Internet X.509 Public Key Infrastructure: Logotypes in X.509 Certificates

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Table of Contents

1. Introduction

This specification supplements [RFC5280], which profiles public-key certificates and certificate revocation lists (CRLs) for use in the Internet, and it supplements [RFC5755] which profiles attribute certificates for use in the Internet.¶

This document obsoletes RFC 3709 [RFC3709] and RFC 6170 [RFC6170]. Appendix C provides a summary of the changes since the publication of RFC 3709 and RFC 6170.¶

The basic function of a certificate is to bind a public key to the identity of an entity (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 Public Key Infrastructure (PKI) has developed certificates far beyond this functionality in order to meet the needs of modern global networks and heterogeneous information and operational technology structures.¶

Certificate users must be able to determine certificate 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. Much of the information contained in certificates is appropriate and effective for machine processing; however, this information is not suitable for a corresponding human trust and recognition process.¶

Humans prefer to structure information into categories and symbols. Most humans associate complex structures of reality with easily 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 agree to in accepting a service, rather they commonly act 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, 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 a member of the 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. We consider certificate-based identification and certificate selection.¶

2. Different Types of Logotypes in Certificates

This specification defines the inclusion of three standard logotype types:¶

• Community logotype¶
• Issuer organization logotype¶
• Subject organization logotype¶

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

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.¶

In addition to the standard logotype types, this specification accommodates inclusion of other logotype types where each class of logotype is defined by an object identifier. The object identifier can be either locally defined or an identifier defined in Section 4.4 of this document.¶

3. Logotype Data

This specification defines two types of logotype data: image data and audio data. Implementations MUST support image data; however, support for audio data is OPTIONAL.¶

Image and audio data for logotypes can be provided by reference by including a URI that identifies the location to the logotype data and a one-way hash of the referenced data in the certificate. The privacy-related properties for remote logotype data depend on four parties: the certificate relying parties that use the information in the certificate extension to fetch the logotype data, the certificate issuers that populate the certificate extension, certificate subscribers that request certificates that include the certificate extension, and server operators that provide the logotype data.¶

Alternatively, embedding the logotype data in the certificate with direct addressing (as defined in Section 4.3) provides improved privacy properties and depends upon fewer parties. However, this approach can significantly increase the size of the certificate.¶

Several image objects, representing the same visual content in different formats, sizes, and color palates, may represent each logotype image. At least one of the image objects representing a logotype SHOULD contain an image with a width between of 60 pixels and 200 pixels and a height between 45 pixels and 150 pixels.¶

Several instances of audio data may further represent the same audio sequence in different formats, resolutions, and languages. At least one of the audio objects representing a logotype SHOULD provide text-based audio data suitable for processing by text-to-speech software.¶

A typical use of text based audio data is inclusion in web applications where the audio text is placed as the "alt" atttribute value of an html image (img) element and the language value obtained from LogotypeAudioInfo is included as the "lang" attribute of that image.¶

If a logotype of a certain type (as defined in Section 2) is represented by more than one image object, then each image object MUST contain variants of roughly the same visual content. Likewise, if a logotype of a certain type is represented by more than one audio object, then the audio objects MUST contain variants of the same audio information. A spoken message in different languages is considered a variation of the same audio information. When more than one image object or more than one audio object for the same logotype type is included in the certificate, the certificate issuer is responsible for ensuring that the objects contain roughly the same content. Compliant applications MUST NOT display more than one of the image objects and MUST NOT play more than one of the audio object for any logotype type (see Section 2) at the same time.¶

A client MAY simultaneously display multiple logotypes of different logotype types. For example, it may display one subject organization logotype while also displaying a community logotype, but it MUST NOT display multiple image variants of the same community logotype.¶

Each logotype present in a certificate MUST be represented by at least one image data object.¶

Client applications SHOULD enhance processing and off-line functionality by caching logotype data.¶

4. Logotype Extension

This section specifies the syntax and semantics of the logotype certificate extension.¶

   id-pe-logotype  OBJECT IDENTIFIER  ::=
      { iso(1) identified-organization(3) dod(6) internet(1)
        security(5) mechanisms(5) pkix(7) id-pe(1) 12 }

LogotypeExtn ::= SEQUENCE {
   communityLogos  [0] EXPLICIT SEQUENCE OF LogotypeInfo OPTIONAL,
   issuerLogo      [1] EXPLICIT LogotypeInfo OPTIONAL,
   subjectLogo     [2] EXPLICIT LogotypeInfo OPTIONAL,
   otherLogos      [3] EXPLICIT SEQUENCE OF OtherLogotypeInfo
                          OPTIONAL }

LogotypeInfo ::= CHOICE {
   direct          [0] LogotypeData,
   indirect        [1] LogotypeReference }

LogotypeData ::= SEQUENCE {
   image           SEQUENCE OF LogotypeImage OPTIONAL,
   audio           [1] SEQUENCE OF LogotypeAudio OPTIONAL }

LogotypeImage ::= SEQUENCE {
   imageDetails    LogotypeDetails,
   imageInfo       LogotypeImageInfo OPTIONAL }

LogotypeAudio ::= SEQUENCE {
   audioDetails    LogotypeDetails,
   audioInfo       LogotypeAudioInfo OPTIONAL }

LogotypeDetails ::= SEQUENCE {
   mediaType       IA5String, -- MIME media type name and optional
                              -- parameters
   logotypeHash    SEQUENCE SIZE (1..MAX) OF HashAlgAndValue,
   logotypeURI     SEQUENCE SIZE (1..MAX) OF IA5String }

LogotypeImageInfo ::= SEQUENCE {
   type            [0] LogotypeImageType DEFAULT color,
   fileSize        INTEGER,  -- In octets, 0=unspecified
   xSize           INTEGER,  -- Horizontal size in pixels
   ySize           INTEGER,  -- Vertical size in pixels
   resolution      LogotypeImageResolution OPTIONAL,
   language        [4] IA5String OPTIONAL }  -- RFC 5646 Language Tag

LogotypeImageType ::= INTEGER { grayScale(0), color(1) }

LogotypeImageResolution ::= CHOICE {
   numBits         [1] INTEGER,   -- Resolution in bits per pixel
   tableSize       [2] INTEGER }  -- Number of colors or grey tones

LogotypeAudioInfo ::= SEQUENCE {
   fileSize        INTEGER,  -- In octets, 0=unspecified
   playTime        INTEGER,  -- In milliseconds, 0=unspecified
   channels        INTEGER,  -- 0=unspecified,
                             -- 1=mono, 2=stereo, 4=quad
   sampleRate      [3] INTEGER OPTIONAL,  -- Samples per second
   language        [4] IA5String OPTIONAL }  -- RFC 5646 Language Tag

OtherLogotypeInfo ::= SEQUENCE {
   logotypeType    OBJECT IDENTIFIER,
   info            LogotypeInfo }

LogotypeReference ::= SEQUENCE {
   refStructHash   SEQUENCE SIZE (1..MAX) OF HashAlgAndValue,
   refStructURI    SEQUENCE SIZE (1..MAX) OF IA5String }
                    -- Places to get the same LogotypeData
                    -- image or audio object

HashAlgAndValue ::= SEQUENCE {
   hashAlg         AlgorithmIdentifier,
   hashValue       OCTET STRING }

   dataurl    := "data:" [ mediatype ] [ ";base64" ] "," data
   mediatype  := [ type "/" subtype ] *( ";" parameter )
   data       := *urlchar
   parameter  := attribute "=" value

   id-logo OBJECT IDENTIFIER ::= { id-pkix 20 }

   id-logo-loyalty    OBJECT IDENTIFIER ::= { id-logo 1 }

   id-logo-background OBJECT IDENTIFIER ::= { id-logo 2 }

   id-logo-certImage OBJECT IDENTIFIER ::= { id-logo 3 }

5. Type of Certificates

Logotypes MAY be included in public key certificates and attribute certificates at the discretion of the certificate issuer; however, the relying party MUST NOT use the logotypes as part of certification path validation or automated trust decision. The sole purpose of logotypes is to enhance the display of a particular certificate, regardless of its position in a certification path.¶

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 certification path is successfully validated, the replying party trusts 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. If the client is unable to support a provided logotype, the client MUST NOT report an error, rather the client MUST behave as though no logotype extension was included in the certificate. Current standards do not provide any mechanism for cross-certifying CAs to constrain subordinate CAs from including private extensions (see Section 9).¶

Consequently, if relying party software accepts a CA, then it should be prepared to (unquestioningly) display the associated logotypes to its human user, given that it is configured to do so. Information about the logotypes is provided so that the replying party software can select the one that will best meet the needs of the human user. This choice depends on the abilities of the human user, as well as the capabilities of the platform on which the replaying party software is running. If none of the provided logotypes meets the needs of the human user or matches the capabilities of the platform, then the logotypes can be ignored.¶

A client MAY, subject to local policy, choose to display none, one, or any number of the logotypes in the logotype extension. In many cases, a client will be used in an environment with a good network connection and also used in an environment with little or no network connectivity. For example, a laptop computer can be docked with a high-speed LAN connection, or it can be disconnected from the network altogether. In recognition of this situation, the client MUST include the ability to disable the fetching of logotypes. However, locally cached logotypes can still be displayed when the user disables the fetching of additional logotypes.¶

A client MAY, subject to local policy, choose any combination of audio and image presentation for each logotype. That is, the client MAY display an image with or without playing a sound, and it MAY play a sound with or without displaying an image. A client MUST NOT play more than one logotype audio sequence at the same time.¶

The logotype is to be displayed in conjunction with other identity information contained in the certificate. The logotype is not a replacement for this identity information.¶

Care is needed when designing replying party software to ensure that an appropriate context of logotype information is provided. This is especially difficult with audio logotypes. It is important that the human user be able to recognize the context of the logotype, even if other audio streams are being played.¶

If the relying party software is unable to successfully validate a particular certificate, then it MUST NOT display any logotype data associated with that certificate.¶

7. Image Formats

Animated images SHOULD NOT be used.¶

The following table lists many common image formats and their corresponding MIME type. The table also indicates the support requirements for these image formats. The filename extensions commonly used for each of these formats is also provided. Implementations MAY support other image formats.¶

NOTE: The image/svg+xml-compressed media type is widely implemented, but it has not yet been registered with IANA.¶

When a Scalable Vector Graphics (SVG) image is used, whether the image is compressed or not, the SVG Tiny profile [SVGT] MUST be followed, with these additional restrictions:¶

• The SVG image MUST NOT contain any Internationalized Resource Identifier (IRI) references to information stored outside of the SVG image of type B, C, or D, according to Section 14.1.4 of [SVGT].¶
• The SVG image MUST NOT contain any 'script' element, according to Section 15.2 of [SVGT].¶
• The XML structure in the SVG file MUST use linefeed (0x0A) as the end-of-line (EOL) character when calculating a hash over the SVG image.¶

When a GZIP-compressed SVG image is fetched with HTTP, the client will receive a response that includes these headers:¶

   Content-Type: image/svg+xml
   Content-Encoding: gzip

In this case, the octet stream of type image/svg+xml is compressed with GZIP [RFC1952] as specified in [SVGR].¶

When a uncompressed SVG image is fetched with HTTP, the client will receive a response with the same Content-Type header, but no Content-Encoding header.¶

Whether the SVG image is GZIP-compressed or uncompressed, the hash value for the SVG image is calculated over the uncompressed SVG content with canonicalized EOL characters as specified above.¶

When a SVG image is embedded in the certificate extension using the "data" URL scheme, the SVG image data MUST be provided in GZIP-compressed form, and the XML structure, prior to compression, SHOULD use linefeed (0x0A) as the end-of-line (EOL) character.¶

When a bitmapped image is used, the PNG [ISO15948] format SHOULD be used.¶

When a Portable Document Format (PDF) document according to [ISO32000] is used, it MUST also be formatted according to the profile PDF/A [ISO19005].¶

8. Audio Formats

Implementations that support audio MUST support the MP3 audio format [MP3] with a MIME type of "audio/mpeg" [RFC3003]. Implementations SHOULD support text-based audio data with a MIME type of "text/plain;charset=UTF-8". Implementations MAY support other audio formats.¶

Text-based audio data using the MIME type of "text/plain;charset=UTF-8" is intended to be used by text-to-speech software. When this audio type is used, the following requirements apply:¶

• LogotypeAudioInfo MUST be present and specify the language of the text.¶
• The fileSize, playTime, and channels elements of LogotypeAudioInfo MUST have the value of 0.¶
• The sampleRate element of LogotypeAudioInfo MUST be absent.¶

9. Security Considerations

Implementations that simultaneously display multiple logotype types (subject organization, issuer, community, or other), MUST ensure that there is no ambiguity as to the binding between the image and the type of logotype that the image represents. "Logotype type" is defined in Section 1.1, and it refers to the type of entity or affiliation represented by the logotype, not the of binary format of the image or audio.¶

Logotypes are very difficult to securely and accurately 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 an entire legal structure around this 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 can be difficult (and sometimes expensive) to verify, the possibility of errors related to assigning wrong logotypes to organizations is increased.¶

This is not a new issue for electronic identification instruments. It is already dealt with in a number of similar situations in the physical world, including physical employee identification cards. In addition, 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.¶

It is impossible to prevent fraudulent creation of certificates by dishonest or badly performing issuers, containing names and logotypes that the issuer has no claim to or has failed to check correctly. Such certificates could be created in an attempt to socially engineer a user into accepting a certificate. The premise used for the logotype work is thus that logotype graphics in a certificate are trusted only if the certificate is successfully validated within a valid path. It is thus imperative that the representation of any certificate that fails to validate is not enhanced in any way by using the logotype data.¶

This underlines the necessity for CAs to provide reliable services, and the relying party's responsibility and need to carefully select which CAs are trusted to provide public key certificates.¶

This also underlines the general necessity for relying parties to use up-to-date software libraries to render or dereference data from external sources, including logotype data in certificates, to minimize risks related to processing potentially malicious data before it has been adequately verified and validated. Implementers should review the guidance in Section 7 of [RFC3986].¶

Referenced image objects are hashed in order to bind the image to the signature of the certificate. Some image types, such as SVG, allow part of the image to be collected from an external source by incorporating a reference to an external file that contains the image. If this feature were used within a logotype image, the hash of the image would only cover the URI reference to the external image file, but not the referenced image data. Clients SHOULD verify that SVG images meet all requirements listed in Section 7 and reject images that contain references to external data.¶

CAs issuing certificates with embedded logotype images should be cautious when accepting graphics from the certificate requestor for inclusion in the certificate if the hash algorithm used to sign the certificate is vulnerable to collision attacks. In such a case, the accepted image may contain data that could help an attacker to obtain colliding certificates with identical certificate signatures.¶

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

Certificate path processing as defined in [RFC5280] does not constrain the inclusion of logotype data in certificates. A parent CA can constrain certification path validation such that subordinate CAs cannot issue valid certificates to end-entities outside a limited name space or outside specific certificate polices. A malicious CA can comply with these name and policy requirements and still include inappropriate logotypes in the certificates that it issues. These certificates will pass the certification path validation algorithm, which means the client will trust the logotypes in the certificates. Since there is no technical mechanism to prevent or control subordinate CAs from including 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.¶

When a relying party fetches remote logotype data, a mismatch between the media type provided in the mediaType field of the LogotypeDetails and the Content-Type HTTP header of the retrieved object MUST be treated as a failure and the fetched logotype data should not be presented to the user. However, if more than one location for the remote logotype data is provided in the certificate extension, the relying party MAY try to fetch the remote logotype data from an alternate location to resolve the failure.¶

When a subscriber requests the inclusion of remote logotype data in a certificate, the CA cannot be sure that any logotype data will be available at the provided URI for the entire validity period of the certificate. To mitigate this concern, the CA may provide the logotype data from a server under its control, rather than a subscriber-controlled server.¶

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

• Contractual agreements of suitable behavior, including terms of liability in case of material breach.¶
• Control mechanisms and procedures to monitor and follow the behavior of subordinate CAs, including Certificate Transparency [RFC9162].¶
• Use of certificate policies to declare an 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.¶

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

10. Privacy Considerations

Certificates are commonly public objects, so the inclusion of privacy-sensitive information in certificates should be avoided. The more information that is included in a certificate, the greater the likelihood that the certificate will reveal privacy-sensitive information. The inclusion of logotype data needs to be considered in this context.¶

Logotype data might be fetched from a server when it is needed. By watching activity on the network, an observer can determine which clients are making use of certificates that contain particular logotype data. Since clients are expected to locally cache logotype data, network traffic to the server containing the logotype data will not be generated every time the certificate is used. Further, when logotype data is not cached, activity on the network would reveal certificate usage frequency. Even when logotype data is cached, regardless of whether direct or indirect addressing is employed, network traffic monitoring could reveal when logotype data is fetched for the first time. Implementations MAY encrypt fetches of logotype data using HTTPS and pad them to a common size to reduce visibility into the data that is being fetched. Likewise, servers MAY reduce visibility into the data that is being returned by encrypting with HTTPS and padding to a few common sizes.¶

Similarly, when fetching logotype data from a server, the server operator can determine which clients are making use of certificates that contain particular logotype data. As above, locally caching logotype data will eliminate the need to fetch the logotype data each time the certificate is used, and lack of caching would reveal usage frequency. Even when implementations cache logotype data, regardless of whether direct or indirect addressing is employed, the server operator could observe when logotype data is fetched for the first time.¶

In addition, the use of an encrypted DNS mechanism, such as DoT [RFC7858] or DoH [RFC9230], hide the name resolution traffic associated fetching remote logotype objects.¶

When the "data" URI scheme is used with direct addressing, there is no network traffic to fetch logotype data, which avoids the observations of network traffic or server operations described above. To obtain this benefit, the certificate will be larger than one that contains a URL. Due to the improved privacy posture, the "data" URI scheme with direct addressing will be the only one that is supported by some CAs. Privacy-aware certificate subscribers MAY wish to insist on their logotype data being embedded in the certificate with the "data" URI scheme with direct addressing.¶

In cases where logotype data is cached by the relying party, the cache index should include the hash values of the associated logotype data with the goal of fetching the logotype data only once, even when it is referenced by multiple URIs. The index should include hash values for all supported hash algorithms. The cached data should include the media type as well as the logotype data. Implementations should give preference to logotype data that is already in the cache when multiple alternatives are offered in the LogotypeExtn certificate extension.¶

When the "data" URI scheme is used, the relying party MAY add the embedded logotype data to the local cache, which could avoid the need to fetch the logotype data if it is referenced by a URL in another certificate.¶

When fetching remote logotype data, relying parties should use the most privacy-preserving options that are available to minimize the opportunities for servers to "fingerprint" clients. For example, avoid cookies, e-tags, and client certificates.¶

When a relying party encounters a new certificate, the lack of network traffic to fetch logotype data might indicate that a certificate with references to the same logotype data has been previously processed and cached.¶

TLS 1.3 [RFC8446] includes the ability to encrypt the server's certificate in the TLS handshake, which helps hide the server's identity from anyone that is watching activity on the network. If the server's certificate includes remote logotype data, the client fetching that data might disclose the otherwise protected server identity.¶

11. IANA Considerations

For the new ASN.1 Module in Appendix A.2, IANA is requested to assign an object identifier (OID) for the module identifier. The OID for the module should be allocated in the "SMI Security for PKIX Module Identifier" registry (1.3.6.1.5.5.7.0).¶

12. Acknowledgments

Appendix A. ASN.1 Modules

<CODE BEGINS>
LogotypeCertExtn
  { iso(1) identified-organization(3) dod(6) internet(1)
    security(5) mechanisms(5) pkix(7) id-mod(0)
    id-mod-logotype(22) }

DEFINITIONS IMPLICIT TAGS ::=
BEGIN

IMPORTS
   AlgorithmIdentifier FROM PKIX1Explicit88 -- RFC 5280
     { iso(1) identified-organization(3) dod(6) internet(1)
       security(5) mechanisms(5) pkix(7) id-mod(0)
       id-pkix1-explicit(18) };

-- Logotype Extension OID

id-pe-logotype  OBJECT IDENTIFIER  ::=
   { iso(1) identified-organization(3) dod(6) internet(1)
     security(5) mechanisms(5) pkix(7) id-pe(1) 12 }


-- Logotype Extension Syntax

LogotypeExtn ::= SEQUENCE {
   communityLogos  [0] EXPLICIT SEQUENCE OF LogotypeInfo OPTIONAL,
   issuerLogo      [1] EXPLICIT LogotypeInfo OPTIONAL,
   subjectLogo     [2] EXPLICIT LogotypeInfo OPTIONAL,
   otherLogos      [3] EXPLICIT SEQUENCE OF OtherLogotypeInfo
                          OPTIONAL }

-- Note: At least one of the OPTIONAL components MUST be present

LogotypeInfo ::= CHOICE {
   direct          [0] LogotypeData,
   indirect        [1] LogotypeReference }

LogotypeData ::= SEQUENCE {
   image           SEQUENCE OF LogotypeImage OPTIONAL,
   audio           [1] SEQUENCE OF LogotypeAudio OPTIONAL }

-- Note: At least one of the OPTIONAL components MUST be present

LogotypeImage ::= SEQUENCE {
   imageDetails    LogotypeDetails,
   imageInfo       LogotypeImageInfo OPTIONAL }

LogotypeAudio ::= SEQUENCE {
   audioDetails    LogotypeDetails,
   audioInfo       LogotypeAudioInfo OPTIONAL }

LogotypeDetails ::= SEQUENCE {
   mediaType       IA5String, -- MIME media type name and optional
                              -- parameters
   logotypeHash    SEQUENCE SIZE (1..MAX) OF HashAlgAndValue,
   logotypeURI     SEQUENCE SIZE (1..MAX) OF IA5String }

LogotypeImageInfo ::= SEQUENCE {
   type            [0] LogotypeImageType DEFAULT color,
   fileSize        INTEGER,  -- In octets, 0=unspecified
   xSize           INTEGER,  -- Horizontal size in pixels
   ySize           INTEGER,  -- Vertical size in pixels
   resolution      LogotypeImageResolution OPTIONAL,
   language        [4] IA5String OPTIONAL }  -- RFC 5646 Language Tag

LogotypeImageType ::= INTEGER { grayScale(0), color(1) }

LogotypeImageResolution ::= CHOICE {
   numBits         [1] INTEGER,   -- Resolution in bits per pixel
   tableSize       [2] INTEGER }  -- Number of colors or grey tones

LogotypeAudioInfo ::= SEQUENCE {
   fileSize        INTEGER,  -- In octets, 0=unspecified
   playTime        INTEGER,  -- In milliseconds, 0=unspecified
   channels        INTEGER,  -- 0=unspecified,
                             -- 1=mono, 2=stereo, 4=quad
   sampleRate      [3] INTEGER OPTIONAL,  -- Samples per second
   language        [4] IA5String OPTIONAL }  -- RFC 5646 Language Tag

OtherLogotypeInfo ::= SEQUENCE {
   logotypeType    OBJECT IDENTIFIER,
   info            LogotypeInfo }

LogotypeReference ::= SEQUENCE {
   refStructHash   SEQUENCE SIZE (1..MAX) OF HashAlgAndValue,
   refStructURI    SEQUENCE SIZE (1..MAX) OF IA5String }
                    -- Places to get the same LogotypeData
                    -- image or audio object

-- Note: The referenced LogotypeData binary file contains a
--       DER-encoded LogotypeData type

HashAlgAndValue ::= SEQUENCE {
   hashAlg         AlgorithmIdentifier,
   hashValue       OCTET STRING }

-- Other logotype type OIDs

id-logo OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
   dod(6) internet(1) security(5) mechanisms(5) pkix(7) 20 }

id-logo-loyalty    OBJECT IDENTIFIER ::= { id-logo 1 }

id-logo-background OBJECT IDENTIFIER ::= { id-logo 2 }

END


CERT-IMAGE-MODULE { iso(1) identified-organization(3) dod(6)
    internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
    id-mod-logotype-certimage(68) }

DEFINITIONS EXPLICIT TAGS ::=
BEGIN

EXPORTS ALL;   -- export all items from this module

id-logo-certImage  OBJECT IDENTIFIER  ::=
   { iso(1) identified-organization(3) dod(6) internet(1)
     security(5) mechanisms(5) pkix(7) id-logo(20) 3 }

END

<CODE ENDS>

<CODE BEGINS>
LogotypeCertExtn
  { iso(1) identified-organization(3) dod(6) internet(1)
    security(5) mechanisms(5) pkix(7) id-mod(0)
    id-mod-logotype(TBD) }

DEFINITIONS IMPLICIT TAGS ::=
BEGIN

IMPORTS
  EXTENSION
  FROM PKIX-CommonTypes-2009  -- RFC 5912
    { iso(1) identified-organization(3) dod(6) internet(1)
      security(5) mechanisms(5) pkix(7) id-mod(0)
      id-mod-pkixCommon-02(57) }

  AlgorithmIdentifier{}, DIGEST-ALGORITHM
  FROM AlgorithmInformation-2009
    { iso(1) identified-organization(3) dod(6) internet(1)
      security(5) mechanisms(5) pkix(7) id-mod(0)
      id-mod-algorithmInformation-02(58) } ;


-- Logotype Extension

ext-logotype EXTENSION ::= {
   SYNTAX LogotypeExtn
   IDENTIFIED BY id-pe-logotype }

-- Logotype Extension OID

id-pe-logotype  OBJECT IDENTIFIER  ::=
   { iso(1) identified-organization(3) dod(6) internet(1)
     security(5) mechanisms(5) pkix(7) id-pe(1) 12 }

-- Logotype Extension Syntax

LogotypeExtn ::= SEQUENCE {
   communityLogos  [0] EXPLICIT SEQUENCE OF LogotypeInfo OPTIONAL,
   issuerLogo      [1] EXPLICIT LogotypeInfo OPTIONAL,
   subjectLogo     [2] EXPLICIT LogotypeInfo OPTIONAL,
   otherLogos      [3] EXPLICIT SEQUENCE OF OtherLogotypeInfo
                          OPTIONAL }
      -- At least one of the OPTIONAL components MUST be present
      ( WITH COMPONENTS { ..., communityLogos PRESENT } |
        WITH COMPONENTS { ..., issuerLogo PRESENT } |
        WITH COMPONENTS { ..., subjectLogo PRESENT } |
        WITH COMPONENTS { ..., otherLogos PRESENT } )

LogotypeInfo ::= CHOICE {
   direct          [0] LogotypeData,
   indirect        [1] LogotypeReference }

LogotypeData ::= SEQUENCE {
   image           SEQUENCE OF LogotypeImage OPTIONAL,
   audio           [1] SEQUENCE OF LogotypeAudio OPTIONAL }
      -- At least one image component MUST be present
      ( WITH COMPONENTS { ..., image PRESENT } )

LogotypeImage ::= SEQUENCE {
   imageDetails    LogotypeDetails,
   imageInfo       LogotypeImageInfo OPTIONAL }

LogotypeAudio ::= SEQUENCE {
   audioDetails    LogotypeDetails,
   audioInfo       LogotypeAudioInfo OPTIONAL }

LogotypeDetails ::= SEQUENCE {
   mediaType       IA5String, -- MIME media type name and optional
                              -- parameters
   logotypeHash    SEQUENCE SIZE (1..MAX) OF HashAlgAndValue,
   logotypeURI     SEQUENCE SIZE (1..MAX) OF IA5String }

LogotypeImageInfo ::= SEQUENCE {
   type            [0] LogotypeImageType DEFAULT color,
   fileSize        INTEGER,  -- In octets, 0=unspecified
   xSize           INTEGER,  -- Horizontal size in pixels
   ySize           INTEGER,  -- Vertical size in pixels
   resolution      LogotypeImageResolution OPTIONAL,
   language        [4] IA5String OPTIONAL }  -- RFC 5646 Language Tag

LogotypeImageType ::= INTEGER { grayScale(0), color(1) }

LogotypeImageResolution ::= CHOICE {
   numBits         [1] INTEGER,   -- Resolution in bits
   tableSize       [2] INTEGER }  -- Number of colors or grey tones

LogotypeAudioInfo ::= SEQUENCE {
   fileSize        INTEGER,  -- In octets, 0=unspecified
   playTime        INTEGER,  -- In milliseconds, 0=unspecified
   channels        INTEGER,  -- 0=unspecified
                             -- 1=mono, 2=stereo, 4=quad
   sampleRate      [3] INTEGER OPTIONAL,  -- Samples per second
   language        [4] IA5String OPTIONAL }  -- RFC 5646 Language Tag

OtherLogotypeInfo ::= SEQUENCE {
   logotypeType    OBJECT IDENTIFIER,
   info            LogotypeInfo }

LogotypeReference ::= SEQUENCE {
   refStructHash   SEQUENCE SIZE (1..MAX) OF HashAlgAndValue,
   refStructURI    SEQUENCE SIZE (1..MAX) OF IA5String }
                    -- Places to get the same LogotypeData
                    -- image or audio object

-- Note: The referenced LogotypeData binary file contains a
--       DER-encoded LogotypeData type

HashAlgAndValue ::= SEQUENCE {
   hashAlg         AlgorithmIdentifier{DIGEST-ALGORITHM, {...}},
   hashValue       OCTET STRING }

-- Other logotype type OIDs

id-logo OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
   dod(6) internet(1) security(5) mechanisms(5) pkix(7) 20 }

id-logo-loyalty    OBJECT IDENTIFIER ::= { id-logo 1 }

id-logo-background OBJECT IDENTIFIER ::= { id-logo 2 }

id-logo-certImage  OBJECT IDENTIFIER  ::= { id-logo 3 }

END

<CODE ENDS>

Appendix B. Examples

30 106: SEQUENCE {
06   8:  OBJECT IDENTIFIER logotype (1 3 6 1 5 5 7 1 12)
04  94:  OCTET STRING, encapsulates {
30  92:   SEQUENCE {
A1  90:    [1] {
A0  88:     [0] {
30  86:      SEQUENCE {
30  84:       SEQUENCE {
30  82:        SEQUENCE {
16   9:         IA5String 'image/gif'
30  33:         SEQUENCE {
30  31:          SEQUENCE {
30   7:           SEQUENCE {
06   5:            OBJECT IDENTIFIER sha1 (1 3 14 3 2 26)
      :             }
04  20:           OCTET STRING
      :            8F E5 D3 1A 86 AC 8D 8E 6B C3 CF 80 6A D4 48 18
      :            2C 7B 19 2E
      :            }
      :           }
30  34:         SEQUENCE {
16  32:          IA5String 'http://logo.example.com/logo.gif'
      :           }
      :          }
      :         }
      :        }
      :       }
      :      }
      :     }
      :    }
      :   }

30 124: SEQUENCE {
06   8:  OBJECT IDENTIFIER logotype (1 3 6 1 5 5 7 1 12)
04 112:  OCTET STRING, encapsulates {
30 110:   SEQUENCE {
A1 108:    [1] {
A0 106:     [0] {
30 104:      SEQUENCE {
30 102:       SEQUENCE {
30 100:        SEQUENCE {
16  10:         IA5String 'image/jpeg'
30  49:         SEQUENCE {
30  47:          SEQUENCE {
30  11:           SEQUENCE {
06   9:            OBJECT IDENTIFIER
      :             sha-256 (2 16 840 1 101 3 4 2 1)
      :             }
04  32:           OCTET STRING
      :            1E 8F 96 FD D3 50 53 EF C6 1C 9F FC F0 00 2E 53
      :            B4 9C 24 9A 32 C5 E9 0C 2C 39 39 D3 AD 6D A9 09
      :            }
      :           }
30  35:         SEQUENCE {
16  33:          IA5String 'http://logo.example.com/logo.jpeg'
      :           }
      :          }
      :         }
      :        }
      :       }
      :      }
      :     }
      :    }
      :   }

30 2160: SEQUENCE {
06    8:  OBJECT IDENTIFIER logotype (1 3 6 1 5 5 7 1 12)
04 2146:  OCTET STRING, encapsulates {
30 2142:   SEQUENCE {
A2 2138:    [2] {
A0 2134:     [0] {
30 2130:      SEQUENCE {
30 2126:       SEQUENCE {
30 2122:        SEQUENCE {
16   24:         IA5String 'image/svg+xml-compressed'
30   49:         SEQUENCE {
30   47:          SEQUENCE {
30   11:           SEQUENCE {
06    9:            OBJECT IDENTIFIER
       :             sha-256 (2 16 840 1 101 3 4 2 1)
       :             }
04   32:           OCTET STRING
       :           C5 AC 94 1A 0A 25 1F B3 16 6F 97 C5 52 40 9B 49
       :           9E 7B 92 61 5A B0 A2 6C 19 BF B9 D8 09 C5 D9 E7
       :            }
       :           }
30 2041:         SEQUENCE {
16 2037:          IA5String
       :          'data:image/svg+xml-compressed;base64,H4sICIGpy2E'
       :          'AA2xvZ28tY29weS5zdmcApVbbbhs3EH3nV0y3Lw2Q9fK2JLe'
       :          'wHDROUBRo2iBxW+RRlTa2UFkypIWV5ut7zlB2UqF9cuLlUkt'
       :          'yLmfOzPD8xafbtdyPu/1qu5k17sw2sp/mm+V8vd2Ms2azbV5'
       :          'cmPNvXv16efXh7WvZ31/L299e/vzTpTRt1/0RLrvu1dUref/'
       :          '7j+KtdXawsete/9IYaW6m6e77rjscDmeHcLbdXXdX7zpu6t6'
       :          '9vmxxon08AREdRDt7tpyWDRRSz7+tgp2b/ew/hEKI5WGoPKy'
       :          'W082s8SmeWf13NzVyM66ub6ZZk+xXH+9X4+Hl9tOssWLly35'
       :          '53ARpd7txP+7uxx/2d+NiejefVttZ8+nNavkBj9yO40RLb8d'
       :          'pvpxP8wtzuRvn07iUP/+Wu+20my9GcWfOPpfDbjVN44YLb8d'
       :          'p3Mn7cb3aXGNCAICCc+a8+yLo/FpwfLP/uN3dzhqdriH5uwf'
       :          'bnj9a+Uz2i/maK66utA+zZ435uFqvZ823R38Q1t32Lw3pZqT'
       :          'hd/PpRpaz5o2LNkocvCzaIm0vrQvSpog359lLy3my0ga+e3H'
       :          'p+B4InjVFPD9awdhnrGEFW30Sl/Pnpvta2QBVxUEVxFbJ2VU'
       :          'FfYC01pUs+O4GK84V/k6CHUFyhvhiDVQF8Y5aPDbmnsrXbS7'
       :          '4DANjguwgENZLPwjUYVTRJQgEpiLR0ctiWj+Ig8rCvZAArxK'
       :          'ExEEWMJLqMA1F+ggnsQDXgpQeomJPCVhtCRycNrAWxgAI+g1'
       :          'Qsr6IUxlomBswjydYBEgOeVCDoRreBjiFjX2SdSA60BP5DgQ'
       :          'M63xoPlWHbNq+egAEeAzxyNAdCQz+sDEMOhaGisKJdSlS6gt'
       :          'WWm4M1rQwP0egEBIhhFLoXuCJhR4mT5RJBaiLKqqFROUEzYr'
       :          '1idG0gahwCzEnk+AMJLdp0FevQQ6VZ+SKOwGlOIJOh1MVjo0'
       :          'eB6DRA10SRpSY6il/eFFKAm+MKSIWNFqSo4OFnORfwH5wJHC'
       :          'MNM0qlDRlcIwUEkDlgiSBhiEpBgMKOx5FdAYqI3KYewKKkAI'
       :          'tTABTkp5khI86kgbOgRywEBR0VGcwAjf8t9wqvdUMG6gLAbI'
       :          '0QQ8CbzCTtCSn/DEhCbm++duQaiRG1mQkdWHnminHA+r5wpL'
       :          'vsJbCALUKsDW5NAj43J+AD5vpfamUzJqiRJACmCWwIMhQq4H'
       :          'mYGKaiiJPmIvpS80UzTtAjdSraApQZogslgFcJHw0y5WoEXD'
       :          'Yr/aTqfxk2qhcg3z6ETQL+S18llvHOZQvlEOVEVpzqCozE9V'
       :          '6JZhh/lCslg7mUFY4AR7IlcApmgV6gz3DCSDe56fQ0SRS7el'
       :          '0NJWO8mQ6mkc6ylPpaL7QUZ5IR/M/dEwoJiEp+L6iT4cdSyI'
       :          'p4ljDkoaZpQlgMoz0ApahjTiTWbZYu9v+MUqVjY61j2Bxr68'
       :          'bPF3uS1232qAyAQDMhr4MRyVZq5l2QcuwgY/oTozbgoIKycH'
       :          '+yQxhzQsPJQ/ne9OmRKvYH1AeKA/EQRtzrmaYUiHUhpJOW4b'
       :          'reSaxZ/TVc3ZAQJKOagAJiw6pRHVkBMIBa5E+SUMWi0ZNW1R'
       :          'fn/xQXywHXyMHN5G8WF6gZ2IVjANHMIJQ1lAJQE8MJjZHJiU'
       :          'tQZAWzmkisDywTVWSqLkkQG2NNB3wwyaerqRGLNKpvwUOhaQ'
       :          'FiYcqviSjvp1n8WnRRzXFs9IXDxiiDd8HU/ROoAGn9+QgTPE'
       :          'Vu6HaN6i0VPuv1SCzwyZeHwBA1EjFYoAk2jJ3OFeJ5Gp1E+3'
       :          'Dlf3Aj70bbvmag5oyKHunVyGPq6+EnvTua/JUn3iadMHlqUa'
       :          'psK2T8SwCBJUF1JnEmhu0ntBthJoQpZqumsBk5mA1hRc0LR5'
       :          'ZFerdjksaCqt3IUWXcXW16vb6xdWyHLTgCaKXWKUKK1kOp9H'
       :          'K5B3ELjSdXb0loB5RYtS01L6h9yTPW51Wpqwgosr5I927aw6'
       :          '401+YfwDria4WoQwAAA=='
       :           }
       :          }
       :         }
       :        }
       :       }
       :      }
       :     }
       :    }
       :   }

30 2914: SEQUENCE {
06    8:  OBJECT IDENTIFIER logotype (1 3 6 1 5 5 7 1 12)
04 2900:  OCTET STRING, encapsulates {
30 2896:   SEQUENCE {
A3 2892:    [3] {
30 2888:     SEQUENCE {
30 2884:      SEQUENCE {
06    8:       OBJECT IDENTIFIER '1 3 6 1 5 5 7 20 3'
A0 2870:       [0] {
30 2866:        SEQUENCE {
30 2862:         SEQUENCE {
30 2858:          SEQUENCE {
16   24:           IA5String 'image/svg+xml-compressed'
30   49:           SEQUENCE {
30   47:            SEQUENCE {
30   11:             SEQUENCE {
06    9:              OBJECT IDENTIFIER
       :               sha-256 (2 16 840 1 101 3 4 2 1)
       :               }
04   32:             OCTET STRING
       :           83 14 B3 26 9B D3 8B 0B 2A E6 6E 42 74 E2 A7 57
       :           7A 40 B7 E1 2E 53 42 44 CC 7C AE 14 68 1B 0E B6
       :              }
       :             }
30 2777:           SEQUENCE {
16 2773:            IA5String
       :          'data:image/svg+xml-compressed;base64,H4sICLXutU0'
       :          'AA0NlcnRJbWFnZURlbW8uc3ZnANVaW2/bOBZ+n19BqBigwdo'
       :          'S7xK9jmeapB0EWHQHzez2WZZoR1tZMiQ5jvvr95CSL7Gl1Em'
       :          '8C9d9iERSPOd85+O5EB3+9jhL0YMuyiTPLh3iYgfpLMrjJJt'
       :          'eOv/661M/cFBZhVkcpnmmL50sd34b/TIsH6YoiS+da11UySS'
       :          'Jwkqj21k41Q6CDbNyUMSTS+e+quYDz1sul+6SuXkx9YhSysP'
       :          'Uo7QPK/rlKqvCx35Wvmu+a/uGYow9EOigh0Qvr/LHSwcjjDj'
       :          'GiGHQ914n0/sKlMf4Vwctk7i6X7/sGEYdNA5L/WeRT5IUDKm'
       :          'SbLVWNoo2cqNCh1XyoKN8Nsuz0iqwVW8Qb1fOF0Vqp+PI06m'
       :          'e6awqPeISzxn9goYzXYVxWIUWpfWLCMwcGoLpgy83n8wzGkb'
       :          'R4GtefENmMBznC7DEroKpOBpM8mIWVqPEYGtA+BvoMfS2E5u'
       :          'F1Wqu7R6FLvNFEelWReNolpiV3l2VpGntMW9nk6RKdf0+9Br'
       :          'FrMbeVuWhtzbHvMR6UlobPyVpBWjXBk7six2vH5nCwY6nXCo'
       :          '5xb7YusvFVPqCOGh16fSxSxglmPkScLfvmDDmC4FlDc1wov8'
       :          'IF2WZhNlVumgEPRliimDD3PhGPyTgUUMC6lKqKAjxaptq1bo'
       :          'UJvQFsvi+LOJyxZkPE/vCwHuAmXmoj1AarnRBatzqkbv7cK5'
       :          'Ls2ORfwM/vsOG5lURZqXxOnDXPKZw5t5jVzIhFKO0B6D6hAR'
       :          'SXDR6Fzqq7H7mQeJAOQiUSPvFIrUHOfuui3zrFI5dYVeAmpc'
       :          'OcOb9u63vLjae4kYX4yRifYPrTa2SlMigYdO+cEWeGADMLZL'
       :          'H96SH4R9xRYApl6q3Y02f+NzlRAl+cZSKhB6qSIVa80fsqMn'
       :          'WOqZJpmsXwAPoyNaQ95uNIGasKPwhxGzQzOXzMIIzBKabmLI'
       :          'il470zfSjWWn+kvpvLQ9g1l3yRIc8gukz0uysEcakcDfy3KM'
       :          'k+l0SOXlOopltJL7EPtUlzZfP4tnM70k8xkKCySt92MwfIXP'
       :          'oTe0pnu4dYbp7hJ/kxWySN0ey0o/1qbiCsxDXJMWWo37QekB'
       :          'cAUFPSGkPCnUJF5wwBacDK5cGlEp4BC2lYoJcrNNGVc7DzIq'
       :          'xT4CKsPlrAG8mL8whRejiQe9EmImIAoz3sds9NxP4RZEzugq'
       :          'zb7c3Q89u3WQKY9aegbsA/AUJB/bJs6pfJt9BHFEuk5DWITz'
       :          'OH5uZSThLUsDjQ5GE6RMsyihMTaQLfA6BIiAQMAhnHHN1sd6'
       :          '1WtUhDVJiuhkrdBXd740+hLB9Vm1HjQe4ywLOBLWOMMiyQAX'
       :          'NB8sm9Gx2qdGgGkMG6wY8aLfqgH4dfnmrVc+pPrE/Z/QnZOs'
       :          '8C1Okb2/ggwLdxlDC1D6DFPZDD98txv8xQf5TEc7Ax6ZyaDf'
       :          '6BC4SylWKCMqtizp80+UMchATal63qHq0M3ZTs83Ob/XO6LY'
       :          'sFzpGVY5+iLxdWvwY+NaKoR/0iJIXL3dBjT2hG+wO+NXm53X'
       :          'StSh1eogfeojV35BTOaqh/cmPUe2Mdp91pQp2CjWOO2k7Oam'
       :          'hjU1HB3DLGm66n6iajz4bqn2oICmNFxDR/x2mC5s+rKhlkUA'
       :          '3Ne3P8lgP0qJfjf9uvu+HWXSfFwNoH4uqGUmTadYMtOc7yjE'
       :          'Ed9EUhkwEEOcDSHKQ+yhnSvUYRH8miQo2FK5TCjWZZGWKB8i'
       :          'HPud16wApnCvTOzjIFAj9TQdCxa+ddOTizaa1xJvD0qMrKx+'
       :          'Ydaj6iwJQG0vaSdYWpTv4HwVRAP3Z6ONjOJunEIeKRVmhujp'
       :          'A2+wPmQR9WFQAFhh9bGQzFEXX+WwOnXq8pV35P2Acdn0pGeb'
       :          'cMg7OgQKaEdOKEAkFlk/9HuEKGBVwucc4AjnJ/LBYU09hVwW'
       :          'Y1F0HlBUC2lbyIuYF58O8p+adMwUt9YAoX/IwRtAC9NAdBAy'
       :          'GuEB3VR59u8/TGYx9/Xjz8bPB/Z/F9B0SghBK+4xxfiwtr0G'
       :          'XECqedQQ9PRVpEAQ+26MidbGSmPm8RwRzcQsT17EPSmoorH3'
       :          '+av4Jcj78O/vIp/uzMEkHKAE6/F7VHHSj8HddR0Q3ymcGZfR'
       :          'VjwfmOnNn3GuWR+FzhcPmPqiptHcayacT28T8j3Cs0/LQCwo'
       :          '6J2iYxP4R58AsobjFegusoJhuq7VNS2evRPcqASvQki+gbkB'
       :          'YwETNPt/1A2pT6UErR1zMzUITZRvF5Lp5basO1fk2U4aBSjk'
       :          'ji8quL3cDyW7TpI3unxezMcSTNhQJhfpGctKgKN2Amo7/7Sh'
       :          'Sev4oXicPSYS+6GkCm9a1Qw3VEchCUA+z5HtTcbQhK6F14YF'
       :          'Up+Yn7WgmzwpZCDf5DDiXT9B7U6RdHAHpdb7IqmLVjqZSLnT'
       :          'W61zjQ7/G7D3hm9E846uTDZoNMADmLlm7IG2ieXfUtu1US9T'
       :          'eNGUHibE9Nv//2jRJGZfQmK3v7ykJJOv1IXjBsDCPpmgWppe'
       :          '6sHxR3KVSQKqp+WIqammuJbtqkxZmMHry4oS/9pLhdCXKq8u'
       :          'R0R+LDEqCKRxqc5VXdvPvIP+ggwR0RkyBfO9iKZvrWGAKVdz'
       :          '31cuocvoO/qemClFMYEFEH7oI+vpkek4s4bCMBqK+5mHQUlD'
       :          'pE/oylpy+2/6pWXK31PEYagP04epV1cE50UMy6IQZeQM7+Ol'
       :          '74Z+eHfpHNc7OjffQ/HeV0X8BopoDkGEkAAA='
       :             }
       :            }
       :           }
       :          }
       :         }
       :        }
       :       }
       :      }
       :     }
       :    }
       :   }

-----BEGIN CERTIFICATE-----
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vct7dXJtjBszpCzerHly2krZ8nmEClhYas4vAoDq16UwIxYhaHR0cDovL3d3dy5z
bWltZS5leGFtcGxlL2xvZ28uanBnMA0GCSqGSIb3DQEBDQUAA4IBAQBbjdCNVFA/
emCc5uKX5WSPrdvRFZSs57SEhE0odxvhTrOs13VM8Om0TxhNJ0Pl6d9CJdbUxtFw
SSnSu9fnghDO7OZDJnPiIYLNY5eTTzY6sx85mde9TLaBTE7RZf0W7NV0hqDqcfM+
9HnQrU4TtPSvtPS5rr5SvqkaMM0k89bpbkgZlh9HH14+x+DIeT0dLythiXJvkVod
qEfyZTcdplQHQ4szWO7lsjmvHrUIbS1tdAJnah8AZRZfqiJEFeiUp06hvAWnPc3y
1TMwYI8onfwPIVzyT6YLgjiT6PuLwSB/wtlhI+vWfdINaHdotegjawLm/3jZ+ceN
tu39FvbV0uKJ
-----END CERTIFICATE-----

30 464: SEQUENCE {
06   8:  OBJECT IDENTIFIER logotype (1 3 6 1 5 5 7 1 12)
04 450:  OCTET STRING, encapsulates {
30 446:   SEQUENCE {
A0 227:    [0] {
30 224:     SEQUENCE {
A0 111:      [0] {
30 109:       SEQUENCE {
30 107:        SEQUENCE {
30 105:         SEQUENCE {
16  10:          IA5String 'image/jpeg'
30  49:          SEQUENCE {
30  47:           SEQUENCE {
30  11:            SEQUENCE {
06   9:             OBJECT IDENTIFIER
      :              sha-256 (2 16 840 1 101 3 4 2 1)
      :              }
04  32:            OCTET STRING
      :            AF FC 10 16 46 CB 56 25 B4 99 7D E5 89 3E AE 3A
      :            84 6F 5A 02 D3 82 D6 DA 8E D4 EE F8 7C BD 1D ED
      :             }
      :            }
30  40:          SEQUENCE {
16  38:           IA5String 'http://www.example.net/images/logo.jpg'
      :            }
      :           }
      :          }
      :         }
      :        }
A0 109:      [0] {
30 107:       SEQUENCE {
30 105:        SEQUENCE {
30 103:         SEQUENCE {
16   9:          IA5String 'image/gif'
30  49:          SEQUENCE {
30  47:           SEQUENCE {
30  11:            SEQUENCE {
06   9:             OBJECT IDENTIFIER
      :              sha-256 (2 16 840 1 101 3 4 2 1)
      :              }
04  32:            OCTET STRING
      :            88 90 81 81 AD FB 66 AE 2F 66 D0 49 A0 4D 8E A0
      :            EC 4E A8 64 42 38 5B 36 4A BF 2C 8B D2 E9 E9 66
      :             }
      :            }
30  39:          SEQUENCE {
16  37:           IA5String 'http://www.example.org/logo-image.gif'
      :            }
      :           }
      :          }
      :         }
      :        }
      :       }
      :      }
A2 213:    [2] {
A0 210:     [0] {
30 207:      SEQUENCE {
30 101:       SEQUENCE {
30  99:        SEQUENCE {
16   9:         IA5String 'image/gif'
30  49:         SEQUENCE {
30  47:          SEQUENCE {
30  11:           SEQUENCE {
06   9:            OBJECT IDENTIFIER
      :             sha-256 (2 16 840 1 101 3 4 2 1)
      :             }
04  32:           OCTET STRING
      :            6A 58 50 2E 59 67 F9 DD D1 8A FE BD 0D B1 FE 60
      :            A5 13 1B DF 0F B2 BE F0 B5 73 45 50 BA 1B BF 19
      :            }
      :           }
30  35:         SEQUENCE {
16  33:          IA5String 'http://www.smime.example/logo.gif'
      :           }
      :          }
      :         }
30 102:       SEQUENCE {
30 100:        SEQUENCE {
16  10:         IA5String 'image/jpeg'
30  49:         SEQUENCE {
30  47:          SEQUENCE {
30  11:           SEQUENCE {
06   9:            OBJECT IDENTIFIER
      :             sha-256 (2 16 840 1 101 3 4 2 1)
      :             }
04  32:           OCTET STRING
      :            BD CB 7B 75 72 6D 8C 1B 33 A4 2C DE AC 79 72 DA
      :            4A D9 F2 79 84 0A 58 58 6A CE 2F 02 80 EA D7 A5
      :            }
      :           }
30  35:         SEQUENCE {
16  33:          IA5String 'http://www.smime.example/logo.jpg'
      :           }
      :          }
      :         }
      :        }
      :       }
      :      }
      :     }
      :    }
      :   }

Appendix C. Changes Since RFC 3709 and RFC 6170

This appendix summarizes the changes since RFC 3709. The changes are:¶

• Combine RFC 3709 and RFC 6170 into one document, and encourage implementers to support the "data" URI scheme (data:...) that was originally specified in RFC 6170. Merging RFC 3709 and RFC 6170 lead to many editoral changes throughout the document.¶
• Drop SHA-1 as the mandatory-to-implement hash algorithm, and encourage use of the one-way hash function that is employed by the certificate signature algorithm.¶
• RFC 3709 required client applications to support both direct and indirect addressing. This requirement is changed to SHOULD support both direct and indirect addressing to allow implementations to be more privacy preserving.¶
• Update the reference for language tags to be RFC 5646 instead of the now obsolete RFC 3066.¶
• Update the reference for the URI Generic Syntax to be RFC 3986 instead of the now obsolete RFC 2396.¶
• Update the reference for the application/pdf media type to be RFC 8118 instead of the now obsolete RFC 3778.¶
• No longer require support for the FTP scheme (ftp://...) URI.¶
• Require support for the HTTP scheme (http://...) URI and the HTTPS scheme (https://...) URI.¶
• Require support for the compressed SVG image format with the image/svg+xml+gzip media type.¶
• Media types MUST follow the ABNF [RFC5234] that is provided in Section 4.2 of [RFC6838]. This change resolves Errata ID 2679.¶
• Remove the requirement that the LogotypeData file name have a file extension of ".LTD". This change resolves Errata ID 2325.¶
• Encourage, instead of requiring, each logotype to be represented by at least one image.¶
• Encourage the inclusion of text-based audio data suitable for processing by a text-to-speech software using the MIME type of "text/plain;charset=UTF-8".¶
• Require that the logotype extension not contain more than one certificate image logotype.¶
• Privacy-related topics that were previously discussed in the Security Considerations section are now covered in a separate Privacy Considerations section. Additional topics are covered in both sections.¶
• Provide ASN.1 modules for both the older syntax [OLD-ASN1] and the most recent ASN.1 syntax [NEW-ASN1].¶
• Provide additional references.¶
• Provide additional examples.¶
• Several editorial changes to improve clarity.¶

Authors' Addresses