Network Working Group J. Schaad
Internet-Draft Soaring Hawk Consulting
Intended status: Informational December 12, 2010
Expires: June 15, 2011
S/MIME Capabilities for Public Key Definitions
draft-ietf-pkix-pubkey-caps-01
Abstract
This document defines a set of S/MIME Capability types for ASN.1
encoding for the current set of public keys define in the PKIX
working group.
Status of this Memo
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This Internet-Draft will expire on June 15, 2011.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. ASN.1 Notation . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Requirements Terminology . . . . . . . . . . . . . . . . . 4
2. RSA Public Keys . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Generic RSA Public Keys . . . . . . . . . . . . . . . . . 5
2.2. RSASSA-PSS Signature Public Keys . . . . . . . . . . . . . 6
2.3. RSA ES-OAEP Key Transport Public Keys . . . . . . . . . . 6
3. Diffie-Hellman Keys . . . . . . . . . . . . . . . . . . . . . 8
3.1. DSA Signature Public Key . . . . . . . . . . . . . . . . . 8
3.2. DH Key Agreement Keys . . . . . . . . . . . . . . . . . . 9
4. Elliptical Curve Keys . . . . . . . . . . . . . . . . . . . . 10
4.1. Generic Elliptical Curve Keys . . . . . . . . . . . . . . 10
4.2. Elliptical Curve DH Keys . . . . . . . . . . . . . . . . . 10
4.3. Elliptical Curve MQV Keys . . . . . . . . . . . . . . . . 11
5. RSASSA-PSS Signature Algorithm Capability . . . . . . . . . . 12
6. Security Considerations . . . . . . . . . . . . . . . . . . . 14
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
8.1. Normative References . . . . . . . . . . . . . . . . . . . 16
8.2. Informative References . . . . . . . . . . . . . . . . . . 16
Appendix A. 2008 ASN.1 Module . . . . . . . . . . . . . . . . . . 17
Appendix B. Future Work . . . . . . . . . . . . . . . . . . . . . 20
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 21
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1. Introduction
In the process of dealing with the OCSP agility issues in
[I-D.ietf-pkix-ocspagility] it was noted that we really wanted to
describe information to be used in selecting a public key, but we did
not currently have any way of doing so at the current time. This
document fills that hole by defining a set of S/MIME Capability types
for a small set of public key representations.
S/MIME Capabilities where originally defined in [SMIMEv3-MSG] as a
way for the sender of an S/MIME message to tell the recipient of the
message the set of encryption algorithms that were supported by the
senders system. In the beginning, the focus was primarily on
communicating the set of encryption algorithms that were supported.
Over time it was expanded to allow for an S/MIME client to say that
it supported the compression data type and binary contents. As
originally defined it was targeted towards supporting items with a
small number of possible parameters. For the RC2 encryption
algorithm only two values from the entire range of values were ever
use. The object of restricting the set of values was so that a
client could do a simple binary comparison without having to decode
the S/MIME capability. This was especially easy since most just
consisted of the object identifier for the algorithm.
Given that we are assigning different data types to the algorithm
descriptors here, and many of the algorithm descriptors are the same
as are used in signature, key transport or key agreement algorithms,
the public key versions of these structures MUST NOT be placed in the
same locations as the other versions. It is expected that the places
where one needs S/MIME capabilities for public keys is going to be
vastly different than for the other values.
1.1. ASN.1 Notation
The main body of the text is written using snippets of ASN.1 that are
extracted from the ASN.1 2008 module in Appendix A. This is because
I am a strong advocate of moving to the current versions of ASN.1 as
they can contain meta-data which is not representable in the 1988
version of ASN.1. In keeping with the current policy of the PKIX
working group, the 1988 module is still to be considered the
normative module in the event of a conflict between the contents of
the two modules.
When reading this document, it is assumed that you will have a degree
of familiarity with the basic object module that is presented in
section 3 of RFC 5912 ([RFC5912]). We use the SMIME-CAPS object in
this document, it associates two fields together in a single object.
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SMIME-CAPS ::= CLASS {
&id OBJECT IDENTIFIER UNIQUE,
&Type OPTIONAL
}
WITH SYNTAX { [TYPE &Type] IDENTIFIED BY &id }
These fields are:
&id contains an object identifier. When placed in an object set,
this element is tagged so that no two elements can be placed in
the set that have the same value in the &id field. Note that this
is not a restriction which says that only a single object can
exist with a single object identifier.
&Type optionally contains an ASN.1 type identifier. If the field
&Type is not defined then the optional parameters field of the
AlgorithmIdentifier type would be omitted.
The class also has a specialized syntax for how to define an object
in this class. The all upper case words TYPE IDENTIFIER and BY are
syntactic sugar to make it easier to read. The square brackets
defined optional pieces of the syntax.
One of the things that can be done is to reference the fields of an
object while defining other objects. This means that if an object
called foo has a field named &value, the value can be directly
referenced as foo.&value. This means that we automatically get any
updates to values or types and we do not need to do any replication
of the data.
1.2. Requirements Terminology
When capitalized the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" in this document are to be interpreted as described in
[RFC2119].
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2. RSA Public Keys
There are currently three different public key object identifiers for
RSA public keys. These are RSA, RSA ES-OCSP and RSA SSA-PSS.
2.1. Generic RSA Public Keys
Almost all RSA keys that are contained in certificates today use the
generic RSA public key format and identifier. This allows for the
public key to be used both for key transport and for signature
validation (assuming it is compatible with the bits in the key usage
extension). The only reason for using one of more specific public
key identifiers is if the user wants to restrict the usage of the RSA
public key with a specific algorithm.
For the generic RSA public key, the S/MIME capability that is
advertised is a request for a specific key size to be used. This
would normally be used for dealing with a request on the key to be
used for a signature that the client would then verify. In general
the user would provide a specific key when a key transport algorithm
is being considered.
The ASN.1 that is used for the generic RSA public key is defined as
below:
scap-pk-rsa SMIME-CAPS ::= {
TYPE RSAKeyCapabilities
IDENTIFIED BY pk-rsa.&id
}
RSAKeyCapabilities ::= SEQUENCE {
minKeySize RSAKeySize,
maxKeySize RSAKeySize OPTIONAL
}
RSAKeySize ::= INTEGER (1024 | 2048 | 3072 | 7680 | 15360 |
4096 | 8192, ...)
In the above ASN.1 we have defined the following:
scap-pk-rsa is a new SMIME-CAP object. This object associates the
existing object identifier (rsaEncryption) used for the public key
in certificates (defined in [RFC3279] and [RFC5912]) with a new
type defined in this document.
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RSAKeyCapabilities carries the set of desired capabilities for an
RSA key. The fields of this type are:
minKeySize contains the minimum length of the RSA modulus to be
used. This field SHOULD NOT contain a value less than 1024.
maxKeySize contains the maximum length of the RSA modules that
should be used. If this field is absent then no maximum length
is requested/expected. This value is normally selected so as
not to cause the current code to run unacceptably long when
processing signatures.
RSAKeySize provides a set of suggested values to be used. The
values 1024, 2048, 3072, 7680 and 15360 are from the NIST guide on
signature sizes [NIST-SIZES] while the others are common powers of
two that would be used. The list is not closed and other values
can be used.
2.2. RSASSA-PSS Signature Public Keys
While most of the time one will use the generic RSA public key
identifier in a certificate, the RSA SSA-PSS identifier can be used
if the owner of the key desires to restrict the usage of the key to
just this algorithm. This algorithm does have the ability to place a
set of algorithm parameters in the public key info structure, they
have not been included in this location s as the same information
should be carried in the signature S/MIME capabilities instead.
The ASN.1 that is used for the RSA SSA-PSS public key is defined
below:
scap-pk-rsaSSA-PSS SMIME-CAPS ::= {
TYPE RSAKeyCapabilities
IDENTIFIED BY pk-rsaSSA-PSS.&id
}
In the above ASN.1 we have defined the following:
scap-pk-rsaSSA-PSS is a new SMIME-CAP object. This object
associates the existing object identifier (id-RSASSA-PSS) used for
the public key certificates (defined in [RFC4055] and [RFC5912])
with type RSAKeyCapabilities.
2.3. RSA ES-OAEP Key Transport Public Keys
While most of the time one will use the generic RSA public key
identifier in a certificate, the RSA ES-OAEP identifier can be used
if the owner of the key desires to restrict the usage of the key to
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just this algorithm. This algorithm does have the ability to place a
set of algorithm parameters in the public key info structure, they
have not been included in this location s as the same information
should be carried in the key transport S/MIME capabilities instead.
The ASN.1 that is used for the RSA ES-OAEP public key is defined
below:
scap-pk-rsaES-OAEP SMIME-CAPS ::= {
TYPE RSAKeyCapabilities
IDENTIFIED BY pk-rsaES-OAEP.&id
}
In the above ASN.1 we have defined the following:
scap-pk-rsaES-OAEP is a new SMIME-CAP object. This object
associates the existing object identifier (id-RSAES-OAEP) used for
the public key certificates (defined in [RFC4055] and [RFC5912])
with type RSAKeyCapabilities.
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3. Diffie-Hellman Keys
There is current two Diffie-Hellman public key object identifiers.
These are DH key agreement and DSA.
3.1. DSA Signature Public Key
This public key type is used for the validation of DSA signatures.
The ASN.1 that is used for DSA keys is defined below:
scap-pk-dsa SMIME-CAPS ::= {
TYPE DSAKeyCapabilities
IDENTIFIED BY pk-dsa.&id
}
DSAKeyCapabilities ::= CHOICE {
keySizes [0] SEQUENCE {
minKeySize DSAKeySize,
maxKeySize DSAKeySize OPTIONAL
},
keyParams [1] pk-dsa.&Params
}
DSAKeySize ::= INTEGER (1024 | 2048 | 3072 | 7680 | 15360 )
In the above ASN.1 we have defined the following:
scap-pk-dsa is a new SMIME-CAP object. This object associated the
existing object identifier (id-dsa) used for the public key in
certificates (defined in [RFC3279] and [RFC5912]) with a new type
defined here, DSAKeyCapabilities.
DSAKeyCapabilities carries the desired set of capabilities for the
DSA key. The fields of this type are:
keySizes is used when only a key size is needed to be specified
and not a specific group. It is expected that this would be
the most commonly used of the two options. In key sizes the
fields are used as follows:
minKeySize contains the minimum length of the DSA modulus to
be used.
maxKeySize contains the maximum length of the DSA modules that
should be used. If this field is absent then no maximum
length is requested/expected.
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keyParams contains the exact set of DSA for the key used to sign
the message.
NOTE: In the original discussions the option keyParams would not have
existed in this structure, and they may not exist in a future version
of the structure. The issue is that we really only need to have the
key size fields, but there seems to be a mis-match between this
structure and that used for ECC where we don't specify anything about
key sizes, but do specify the exact group to be used. We should
probably have a discussion about rationalizing these together.
3.2. DH Key Agreement Keys
This public key type is used with the Diffie-Hellman key agreement
algorithm.
The ASN.1 that is used for DH keys is defined below:
scap-pk-dh SMIME-CAPS ::= {
TYPE INTEGER
IDENTIFIED BY pk-dh.&id
}
In the above ASN.1 we have defined the following:
scap-pk-dh is a new SMIME-CAP object. This object associates the
existing object identifier (id-dh) used for the public key
algorithm in the certificates (defined in [RFC3279] and [RFC5912])
with a new type defined above, DSAKeyCapabilities.
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4. Elliptical Curve Keys
There are currently three Elliptical Curve public key object
identifiers. These are EC, EC-DH and EC-MQV
4.1. Generic Elliptical Curve Keys
All most all ECC keys that are contained in certificates today use
the generic ECC public key format and identifier. This allows for
the public key to be used both for key agreement and for signature
validation (assuming the appropriate bits are in the certificate).
The only reason for using one of the more specific public key
identifier is if the user wants to restrict the usage of the ECC
public key with a specific algorithm.
For the generic ECC public key, the S/MIME capability that is
advertised is a request for a specific group to be used.
The ASN.1 that is used for the generic ECC public key is defined as
below:
scap-pk-ec SMIME-CAPS ::= {
TYPE pk-ec.&Type
IDENTIFIED BY pk-ec.&id
}
In the above ASN.1 we have defined the following:
scap-pk-ec is a new SMIME-CAP object. This object associated the
existing object identifier (id-ecPublicKey) used for the public
key algorithm in the certificates (defined in [RFC3279] and
[RFC5912]) with the same type used for the public key (ECPoint).
4.2. Elliptical Curve DH Keys
This public key type is used with the Elliptical Curve Diffie-Hellman
key agreement algorithm.
The ASN.1 that is used for EC-DH keys is defined below:
scap-pk-ecDH SMIME-CAPS ::= {
TYPE pk-ecDH.&Type
IDENTIFIED BY pk-ecDH.&id
}
In the above ASN.1 we have defined the following:
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scap-ec-dh is a new SMIME-CAP object. This object associated the
existing object identifier (id-??) used for the public key
algorithm in the certificate (defined in [RFC3279] and [RFC5912])
with the same type structure used for public keys.
4.3. Elliptical Curve MQV Keys
This public key type is used with the Elliptical Curve MQV key
agreement algorithm.
The ASN.1 that is used for EC-MQV keys is defined below:
scap-pk-ecMQV SMIME-CAPS ::= {
TYPE pk-ecMQV.&Type
IDENTIFIED BY pk-ecMQV.&id
}
In the above ASN.1 we have defined the following:
scap-ec-MQV is a new SMIME-CAP object. This object associated the
existing object identifier (id-??) used for the public key
algorithm in the certificate (defined in [RFC3279] and [RFC5912])
with the same type structure used for public keys.
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5. RSASSA-PSS Signature Algorithm Capability
This document defines a new S/MIME Capability for the RSA-SSA-PSS
signature algorithm. There already exists one in [RFC4055] where the
parameters field is not used.
When the S/MIME group defined a S/MIME Capability for the RSA-SSA-PSS
signature algorithm, it was done so in the context of how S/MIME
defines and uses S/MIME Capabilities. When placed in an S/MIME
message [RFC3851] or in a certificate [RFC4262] it is always placed
in a sequence of capabilities. This meant that one can place the
identifier for RSA-SSA-PSS in the sequence along with the identifier
for MD5, SHA-1 and SHA-256. The assumption was then made that one
could compute the matrix of all answers and the publisher would
support all elements in the matrix. This has the possibility that
the publisher could accidently publish a point in the matrix that is
not supported.
In this situation, there is only a single item that is published.
This means that we need to publish all of the associated information
along with the identifier for the signature algorithm in a single
entity. For this reason we now define a new parameter type to be
used as the S/MIME capability type which contains a hash identifier
and a mask identifier. The ASN.1 used for this is as follows:
scap-sa-rsaSSA-PSS SMIME-CAPS ::= {
TYPE RsaSsa-Pss-sig-caps
IDENTIFIED BY sa-rsaSSA-PSS.&id
}
RsaSsa-Pss-sig-caps ::= SEQUENCE {
hashAlg SMIMECapability{{ HashAlgorithms }},
maskAlg SMIMECapability{{ MaskAlgorithmSet }} OPTIONAL,
trailerField INTEGER DEFAULT 1
}
scap-mf-mgf1 SMIME-CAPS ::= {
TYPE SMIMECapability{{ HashAlgorithms }}
IDENTIFIED BY id-mgf1
}
MaskAlgorithmSet SMIME-CAPS ::= {scap-mf-mgf1, ...}
In the above ASN.1 we have defined the following:
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scap-sa-rsaSSA-PSS is a new SMIME-CAP object. This object
associates the existing object identifier (id-RSASSA-PSS) used for
the signature algorithm (defined in [RFC4055] and [RFC5912]) with
the new type RsaSsa-Pss-sig-caps.
RsaSsa-Pss-sig-caps carries the desired set of capabilities for the
RSA SSA-PSS signature algorithm. The fields of this type are:
hashAlg contains the S/MIME capability for the hash algorithm we
are declaring we support with the RSA-SSA-PSS signature
algorithm.
maskAlg contains the S/MIME capability for the mask algorithm we
are declaring we support with the RSA-SSA-PSS signature
algorithm.
trailerField specifies which trailer field algorithm is being
supported. This MUST be the value 1.
NOTE: In at least one iteration of the design we used a sequence of
hash identifiers and a sequence of masking functions and again made
the assumption that entire matrix would be supported. This has been
removed at this point since the original intent of S/MIME
capabilities is that one should be able to do a binary comparison of
the DER encoding of the field and determine a specific capability was
published. We could return back to using the sequence if we wanted
to lose the ability to do a binary compare but needed to shorten the
encodings. This does not currently appear to be an issue at this
point.
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6. Security Considerations
This document provides new fields that can be placed in an S/MIME
capabilities sequence. There are number of considerations that need
to be taking into account when doing this.
As mentioned above, there are a small number of cases where the same
object identifier may be used to identify a public key and an
algorithm. This is the case for many years with the OID
rsaEncryption where it identifies both a public key and the RSA v1.5
key transport algorithm. This means that when an S/MIME capabilities
sequence is defined care needs to be taken to specify the types of
algorithms and/or public keys that are to be specified in that
sequence. In general, it is expected that algorithms and public keys
will be segregated.
The more detailed the information that is communicated, the better
the end results are going to be. If you can state you do RSA v1.5,
EC-DSA, SHA-1 and SHA-256, then it would imply that all four values
are supported. It may be however that EC-DSA with SHA-1 is not
supported. Not including the SHA-1 hash algorithm could lead to
problems as RSA with SHA-1 could be the only point of intersection,
but including it means that a result may be returned that cannot be
processed.
The more information passed the better. The more choices that are
passed, the better the odds that both parties will be able to agree
on a common algorithm.
The less information passed the better. Passing too much information
can lead to computational issues in trying to deal with the
possibilities. This becomes acute when a negotiation over algorithms
is going on between multiple parties (such as sending an encrypted
S/MIME message) where the amount of memory and processing time can be
greatly expanded if there are a large number of choices for each
recipient.
Ordering of preference of algorithms is not always supported by all
places where S/MIME capabilities are used. The addition of
preference ordering greatly complicates the decisions to be used,
especially as it is expected that not all parties will agree on the
same ordering.
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7. IANA Considerations
This document has no IANA considerations.
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8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3279] Bassham, L., Polk, W., and R. Housley, "Algorithms and
Identifiers for the Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 3279, April 2002.
[RFC4055] Schaad, J., Kaliski, B., and R. Housley, "Additional
Algorithms and Identifiers for RSA Cryptography for use in
the Internet X.509 Public Key Infrastructure Certificate
and Certificate Revocation List (CRL) Profile", RFC 4055,
June 2005.
[RFC5912] Hoffman, P. and J. Schaad, "New ASN.1 Modules for the
Public Key Infrastructure Using X.509 (PKIX)", RFC 5912,
June 2010.
8.2. Informative References
[I-D.ietf-pkix-ocspagility]
Hallam-Baker, P. and S. Santesson, "OCSP Algorithm
Agility", draft-ietf-pkix-ocspagility-08 (work in
progress), March 2010.
[RFC3851] Ramsdell, B., "Secure/Multipurpose Internet Mail
Extensions (S/MIME) Version 3.1 Message Specification",
RFC 3851, July 2004.
[RFC4262] Santesson, S., "X.509 Certificate Extension for Secure/
Multipurpose Internet Mail Extensions (S/MIME)
Capabilities", RFC 4262, December 2005.
[SMIMEv3-MSG]
Ramsdell, B., "S/MIME Version 3 Message Specification",
RFC 2633, June 1999.
[NIST-SIZES]
Barker, E., Barker, W., Burr, W., Polk, W., and M. Smid,
"Recommendation for Key Management -- Part 1: General",
NIST Special Publication 800-57, March 2007.
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Appendix A. 2008 ASN.1 Module
PUBLIC-KEY-SMIME-CAPIBLITIES
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0) TBD5 }
DEFINITIONS ::=
BEGIN
IMPORTS
SMIME-CAPS, PUBLIC-KEY, SMIMECapability
FROM AlgoritrithmInformation-2009
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-algorithmInformation-02(58)}
pk-rsa, pk-dsa, pk-dh, pk-ec, pk-ecDH, pk-ecMQV
FROM PKIXAlgs-2009
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-pkix1-algorithms2008-02(56) }
pk-rsaSSA-PSS, pk-rsaES-OAEP, sa-rsaSSA-PSS,
HashAlgorithms, id-mgf1
FROM PKIX1-PSS-OAEP-Algorithms-2009
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-pkix1-rsa-pkalgs-02(54)}
;
--
-- Define a set containing all of the S/MIME capabilties defined
-- by this document
--
SMimeCaps SMIME-CAPS ::= {
PubKeys-SMimeCaps |
scap-sa-rsaSSA-PSS
}
PubKeys-SMimeCaps SMIME-CAPS ::= {
scap-pk-rsa | scap-pk-rsaSSA-PSS |
scap-pk-dsa |
scap-pk-ec | scap-pk-ecDH
}
--
-- We defined RSA keys from the modules RFC3279 and RFC4055
--
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scap-pk-rsa SMIME-CAPS ::= {
TYPE RSAKeyCapabilities
IDENTIFIED BY pk-rsa.&id
}
RSAKeyCapabilities ::= SEQUENCE {
minKeySize RSAKeySize,
maxKeySize RSAKeySize OPTIONAL
}
RSAKeySize ::= INTEGER (1024 | 2048 | 3072 | 7680 | 15360 |
4096 | 8192, ...)
scap-pk-rsaES-OAEP SMIME-CAPS ::= {
TYPE RSAKeyCapabilities
IDENTIFIED BY pk-rsaES-OAEP.&id
}
scap-pk-rsaSSA-PSS SMIME-CAPS ::= {
TYPE RSAKeyCapabilities
IDENTIFIED BY pk-rsaSSA-PSS.&id
}
scap-sa-rsaSSA-PSS SMIME-CAPS ::= {
TYPE RsaSsa-Pss-sig-caps
IDENTIFIED BY sa-rsaSSA-PSS.&id
}
RsaSsa-Pss-sig-caps ::= SEQUENCE {
hashAlg SMIMECapability{{ HashAlgorithms }},
maskAlg SMIMECapability{{ MaskAlgorithmSet }} OPTIONAL,
trailerField INTEGER DEFAULT 1
}
scap-mf-mgf1 SMIME-CAPS ::= {
TYPE SMIMECapability{{ HashAlgorithms }}
IDENTIFIED BY id-mgf1
}
MaskAlgorithmSet SMIME-CAPS ::= {scap-mf-mgf1, ...}
--
-- we define DH/DSA keys from the module RFC3279
--
scap-pk-dsa SMIME-CAPS ::= {
TYPE DSAKeyCapabilities
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IDENTIFIED BY pk-dsa.&id
}
DSAKeyCapabilities ::= CHOICE {
keySizes [0] SEQUENCE {
minKeySize DSAKeySize,
maxKeySize DSAKeySize OPTIONAL
},
keyParams [1] pk-dsa.&Params
}
DSAKeySize ::= INTEGER (1024 | 2048 | 3072 | 7680 | 15360 )
scap-pk-dh SMIME-CAPS ::= {
TYPE INTEGER
IDENTIFIED BY pk-dh.&id
}
--
-- we define Eliptical Curve keys from the module RFC3279
--
scap-pk-ec SMIME-CAPS ::= {
TYPE pk-ec.&Type
IDENTIFIED BY pk-ec.&id
}
scap-pk-ecDH SMIME-CAPS ::= {
TYPE pk-ecDH.&Type
IDENTIFIED BY pk-ecDH.&id
}
scap-pk-ecMQV SMIME-CAPS ::= {
TYPE pk-ecMQV.&Type
IDENTIFIED BY pk-ecMQV.&id
}
END
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Appendix B. Future Work
A future revision of [RFC5912] should be done at some point which
expands the definition of the PUBLIC-KEY class and allows for an
S/MIME Capability to be included in the class definition. This would
encourage people to think about this as an issue when defining new
public key structures in the future.
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Author's Address
Jim Schaad
Soaring Hawk Consulting
Email: jimsch@augustcellars.com
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