characters long


4.2.5.  Public Key

The public key used to create a PEM message.  Within certificates, [4] requires identifier has the
use of distinguished names following syntax.  This identifer, as specified by the X.500 Series of
Recommendations.  However,
compared to the Internet community others, has a great deal more
experience with the use of electronic mail addresses as identifiers and
there is a desire to be able to use arbitrary strings to identify unique property that the
owners of public keys.  Hence, there STRING element
is optional and, when included, is not a need to support name forms
which do not conform to the expected usage string but rather one of distinguished names.

In addition, users may distribute their public keys via mechanisms
outside the scope four
of the PEM specification, for example, in a file via
FTP as opposed to in a certificate.  As other identifiers.

    <id-publickey>  ::= "PK"  "," <publickey> [ "," <nameid> ] CRLF

    <publickey>     ::= <encbin>
                        ; a result, it printably encoded, ASN.1 encoded
                        ; subjectPublicKeyInfo


In normal usage, the STRING element is desirable expected to be
able to explicitly specify the public key used rather than absent.  When
present, it represents a mechanism by which an identifier
of the (name form and
key identifier) can be associated with a public key.

The objective  Recipients of the various Originator and Recipient fields specified
in [3] is to indicate which a
public key has been used or is required.
This document simplifies identifier must take care to verify the set accuracy of fields by specifying exactly two:
Originator-ID: the
purported association.  If not, it may be possible for originators and Recipient-ID: a malicious
originator to assert an identifier that accords the originator
unauthorized privileges.  See Section 7.2 for recipients. more details.

The object subjectPublicKeyInfo is imported from the X.500 Directory
from the certificate object.  It is currently the best choice for a





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value of each of these fields is indicated by


general purpose public key encoding.

4.2.6.  Issuer Name and Serial Number

The issuer name and serial number identifier has the token <id>, which is
defined as follows.

    <id>           ::=   <id-email> / <id-string> / <id-dname>
                       / <id-publickey> / <id-issuer>

    <id-email>      ::= "EN"  "," <atstring>
                              "," <hashalgid> "," <hashpublickey>
    <id-string>     ::= "STR" "," <string>
                              "," <hashalgid> "," <hashpublickey>
    <id-dname>      ::= "DN"  "," <dname>
                              "," <hashalgid> "," <hashpublickey>
    <id-publickey>  ::= "PK"  ","
                              "," <pkalgid>   "," <publickey>
                              "," ( <string> / <atstring> ) following syntax.

    <id-issuer>     ::= "IS"  "," <dname> <dnamestr>  "," <serial>

    <atstring> CRLF

    <serial>        ::= <encbin> 1*<hexchar>
                        ; a printably encoded, ASN.1 encoded
                        ; string containing exactly one '@'
    <string>        ::= <encbin>
                        ; "a sequence of characters excluding '@'"
                        ; a printably encoded, ASN.1 value

    <hashalgid>     ::= "to be defined by RFC 1423"
    <hashpublickey> ::= 1*<hexchar>
                        ; hex dump of the <hashalgid> hash of the
                        ; public key

    <pkalgid>       ::= "to be defined by RFC 1423"
    <publickey>     ::= <encbin>
                        ; a printably encoded, ASN.1 encoded public key

    <dname>         ::= <encbin>
                        ; a printably encoded, ASN.1 encoded
                        ; distinguished name
    <serial>        ::= 1*<hexchar>
                        ; hex dump of the serial number of hex dump of the serial number of a certificate


The inclusion of the hash of the public key is intended to facilitate
the recognition of which public key among several that may be associated
with the string or distinguished name.







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The identifiers <id-email> and <id-string> are distinguished only by the
presence or absence of the character '@'.  In all other respects they
are equivalent and are encoded strings that are to be used as the
subject name in a certificate.  This distinguishing characteristic was
chosen as opposed to defining a new object identifier to represent email
addresses because of the perceived difficulty in distributing and
implementing the definition of a new object identifier.

The <id-publickey> identifier allows for the direct distribution and
indication of the public key that was or is to be used to process the
message.

The <id-issuer> identifier is included for backward compatibility with
the ID-ASymmetric fields defined in [3].  The older fields are easily
converted to this new form by prefixing the old value with "IS," and
replacing the field name with an appropriate new ID field.

6.  Definition of New Content Types

This document defines two new content types,

5.  Applying PEM Security Services to MIME Body Parts

The next section describes the contents of which
comprise processing steps necessary to prepare a replacement mechanism
MIME body part for [6]. the application of PEM security services.  The first content type is
application/key-request, which replaces
succeeding two sections describe the certification content of the multipart/signed and
multipart/encrypted body parts resulting from the application of PEM
security services to MIME body parts.

5.1.  PEM Processing Steps

The definition of the multipart/signed and multipart/encrypted body
parts in [7] specifies three steps for creating both body parts.

(1)  The body part is to be protected is created according to a local
     convention.

(2)  The body part is prepared for protection according to the protocol
     parameter.

(3)  The prepared body part is protected according to the protocol
     parameter.

This specification makes no changes to step one in the sequence.  For
step two, there is no preparation necessary for the encryption service.
For the digital signature service, the body part must be canonicalized
as described below.  This specification makes no changes to step three
in the sequence.






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Prior to the application of the digital signature service, the body part
must be in a canonical form.  Transforming the body part to be signed
into a canonical form is a necessary and essential step in the digital
signature process.  The canonical form must satisfy the property that it
is uniquely and unambiguously representable in both the originator and
recipient's local environment.  This is required in order to ensure that
both the originator and recipient have the same data with which to
calculate the digital signature; the originator needs to be able to
include the digital signature value when transferring the body part,
while the recipient needs to be able to compare a re-computed value with
the received value.  Further, the canonical form should satisfy the
property that it is representable on as many different host computers as
possible.  By satisfying this property, signed data may be forwarded by
recipients to additional recipients, who will also be able to verify the
original signature.  This service is called forwardable authentication.

The canonicalization transformation is a two step process.  First, the
body part must be converted to canonical representation suitable for
transport between originators and recipients.  Second, the body part
must have its line delimiters canonicalized prior to computing the
digital signature and prior to each verification of the digital
signature.

The canonical representation of all body parts is specified to be 7bit,
as defined by [2].  Since the headers of body parts are already required
to be representable in 7bit, this step requires that if the data to be
signed is not already 7bit it must be encoded with an appropriate MIME
content transfer encoding.  Note, since the MIME standard explicitly
disallows nested content transfer encodings, i.e., the content types
multipart and message may not themselves be encoded, body parts enclosed
within, for example, a multipart content type, must be encoded in a 7bit
representation.  Any valid MIME encoding may be selected.

The 7bit representation of the data must be transferred to the
recipient.  As may be required by MIME, an appropriate Content-
Transfer-Encoding: header is included with the data.  Upon receipt, a
MIME implementation would verify the signature of the data prior to
decoding the data and displaying it to the recipient.

Representing all complex content types as 7bit transforms them into
text-based content types.  However, text-based content types present a
unique problem.  In particular, the line delimiter used on a text-based
content type is specific to a local environment; different environments
use the single character carriage-return (<CR>), the single character
line-feed (<LF>), or the two character sequence "carriage-return line-





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feed (<CR><LF>)."

The application of the digital signature service requires that the same
line delimiter be used by both the originator and the recipient.  This
document specifies that the two character sequence "<CR><LF>" must be
used as the line delimiter.  Thus, the canonicalization transformation
includes the transformation of the local line delimiter to the two
character sequence "<CR><LF>".

The transformation to the canonical line delimiter is only required for
the purposes of computing the digital signature.  Thus, originators must
apply the canonical line delimiter transformation before computing the
digital signature but must transfer the data without the canonical line
delimiter transformation.  Similarly, recipients must apply the
canonical line delimiter transformation before computing the digital
signature.

    NOTE: An originator can not transfer the content with the
    canonical line delimiter transformation intact because the
    transformation process is not idempotent.  In particular, SMTP
    servers may themselves convert the canonical line delimiter to a
    local line delimiter, prior to the message being delivered to
    the user.  Thus, a recipient has no way of knowing if the
    transformation is present or not.  Thus, if the recipient
    applies the transformation to a content in which it is already
    present, the resulting content may have two line delimiters
    present, which would cause the verification of the signature to
    fail.


    IMPLEMENTORS NOTE: Implementors should be aware that the
    transformation to a canonical representation is a function that
    is available even in a minimally compliant MIME user agent.
    Further, the canonical line delimiter transformation required
    here is distinct from the same transformation included in that
    function.  Specifically, the line delimiter transformation in
    the former case is performed prior to the application of the
    canonical representation while it is performed after the
    application of the canonical representation in the latter case.


5.2.  Use of multipart/signed Content Type

When this content type is used, the value of the required parameter
"protocol" is "pem" and CRL-
retrieval request messages. the value of the required parameter "hashalg" is





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one of the valid choices from [5], for example:

    Content-Type: multipart/signed; protocol="pem"; hashalg="md5";
      boundary="Signed Message"

    --Signed Message
    Content-Type: text/plain

    This is some example text.

    --Signed Message
    Content-Type: application/signature

    <pemsig>
    --Signed Message--


where the <pemsig> token is defined as follows.

    <pemsig>             ::= <version> ( 1*<origasymflds> )

    <version>            ::= "Version:" "5" CRLF

    <origasymflds>       ::= <origid> <micinfo>

    <origid>             ::= "Originator-ID:" <id> CRLF


The second token <id> is defined in Section 4.2.

The only valid value for a Content-Transfer-Encoding: header, if
included, is "7bit".

5.3.  Use of multipart/encrypted Content Type

When this content type is
application/key-data, which replaces the certification reply message, used, the crl-storage request message, and value of the crl-retrieval reply message.
There were no requirements required parameter
"protocol" is "pem", for a crl-storage reply message example:













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    Content-Type: multipart/encrypted; protocol="pem";
      boundary="Encrypted Message"

    --Encrypted Message
    Content-Type: application/keys

    <pemkeys>

    --Encrypted Message
    Content-Type: application/octet-stream

    <encrypted data>
    --Encrypted Message--


where the <pemkeys> token is defined as follows.

    <pemkeys>            ::= <version> <dekinfo> 1*<recipasymflds>

    <version>            ::= "Version:" "5" CRLF

    <recipasymflds>      ::= <recipid> <asymkeyinfo>

    <recipid>            ::= "Recipient-ID:" <id> CRLF

    <asymkeyinfo>        ::= "Key-Info" ":" <ikalgid> "," <asymencdek> CRLF


The token <id> is defined in this document. Section 4.2.

6.  Removing PEM Security Services from PEM Body Parts

This document section describes the processing steps necessary to verify or
decrypt the PEM security services that have been applied to MIME body
parts.  Outer layers of PEM security services must be processed prior to
processing inner layers of PEM security services.  Processing includes a specification for
user choosing to display a certificate request message, which was previously undefined.

    NOTE: RFC1424 has some descriptive text, especially content without removing the PEM security
services.

The definition of the multipart/signed and multipart/encrypted body
parts in [7] specifies three steps for
    certification messages, that should probably be included.


6.1.  application/key-request Content Type Definition receiving both body parts.

(1)  MIME type name: application

(2)  MIME subtype name: key-request

(3)  Required parameters: none

(4)  Optional parameters: none

(5)  Encoding considerations: quoted-printable is always sufficient  The protected body part and the control information body part are
     prepared for processing.






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(6)  Security Considerations: none


(2)  The content of this prepared body part corresponds parts are made available to the following production.


    <request>            ::= <version>
                             ( <subject> / <issuer> / <certification> )
    <version>            ::= "Version:" "5" CRLF
    <subject>            ::= "Subject:" <id> CRLF
    <issuer>             ::= "Issuer:" <id> CRLF
    <certification>      ::= "Certification:" <encbin> CRLF



This content type is used to provide for some protection
     removal process.

(3)  The results of the requests described
in [6].  The information in protection removal process are made available to
     the body part is entirely independent of any
other body part.  As such, user and processing continues with the application/key-request content type is
an independent unprotected body part.

The certification request, certificate-retrieval request and crl-
retrieval request are provided for directly.  If part,
     as returned by the content contains a
Certification: field it requests certification of protection removal process.

For step one, the self-signed
certificate preparation for digitally signed and encrypted body
parts is different, as described below.  No changes are required to
steps two and three in the field value.  If sequence.

For multipart/signed body parts, the control information is prepared by
removing any content contains an Issuer:
field it requests the certificate revocation list chain beginning with
the issuer identified in the field value.  If transfer encodings that may be present.  The
digitally signed body part is prepared by leaving the content contains a
Subject: field it requests transfer
encodings intact and canonicalizing the certificate chain beginning with line delimiters according to
Step 2 of Section 5.1.

Multipart/encrypted body parts are prepared by removing the
subject identified in content
transfer encodings, if present, from both the field value.

The Subject: control information and Issuer: fields each contain a value of type Name,
encoded according to
the Basic Encoding Rules, then in ASCII, as for encrypted body part.

7.  Definition of New Content Types

This document defines two new content types, the
Originator-ID-Asymmetric: field contents of [3]. which
comprise a replacement mechanism for [6].  The crl-storage request first content type is provided for by
application/key-request, which replaces the application/key-data certification and CRL-
retrieval request messages.  The second content type described in is
application/key-data, which replaces the next section.

In each case, certification reply message,
the response is transmitted in an application/key-data
content type.  When returning certificate crl-storage request message, and certificate revocation
list chains, if there exists more than one chain, several
application/key-data contents are to be returned in the crl-retrieval reply message.
There were no requirements for a crl-storage reply message and none are
specified in this document.  This document includes a specification for
a public key and certificate request message,
one which were previously
undefined.

    NOTE: RFC1424 has some descriptive text, especially for each chain.

6.2.  application/key-data
    certification messages, that should probably be included.


7.1.  application/key-request Content Type Definition

(1)  MIME type name: application

(2)  MIME subtype name: key-request







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(2)  MIME subtype name: key-data


(3)  Required parameters: none

(4)  Optional parameters: none

(5)  Encoding considerations: quoted-printable is always sufficient. sufficient

(6)  Security Considerations: none

The content of this body part corresponds to the following production.


    <certdata>           ::= <certchain> / <crlchain>
    <certchain>          ::= <version> <cert> *( [ <crl> ] <cert> )
    <crlchain>


    <request>            ::= <version> 1*( <crl> [ <cert> ]
                             ( <subject> / <issuer> / <certification> )
    <cert>
    <version>            ::= "Certificate:" <encbin> "Version:" "5" CRLF
    <crl>
    <subject>            ::= "CRL:" <encbin> "Subject:" <id> CRLF
    <version>
    <issuer>             ::= "Version:" "5" "Issuer:" <id> CRLF
    <certification>      ::= "Certification:" <encbin> CRLF



This content type is used to transfer certificate or Certificate
Revocation List (CRL) information. provide for some of the requests described
in [6].  The information in the body part is entirely independent of any particular privacy enhanced message.  (Note
that the converse is not true: the validity of a privacy enhanced
message cannot be determined without the proper certificates or current
CRL information.)
other body part.  As such, the application/key-data application/key-request content type is
an independent body part.

The <certchain> production contains one certificate chain.  A
certificate chain starts with a certificate certification request, certificate-retrieval request and continues with crl-
retrieval request are provided for directly.  If the
certificates content contains a
Certification: field it requests certification of subsequent issuers.  Each issuer certificate included
must have issued the preceding certificate.  For each issuer, a CRL may
be supplied.  A CRL self-signed
certificate in the chain belongs to field value.  If the immediately following
issuer.  Therefore, it potentially content contains an Issuer:
field it requests the immediately preceding
certificate.

The <crlchain> production contains one certificate revocation list
chain.  The CRLs chain beginning with
the issuer identified in the field value.  If the content contains a
Subject: field it requests either the public key of the subject or the
certificate chain begin beginning with the requested CRL and continue
with subject identified in the CRLs of subsequent issuers. field
value, or both.

The issuer Subject: and Issuer: fields each contain a value of type <id>, which
is defined in Section 4.2.

The crl-storage request is provided for by the application/key-data
content type described in the next section.

In each CRL case, the response is presumed
to have issued a transmitted in an application/key-data
content type.  When returning public keys, certificate for the issuer of the preceding CRL.  For
each CRL, the issuer's chains, and
certificate may revocation list chains, if there exists more than one,
several application/key-data contents are to be supplied.  A certificate returned in the chain must belong to the issuer of the immediately preceding CRL. reply





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message, one for each.

7.2.  application/key-data Content Type Definition

The relationship between a certificate and an immediately preceding CRL principal objective of this content type is the same in both cases.  In a <certchain> the crl's are optional.  In
a <crlchain> the certificates are optional.

7.  Message Processing

When a user composes to convey cryptographic
keying material from an originator to a message, it recipient.  However, no explicit
provision is made for determining the responsibility authenticity or accuracy of the user
agent to construct a valid MIME message.
data being conveyed.  In particular, Content-Type: when a public key and Content-Transfer-Encoding: headers should be used wherever they are
appropriate.  This allows the receiving user agent
identifier for its owner is conveyed, there is nothing to unambiguously
interpret the message body and process it accordingly.

Each block of content headers associated with either prevent an RFC822 <message>
or with a MIME <body-part> represents a logical place where security
enhancement can be requested.  A security enhancement request associated
with a particular <message>
originator or <body-part> content is taken to apply to any interloper along the entire content; it is not possible to security-enhance only a
portion of a body part.

The mechanism used to communicate security enhancement requests path from an originator to the
pre-submission processor described below is strictly a local
implementation issue.  However, the interface between the message
composer and pre-submission processing MUST be trustworthy, since the
message composer relies on pre-submission processing to
recipient from substituting alternate values for either perform the requested security enhancement operation public key
or return an error.
Regardless of the mechanism chosen, great care should identifier, thus setting up the recipient to potentially send
sensitive information that may be taken intercepted and disclosed
inappropriately.

It is incumbent upon a recipient to verify the authenticity and accuracy
of the data received prior to
safeguard against both its use.  The problem is addressed by the release
use of information certificates, since a certification hierarchy is a well-defined
mechanism that has not received conveniently supports the requested type automatic verification of security enhancement as well as tampering with the
enhancement request itself.

7.1.  Pre-Submission Algorithm

The user agent first composes
data.  Alternatively, the application/key-data body part could be
digitally signed by the originator.  In this way, if a MIME-compliant message recipient
believes that correct originator's public key is available locally and
if the recipient believes the originator would convey accurate data,
then applies
this algorithm:

(1)  If the content at this (initially top) level has NOT been selected key data received from the originator can be believed.

    NOTE: Insofar as a certificate represents a mechanism by which
    an issuer vouches for security enhancement, the user agent sees if binding between the content is
     either multipart or message.  If so, name and public
    key it then recursively applies
     this algorithm to embodies, the encapsulated signing of an application/key-data body parts; if not, it
     terminates processing for this content.
    part is a similar mechanism.


(1)  MIME type name: application

(2)  If the  MIME subtype name: key-data

(3)  Required parameters: none

(4)  Optional parameters: none

(5)  Encoding considerations: quoted-printable is always sufficient.

(6)  Security Considerations: none

The content at of this level has been selected for security
     enhancement, then the content, including its headers, constitutes
     the object that is to be made available body part corresponds to the security enhancement
     process.  The headers at a minimum will include a Content-Type following production.






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     header, either explicit


    <certdata>           ::= <version>
                             ( <keydata> / <certchain> / <crlchain> )
    <version>            ::= "Version:" "5" CRLF
    <keydata>            ::= "Key:" <id> "," <nameid> CRLF
    <certchain>          ::= <cert> *( [ <crl> ] <cert> )
    <crlchain>           ::= 1*( <crl> [ <cert> ] )
    <cert>               ::= "Certificate:" <encbin> CRLF
    <crl>                ::= "CRL:" <encbin> CRLF



This content type is used to transfer public keys, certificate chains,
or implicit. Certificate Revocation List (CRL) chains.  The object will eventually be
     replaced with information in the multipart content that
body part is produced by entirely independent of any other body part.  (Note that
the
     security enhancement operation.

(3)  The selected security enhancement converse is performed.  This enhancement
     produces two data streams: not true: the enhanced object and a control stream
     comprised validity of a set of headers as defined in the <pemsig> or
     <pemkeys> productions.

(4)  A new protected body part is then constructed, of cannot
be determined without the proper public keys, certificates, or current
CRL information.)  As such, the application/key-data content type
     multipart/signed or multipart/encrypted.  The new is an
independent body part part.

The <keydata> production contains two body parts, whose content depends on the enhancement
     requested, which are constructed according exactly one public key.  It is used to the specifications in
     this document.

(5)  This multipart content replaces the original object.

7.2.  Post-Delivery Algorithm

When a user receives a message containing
bind a multipart content, the user
agent may transform the content back into public key with its original corresponding name form prior to
privacy-enhancement.  This operation, the post-delivery algorithm, and key identifier.
It is
performed recommended that when responders are returning this information
that the enclosing body part be digitally signed by reversing the steps performed during responder in
order to protect the pre-submission
algorithm.

When information.

The <certchain> production contains one certificate chain.  A
certificate chain starts with a certificate and continues with the original content is reconstituted, it may use octet values
outside
certificates of subsequent issuers.  Each issuer certificate included
must have issued the US-ASCII repertoire and preceding certificate.  For each issuer, a CRL may contain body parts without
line breaks.  If
be supplied.  A CRL in the user agent replaces chain belongs to the immediately following
issuer.  Therefore, it potentially contains the immediately preceding
certificate.

The <crlchain> production contains one certificate revocation list
chain.  The CRLs in the chain begin with the multipart content requested CRL and continue
with the
original content, then it must select appropriate Content-Transfer-
Encodings for CRLs of subsequent issuers.  The issuer of each body part and add corresponding Content-Transfer-
Encoding: headers.

Upon successful completion CRL is presumed
to have issued a certificate for the issuer of the post-delivery algorithm for preceding CRL.  For
each
content, CRL, the type of enhancement that was in effect for that content
must issuer's certificate may be communicated to supplied.  A certificate in
the user.  The mechanism used to do this is a
local implementation issue.  As with requests for enhancement chain must belong to the
pre-submission algorithm, issuer of the path immediately preceding CRL.

The relationship between post-delivery processing a certificate and
actual display of an immediately preceding CRL
is the message must be same in both <certchain> and <crlchain>.  In a trusted one, lest <certchain> the
CRLs are optional.  In a message be
presented that purports to have undergone some form of enhancement it
did not in fact receive. <crlchain> the certificates are optional.







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8.  Examples

    NOTE: To be included upon completion of implementation.






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9.  Observations

The use of the pre-submission and post-delivery algorithms to combine
PEM and MIME capabilities exhibits several properties:

(1)  It allows privacy-enhancement of an arbitrary content, not just the
     body of an RFC 822 RFC822 message.

(2)  For a multipart or message content, it allows the user to specify
     different privacy enhancements to be applied to different
     components of the structure of the content.

(3)  It provides for messages containing several privacy enhanced
     contents, thereby removing the requirement for PEM software to be
     able to generate or interpret a single content which intermixes
     both unenhanced and enhanced components.

The use of a MIME-capable user agent makes complex nesting of enhanced
message body parts much easier.  For example, the user can separately
sign and encrypt a message.  This motivates a complete separation of the
confidentiality security service from the digital signature security
service.  That is, different keys key pairs could be used for the different
services and could be protected separately.  In the asymmetric case,
this  This means an employee's
company could be given access to the (private) decryption key but not
the (private) signature key, thereby granting the company the ability to
decrypt messages addressed to the employee in emergencies without also
granting the company the ability to sign messages as the employee.

The use of two private keys requires the ability to maintain multiple
certificates for each user.

10.  Summary of Changes to PEM Specification

This document updates the message encryption and signature procedures
defined by [3] and obsoletes the key certification and related services
defined by [6].  The changes are enumerated below.

(1)  The PEM specification currently requires that encryption services
     be applied only to message bodies that have been signed.  By
     providing for each of the services separately, they may be applied





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     recursively in any order according to the needs of the requesting
     application.







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(2)  PEM implementations are currently restricted to processing only
     text-based electronic mail messages.  In fact, the message text is
     required to be represented by the ASCII character set with
     "<CR><LF>" line delimiters.  This restriction no longer applies.

(3)  With the removal of the text restriction it is not possible to
     specify a universal canonical form.  However, canonicalization is
     required for the digital signature service, so the content of each
     body part must be transformed into a canonical form according to
     its type.

(4)  MIME includes transfer encoding operations to ensure the unmodified
     transfer of body parts, which obviates these services in PEM.

(5)

(4)  PEM specifies a Proc-Type: header field to identify the type of
     processing that was performed on the message.  This functionality
     is subsumed by the MIME Content-Type: headers.  The Proc-Type:
     header also included a decimal number that was used to distinguish
     among incompatible encapsulated header field interpretations which
     may arise as changes are made to the PEM standard.  This
     functionality is replaced by the Version: header specified in this
     document.

(6)

(5)  PEM specifies a Content-Domain: header, the purpose of which is to
     describe the type of the content which is represented within a PEM
     message's encapsulated text.  This functionality is subsumed by the
     MIME Content-Type: headers.

(7)

(6)  The PEM specifications include a document that defines new types of
     PEM messages, specified by unique values used in the Proc-Type:
     header, to be used to request certificate and certificate
     revocation list information.  This functionality is subsumed by two
     new content types specified in this document.

(8)

(7)  The header fields having to do with certificates (Originator-
     Certificate: and Issuer-Certificate:) and CRLs (CRL:) are relegated
     for use only in the application/key-data and application/key-
     request content types and are no longer allowed in the header
     portion of a PEM signed or encrypted message.

(9)

(8)  The grammar specified here explicitly separates the header fields
     that may appear for the encryption and signature security services.
     It is the intent of this document to specify a precise expression
     of the allowed header fields; there is no intent to reduce the
     functionality of combinations of encryption and signature security
     from those of [3].







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     from those of [3].

(10)                PEM and MIME                     July 1994


(9)  With the separation of the encryption and signature security
     services, there is no need for a MIC-Info: field in the headers
     associated with an encrypted message under asymmetric key
     management.

(11) message.

(10) In [3], when asymmetric key management is used, an Originator-ID
     field is required in order to identify the private key used to sign
     the MIC argument in the MIC-Info: field.  Because no MIC-Info:
     field is associated with the encryption security service under
     asymmetric key managment, there is no requirement in that case to
     include an Originator-ID field.

These changes represent a departure in mechanism, not in effect, from
those specified in [3] and [6].  The following technical changes to [3]
and [4] are also specified by this document.

(1)  The grammar specified here explicitly excludes symmetric key
     management.  Currently, there are no generally available
     implementations of symmetric key management nor are there any known
     plans for implementing it.  As a result, the IETF standards process
     will require this feature to be dropped when the documents are
     promoted to draft standard status from proposed standard status.

(2)  This document requires all data that is to be digitally signed to
     be represented in 7bit form.

(3)  This document relaxes the syntax of distinguished names.  In
     particular, distinguished names are not constrained to conform to broadens the X.500 Series of Recommendations.  Instead allowable name forms that users may use
     to identify their public keys.  Users may use arbitrary strings and
     email addresses as their name.  Further, users may distribute their
     public key directly in lieu of using certificates.  In support of
     this change the Originator-ID-
     ASymmetric: Originator-ID-ASymmetric: and Recipient-ID-ASymmetric: Recipient-ID-
     ASymmetric: fields are deprecated in favor of Originator-ID: and
     Recipient-ID: fields, respectively.

11.  Collected Grammar

The following is a summary of the grammar presented in this document.

(1)  Signature headers












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         <pemsig>             ::= <version> (1*<origasymflds>) ( 1*<origasymflds> )

         <version>            ::= "Version:" "5" CRLF

         <origasymflds>       ::= <origid> <micinfo>

         <origid>             ::= "Originator-ID:" <id> CRLF


(2)  Encryption Headers


         <pemkeys>            ::= <version> <dekinfo> 1*<recipasymflds>

         <version>            ::= "Version:" "5" CRLF

         <recipasymflds>      ::= <recipid> <asymkeyinfo>

         <recipid>            ::= "Recipient-ID:" <id> CRLF

         <asymkeyinfo>        ::= "Key-Info" ":" <ikalgid> "," <asymencdek> CRLF


(3)  Identifier Name Forms


























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         <id>            ::= <nameid> / <id-publickey> / <id-issuer>

         <nameid>        ::= <id-email> / <id-string> / <id-dname> / <id-pgp>

         <id-email>      ::= "EN"  "," <keyid> "," <emailstr> CRLF

         <id-string>     ::= "STR" "," <keyid> "," <string> CRLF

         <id-dname>      ::= "DN"  "," <keyid> "," <dnamestr> CRLF

         <id-pgp>        ::= "PGP2" ",0x" <pgp-keyid> "," <string> CRLF

         <id-publickey>  ::= "PK"  "," <publickey> [ "," <nameid> ] CRLF

         <id-issuer>     ::= "IS"  "," <dnamestr>  "," <serial> CRLF

         <keyid>         ::= <encbin>
                             ; a printably encoded non-null sequence of octets

         <emailstr>      ::= <addr-spec> / <route-addr>
                             ; an electronic mail address as defined by
                             ; these two tokens from RFC822

         <string>        ::= ; a non-null sequence of us-ascii characters

         <dnamestr>      ::= <encbin>
                             ; a printably encoded, ASN.1 encoded
                             ; distinguished name

         <pgp-keyid>     ::= ; a sequence from the following alphabet: {0-9, A-F}
                             ; which is either exactly six or eight characters long

         <publickey>     ::= <encbin>
                             ; a printably encoded, ASN.1 encoded
                             ; subjectPublicKeyInfo

         <serial>        ::= 1*<hexchar>
                             ; hex dump of the serial number of a certificate


(4)  Request Headers (certificate, certification, etc.)









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         <request>            ::= <version>
                                  ( <subject> / <issuer> / <certification> )
         <version>            ::= "Version:" "5" CRLF
         <subject>            ::= "Subject:" <id> CRLF
         <issuer>             ::= "Issuer:" <id> CRLF
         <certification>      ::= "Certification:" <encbin> CRLF


(4)  Certificate


(5)  Data Headers (certificate, certification revocation list)

         <certdata>           ::= <certchain> / <crlchain>
         <certchain>          ::= <version> <cert> *( [ <crl> ] <cert> )
         <crlchain>           ::= <version> 1*( <crl> [ <cert> ] )
         <cert>               ::= "Certificate:" <encbin> CRLF
         <crl>                ::= "CRL:" <encbin> CRLF
         <version>            ::= "Version:" "5" CRLF








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12.  Security Considerations

    NOTE: to be done


13.  Acknowledgements

David H. Crocker suggested the use of a multipart structure for MIME-PEM
interaction.

14.  References

[1]  David H. Crocker.  Standard for the Format of ARPA Internet Text
     Messages.  RFC 822, University of Delaware, August 1982.

[2]  Nathaniel Borenstein and Ned Freed. MIME (Multipurpose Internet
     Mail Extension) Part One: Mechanisms for Specifying and Describing
     the Format of Internet Message Bodies.  RFC 1521, Bellcore and
     Innosoft, September 1993.  Obsoletes RFC 1341.

[3]  John Linn.  Privacy Enhancement for Internet Electronic Mail: Part
     I: Message Encryption and Authentication Procedures.  RFC 1421,
     February 1993.  Obsoletes RFC 1113.

[4]  Steve Kent.  Privacy Enhancement for Internet Electronic Mail: Part
     II: Certificate-Based Key Management.  RFC 1422, BBN
     Communications, February 1993.





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[5]  David M. Balenson.  Privacy Enhancement for Internet Electronic
     Mail: Part III: Algorithms, Modes, and Identifiers.  RFC 1423,
     Trusted Information Systems, February 1993.

[6]  Burton S. Kaliski.  Privacy Enhancement for Internet Electronic
     Mail: Part IV: Key Certification and Related Services.  RFC 1424,
     RSA Laboratories, February 1993.

[7]  David Crocker.  Multipart/Family Content Types.  Work in progress.

[8]  James Galvin. Galvin, Sandy Murphy, Steve Crocker, and Ned Freed.  Security
     Multiparts for MIME: Multipart/Signed and Multipart/Encrypted.  Work in progress.

[9]  Jon Postel.  Simple Mail Transfer Protocol.
     RFC 821, ISI, August
     1982.







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15.  Authors' Addresses

    Steve Crocker
    email:  crocker@tis.com

    James M. Galvin
    email:  galvin@tis.com

    Sandra Murphy
    email:  murphy@tis.com

    Trusted Information Systems
    3060 Washington Road
    Glenwood, MD  21738
    Tel:    +1 301 854 6889
    FAX:    +1 301 854 5363
    email:  crocker@tis.com



    Ned Freed
    Innosoft International, Inc.
    250 West First Street, Suite 240
    Claremont, CA 91711
    Tel:    +1 909 624 7907
    FAX:    +1 909 621 5319
    email:  ned@innosoft.com



    James M. Galvin
    Trusted Information Systems
    3060 Washington Road
    Glenwood, MD  21738
    Tel:    +1 301 854 6889
    FAX:    +1 301 854 5363
    email:  galvin@tis.com



    Sandra Murphy
    Trusted Information Systems
    3060 Washington Road
    Glenwood, MD  21738
    Tel:    +1 301 854 6889
    FAX:    +1 301 854 5363
    email:  murphy@tis.com












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16.  Appendix: Imported Grammar

The following productions are taken from [3].  The grammar presented in
[3] remains the authoritative source for these productions; they are
repeated here for the convenience of the reader.

    <dekinfo>    ::= "DEK-Info" ":" <dekalgid> [ "," <dekparameters> ] CRLF

    <micinfo>    ::= "MIC-Info" ":" <micalgid> "," <ikalgid> ","
                     <asymsignmic> CRLF

    <encbin>     ::= 1*<encbingrp>
    <encbingrp>  ::= 4*4<encbinchar>
    <encbinchar> ::= ALPHA / DIGIT / "+" / "/" / "="


The following productions are taken from [5].  The grammar presented in
[5] remains the authoritative source for these productions; they are
repeated here for the convenience of the reader.

    <dekalgid>         ::= "DES-CBC"
    <ikalgid>          ::= "DES-EDE" / "DES-ECB" / "RSA"
    <micalgid>         ::= "RSA-MD2" / "RSA-MD5"

    <dekparameters>    ::= <DESCBCparameters>
    <DESCBCparameters> ::= <IV>
    <IV>               ::= <hexchar16>

    <asymsignmic>      ::= <RSAsignmic>
    <RSAsignmic>       ::= <encbin>

    <asymencdek>       ::= <RSAencdek>
    <RSAencdek>        ::= <encbin>

    <hexchar16>        ::= 16*16<hexchar>
    <hexchar>          ::= DIGIT / "A" / "B" / "C" / "D" / "E" / "F"
                                                        ; no lower case


The following productions are taken from [1].  The grammar presented in
[1] remains the authorative source for these productions; they are
repeated here for the convenience of the reader.








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    <addr-spec>     ::= <local-part> "@" <domain>        ; global address

    <local-part>    ::= <word> *( "." <word> )           ; uninterpreted
                                                         ; case-preserved

    <domain>        ::= <sub-domain> *( "." <sub-domain> )

    <sub-domain>    ::= <domain-ref> / <domain-literal>

    <domain-ref>    ::= <atom>                           ; symbolic reference

    <route-addr>    ::= "<" [ <route> ] <addr-spec> ">"

    <route>         ::=  1# ( "@" <domain> ) ":"         ; path-relative



    <word>          ::= <atom> / <quoted-string>

    <quoted-string> ::= """ *( <qtext> / <quoted-pair> ) """

    <qtext>         ::= (any <CHAR> excepting """, "
                         and including <linear-white-space>)

    <quoted-pair>   ::= "

    <linear-white-space> ::= 1*( [ CRLF ] <LWSP-char> )  ; semantics = SPACE
                                                         ; CRLF => folding
    <LWSP-char>     ::= SPACE / HTAB                     ; semantics = SPACE



    <atom>          ::= 1*(any <CHAR> except <specials>, SPACE and <CTL>s)

    <CHAR>          ::= <any ASCII character>

    <CTL>           ::= <any ASCII control character and DEL>

    <specials>      ::=  "(" / ")" / "<" / ">" / "@"     ; Must be in quoted-
                         /  "," / ";" / ":" / "
                         /  "." / "[" / "]"              ;  within a word.









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Table of Contents


1 Status of this Memo .............................................    1
2 Abstract ........................................................    1
3 Introduction ....................................................    2
4 Name Forms and Identifiers ......................................    3
4.1 Name Forms ....................................................    4
4.1.1 Email Addresses .............................................    4
4.1.2 Arbitrary Strings ...........................................    5
4.1.3 Distinguished Names .........................................    5
4.2 Identifiers ...................................................    5
4.2.1 Email Address ...............................................    6
4.2.2 Arbitrary String ............................................    6
4.2.3 Distinguished Name ..........................................    7
4.2.4 PGP Public Key ..............................................    7
4.2.5 Public Key ..................................................    7
4.2.6 Issuer Name and Serial Number ...............................    8
5 Applying PEM Security Services to MIME Body Parts ...............    2
3.1    8
5.1 PEM Processing Steps ..........................................    3
3.1.1 Step 1: Local Form ..........................................    3
3.1.2 Step 2: Canonical Form ......................................    3
3.1.3 Step 3: Security Form .......................................    5
3.2    8
5.2 Use of multipart/signed Content Type ..........................    5
3.3   10
5.3 Use of multipart/encrypted Content Type .......................   11
6
4 Removing PEM Security Services from PEM Body Parts ..............   12
7
5 Definition of New Name Forms ....................................    7
6 Definition of New Content Types .................................    9
6.1   13
7.1 application/key-request Content Type Definition ...............    9
6.2   13
7.2 application/key-data Content Type Definition ..................   10
7 Message Processing ..............................................   12
7.1 Pre-Submission Algorithm ......................................   12
7.2 Post-Delivery Algorithm .......................................   13   15
8 Examples ........................................................   13   17
9 Observations ....................................................   14   17
10 Summary of Changes to PEM Specification ........................   14   17
11 Collected Grammar ..............................................   16   19
12 Security Considerations ........................................   18   22
13 Acknowledgements ...............................................   18   22
14 References .....................................................   18   22
15 Authors' Addresses .............................................   19   23
16 Appendix: Imported Grammar .....................................   20   24















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