wdiff rfc9795.original rfc9795.txt

Network Working Group

Internet Engineering Task Force (IETF) C. Wendt
Internet-Draft
Request for Comments: 9795 Somos Inc.
Intended status:
Category: Standards Track J. Peterson
Expires: 7 December 2023
ISSN: 2070-1721 Neustar Inc.
5 June 2023

PASSporT
May 2025

Personal Assertion Token (PASSporT) Extension for Rich Call Data
draft-ietf-stir-passport-rcd-26

Abstract

This document extends PASSporT, Personal Assertion Token (PASSporT), a token
for conveying
cryptographically-signed cryptographically signed call information about
personal communications, to include rich meta-data metadata about a call and
caller that can be signed and integrity protected, transmitted, and
subsequently rendered to the called party. This framework is
intended to include and extend caller caller- and call specific call-specific information
beyond human-readable display name name, comparable to the "Caller ID"
function common on the telephone network and network. It is also enhanced with a
an integrity mechanism that is designed to protect the authoring and
transport of this information for different authoritative use-cases. use cases.

Status of This Memo

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This Internet-Draft will expire on 7 December 2023.
https://www.rfc-editor.org/info/rfc9795.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Overview of the use Use of the Rich Call Data PASSporT
extension . . . . . . . . . . . . . . . . . . . . . . . . 4 Extension
4. Overview of Rich Call Data Integrity . . . . . . . . . . . . 5
5. PASSporT Claim "rcd" Definition and Usage . . . . . . . . . . 7
5.1. PASSporT "rcd" Claim . . . . . . . . . . . . . . . . . . 7
5.1.1. "nam" key . . . . . . . . . . . . . . . . . . . . . . 7
5.1.2. "apn" key . . . . . . . . . . . . . . . . . . . . . . 7
5.1.3. "icn" key . . . . . . . . . . . . . . . . . . . . . . 8
5.1.4. "jcd" key . . . . . . . . . . . . . . . . . . . . . . 9
5.1.5. "jcl" key . . . . . . . . . . . . . . . . . . . . . . 9
6. "rcdi" RCD Integrity Claim Definition and Usage . . . . . . . 10
6.1. Creation of the "rcd" element digests . . . . . . . . . . 11 Element Digests
6.1.1. "nam" and "apn" elements . . . . . . . . . . . . . . 12 Elements
6.1.2. "icn" elements . . . . . . . . . . . . . . . . . . . 12 Elements
6.1.3. "jcd" elements . . . . . . . . . . . . . . . . . . . 12 Elements
6.1.4. "jcl" elements . . . . . . . . . . . . . . . . . . . 14 Elements
6.2. JWT Claim Constraints for "rcd" claims . . . . . . . . . 15 Claims
6.3. JWT Claim Constraints usage Usage for "rcd" and "rcdi"
claims . . . . . . . . . . . . . . . . . . . . . . . . . 15 Claims
7. PASSporT "crn" claim Claim - Call Reason Definition and Usage . . . 16
7.1. JWT Constraint for "crn" claim . . . . . . . . . . . . . 16 Claim
8. Rich Call Data Claims Usage Rules . . . . . . . . . . . . . . 16
8.1. "rcd" PASSporT Verification . . . . . . . . . . . . . . . 17
8.2. "rcdi" Integrity Verification . . . . . . . . . . . . . . 17
8.3. Example "rcd" PASSporTs . . . . . . . . . . . . . . . . . 18
9. Compact form Form of "rcd" PASSporT . . . . . . . . . . . . . . . 21
9.1. Compact form Form of the "rcd" PASSporT claim . . . . . . . . 21 Claim
9.2. Compact form Form of the "rcdi" PASSporT claim . . . . . . . . 21 Claim
9.3. Compact form Form of the "crn" PASSporT claim . . . . . . . . 21 Claim
10. Third-Party Uses . . . . . . . . . . . . . . . . . . . . . . 21
10.1. Signing as a Third Party . . . . . . . . . . . . . . . . 23
10.2. Verification using Third Party Using Third-Party RCD . . . . . . . . . . . 23
11. Levels of Assurance . . . . . . . . . . . . . . . . . . . . . 24
12. Use of "rcd" PASSporTs in SIP . . . . . . . . . . . . . . . . 24
12.1. Authentication Service Behavior for SIP protocol . . . . 25 Protocol
12.2. Verification Service Behavior for SIP protocol . . . . . 26 Protocol
13. Using "rcd", "rcdi", and "crn" as additional claims Additional Claims to other Other
PASSporT extensions . . . . . . . . . . . . . . . . . . . 27 Extensions
13.1. Procedures for applying Applying RCD claims Claims as claims only . . . 27 Claims Only
13.2. Example for applying Applying RCD claims Claims as claims only . . . . . 27 Claims Only
14. Further Information Associated with Callers . . . . . . . . . 28
15. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 29
16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29
16.1.
15.1. JSON Web Token Claim . . . . . . . . . . . . . . . . . . 29
16.2.
15.2. Personal Assertion Token (PASSporT) Extensions . . . . . 30
16.3.
15.3. PASSporT RCD Claim Types . . . . . . . . . . . . . . . . 30
17.
16. Security Considerations . . . . . . . . . . . . . . . . . . . 30
17.1. The use
16.1. Use of JWT Claim Constraints in delegate certificates Delegate Certificates to exclude unauthorized claims . . . . . . . . . . . . . 32
18.
Exclude Unauthorized Claims
17. References . . . . . . . . . . . . . . . . . . . . . . . . . 32
18.1.
17.1. Normative References . . . . . . . . . . . . . . . . . . 32
18.2.
17.2. Informative References . . . . . . . . . . . . . . . . . 34
Acknowledgements
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 34

1. Introduction

PASSporT [RFC8225] is a token format based on JWT JSON Web Token (JWT)
[RFC7519] for conveying cryptographically-signed cryptographically signed information about
the parties involved in personal communications; it is used to convey
a signed assertion of the identity of the participants in real-time
communications established via a protocol like SIP [RFC8224]. The
STIR
Secure Telephone Identity Revisited (STIR) problem statement
[RFC7340] declared securing the display name of callers outside of
STIR's initial scope. This document extends the use of JWT and
PASSporT in the overall STIR framework by defining a PASSporT
extension and the associated STIR procedures to protect additional caller
caller- and call related call-related information. This is additional information beyond the
calling party originating identity (e.g. (e.g., telephone number or SIP
URI) that is intended to be rendered to assist a called party in
determining whether to accept or trust incoming communications. This
includes information such as the name of the person or entity on one
side of a communications session, for example, the traditional
"Caller ID" of the telephone network along with related display
information that would be rendered to the called party during
alerting or potentially used by an automaton to determine whether and
how to alert a called party to a call and whom is calling.

Traditional telephone network signaling protocols have long supported
delivering a 'calling name' from the originating side, though in
practice,
practice the terminating side is often left to determine a name from
the calling party number by consulting a local address book or an
external database. SIP, for example, similarly can carry this
information in a 'display-name' display-name in the From header field value (or
alternatively the Call-Info header field) from the originating to
terminating side, or alternatively in the Call-
Info header field. side. In this document, we utilize the STIR framework to
more generally extend the assertion of an extensible set of identity
information not limited to but including calling name.

This document extends PASSporT to provide cryptographic protection
for the "display-name" field of SIP requests, or similar name fields
in other protocols, as well as further "rich call data" (RCD) about
the caller, which includes the contents of the Call-Info header field
or other data structures that can be added to the PASSporT. In
addition, Section 12 describes use-cases use cases that enable external third-
party authorities to convey rich information associated with a
calling number via a an "rcd" PASSporT while clearly identifying the
third-party as the source of the Rich Call Data information.
Finally, this document describes how to preserve the integrity of the
RCD in scenarios where there may be non-authoritative users
initiating and signing RCD and therefore a constraint on the RCD data that
a PASSporT can attest via certificate-level controls.

2. Terminology

The keywords key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.

3. Overview of the use Use of the Rich Call Data PASSporT extension Extension

This document defines Rich Call Data (RCD) (RCD), which is a PASSporT
extension [RFC8225] that defines an extensible claim for asserting
information about the call beyond the telephone number. This
includes information such as more detailed information about the calling party or party, calling number being presented
number, or the purpose of the call. There are many use-cases use cases that will be described in
this document describes around the entities responsible for the
signing and integrity of this information, whether it is the entity
that originates a call, a service provider acting on behalf of a caller
caller, or
use-cases where when third-party services may be authoritative over the
rich call data
RCD on behalf of the caller. In general, PASSporT [RFC8225] has been
defined to be a communications protocol independent technology, of the communications protocol, but it's its
initial usage as detailed in [RFC8224] is with the SIP protocol
[RFC3261]. There are many SIP
specific SIP-specific references and definitions in
this document, but future specifications may extend the usage of RCD
PASSporTs and claims to other protocol specific protocol-specific usage and
definitions.

The RCD associated with the identity of the calling party described
in this document is of two main categories. The first data is a more
traditional set of info information about a caller associated with
"display-name" in SIP [RFC3261], typically a textual description of
the caller, or alternate presentation numbers often used in the From Header
header field [RFC3261] or P-Asserted-Identity header field [RFC3325],
or an icon associated with the caller. The second category is a set
of RCD that is defined as part of the jCard definitions or extensions
to that data.
[I-D.ietf-sipcore-callinfo-rcd] [RFC9796] describes the optional use of jCard in the
Call-Info header field as RCD with the "jcard" Call-Info purpose
token. Either or both of these two types of data can be incorporated
into an "rcd" claim as defined in this document.

Additionally, in relation to the description of the specific
communications event itself (versus the identity description in the
previous paragraph), [I-D.ietf-sipcore-callinfo-rcd] [RFC9796] also describes a "call-reason"
parameter intended for description of the intent or reason for a
particular call. A new PASSporT claim "crn", or call reason, can
contain a string that describes the intent of the call. This claim
is intentionally kept separate from the "rcd" claim because it is
envisioned that call reason is not the same as information associated
with the caller and may change on a more frequent, per call, type of per-call basis.

4. Overview of Rich Call Data Integrity

When incorporating call data that represents a user, even in
traditional calling name services today, often there are policy and
restrictions around what data elements are allowed to be used.
Whether preventing offensive language or icons or icons, enforcing uniqueness,
notifying about potential trademark or copyright violations violations, or
enforcing other
policy enforcement, policies, there might be the desire to pre-certify or
"vet" the specific use of rich call data. RCD. This document defines a mechanism
that allows for a direct or indirect party that enforces the policies
to approve or certify the content, create a cryptographic digest that
can be used to validate that data and applies a constraint in the
certificate to allow the recipient and verifier to validate that the
specific content of the RCD is as intended at its creation and its
approval or certification.

There are two mechanisms that are defined to accomplish that for two
distinct categories of purposes. The first of the mechanisms include
the definition of an integrity claim. The RCD integrity mechanism is
a process of generating a cryptographic digest for each resource
referenced by a URI within a claim value (e.g., an image file
referenced by "jcd" or a jCard referenced by "jcl"). This mechanism
is inspired by and based on the W3C Subresource Integrity
specification [W3C-SubresourceIntegrity]. The second of the
mechanisms uses the capability called JWT Claim Constraints, defined
in [RFC8226] and extended in [RFC9118]. The JWT Claim Constraints
specifically guide the verifier within the certificate used to
compute the signature in the PASSporT for the inclusion (or
exclusion) of specific claims and their values, so that the content
intended by the signer can be verified to be accurate.

Both of these mechanisms, integrity digests and JWT Claims
Constraints, can be used together or separately depending on the
intended purpose. The first category of purpose is whether the rich
call data RCD
conveyed in the PASSporT claims is pass-by-value passed by value or pass-
by-reference; passed by
reference; i.e., is the information contained in the PASSporT claims
and therefore integrity protected by the PASSporT signature, or is
the information contained in an external resource referenced by a URI
in the PASSporT. PASSporT? The second category of purpose is whether the
signer is authoritative or has responsibility for the accuracy of the
RCD based on the policies of the eco-system ecosystem the "rcd" PASSporTs or
"rcd" claims are being used.

The following table provides an overview of the framework for how
integrity should be used with RCD. ("Auth" represents
"authoritative" in this table.)

+----------+---------------------+--------------------------------+

+==========+=====================+==================================+
| Modes | No URI refs | Includes URI refs |
+----------+---------------------+--------------------------------+
+==========+=====================+==================================+
| Auth | 1: No integrity req | 2: RCD Integrity |
+----------+---------------------+--------------------------------+
+==========+---------------------+----------------------------------+
| Non-Auth | 3: JWT Claim Const. | 4: RCD Integ./JWT Integ. / |
| | | JWT Claim Const. |
+----------+---------------------+--------------------------------+
+==========+---------------------+----------------------------------+

Table 1

The first and simplest mode is exclusively for when all RCD content
is directly included as part of the claims (i.e. (i.e., no URIs referencing
external content are included in the content) and when the signer is
authoritative over the content. In this mode, integrity protection
is not required required, and the set of claims is simply protected by the
signature of the standard PASSporT [RFC8225] and SIP identity header
[RFC8224] procedures. The second mode is an extension of the first
where the signer is authoritative authoritative, and an "rcd" claim contents
include a URI identifying external resources. In this mode, an RCD
Integrity or "rcdi" claim MUST be included. This integrity claim is
defined later in this document and provides a digest of the "rcd"
claim content so that, particularly for the case where there are URI
references in the RCD, the content of that RCD can be comprehensively
validated that it was received as intended by the signer of the
PASSporT.

The third and fourth modes cover cases where there is a different
authoritative entity responsible for the content of the RCD, separate
from the signer of the PASSporT itself, allowing the ability, in
particular when delegating signing authority for PASSporT, to enable
a mechanism for allowing agreed or vetted content included in or
referenced by the RCD claim contents. The primary framework for
allowing the separation of authority and the signing of PASSporTs by
non-authorized entities is detailed in [RFC9060] [RFC9060], although other
cases may apply. As with the first and second modes, the third and
fourth modes differ with the absence or inclusion of referenced
external content using URIs.

5. PASSporT Claim "rcd" Definition and Usage

5.1. PASSporT "rcd" Claim

This document defines a new JSON Web Token claim for "rcd", Rich Call
Data, the value of which is a JSON object that can contain one or
more key value pairs. This document defines a default set of key
values.

5.1.1. "nam" key

The "nam" key value is a display name, associated with the originator
of personal communications, which may may, for example example, match the display-
name
display-name component of the From header field value of a SIP
request [RFC3261] or alternatively from of the P-Asserted-Identity header
field value [RFC3325], or a similar field in other PASSporT using
protocols. This key MUST be included once as part of the "rcd" claim
value JSON object. The key syntax of "nam" MUST follow the display-
name ABNF given in [RFC3261]. If there is no string associated with
a display name, the claim value MUST then be an empty string.

5.1.2. "apn" key

The "apn" key value is an optional alternate presentation number
associated with the originator of personal communications, which may may,
for example example, match the user component of the From header field value
of a SIP request (in cases where a network number is carried in the
P-Asserted-Identity [RFC3325]), or alternatively from of the Additional-
Identity header field value [3GPP TS 24.229 v16.7.0], [TS.3GPP.24.229], or a similar field in
other PASSporT using PASSporT-using protocols. Its intended semantics are to convey
a number that the originating user is authorized to show to called
parties in lieu of their default number, such as cases where a remote
call agent uses the main number of a call center instead of their
personal telephone number. The "apn" key value is a canonicalized
telephone number per [RFC8224] [RFC8224], Section 8.3. If present, this key
MUST be included once as part of the "rcd" claim value JSON object.

The use of the optional "apn" key is intended for cases where the
signer of an "rcd" PASSporT or "rcd" claims authorizes the use of an
alternate presentation number by the user. How the signer determines
that a user is authorized to present the number in question is a
policy decision outside the scope of this document, however, document. However, the
vetting of the alternate presentation number should follow the same
level of vetting as telephone identities or any other information
contained in an "rcd" PASSporT or "rcd" claims. This usage is
intended as an alternative to conveying the presentation number in
the "tel" key value of a jCard, in situations where no other rich
jCard data needs to be conveyed with the call. Only one "apn" key
may be present. "apn" MUST be used when it is the intent of the
caller or signer to display the alternate presentation number even if
"jcd" or "jcl" keys are present in a PASSporT with a "tel" key value.

5.1.3. "icn" key

The "icn" key value is an optional HTTPS URL reference to an image
resource that can be used to pictorially represent the originator of
personal communications. This icon key value should be used as a
base or default method of associating an image with a calling party.

When being used for SIP [RFC3261] [RFC3261], this claim key value is used to
protect the Call-Info header field with a purpose parameter value of
"icon" as described in Section 20.9 of [RFC3261]. Example as follows: For example:

Call-Info: <http://wwww.example.com/alice/photo.jpg>;
purpose=icon

Note that [I-D.ietf-sipcore-callinfo-rcd] [RFC9796] extends the specific usage of "icon" in SIP in
the context of the larger rich call data framework with specific
guidance on referencing images and image types, sizes sizes, and formats.

It should be also noted that with jCard, as described in the
following for "jcd" and
"jcl" key value sections values (Sections 5.1.4 and 5.1.5) and in
[I-D.ietf-sipcore-callinfo-rcd], [RFC9796], there
are alternative ways of including photos and logos as HTTPS URL
references. The "icn" key should be then considered a base or default image
image, and jCard usage should be considered for profiles and
extensions that provide more direct guidance on the usage of specific defined usage of what
each image type represents for the proper rendering to end users.

5.1.4. "jcd" key

The "jcd" key value is defined to contain a jCard [RFC7095] JSON
object. object
[RFC7095]. The jCard is defined in this specification as an
extensible object format used to contain RCD information about the
call initiator. This object is intended to directly match the Call-Info Call-
Info header field value defined in [I-D.ietf-sipcore-callinfo-rcd] [RFC9796] with a type of "jcard" "jcard",
where the format of the jCard and properties used should follow the
normative usage and formatting rules and procedures in that document.
It is an extensible object where the calling party can provide both
the standard types of information defined in jCard or can use the
built-in extensibility of the jCard specification to add additional
information. The "jcd" key is optional. Either a "jcd" or "jcl" MAY
appear in the "rcd" claim, but not both.

The jCard object value for "jcd" MUST be a jCard JSON object that MAY
have URI referenced URI-referenced content, but that URI referenced URI-referenced content MUST NOT
further reference URIs. Future specifications may extend this
capability, but as stated in [I-D.ietf-sipcore-callinfo-rcd] it [RFC9796] constrains the security properties of RCD
information and the integrity of the content referenced by URIs.

Note: even Even though we refer to [I-D.ietf-sipcore-callinfo-rcd] [RFC9796] as the definition of the jcard
jCard properties for usage in "rcd" claims, using Call-Info as
protocol with the addition of an identity header carrying the PASSPorT
PASSporT is not required. The identity header carrying a PASSporT
with an "rcd" claim including a "jcd" value can be used as the
primary and only transport of the RCD information.

5.1.5. "jcl" key

The "jcl" key value is an HTTPS URL that refers to a jCard [RFC7095] JSON
object [RFC7095] on a web server. The web server MUST use the MIME media
type for JSON text as application/json with a default encoding of
UTF-8 [RFC8259]. This link may correspond to the Call-Info header
field value defined in [I-D.ietf-sipcore-callinfo-rcd] [RFC9796] with a type of "jcard". As also
defined in [I-D.ietf-sipcore-callinfo-rcd], [RFC9796], the format of the jCard and properties used
should follow the normative usage and formatting rules and
procedures. The "jcl" key is optional. The "jcd" or "jcl" keys MAY
only appear once in the "rcd" claim but MUST be mutually exclusive.

The jCard object referenced by the URI value for "jcl" MUST be a
jCard JSON object that MAY have URI referenced URI-referenced content, but that URI URI-
referenced content MUST NOT further reference URIs. Future
specifications may extend this capability, but as stated in
[I-D.ietf-sipcore-callinfo-rcd] it [RFC9796] constrains
the security properties of RCD information and the integrity of the
content referenced by URIs.

6. "rcdi" RCD Integrity Claim Definition and Usage

The "rcdi" claim is included for the second and fourth modes
described in the integrity overview Section 4 of this document. (Section 4). "rcdi" and "rcd"
claims MAY each appear once in a PASSporT, but if "rcdi" is included included,
the "rcd" MUST correspondingly be present also. correspondingly. The value of the "rcdi"
claim is a JSON object that is defined as follows.

The claim value of the "rcdi" claim key is a JSON object with a set
of JSON key/value pairs. These objects correspond to each of the
elements of the "rcd" claim object that require integrity protection
with an associated digest over the content referenced by the key
string. The individual digest of different elements of the "rcd"
claim data and URI referenced URI-referenced external content is kept specifically
separate to allow the ability to verify the integrity of only the
elements that are ultimately retrieved or downloaded retrieved, downloaded, or rendered to
the end-user. end user.

The key value references a specific object within the "rcd" claim
value using a JSON pointer defined in [RFC6901] with a minor
additional rule to support URI references to external content that
include JSON objects themselves, for the specific case of the use of
"jcl", defined in Section 6.1.4. JSON pointer syntax is the key
value that documents exactly the part of JSON that is used to
generate the digest which produce that produces the resulting string that makes up
the value for the corresponding key. Detailed procedures are
provided below, but an example "rcdi" is provided here:

"rcdi" : {
"/jcl": "sha256-7kdCBZqH0nqMSPsmABvsKlHPhZEStgjojhdSJGRr3rk",
"/jcl/1/2/3": "sha256-jL4f47fF82LuwcrOrSyckA4SWrlElfARHkW6kYo1JdI"
}

The values of each key/value pair consists of a digest across one of
the following objects referenced by the JSON pointer key, key:

* the content inline to the referenced object object,

* the content of a resource referenced by an inline URI object object, or

* the content of a resource specified by a URI that is in embedded
in content specified by an inline URI object(e.g., jcl) object (e.g., "jcl")

This is combined with a string that defines the crypto cryptographic
algorithm used to generate the digest. RCD implementations MUST
support the hash algorithms SHA-256, SHA-384, and SHA-512. These
hash algorithms are identified by "sha256", "sha384", and "sha512",
respectively. SHA-
256, SHA-256, SHA-384, and SHA-512 are part of the SHA-2
set of cryptographic hash functions [RFC6234] defined by the US
National Institute of Standards and Technology (NIST).
Implementations MAY support additional recommended hash algorithms in [IANA-COSE-ALG];
[IANA-COSE-ALG], that is, the hash algorithm has algorithms with "Yes" in the
"Recommended" column of the IANA registry. Hash algorithm
identifiers MUST use only lowercase letters, and they MUST NOT
contain hyphen characters. The character following the algorithm
string MUST be a hyphen character, "-", or ASCII 45. The subsequent
characters are the base64 encoded [RFC4648] digest of a canonicalized
and concatenated string or binary data based on the JSON pointer
referenced elements of the "rcd" claim or the
URI referenced URI-referenced content
contained in the claim. The next section covers the details of the
determination of the input string used to determine the digest are
defined in the next section. digest.

6.1. Creation of the "rcd" element digests Element Digests

"rcd" claim objects can contain "nam", "apn", "icn", "jcd", or "jcl"
keys as part of the "rcd" JSON object claim value. This document
defines the use of JSON pointer [RFC6901] as a mechanism to reference
specific "rcd" claim elements.

In order to facilitate proper verification of the digests and to
determine whether the "rcd" elements or content referenced by URIs
were modified, the input to the digest must be completely
deterministic at three points in the process. First, at the
certification point where the content is evaluated to conform to the
application policy and the JWT Claim Constraints is applied to the
certificate containing the digest. Second, when the call is signed
at the Authentication Service, there may be a local policy to verify
that the provided "rcd" claim corresponds to each digest. Third,
when the "rcd" data is verified at the Verification Service, verification service, the
verification is performed for each digest by constructing the input
digest string for the element being verified and referenced by the
JSON pointer string.

The procedure for the creation of each "rcd" element digest string
corresponding to a JSON pointer string key is as follows.

1. The JSON pointer either refers to a value that is a part or the
whole of a JSON object or to a string that is a URI referencing
an external resource.

2. For a JSON value, serialize the JSON to remove all white space
and line breaks. The procedures of this deterministic JSON
serialization are defined in [RFC8225], Section 9. The resulting
string is the input for the hash function.

3. For any URI referenced URI-referenced content, the bytes of the body of the HTTP
response is are the input for the hash function.

Note that the digest is computed on the Json JSON representation of the
string, which necessarily includes the beginning and ending double-
quote characters.

6.1.1. "nam" and "apn" elements Elements

In the case of "nam" and "apn", the only allowed value is a string.
For both of these key values values, an "rcdi" JSON pointer or integrity
digest is optional because the direct value is protected by the
signature and can be constrained directly with JWTClaimConstraints.

6.1.2. "icn" elements Elements

In the case of "icn", the only allowed value is a URI value that
references an image file. If the URI references externally linked
content
content, there MUST be a JSON pointer and digest entry for the
content in that linked resource. When creating a key/value
representing "icn", the key is the JSON pointer string "/icn" "/icn", and
the digest value string would be is created using the image file byte data
referenced in the URI.

6.1.3. "jcd" elements Elements

In the case of "jcd", the value associated is a jCard JSON object,
which happens to be a JSON array with sub-arrays. JSON pointer
notation uses numeric indices into elements of arrays, including when
those elements are arrays themselves.

As an example, for we have the following "rcd" claim:

"rcd": {
"jcd": ["vcard",
[ ["version",{},"text","4.0"],
["fn",{},"text","Q Branch"],
["org",{},"text","MI6;Q Branch Spy Gadgets"],
["photo",{},"uri",
"https://example.com/photos/quartermaster-256x256.png"],
["logo",{},"uri",
"https://example.com/logos/mi6-256x256.jpg"],
["logo",{},"uri",
"https://example.com/logos/mi6-64x64.jpg"]
]
],
"nam": "Q Branch Spy Gadgets"
}

In order to use a JSON pointer to refer to the URIs, the following
example "rcdi" claim includes a digest for the entire "jcd" array
string as well as three additional digests for the URIs, where, as
defined in [RFC6901] [RFC6901], zero-based array indices are used to reference
the URI strings.

"rcdi": {
"/jcd": "sha256-7kdCBZqH0nqMSPsmABvsKlHPhZEStgjojhdSJGRr3rk",
"/jcd/1/3/3": "sha256-RojgWwU6xUtI4q82+kHPyHm1JKbm7+663bMvzymhkl4",
"/jcd/1/4/3": "sha256-jL4f47fF82LuwcrOrSyckA4SWrlElfARHkW6kYo1JdI",
"/jcd/1/5/3": "sha256-GKNxxqlLRarbyBNh7hc/4lbZAdK6B0kMRf1AMRWPkSo"
}
}

The use of a JSON pointer and integrity digest for the "jcd" claim
key and value is optional. The "jcd" value is the directly included
jCard array and array; it can be protected by the signature and can be
constrained directly with JWTClaimConstraints. However, for data
length reasons (as with "icn" above) or more importantly for
potential privacy and/or security considerations with a publically publicly
accessible certificate, the use of the "rcdi" JSON pointer and
integrity digest as the constraint value in JWTClaimConstraints over
the jCard data is RECOMMENDED.

It is important to remember the array indices for JSON Pointer pointer are
dependent on the order of the elements in the jCard. The use of
digest for the "/jcd" corresponding to the entire jCard array string
can be included as a redundant mechanism to avoid any possibility of
substitution, insertion attacks, or other potential techniques that
may be possible to avoid
undermine integrity detection.

Each URI referenced in the jCard array string MUST have a
corresponding JSON pointer string key and digest value.

6.1.4. "jcl" elements Elements

In the case of the use of a "jcl" URI reference to an external jCard,
the procedures are similar to "jcd" with the exception and the minor
modification to JSON pointer, where "/jcl" is used to refer to the
external jCard array string and any following numeric array indices
added to the "jcl" (e.g., "/jcl/1/2/3") are treated as if the
external content referenced by the jCard was directly part of the
overall "rcd" claim JSON object. The following example illustrates a
"jcl" version of the above "jcd" example.

"rcd": {
"jcl": "https://example.com/qbranch.json",
"nam": "Q Branch Spy Gadgets"
},
"rcdi": {
"/jcl": "sha256-7kdCBZqH0nqMSPsmABvsKlHPhZEStgjojhdSJGRr3rk",
"/jcl/1/3/3": "sha256-RojgWwU6xUtI4q82+kHPyHm1JKbm7+663bMvzymhkl4",
"/jcl/1/4/3": "sha256-jL4f47fF82LuwcrOrSyckA4SWrlElfARHkW6kYo1JdI",
"/jcl/1/5/3": "sha256-GKNxxqlLRarbyBNh7hc/4lbZAdK6B0kMRf1AMRWPkSo"
}

The "rcdi" MUST have a "/jcl" key value and digest value to protect
the referenced jCard object object, and each URI referenced in the
referenced jCard array string MUST have a corresponding JSON pointer
string key and digest value.

The following is the example contents of the resource pointed to by
https://example.com/qbranch.json
https://example.com/qbranch.json; it is used to calculate the above
digest for "/jcl"

["vcard",
[ ["version",{},"text","4.0"],
["fn",{},"text","Q Branch"],
["org",{},"text","MI6;Q Branch Spy Gadgets"],
["photo",{},"uri",
"https://example.com/photos/quartermaster-256x256.png"],
["logo",{},"uri",
"https://example.com/logos/mi6-256x256.jpg"],
["logo",{},"uri",
"https://example.com/logos/mi6-64x64.jpg"]
]
]

6.2. JWT Claim Constraints for "rcd" claims Claims

When using JWT Claim Constraints for "rcd" claims claims, the procedure when
creating the signing certificate should follow adhere to the following
guidelines.

The "permittedValues" for the "rcd" claim MAY contain a single entry
or optionally MAY contain multiple entries with the intent of
supporting cases where the certificate holder is authorized to use
different sets of rich call data corresponding to different call
scenarios.

Only including "permittedValues" for "rcd", with no "mustInclude",
provides the ability for the construction a valid PASSPorT PASSporT that can
either have no "rcd" claim within or only the set of constrained
"permittedValues" values for an included "rcd" claim.

6.3. JWT Claim Constraints usage Usage for "rcd" and "rcdi" claims Claims

The use of JWT Claim Constraints with an "rcdi" claim is for cases
where URI referenced URI-referenced content is to be protected by the authoritative
certificate issuer. The objective for the use of JWT Claim
Constraints for the combination of both "rcd" and "rcdi" claims is to
constrain the signer to only construct the "rcd" and "rcdi" claims
inside a PASSporT to contain and reference only a pre-determined predetermined set
of content. Once both the contents of the "rcd" claim and any
referenced content is are certified by the party that is authoritative
for the certificate being issued to the signer, the "rcdi" claim is
constructed and linked to the STIR certificate associated with the
signature in the PASSporT via the JWT Claim Constraints extension as
defined in [RFC8226] [RFC8226], Section 8 and extended in [RFC9118]. It should
be recognized that the "rcdi" set of digests is intended to be unique
for only a specific combination of "rcd" content and URI referenced URI-referenced
external content, and therefore the set provides a robust integrity
mechanism for an authentication service being performed by a non-authoritative non-
authoritative party. This would often be associated with the use of
delegate certificates [RFC9060] for the signing of calls by the
calling party
directly directly, as an example, even though the "authorized
party" is not necessarily the subject of a STIR certificate.

For the cases that there should always be where both "rcd" and "rcdi" claims should always be
included in the PASSporT, the certificate JWT Claims Constraint
extension MUST include both of the following:

* a "mustInclude" for the "rcd" claim, which simply constrains the
fact that an "rcd" must be included

* a "mustInclude" for the "rcdi" claim and a "permittedValues" equal
to the created "rcdi" claim value string.

Note that optionally the "rcd" claims may be included in the
"permittedValues" however
"permittedValues"; however, it is recognized that this may be
redundant with the "rcdi" permittedValues because the "rcdi" digest
will imply the content of the "rcd" claims themselves.

The "permittedValues" for the "rcdi" claims (or "rcd" claims more
generally) may contain multiple entries, entries to support the case where the
certificate holder is authorized to use different sets of rich
call data. RCD.

7. PASSporT "crn" claim Claim - Call Reason Definition and Usage

This document defines a new JSON Web Token claim for "crn", Call
Reason, the value of which is a single string that can contain
information as defined in [I-D.ietf-sipcore-callinfo-rcd] [RFC9796] and corresponding to the "call-reason" "call-
reason" parameter for the Call-Info header. This claim is optional.

Example "crn" claim with "rcd":

"crn" : "For your ears only",
"rcd": { "nam": "James Bond",
"jcl": "https://example.org/james_bond.json"}

7.1. JWT Constraint for "crn" claim Claim

The integrity of the "crn" claim contents can optionally be protected
by the authoritative certificate issuer using JWT Constraints in the
certificate. When the signer of the PASSporT intends to always
include a call reason string of any value, a "mustInclude" for the
"crn" claim in the JWT Claim Constraints indicates that a "crn" claim
must always be present and is RECOMMENDED to be included by the
certificate issuer. If the signer of the "crn" claim wants to
constrain the contents of "crn", then "permittedValues" for "crn" in
JWT Claim Constraints should match the contents of the allowed
strings and is RECOMMENDED to be included by the certificate issuer.

8. Rich Call Data Claims Usage Rules

The "rcd" or "crn" claims MAY appear in any PASSporT claims object as
optional elements. The creator of a PASSporT MAY also add a PASSporT
extension ("ppt") value, defined in [RFC8225] [RFC8225], Section 8.1, of "rcd"
to the header of a PASSporT as well, in which case PASSporT. In that case, the PASSporT claims MUST
contain at least one or both an "rcd" or "crn" claim. Any entities
verifying the PASSporT claims defined in this document are required
to understand the PASSporT extension in order to process the PASSporT
in question. An example PASSporT header with the PASSporT extension
("ppt") value of "rcd" included is shown as follows:

{ "typ":"passport",
"ppt":"rcd",
"alg":"ES256",
"x5u":"https://www.example.com/cert.cer" }

The PASSporT claims object contains the "rcd" key with its
corresponding value. The value of "rcd" is an array of JSON objects,
of which one, the "nam" key and value, is mandatory.

After the header and claims PASSporT objects have been constructed,
their signature is computed normally per the guidance in [RFC8225].

8.1. "rcd" PASSporT Verification

A verifier that successfully verifies a PASSportT PASSporT that contains an
"rcd" claim MUST ensure the following about the PASSporT:

* it It has a valid signature per the verification procedures detailed
in [RFC8225] [RFC8225].

* it It abides by all rules set forth in the proper construction of the
claims defined in Section 5 of this document 5.

* it It abides by JWT Claims Constraint rules defined in [RFC8226] [RFC8226],
Section 8 or extended in by [RFC9118] if present in the certificate
used to compute the signature in the PASSporT PASSporT.

In addition addition, if the "iss" claim is included in the PASSPorT, PASSporT,
verification should follow procedures described in Section 10.2.

Consistent with the verification rules of PASSporTs more generally
[RFC8225], if any of the above criteria is not met, relying parties
MUST NOT use any of the claims in the PASSporT.

8.2. "rcdi" Integrity Verification

When the "rcdi" claim exists, the verifier should verify the digest
for each JSON pointer key. Any digest string that doesn't match a
generated digest MUST be considered a failure of the verification of
the content referenced by the JSON pointer.

If there is any issue with completing the integrity verification
procedures for referenced external content, including HTTP or HTTPS
errors, the referenced content MUST be considered not verified. This
However, this SHOULD NOT however impact the result of base PASSporT
verification for claims content that is directly included in the
claims of the PASSporT.

As a potential optimization of verification procedure, procedures, an entity
that does not otherwise need to dereference a URI from the "rcd"
claim for display to end-user the end user is NOT RECOMMENDED to unnecessarily
dereference the URI solely to perform integrity verification.

8.3. Example "rcd" PASSporTs

An example of a "nam" only "nam"-only PASSporT claims object is shown next (with
line breaks for readability only).

{ "orig":{"tn":"12025551000"},
"dest":{"tn":["12025551001"]},
"iat":1443208345,
"rcd":{"nam":"James Bond"} }

An example of a "nam", "apn", and "icn" using an https URI PASSporT
claims object is shown next (with line breaks for readability only).
Note, in this example, there is no integrity protection over the
"icn" element in the "rcd" claim.

{ "orig":{"tn":"12025551000"},
"dest":{"tn":["12155551001"]},
"iat":1443208345,
"rcd":{
"apn":"12025559990",
"icn":"https://example.com/photos/quartermaster-256x256.png",
"nam":"Her Majesty's Secret Service" } }

An example of a "nam", "apn", and "icn" using data URI PASSporT
claims object is shown next (with line breaks for readability only).
Note, in this example, the "icn" data is incorporated directly in the
"rcd" claim claim, and therefore separate integrity protection is not
required.

{ "orig":{"tn":"12025551000"},
"dest":{"tn":["12155551001"]},
"iat":1443208345,
"rcd":{
"apn":"12025559990",
"icn":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAY
AAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OH
wAAAABJRU5ErkJggg==",
"nam":"Her Majesty's Secret Service" } }

An example of an "rcd" claims object that includes the "jcd" and also
contains URI references to content content, which requires require the inclusion of an
"rcdi" claim and corresponding digests. Note, in this example, the
"rcdi" claim includes integrity protection of the URI referenced URI-referenced
content.

{
"crn": "Rendezvous for Little Nellie",
"orig": { "tn": "12025551000"},
"dest": { "tn": ["12155551001"]},
"iat": 1443208345,
"rcd": {
"jcd": ["vcard",
[ ["version",{},"text","4.0"],
["fn",{},"text","Q Branch"],
["org",{},"text","MI6;Q Branch Spy Gadgets"],
["photo",{},"uri","https://example.com/photos/q-256x256.png"],
["logo",{},"uri","https://example.com/logos/mi6-256x256.jpg"],
["logo",{},"uri","https://example.com/logos/mi6-64x64.jpg"]
] ],
"nam": "Q Branch Spy Gadgets"
},
"rcdi": {
"/jcd/1/3/3":"sha256-RojgWwU6xUtI4q82+kHPyHm1JKbm7+663bMvzymhkl4",
"/jcd/1/4/3":"sha256-jL4f47fF82LuwcrOrSyckA4SWrlElfARHkW6kYo1JdI",
"/jcd/1/5/3":"sha256-GKNxxqlLRarbyBNh7hc/4lbZAdK6B0kMRf1AMRWPkSo"
}
}

In an example PASSporT, where a jCard is linked via HTTPS URL using
"jcl", a jCard file is served at a particular URL.

An example jCard JSON file hosted at the example web address of
https://example.com/qbranch.json is shown as follows:

["vcard",
[ ["version",{},"text","4.0"],
["fn",{},"text","Q Branch"],
["org",{},"text","MI6;Q Branch Spy Gadgets"],
["photo",{},"uri","https://example.com/photos/q-256x256.png"],
["logo",{},"uri","https://example.com/logos/mi6-256x256.jpg"],
["logo",{},"uri","https://example.com/logos/mi6-64x64.jpg"]
]
]

For the above referenced jCard, the corresponding PASSporT claims
object would be as follows:

{
"crn": "Rendezvous for Little Nellie",
"orig": {"tn": "12025551000"},
"dest": {"tn": ["12155551001"]},
"iat": 1443208345,
"rcd": {
"nam": "Q Branch Spy Gadgets",
"jcl": "https://example.com/qbranch.json"
},
"rcdi": {
"/jcl":"sha256-qCn4pEH6BJu7zXndLFuAP6DwlTv5fRmJ1AFkqftwnCs",
"/jcl/1/3/3":"sha256-RojgWwU6xUtI4q82+kHPyHm1JKbm7+663bMvzymhkl4",
"/jcl/1/4/3":"sha256-jL4f47fF82LuwcrOrSyckA4SWrlElfARHkW6kYo1JdI",
"/jcl/1/5/3":"sha256-GKNxxqlLRarbyBNh7hc/4lbZAdK6B0kMRf1AMRWPkSo"
}
}

An example "rcd" PASSporT that uses "nam" and "icn" keys with "rcdi"
for calling name and referenced icon image content:

{
"crn": "Rendezvous for Little Nellie",
"orig": {"tn": "12025551000"},
"dest": {"tn": ["12155551001"]},
"iat": 1443208345,
"rcd": {
"nam": "Q Branch Spy Gadgets",
"icn": "https://example.com/photos/q-256x256.png"
},
"rcdi": {
"/nam": "sha256-sM275lTgzCte+LHOKHtU4SxG8shlOo6OS4ot8IJQImY",
"/icn": "sha256-RojgWwU6xUtI4q82+kHPyHm1JKbm7+663bMvzymhkl4"
}
}

9. Compact form Form of "rcd" PASSporT

9.1. Compact form Form of the "rcd" PASSporT claim Claim

The specific usage of the compact form of an "rcd" PASSporT claim,
defined in [RFC8225] [RFC8225], Section 7, has some restrictions that will be
enumerated below, but it mainly follows standard PASSporT compact
form procedures. Compact form only provides the signature from the
PASSporT, requiring the re-construction reconstruction of the other PASSporT claims
from the SIP header fields as discussed in [RFC8224] Section 4.1. 4.1 of [RFC8224].

The re-construction reconstruction of the "nam" claim, if using the SIP protocol,
should use the display-name string in the From header field. For
other protocols, if there is a display name field that exists, the
string should be used, otherwise used; otherwise, the string should be an empty
string, e.g., "". "jcl" and "jcd" MUST NOT be used with compact form
due to integrity rules and URI reference rules in this document
leading to too restrictive of a set of constraints. Future
specifications may revisit this to propose a consistent and
comprehensive way of addressing integrity and security of information
and to provide specific guidance for other protocol usage.

9.2. Compact form Form of the "rcdi" PASSporT claim Claim

The use of the compact form of a PASSporT using an "rcdi" claim is
not supported, so if "rcdi" is required required, compact form MUST NOT be
used.

9.3. Compact form Form of the "crn" PASSporT claim Claim

Compact form of a "crn" PASSporT claim shall be re-constructed reconstructed using
the "call-reason" parameter of a Call-Info header as defined by
[I-D.ietf-sipcore-callinfo-rcd].
[RFC9796].

10. Third-Party Uses

While rich data about the call can be provided by an originating
authentication service, an intermediary in the call path could also
acquire rich call data by querying a third-party service. Such a
service effectively acts as a STIR Authentication Service, generating
its own PASSporT, and that PASSporT could be attached to a call by
either the originating or terminating side. This third-party
PASSporT attests information about the calling number, rather than
the call or caller itself, and as such its RCD MUST NOT be used when
a call lacks a first-party PASSporT that assures verification
services that the calling party number is not spoofed. It is
intended to be used in cases when the originating side does not
supply a display-name for the caller, so instead some entity in the
call path invokes a third-party service to provide rich caller data
for a call.

In telephone operations today, a third-party information service is
commonly queried with the calling party's number in order to learn
the name of the calling party, and potentially other helpful
information could also be passed over that interface. The value of
using a PASSporT to convey this information from third parties lies
largely in the preservation of the third party's signature over the
data, and the potential for the PASSporT to be conveyed from
intermediaries to endpoint devices. Effectively, these use cases
form a sub-case of out-of-band [RFC8816] use cases. cases [RFC8816]. The manner in
which third-party services are discovered is outside the scope of
this document.

An intermediary use case might look as follows using the SIP protocol
for this example: a SIP INVITE carries a display name in its From
header field value and an initial PASSporT object without the "rcd"
claim. When a terminating verification service implemented at a SIP
proxy server receives this request, request and determines that the signature
is valid, it might query a third-party service that maps telephone
numbers to calling party names. Upon receiving the PASSporT in a
response from that third-party service, the terminating side could
add a new Identity header field to the request for the PASSporT
object provided by the third-party service. It would then forward
the INVITE to the terminating user agent. If the display name in the
PASSporT object matches, or is string equivelent string-equivalent to, the display name
in the INVITE, then the name would presumably be rendered to the end
user by the terminating user agent.

A very similar flow could be followed by an intermediary closer to
the origination of the call. Presumably such a service could be
implemented at an originating network in order to decouple the
systems that sign for calling party numbers from the systems that
provide rich data about calls.

In an alternative use case, the terminating user agent might query a
third-party service. In this case, no new Identity header field
would be generated, though the terminating user agent might receive a
PASSporT object in return from the third-party service, and use the
"rcd" field in the object as a calling name to render to users while
alerting.

While in the traditional telephone network, the business relationship
between calling customers and their telephone service providers is
the ultimate root of information about a calling party's name, some
other forms of data like crowdsourced reputation scores might derive
from third parties. When those elements are present, they MUST be in
a third-party "rcd" PASSporT using the "iss" claim described in the
next section.

10.1. Signing as a Third Party

A third-party PASSporT contains an "iss" element to distinguish its
PASSporTs from first-party PASSporTs. Third-party "rcd" PASSporTs
are signed with credentials that do not have authority over the
identity that appears in the "orig" element of the PASSporT claims.
The presence of "iss" signifies that a different category of
credential is being used to sign a PASSporT than the [RFC8226] certificates (as
defined in [RFC8226]) used to sign STIR calls; it is instead a
certificate that identifies the source of the "rcd" data. How those
credentials are issued and managed is outside the scope of this
document; however, the value of "iss" however MUST reflect the Subject of the
certificate used to sign a third-party PASSporT. The explicit
mechanism for reflecting the subject Subject field of the certificate is out
of scope of this document and left to the certificate governance
policies that define how to map the "iss" value in the PASSporT to
the subject Subject field in the certificate. Relying parties in STIR have
always been left to make their own authorization decisions about
whether to trust the signers of PASSporTs, and PASSporTs; in the third-party case,
where an entity has explicitly queried a service to acquire the
PASSporT object, it may be some external trust or business
relationship that induces the relying party to trust a PASSporT.

An example of a Third Party issued PASSporT claims object issued by a third party is as
follows.

{ "orig":{"tn":"12025551000"},
"dest":{"tn":["12025551001"]},
"iat":1443208345,
"iss":"Zorin Industries",
"rcd":{"nam":"James St. John Smythe"} }

10.2. Verification using Third Party Using Third-Party RCD

The third-party "rcd" PASSporT cases must be considered in the
verification service, as an attacker could attempt to cut-and-paste cut and paste
such a third-party PASSporT into a SIP request in an effort to get
the terminating user agent to render the display name or confidence
values it contains to a call that should have no such assurance.
Following the rules of [RFC8225] and in particular if there is are
multiple identity headers, for example with headers (as in the case of the inclusion of an
"rcd" and "shaken" PASSporTs from two different signing
providers, providers), a
verification service MUST determine that the calling party number
shown in the "orig" of the "rcd" PASSporT corresponds to the calling
party number of the call it has received, and that the "iat" field of
the "rcd" PASSporT is within the date interval that the verification
service would ordinarily accept for a PASSporT. It is possible that
if there is multiple identity headers are present, only the verified identity
information should be considered when presenting call information to
an end user.

Verification services may alter their authorization policies for the
credentials accepted to sign PASSporTs when third parties generate
PASSporT objects, per Section 10.1. This may include accepting a
valid signature over a PASSporT even if it is signed with a
credential that does not attest authority over the identity in the
"orig" claim of the PASSporT, provided that the verification service
has some other reason to trust the signer. No further guidance on
verification service authorization policy is given here.

11. Levels of Assurance

As "rcd" can be provided by either first party first-party providers that are
directly authorized to sign PASSporTs in the STIR eco-system ecosystem or third third-
party providers that are indirectly or delegated authority to sign
PASSporTs. Relying parties could benefit from an additional claim
that indicates the identification, in the form of a uniquely
identifiable name, of the attesting party to the caller. Even in
first party
first-party cases, the Communications Service Provider (CSP) to which
a number was assigned might in turn delegate the number to a
reseller, who would then sell the number to an enterprise, in which
case the CSP might have little insight into the caller's name. In
third party
third-party cases, a caller's name could be determined from any
number of data sources, on a spectrum between public data scraped
from web searches to a direct business relationship to the caller.
As multiple PASSporTs can be associated with the same call,
potentially a verification service could receive attestations of the
caller name from multiple sources, which have different levels of
granularity or accuracy. Therefore, third-party PASSporTs that carry
"rcd" data are RECOMMENDED to also carry an indication of the
identity of the generator of the PASSporT in the form of the 'iss'
claim.

12. Use of "rcd" PASSporTs in SIP

This section documents SIP-specific usage for "rcd" PASSporTs and in
the SIP Identity header field value. Other using protocols of using PASSporT
may define their own usages guidance for the "rcd" PASSporTs.

12.1. Authentication Service Behavior for SIP protocol Protocol

An authentication service creating a PASSporT containing an "rcd"
claim MAY include a PASSporT extension ("ppt" value) of "rcd" or not. "rcd".
Third-party authentication services following the behavior in
Section 10.1 MUST include a PASSporT extension value of "rcd". If
the PASSporT extension does contain an "rcd", then any SIP
authentication services MUST add a PASSporT extension "ppt" parameter
to the Identity header field containing that PASSporT with a value of
"rcd". The resulting Identity header field might look as follows:

Identity: sv5CTo05KqpSmtHt3dcEiO/1CWTSZtnG3iV+1nmurLXV/HmtyNS7Ltrg9
dlxkWzoeU7d7OV8HweTTDobV3itTmgPwCFjaEmMyEI3d7SyN21yNDo2ER/Ovgt
w0Lu5csIppPqOg1uXndzHbG7mR6Rl9BnUhHufVRbp51Mn3w0gfUs=;
info=<https://biloxi.example.org/biloxi.cer>;alg=ES256;
ppt="rcd"

This document assumes that by default when using the SIP protocol, an
authentication service determines the value of "rcd", specifically
only for the "nam" key value, from the display-name component of the
From header field value of the request, alternatively request. Alternatively, for some
calls this may come from the P-Asserted-ID header. It is however a
matter of authentication service policy to decide how it populates
the value of the "nam" key, which MAY also match or be determined by
other fields in the request, from customer profile data, data or from
access to external services. If the authentication service generates
an "rcd" claim containing "nam" with a value that is not string string-
equivalent to the From header field display-name value, it MUST use
the full form of the PASSporT object in SIP.

In addition, {I-D.ietf-sipcore-callinfo-rcd}} [RFC9796] defines a Call-Info header field that MAY be
used as a source of RCD information that an authentication services service
uses to construct the appropriate PASSporT RCD claim types used.

Note also that, as a best practice, the accuracy and legitimacy of
Rich Call Data information that is included in the claims is
RECOMMENDED to follow a trust framework that is out of scope of this
document. As with telephone numbers for the STIR framework framework, the
authentication of Rich Call Data should follow some type of vetting
process by an entity that is authoritative over determining the
accuracy and legitimacy of that information. This includes the
mechanisms for how and from whom that information is received by the
authentication service. For example, the general use of Call-Info
via SIP as a trusted source of RCD information on the authentication
side is NOT RECOMMENDED.

12.2. Verification Service Behavior for SIP protocol

[RFC8224] Protocol

[RFC8224], Section 6.2 6.2, Step 5 requires that future specifications
defining PASSporT extension ("ppt") values describe any additional
verifier behavior specific to the SIP protocol. The general
verification proceedures procedures defined in Section 8.1 should be followed,
but the following paragraphs describe some of the specifics needed to
implement a verification service using the SIP protocol.

If the PASSporT is in compact form, then the verification service
MUST extract the display-name from the From header field value, if
any, and MUST use that as the string value for the "nam" key when it
recomputes the header and claims of the PASSporT object.
Additionally, if there exists a Call-Info header field as defined in
[I-D.ietf-sipcore-callinfo-rcd],
[RFC9796], the "jcard" JSON object value MUST be used to construct
the "jcd" key value when it recomputes the header and claims of the
PASSporT object. If the signature validates over the recomputed
object, then the verification is considered successful.

If the PASSporT is in full form with a PASSporT extension value of
"rcd", then the verification service MUST extract the value
associated with the "rcd" claim "nam" key in the object. If the
PASSporT signature is verified successfully successfully, then the verification
service MUST additionally compare the string value of the "rcd" claim
"nam" key value with the From header field value or the preferred
value. The preferred value depends on local policy of the SIP
network technique that conveys the display name string through a
field other than the From header field to interoperate with this
specification (e.g. (e.g., P-Asserted-Identity) as discussed in [RFC8224].
Similarly, "jcd" or "jcl" jcard jCard information, "icn", "apn", or "crn"
can be optionally, based on local policy for devices that support it,
used to populate a Call-Info header field following the format of
[I-D.ietf-sipcore-callinfo-rcd].
[RFC9796]. If future defined PASSporT RCD claims types defined in the future are
present, they should follow similar defined proceedures and policies.

The behavior of a SIP UAS User Agent Server (UAS) upon receiving an
INVITE or other type of session initiation request containing a
PASSporT object with an "rcd" claim largely remains a matter of
implementation policy. In most cases, implementations would render
this calling party name information to the user while alerting. Any
user interface additions to express confidence in the veracity of
this information are outside the scope of this specification.

13. Using "rcd", "rcdi", and "crn" as additional claims Additional Claims to other Other
PASSporT
extensions Extensions

Rich Call Data, including calling name information, as a common
example, is often data that is additive to the personal
communications information defined in the core PASSporT data required
to support the security properties defined in [RFC8225]. For cases
where the entity originating the personal communications is
supporting the authentication service for the calling identity and is
the authority of the Rich Call Data, rather than creating multiple
Identity header fields corresponding to multiple PASSporT extensions,
the authentication service can alternatively directly add the "rcd"
claim to a PASSporT that authenticates the calling identity.

13.1. Procedures for applying Applying RCD claims Claims as claims only Claims Only

For a given PASSporT using some other extension than "rcd", the
Authentication Service MAY additionally include the "rcd" defined in
{#rcd_define},
Section 5, "rcdi" defined in {#rcdi_define}, Section 6, and "crn" defined in
{#crn_define}
Section 7 claims. This would result in a set of claims that
correspond to the original intended extension with the addition of
the "rcd" claim.

The Verification verification service that receives the PASSporT, if it supports
this specification and chooses to, should interpret the "rcd" claim
as simply just an additional claim intended to deliver and/or
validate delivered Rich Call Data.

13.2. Example for applying Applying RCD claims Claims as claims only Claims Only

In the case of [RFC8588] [RFC8588], which is the PASSporT extension supporting
the SHAKEN Signature-based Handling of Asserted information using toKENs
(SHAKEN) specification [ATIS-1000074.v002], a common case is for an
Authentication
authentication service to co-exist coexist in a CSP network along with the
authority over the calling name used for the call. Rather than
require two identity headers, the CSP Authentication Service authentication service can
apply both the SHAKEN PASSporT claims and extension and simply add
the "rcd" required claims defined in this document.

For example, the PASSporT claims for the "shaken" PASSporT with "rcd"
claims would be as follows:

Protected Header
{
"alg":"ES256",
"typ":"passport",
"ppt":"shaken",
"x5u":"https://cert.example.org/passport.cer"
}
Payload
{
"attest":"A",
"dest":{"tn":["12025551001"]},
"iat":1443208345,
"orig":{"tn":"12025551000"},
"origid":"123e4567-e89b-12d3-a456-426655440000",
"rcd":{"nam":"James Bond"}
}

A Verification Service verification service that understands and supports claims defined
in the "rcd" and "shaken" PASSporT extensions is able to receive the
above PASSporT and interpret both the "shaken" claims as well as the
"rcd" defined claims.

If the Verification Service verification service only understands the "shaken" PASSporT
extension claims and doesn't support the "rcd" PASSporT extension or
claims, then the "rcd" claim, claim in this example, example is used during PASSporT
signature validation but is otherwise ignored and disregarded.

14. Further Information Associated with Callers

Beyond naming information and the information that can be contained
in a jCard [RFC7095] object, object [RFC7095], there may be additional human-readable
information about the calling party that should be rendered to the
end user in order to help the called party decide whether or not to
pick up the phone. This is not limited to information about the
caller, but
caller; it includes information about the call itself, which may
derive from analytics that determine based (based on call patterns or
similar data data) if the call is likely to be one the called party wants
to receive. Such data could include:

* information related to the location of the caller, or

* any organizations or institutions that the caller is associated
with, or even categories of institutions (is (whether this a
government agency, or a bank, or what have you), or

* hyperlinks to images, such as logos or pictures of faces, or to
similar external profile information, or

* information processed by an application before rendering it to a
user, like social networking data that shows that an unknown
caller is a friend-of-a-friend, or reputation scores derived from
crowdsourcing, or confidence scores based on broader analytics
about the caller and callee.

All of these data elements would benefit from the secure attestations
provided by the STIR and PASSporT frameworks. A new IANA registry
has been defined to hold potential values of the "rcd" array; see
Section 16.3. 15.3. Specific extensions to the "rcd" PASSporT claim are
left for future specification.

There is are a few ways RCD can be extended in the future, future; jCard is an
extensible object and the key/values in the RCD claim object can also
be extended. General guidance for future extensibility that were was
followed by the authors is that jCard generally typically should refer to data
that references the caller as an individual or entity, where whereas other
claims, such as "crn" "crn", refer to data regarding the specific call.
There may be other considerations discovered in the future, but this
logical grouping of data should be followed to the extent possible should be followed
for future extensibility.

15. Acknowledgements

We would like to thank David Hancock, Robert Sparks, Russ Housley,
Eric Burger, Alec Fenichel, Ben Campbell, Jack Rickard, Jordan
Simpson for helpful suggestions, review, and comments.

16. IANA Considerations

16.1.

15.1. JSON Web Token Claim

This document requests that the

Per this document, IANA add has added three new claims to the JSON "JSON Web
Token Claims Claims" registry as defined in [RFC7519].

Claim Name: "rcd"
Claim Description: Rich Call Data Information
Change Controller: IESG

Specification Document(s): [RFCThis] IETF
Reference: RFC 9795

Claim Name: "rcdi"
Claim Description: Rich Call Data Integrity Information
Change Controller: IESG
Specification Document(s): [RFCThis] IETF
Reference: RFC 9795

Claim Name: "crn"
Claim Description: Call Reason
Change Controller: IESG

Specification Document(s): [RFCThis]

16.2. IETF
Reference: RFC 9795

15.2. Personal Assertion Token (PASSporT) Extensions

This document requests that the

Per this document, IANA add has added a new entry to the Personal "Personal
Assertion Token (PASSporT) Extensions Extensions" registry for the type "rcd"
which is specified in [RFCThis].

16.3. this document.

15.3. PASSporT RCD Claim Types

This document requests that the

IANA create has created a new registry for
PASSporT "PASSporT RCD claim types. This new Claim Types" registry should be added to in the
"Personal Assertion Token (PASSporT)" registry group. Registration
of new PASSporT RCD claim types shall be under the Specification
Required
policy. policy [RFC8126].

This registry is to be initially populated with five claim name values,
"nam", "apn", "icn", "jcd", and "jcl", which are specified in
[RFCThis]. This is a two column registry with column1 = this
document. The columns are "Name" and
column2 = "Reference Document". "Reference". Any new
registrations should consist of only of the name and the reference
document. There is an obligation for expert review, where the
designated expert should validate that the proposed new PASSporT RCD
claim type has a scope that doesn't potentially conflict or overlap
with the usage or interpretation of the other existing types in the
registry.

17.

16. Security Considerations

The process of signing information contained in a "rcd" PASSporT,
whether PASSporT
(whether the identities, identifiers, alternate identities or
identifiers, images, logos, physical addresses, or otherwise otherwise) should
follow some vetting process in which an authoritative entity should
follow follows
an appropriate consistent policy defined and governed by the
eco-system
ecosystem using RCD and the STIR framework. This can be of many
forms, depending on the setup and constraints of the policy
requirements of the eco-system ecosystem, and is therefore out-of-scope out of scope of this
document. However, the general chain of trust that signers of "rcd"
PASSporT are either directly authoritative or have been delegated
authority through certificates using JWT Claim Constraints and
integrity mechanisms defined in this and related documents is
critical to maintain the integrity of the eco-system ecosystem utilizing this
and other STIR related STIR-related specifications.

Revealing information such as the name, location, and affiliation of
a person necessarily entails certain privacy risks. Baseline
PASSporT has no particular confidentiality requirement, as the
information it signs in many current base communications protocols,
for example SIP, protocols
(for example, SIP) is information that is carried in the clear
anyway. Transport-level security can hide those SIP fields from
eavesdroppers, and the same confidentiality mechanisms would protect
any PASSporT(s) carried in SIP.

The dereferencing and download of any RCD URI linked URI-linked resources as
part of verification either in-network or on device could provide
some level of information about calling patterns, so this should be
considered when making these resources available.

The use of JWTClaimConstraints, a mechanism defined in [RFC8226] and
extended in [RFC9118] [RFC9118], to constrain any of the RCD information in the
public certificate by including that information in the certificate,
depending on the availability in the deployment of the PKI system,
may present a privacy issue. The use of the "rcdi" claim and digests
for representing JWT claim contents is RECOMMENDED for the prevention
of the exposure of that information through the certificates which that are
often publically publicly accessible and available.

Since computation of "rcdi" digests for URIs requires the loading of
referenced content, it would be best practice to validate that
content at the creation of the "rcdi" or corresponding JWT claim
constraint value by checking for content that may cause issues for
verification services or that doesn't follow the behavior defined in
this document, e.g., unreasonably sized data, the inclusion of
recursive URI references, etc. Along the same lines, the
verification service should also use precautionary best practices to
avoid attacks when accessing URI linked URI-linked content.

As general guidance, the use of URLs and URIs that reference
potentially dangerous or intentionally harmful content should be
considered in implimenting implementing this specification. [RFC3986] [RFC3986], Section 7
contains good additional guidance to consider when communicating or
dereferencing URLs and URIs.

17.1. The use

16.1. Use of JWT Claim Constraints in delegate certificates Delegate Certificates to
exclude unauthorized claims Exclude
Unauthorized Claims

While this can apply to any PASSporT that is signed with a STIR
Delegate Certificates Certificate [RFC9060], it is important to note that when
constraining PASSporTs to include specific claims or contents of
claims, it is also important to consider potential attacks by non-
authorized signers that may include other potential PASSporT claims
that weren't originally vetted by the authorized entity providing the
delegate certificate. The use of JWT claims constraints as (as defined
in [RFC9118] [RFC9118]) for preventing the ability to include claims beyond the
claims defined in this document may need to be considered.

18.

17. References

18.1.

17.1. Normative References

[I-D.ietf-sipcore-callinfo-rcd]
Wendt, C. and J. Peterson, "SIP Call-Info Parameters for
Rich Call Data", Work in Progress, Internet-Draft, draft-
ietf-sipcore-callinfo-rcd-06, 3 June 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-sipcore-
callinfo-rcd-06>.

[IANA-COSE-ALG]
IANA, "COSE Algorithms
<https://www.iana.org/assignments/cose/cose.xhtml>", n.d.. Algorithms",
<https://www.iana.org/assignments/cose>.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.

[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
DOI 10.17487/RFC3261, June 2002,
<https://www.rfc-editor.org/info/rfc3261>.

[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.

[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<https://www.rfc-editor.org/info/rfc4648>.

[RFC6234] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and SHA-based HMAC and HKDF)", RFC 6234,
DOI 10.17487/RFC6234, May 2011,
<https://www.rfc-editor.org/info/rfc6234>.

[RFC6901] Bryan, P., Ed., Zyp, K., and M. Nottingham, Ed.,
"JavaScript Object Notation (JSON) Pointer", RFC 6901,
DOI 10.17487/RFC6901, April 2013,
<https://www.rfc-editor.org/info/rfc6901>.

[RFC7095] Kewisch, P., "jCard: The JSON Format for vCard", RFC 7095,
DOI 10.17487/RFC7095, January 2014,
<https://www.rfc-editor.org/info/rfc7095>.

[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/info/rfc7519>.

[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.

[RFC8224] Peterson, J., Jennings, C., Rescorla, E., and C. Wendt,
"Authenticated Identity Management in the Session
Initiation Protocol (SIP)", RFC 8224,
DOI 10.17487/RFC8224, February 2018,
<https://www.rfc-editor.org/info/rfc8224>.

[RFC8225] Wendt, C. and J. Peterson, "PASSporT: Personal Assertion
Token", RFC 8225, DOI 10.17487/RFC8225, February 2018,
<https://www.rfc-editor.org/info/rfc8225>.

[RFC8226] Peterson, J. and S. Turner, "Secure Telephone Identity
Credentials: Certificates", RFC 8226,
DOI 10.17487/RFC8226, February 2018,
<https://www.rfc-editor.org/info/rfc8226>.

[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/info/rfc8259>.

[RFC8588] Wendt, C. and M. Barnes, "Personal Assertion Token
(PaSSporT) Extension for Signature-based Handling of
Asserted information using toKENs (SHAKEN)", RFC 8588,
DOI 10.17487/RFC8588, May 2019,
<https://www.rfc-editor.org/info/rfc8588>.

[RFC9060] Peterson, J., "Secure Telephone Identity Revisited (STIR)
Certificate Delegation", RFC 9060, DOI 10.17487/RFC9060,
September 2021, <https://www.rfc-editor.org/info/rfc9060>.

[RFC9118] Housley, R., "Enhanced JSON Web Token (JWT) Claim
Constraints for Secure Telephone Identity Revisited (STIR)
Certificates", RFC 9118, DOI 10.17487/RFC9118, August
2021, <https://www.rfc-editor.org/info/rfc9118>.

18.2.

[RFC9796] Wendt, C. and J. Peterson, "SIP Call-Info Parameters for
Rich Call Data", RFC 9796, DOI 10.17487/RFC9796, May 2025,
<https://www.rfc-editor.org/info/rfc9796>.

17.2. Informative References

[ATIS-1000074.v002]
ATIS/SIP Forum NNI Task Group,
Alliance for Telecommunications Industry Solutions,
"Signature-based Handling of Asserted information using
toKENs (SHAKEN)
<https://access.atis.org/apps/group_public/
download.php/62391/ATIS-1000074.v002.pdf>", (SHAKEN)", November 2021.

[RFC3325] Jennings, C., Peterson, J., and M. Watson, "Private
Extensions to the Session Initiation Protocol (SIP) for
Asserted Identity within Trusted Networks", RFC 3325,
DOI 10.17487/RFC3325, November 2002,
<https://www.rfc-editor.org/info/rfc3325>.

[RFC7340] Peterson, J., Schulzrinne, H., and H. Tschofenig, "Secure
Telephone Identity Problem Statement and Requirements",
RFC 7340, DOI 10.17487/RFC7340, September 2014,
<https://www.rfc-editor.org/info/rfc7340>.

[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.

[RFC8816] Rescorla, E. and J. Peterson, "Secure Telephone Identity
Revisited (STIR) Out-of-Band Architecture and Use Cases",
RFC 8816, DOI 10.17487/RFC8816, February 2021,
<https://www.rfc-editor.org/info/rfc8816>.

[TS.3GPP.24.229]
3GPP, "IP multimedia call control protocol based on
Session Initiation Protocol (SIP) and Session Description
Protocol (SDP); Stage 3", 16.7.0, 3GPP TS 24.229,
September 2020,
<https://www.3gpp.org/ftp/Specs/html-info/24229.htm>.

[W3C-SubresourceIntegrity]
W3C,
Akhawe, D., Ed., Braun, F., Ed., Marier, F., Ed., and J.
Weinberger, Ed., "Subresource Integrity <https://www.w3.org/TR/SRI/>", Integrity", W3C
Recommendation, 23 June 2016. 2016,
<https://www.w3.org/TR/2016/REC-SRI-20160623/>.

Acknowledgements

We would like to thank David Hancock, Robert Sparks, Russ Housley,
Eric Burger, Alec Fenichel, Ben Campbell, Jack Rickard, Jordan
Simpson for helpful suggestions, review, and comments.

Authors' Addresses

Chris Wendt
Somos Inc.
Email: chris-ietf@chriswendt.net

Jon Peterson
Neustar Inc.
Email: jon.peterson@neustar.biz