wdiff draft-ietf-pkix-logotypes-01.txt draft-ietf-pkix-logotypes-02.txt

PKIX Working Group S. Santesson (AddTrust)
INTERNET-DRAFT R. Housley (RSA Laboratories)
Expires August 2002 February T. Freeman (Microsoft)
April 2002

Internet X.509 Public Key Infrastructure

Logotypes in X.509 certificates

<draft-ietf-pkix-logotypes-01.txt>

<draft-ietf-pkix-logotypes-02.txt>

Status of this Memo

This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.

Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other
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The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.

Abstract

This document contains an initial outline of specifies a standard certificate extension for attaching including
logotypes to certificates. The draft includes background discussions
around different aspects of problems in public key certificates and solutions, forming a
starting point for the creation of a complete standard. attribute certificates.

Please send comments on this document to the ietf-pkix@imc.org
mailing list.

Table of Contents

1 Introduction ................................................. 3
1.1 Are human recognition concepts relevant ................... Certificate-based Identification .......................... 4
1.2 Selection of Certificates ................................. 4
1.3 Combination of verification techiques ..................... Verification Techniques .................... 5
1.4 Terminology ............................................... 6
2 Different types of logotypes in certificates.................. 5
3 Technical solutions .......................................... Certificates ................. 6
3.1 General .......................................
3 Image formats ................................................ 6
3.2
4 Logotype extension ........................................... 7
5 Type of certificates ...................................... 7
3.3 Logotype placement ........................................ 8
3.3.1 Qualifier .............................................. 8
3.3.2 Issuer and Subject Alt Names ........................... 8
3.3.3 New extension .......................................... ......................................... 9
3.3.4 Conclusion ............................................. 10
4
6 Use in Clients ............................................... 10
5 9
7 Security considerations ...................................... 10
6
8 References ................................................... 12
7 11
9 Intellectual Property Right .................................. Rights ................................. 12

Appendices

A. ASN.1 definitions ........................................... 13
B. Logotype placement .......................................... 13
B.1 Qualifier ................................................. 13
B.2 Issuer and Subject Alt Names .............................. 13
B.3 New extension ............................................. 14
B.4 Conclusion ................................................ 14
C. Author Addresses ............................................ 13
C. 15
D. Full Copyright Statement .................................... 13

1 16

1. Introduction

The basic function of a certificate is to bind a public key to the
identity of an entity (subject). (the subject). From a strictly technical
viewpoint, this goal could be achieved by signing the identity of the
subject together with its public key. However, the art of PKI has
developed certificates far beyond this functionality in order to meet
the needs
from of modern global networks and heterogeneous IT structures.

One driver of the evolution from simple certificate formats to more
complex structures is the need

Certificate users must be able to distinguish between different determine certificate concepts, such as assurance level, policies,
appropriate key usage, assurance level, and name form constraints.
Before a relying party can make an informed decision whether a
particular certificate is trustworthy and relevant for its intended
usage, a certificate may be examined from several different
perspectives.

Systematic processing is necessary to determine whether a particular
certificate meets the predefined prerequisites for an intended usage.
Even though
Much of the information objects contained in certificates are is appropriate and
effective for machine processing, they are poor instruments processing; however, this information is not
suitable for a corresponding human trust and recognition process.

The human prefers

Humans prefer to structure information into categories and symbols.
Most humans associate complex structures of reality with easy
recognizable logotypes and marks. Humans tend to trust things that
they recognize from previous experiences. Humans may examine
information to confirm their initial reaction. Very few consumers
actually read all terms and conditions they accept when accepting a
service, instead rather they most commonly act in trust based on trust derived from previous
experience and recognition.

A big part of this process is branding. Service providers and product
vendors invest a lot of money and resources into creating a strong
relation between positive user experiences and easily recognizable
trademarks
trademarks, servicemarks, and logotypes.

Branding is also pervasive in identification instruments, including
identification cards, passports, driver's licenses, credit cards,
gasoline cards, and loyalty cards. Identification instruments are
intended to identify the holder as a particular person or as member
of community. The community may represent the subscribers of a
service or any other group. Identification instruments, in physical
form, commonly use logotypes and symbols, solely to enhance human
recognition and trust in the identification instrument itself. They
may also include a registered trademark to allow legal recourse for
unauthorized duplication.

Since certificates play an equivalent role in electronic exchanges,
we examine the inclusion of logotypes in certificates.

1.1 Are We consider
certificate-based identification and certificate selection.

1.1. Certificate-based Identification

The need for human recognition concepts relevant?

The answer depends on the manner in which certiciates
certificates are used. Are used and whether certificates need to be visible or invisible to
human users? Will the
certificates be used in open environments? users. If certificates are to be used in open environments and
in applications that brings bring the user in conscious contact with the
result of a certificate-based identification process, then human
recognition is highly relevant, and it may be a necessity.

Examples of sucha such applications include:

- Web server identification where a user identifies the owner
of the web site.
- Peer e-mail exchange in B2B, B2C, and private communications.
- Exchange of medical records, and system for medical
prescriptions.
- Unstructured e-business applications (i.e. (i.e., non-EDI
applications).
- Wireless client authenticating to a service provider.

Most applications provide the human user with an opportunity to view
the results of a successful certificate-based identification process.
When the user takes the steps necessary to view these results, the
user is presented with a view of a certificate. This solution has
however two
major problems.

1) The First, the function to view a certificate is often
rather hard to find for a non-technical user.

2) The Second, the
presentation of the certificate is rather too technical and and, it is not user
friendly. Further it It contains no graphic symbols and or logotypes to enhance
human recognition.

Many investigations have shown that users of today's applications do
not take the steps necessary to view certificates. This could be due
to poor user interfaces. However, Further, many applications are structured to
hide certificates from users. The application designers do not want
to expose certificates to users at all.

1.2

1.2. Selection of Certificates

One situation where software applications must expose human users to
certificates is when the user must select a single certificate from a
portfolio of certificates. In some cases, the software application
can use information within the certificates to filter the list for
suitability; however, the user must be queried if more than one
certificate is suitable. The human user must select one of them.

This situation is comparable to a person selecting a suitable plastic
card from his wallet. In this situation, substantial assistance is
provided by card color, location, and branding.

In order to provide similar support for certificate selection, the
users need tools to easily recognize and distinguish certificates.
Introduction of logotypes into certificates provides the necessary
graphic.

1.3. Combination of verification techiques

Can Verification Techniques

The use of logotypes will in many cases affect the concepts users decision to
trust and use a certificate. It is therefore important that there is
a distinct and clear architectural and functional distinction between
the processes and objectives of the systematic certification path certificate
verification and human recognition be combined in any sensible manner? recognition.

Systematic certification path verification determines whether the
end-entity certificate can be verified according to defined policy.
The algorithm for this verification is specified in RFC <TBD>
[PKIX-1].

The systematic processing provides assurance that the certificate is
a valid document.
valid. It does not indicate whether the subject is entitled to any
particular information, information or whether the subject ought to be trusted to
perform a particular service. These are access control function decisions. Some
Automatic processing will make some access control decisions may be made
by a systematic process, decisions, but
others, depending on the application context, involve the human user.

In some situations, where automated procedures have failed to
establish the suitability of the certificate to the task, the human
user is the sole handler final arbitrator of the post
certification path certificate verification
access control decisions. In the end, the human will decide whether
or not to accept an executable email attachment, to release personal
information, or follow the instructions displayed by a web browser. As we have seen, this
This decision will often be based on recognition and previous
experience.

The distinction between systematic processing and human processing is
rather straightforward. They can be complementary. While the
systematic process is focused on certification path construction and
verification, the human acceptance process is focused on recognition
and related previous experience.

There are some situations where systematic processing and human
processing interfer interfere with each other. These issues are discussed in
the Security Considerations section.

1.3

1.4. Terminology

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 RFC 2119 [STDWORDS].

2. Different types Types of logotypes Logotypes in certificates Certificates

This draft suggests standardization specification defines the inclusion of 3 three predefined logotype
types.

1) Concept Community logotype
2) Issuer organization logotype
3) Subject organization logotype

The concept community logotype - is the general mark for a community. It
identifies a service concept for entity identification and
certificate issuance. Many issuers may use
the concept logotypes a community logotype to
co-brand with a global concept community in order to gain global recognition
of its local service provision. This type of
concept community branding is
very common in the credit card business where local independent card
issuers issue cards within include a globally branded
concept recognized brand (such as VISA and
MasterCard).

Issuer organization logotype - is a logotype representing the
organization identified as part of the issuer name in the
certificate.

Subject organization logotype - is a logotype representing the
organization identified in the subject name in the certificate.

3 Technical solution

3.1 General

3. Image formats

This specification defines two image format types:

- High Resolution (included by reference)
- Low Resolution (icon-sized image embedded in the extension)

A high resolution image SHOULD include a black border. Exceptions are
such things as arrows or X's. These images SHOULD be fairly flat in
appearance with little dimensioning or shading.

There is no need to significantly increase the size of the
certificate by including logotype image data of logotypes in a certificate. high quality
format. Rather, a URI identifying the location to the logotype image
and a one-way hash of the referenced data is included in the
certificate.

To enhance functionality for off-line and low bandwidth situations
where reasonable access to high quality logotypes are not available,
the icon-sized version of the logotype may optionally be stored
directly in the certificate extension.

Applications may also enhance processing and off-line functionality
by cashing the higher quality logotype data.

4. Logotype extension

The URI defines the file format for the logotype image. extension MAY be included in public key certificates
[PKIX-1] or attribute certificates [PKIX-AC]. The solution explicitly identifies logotype extension
MUST be identified by the one-way hash function
employed. following object identifier:

id-pe-logotypeInfo OBJECT IDENTIFIER ::= {id-pe XX}

The general structure for logotype data is:

LogotypeData extension MUST have the following syntax:

LogotypeInfo ::= SEQUENCE {
typeOfLogotype TypeOfLogotype,
hashAlgorithm AlgorithmIdentifier,
logotypeDataHash OCTET STRING,
logotypeDataUri IA5String
communityLogo [0] LogotypeData OPTIONAL,
issuerLogo [1] LogotypeData OPTIONAL,
subjectLogo [2] LogotypeData OPTIONAL,
otherLogos [3] SEQUENCE OF OtherLogotypeData OPTIONAL }

TypeOflogotype

OtherLogotypeData ::= CHOICE SEQUENCE {
predefinedLogotypeType PredefinedLogotypeType,
logotypeTypeID OBJECT IDENTIFIER IDENTIFIER,
logotypeData LogotypeData }

LogotypeData ::= SEQUENCE {
highRes LogotypeReference OPTIONAL,
lowRes EmbeddedLogotype OPTIONAL }

PredefinedLogotypeType

LogotypeReference ::= INTEGER SEQUENCE {
subject-organization-logotype(0),
issuer-organization-logotype(1)
concept-logotype(2)
hashAlgorithm AlgorithmIdentifier,
logotypeHash OCTET STRING,
logotypeUri IA5String }

EmbeddedLogotype ::= SEQUENCE {
imageFileExtn IA5String, -- MUST be "JPEG" or "JPG" or "GIF"
image OCTET STRING }

This extension MUST NOT be marked critical.

At least one of the optional elements in the LogotypeInfo structure
MUST be present. Whenever possible, the use of otherLogos should be
avoided.

The LogotypeReference structure explicitly identifies the one-way
hash function employed. Implementations MUST support the SHA-1 [FIPS
180-1] algorithm, and implementations MAY support other one-way hash
functions.

The predefined logotype types are:

subject-organization-logotype, if used, SHALL be used

Community Logotype. If communityLogo is present, the logotype MUST
represent the community to include which the certificate issuer is a
member. The communityLogo MAY be present in an end entity
certificate or an attribute certificate. The communityLogo MUST
NOT be present in a CA certificate.

Issuer Organization Logotype. If issuerLogo is present, the
logotype of MUST represent the subject issuer's organization. The logotype SHALL
MUST be consistent with, and require the presence of, an
organization name stored in the organization attribute in the subject field.

issuer-organization-logotype, if used, SHALL
issuer field (for either a public key certificate or attribute
certificate). The issuerLogo MAY be used to include present in an end entity
certificate, a CA certificate, or an attribute certificate.

Subject Organization Logotype. If subjectLogo is present, the
logotype of MUST represent the issuer subject's organization. The logotype SHALL
MUST be consistent with, and require the presence of, an
organization name stored in the organization attribute in the issuer field.

Concept-logotype, if used, SHALL be used to include
subject field (for either a logotype
representing the concept under which the issuer claims to issue this
certificate.

A concept may public key certificate or attribute
certificate). The subjectLogo MAY be shared within present in an end entity
certificate, a network of certification authority
(CA) services, provided by one or several independent CA
organizations. certificate, or an attribute certificate.

The relationship between the subject organization and the subject
organization logotype and the relationship between the issuer and
either the issuer organization logotype or the concept community logotype,
are relationships claimed by the issuer. The policy under which the
issuer checks these logotypes is outside the scope of this standard.

Any URI pointing to a file containing the logotype data SHALL MUST include
a file extension defining the image file format. The file extension
is the last three or four letters of the file name, immediately
following a period. Implementations MUST support both the JPEG and
GIF image formats. The JPEG image format MUST be identifier using a
file extension of "JPG" or "JPEG". The GIF image format MUST be
identified using the "GIF" file extension.

The same three file extension strings ("JPG," "JPEG," and "GIF") are
used to identify the format (i.e. .GIF, .TIF,
.TIFF, .JPG, .JPEG, etc.).

3.2 of embedded images.

To ensure that certificates are not greatly enlarged by including
embedded logotypes, restrictions are imposed on image size and color
definition. Embedded images MUST NOT exceed 20 pixels by 20 pixels.
Embedded images MUST use a 256-color (8-bit) palette. The size of an
image conforming to these restrictions is about 750 octets.

5. Type of certificates

Logotypes according to the present model may MAY be used present in 3 three types of certificates:

- Self-signed CA certificates (root certificates)
- Intermediate CA End-entity certificates
- End-entity Attribute certificates

A reason to constrain inclusion of logotypes to end-entity

CA certificates would be include self-signed certificates (often used to exclude the aspect
represent trust anchors) or Intermediate CA certificates.

Some types of logotypes are not permitted in CA certificates. This
ensures that logotypes are excludes from path
processing issues, where a path validating service would want to
check consistency all aspects of logotypes in a certification path.

However, as
path processing. As discussed above, logotypes are not aimed intended to be
part of certification path validation or any type of systematic processing
since its
processing. The sole purpose of logotypes is to enhance display of a single
particular
certificate to a user certificate, regardless of its position or function in a certification
path.

Logotypes should not MUST NOT be an active component in certification path
processing, and
logotypes should be allowed in all types of certificates, at the
discretion of the CA.

3.3 Logotype placement
So far, there have been 3 solutions discussed regarding the placement
of the logotype data in certificates.

- Inclusion in a policy qualifier
- Inclusion in Issuer and Subject Alternative names extensions
- Inclusion in a separate private extension

3.3.1 Qualifier

This solution would include logotype data as a newly defined policy
qualifier.

Pros:

- This solution provides a mechanism to directly control the use and
display of logotypes under a particular policy

Cons:

- Current practice and standards (RFC 2459) recommends against use of
qualifiers

- This is generally considered to be a major hack and stretch of
semantics, since this type of data doesn't qualify a policy in any
way.

3.3.2 Issuer and Subject Alt Names

This solution would use the other name form to include;

- issuer and concept logotypes in the issuer alt name extension;
and,
- subject organization logo in the subject alt name extension.

Pros:

- This mechanism could possibly enable cross certifying CAs to deny
any subordinate CA the right to include logotypes in descending end
entity certificates by listing the logotypes name form in
excludedSubtrees.

Cons:

- Logotypes they are not a name form and should not be treated as a
displayable name.

- It is generally understood that it should be possible to apply
general name constraint mechanisms (as described in RFC 2459 as
well as son-of-2459) to names included in the subject public key certificates and issuer alt name
extension. This is not possible to do with logotypes since it is
not a name form.

- This split storage of logotype data into 2 different locations,
which may make life worse for applications with no interest in
logotypes.

- It is generally agreed that inclusion of logotype data by no means
should be regarded as critical data. This may interfere with
attribute certificates at the
criticality policy discretion of the alt name extensions, especially if the certificate has no attributes in the subject field, forcing the
subject alt name to be set to critical.

- This usage would possibly interfere with the resolution between
IETF and ITU-T regarding use of permitted subtrees.

- Since this solution may break current implementations it would
possibly block adoption of logotypes.

3.3.3 New extension

logotypeInfo EXTENSION ::= {
SYNTAX LogotypeSyntax
IDENTIFIED BY id-pe-logotypeInfo }

id-pe-logotypeInfo OBJECT IDENTIFIER ::= {id-pe XX}

LogotypeSyntax ::= SEQUENCE OF LogotypeData

Pros:

- This is the cleanest solution.

- Do not impact on legacy implementations.

Cons:

- This solution activates the issue whether this extension may be
abused by a CA who include logotypes (in EE certificates) that
violates the intention of a name constraints set by a chaining CA.
This issue is addressed in the security consideration section
below.

3.3.4 Conclusion

We must not destroy current structures. We must not create problems
and confusion.

Only the private extension solution satisfies both of these desires.
Therefore, the private extension should be selected.

4 issuer.

6. Use in Clients

All PKI implementations require relying party software to have some
mechanism to determine whether a trusted CA issues a particular
certificate. This is an issue for certification path validation,
including consistent policy and name checking.

After a certificatin certification path is successfully validated, the replying
party must trust the information that the CA includes in the
certificate, including any certificate extensions. The client
software can choose to make use of such information, or the client
software can ignore it. Current standards do not provide any
mechanism for cross-certifying CAs to constrain subordinate CAs from
including private extensions (see the security considerations). considerations
section).

Consequently, if relying party software accepts a CA, then it should
be prepared to (unquestioningly) display the associated logos logotypes to
its human user, given that it is configured to do so.

However, if the relying party software is unable to successfully
validate a particular certificate, then it MUST NOT display any
associated logotype graphics.

7. Security considerations

Logotypes are even worse than names regarding the possibility very difficult to securely and accurately define define. Names
are also difficult in this regard, but logotypes are even worse. It
is quite difficult to specify what is, and what is not, a legitimate
logotype of an organization. There is a whole legal structure around
this issue that doesn't need repetition in this document. issue, and it will not be repeated here. However, issuers should
be aware of the implications of including images associated with a
trademark or servicemark before doing so.

As logotypes are hard can be difficult (and sometimes expensive) to verify,
this increases the possibility of errors related to falsely assigning wrong
logotypes to organizations.

This is not a new issue for electronic identification instruments.
It is already dealt with in numerous of similar situations in the
physical world, including physical employee identification cards.
Secondly, there are situations where identification of logotypes is
rather simple and straightforward, such as logotypes for well-known
industries and institutes. These issues should not stop those service
providers who want to issue logotypes from doing so, where relevant.

There

The premise used for the logotype work is that logotype graphics in a new problem related
certificate are trusted only if the certificate is successfully
validated within a valid path. It is however impossible to electronic identification
instruments prevent
fraudulent creation of certificates by non-validated issuers,
containing names and logotypes that the issuer has no claim to. Such
certificates could be created in an attempt to socially engineer a
user into accepting a certificate. It is thus imperative that the form
representation of certificates. any certificate that fails to validate is not
enhanced in any way by using the logotype graphic.

Certification paths may also impose name constraints that are
systematically checked during certification path processing, which,
in theory, may be violated circumvented by logotypes.

Certification

Certificate path processing does not, should not, and will never be
able to control not constrain the inclusion of
logotype data in certificates. That
is, a A parent CA may constraint can constrain
certification path validation such that subordinate CAs to only cannot issue
valid certificates to end-entities within outside a limited name space. space or
outside specific certificate polices. A
potentially bad malicious CA may can comply with this
these name constraint and policy requirements and still include a subject organization logotype. The inappropriate
logotypes in the parent CA has no certificates that it issues. These certificates will
pass the certification path validation algorithm, which means of preventing logotype data inclusion since the
client will trust the logotypes in the certificates. Since there is
no technical mechanism to prevent or control subordinate CAs from
including new extensions. the logotype extension or its contents, where appropriate,
a parent CA could employ a legal agreement to impose a suitable
restriction on the subordinate CA. This situation is not unique to
the logotype extension. No technical means are
provides for constraining subordinate CAs to a particular certificate
profile.

The controls available to a parent CA to protect itself from rogue
subordinate CAs are nontechnical. non-technical. They include:

- Contractual agreements of suitable behaviour, behavior, including
terms of liability and severance pay in case of material
breach.

- Control mechanisms and procedures to monitor and
follow-up behaviour behavior of subordinate CAs.

- Use of certificate policies to declare assurance level
of logotype data as well as to guide applications on how
to treat and display logotypes.

- Use of revocation functions to revoke any misbehaving CA.

This issue cannot be given an easy

There is not a simple, straightforward, and absolute technical
solution.
Maybe the correct response is to surrender to the fact that Rather, involved parties must settle some aspects of PKI
outside the scope of technical controls, and controls. As such, issuers need to
clearly identify and communicate the associated risks.

8. References

[STDWORDS] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", March 1997.

[RFC 2459]

[FIPS 180-1] Federal Information Processing Standards Publication
(FIPS PUB) 180-1, Secure Hash Standard, 17 April 1995.
[Supersedes FIPS PUB 180 dated 11 May 1993.]

[OLD-PKIX-1] R. Housley, W. Ford, W. Polk, and D.Solo, D. Solo, "Internet
X.509 Public Key Infrastructure: Certificate and
CRL Profile", January 1999.

[PKIX-1] R. Housley, W. Ford, W. Polk, and D. Solo, "Internet
X.509 Public Key Infrastructure: Certificate and
CRL Profile", January 1999.
{Replace with Son-of-2459 as soon as it is published.}

[STDWORDS] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", March 1997.

9. Intellectual Property Rights

The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
standards related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances of
licenses to be made available, or the result of an attempt made to
obtain ageneral a general license or permission for the use of such
proprietary rights by implementors implementers or users of this specification can
be obtained from the IETF Secretariat.

The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive
Director.

APPENDICES

A. ASN.1 definitions

TBD

B. Logotype Placement

This Appendix documents reasons and rationales behind the technical
solution selected in this standard.

Three alternatives for the placement of the logotypes in a
certificate have been considered. They are:

1. Inclusion in a policy qualifier;
2. Inclusion in Issuer and Subject Alternative names extensions; and
3. Inclusion in a separate certificate extension.

B.1 Qualifier

This alternative would include logotype data as a newly defined
policy qualifier.

Pros:

- This solution provides a mechanism to directly control the use and
display of logotypes under a particular policy.

Cons:

- RFC <TBD> [PKIX-1] recommends against use of qualifiers.

- This is generally considered to be a major hack and stretch of
semantics, since this type of data doesn't qualify a policy in any
way.

B.2 Issuer and Subject Alt Names

This solution would use the other name form to include the issuer and
community logotypes in the issuer alt name extension, and subject
organization logo in the subject alt name extension.

Pros:

- This mechanism could possibly enable cross-certifying CAs to deny
any subordinate CA the right to include logotypes in descending end
entity certificates by listing the logotypes name form in
excludedSubtrees.

Cons:

- Logotypes are not a name form and should not be treated as a
displayable name.

- It is generally understood that it should be possible to apply
general name constraint mechanisms (as described in RFC 2459 as
well as RFC <TBD> [PKIX-1]) to names in the subject and issuer
alt name extension. This is not possible to do with logotypes
since it is not a name form.

- This split storage of logotype data into 2 different locations,
which may make life worse for applications with no interest in
logotypes.

- It is generally agreed that inclusion of logotype data by no means
should be regarded as critical data. This may interfere with the
criticality policy of the alt name extensions, especially if the
certificate has no attributes in the subject field, forcing the
subject alt name to be set to critical.

- This usage would possibly interfere with the resolution between
IETF and ITU-T regarding use of permitted subtrees.

- Since this solution may break current implementations it would
possibly block adoption of logotypes.

B.3 New extension

This solution places logotype data in a new extension.

Pros:

- This is the cleanest solution.

- This does not impact on legacy implementations.

Cons:

B.4 Conclusion

We must not destroy current structures. We must not create problems
or confusion.

Only the private extension solution satisfies both of these criteria.
Therefore, the private extension was selected to carry logotype
information.

While the syntax and semantics of the X.509 public key certificate
were used in this analysis, the logotype private extension can also
be included in an X.509 attribute certificate.

C. Author Addresses

Stefan Santesson
AddTrust AB
P.O. Box 465
S-201 24 Malmoe
Sweden
stefan@addtrust.com

Russell Housley
RSA Laboratories
918 Spring Knoll Drive
Herndon, VA 20170
USA
rhousley@rsasecurity.com

Trevor Freeman
Microsoft Corporation
One Microsoft Way
Redmond WA 98052
USA
trevorf@microsoft.com

D. Full Copyright Statement

This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. In addition, the
ASN.1 modules presented in Appendices A and B may be used in whole or
in part without inclusion of the copyright notice. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
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