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ART STIR Internet-Draft This document extends PASSporT, which is a token object that conveys cryptographically-signed information about the participants involved in communications, to include information defined as part of the SHAKEN specification from ATIS (Alliance for Telecommunications Industry Solutions) and the SIP Forum IP-NNI Joint Task Force. These extensions provide a level of confidence in the correctness of the originating identity for a telephone network that has communications coming from both STIR participating originating communications as well as communications that does not include STIR information.

The SHAKEN specification defines a framework for using STIR protocols including PASSporT , SIP Authenticated Identity Management and the STIR certificate framework for implementing the cryptographic validation of an authorized originator of telephone calls using SIP. Because the current telephone network contains both VoIP and TDM/SS7 originated traffic, there are many scenarios that need to be accounted for where PASSporT signatures may represent either direct or indirect call origination scenarios. The SHAKEN specification defines levels of attestation of the origination of the call as well as an origination identifier that can help create a unique association with the origination of calls from various parts of the VoIP or TDM telephone network. This document specifies these indicators as a specified PASSporT extension.

The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in .

The SHAKEN framework is designed to use PASSporT as a method of asserting the telephone number calling identity. In addition to the PASSporT base claims, there are two additional claims that have been defined for the needs of a service provider to signal information beyond just the telephone identity. First, in order to help bridge the transition of the state of the current telephone network which has calls with no authentication and non-SIP signaling not compatible with the use of PASSporT and Secure Telephone Identity (STI) in general, there is an attestation claim. This provides three levels of attestation, including a full attestation when the service provider can fully attest to the calling identity, a partial attestation, when the service provider originated a telephone call but can not fully attest to the calling identity, and a gateway attestation which is the lowest level of attestation and represents the service provider receiving a call from a non PASSporT or STI supporting telephone gateway. The second claim is a unique origination identifier that should be used by the service provider to identify different sources of telephone calls to support a traceback mechanism that can be used for enforcement and identification of a source of illegitimate calls. The use of the compact form of PASSporT is not specified in this document and is not specified for use in SHAKEN . The next two sections define these new claims.

This indicator allows for both identifying the service provider that is vouching for the call as well as clearly indicating what information the service provider is attesting to. The ‘attest’ claim can be one of the following three values, ‘A’, ‘B’, or ‘C’ as defined in . ‘A’ represents ‘Full Attestation’ where the signing provider MUST satisfy all of the following conditions: Is responsible for the origination of the call onto the IP based service provider voice network. Has a direct authenticated relationship with the initiator of the call and can identify the customer associated with the initiator. Has established a verified association with the calling party telephone number used for the call. ‘B’ represents ‘Partial Attestation’ where the signing provider MUST satisfy all of the following conditions: Is responsible for the origination of the call onto its IP-based voice network. Has a direct authenticated relationship with the initiator of the call and can identify the customer associated with the initiator. Has NOT established a verified association with the calling party telephone number being used for the call. ‘C’ represents ‘Gateway Attestation’ where the signing provider MUST satisfy all of the following conditions: Is the entry point of the call into its VoIP network. Has no relationship with the initiator of the call (e.g., international gateways)

The purpose of the unique origination identifier is to assign an opaque identifier corresponding to the service provider-initiated calls themselves, customers, classes of devices, or other groupings that a service provider might want to use for determining things like reputation or trace back identification of customers or gateways. The value of ‘origid’ claim is a UUID as defined in . SHAKEN isn’t prescriptive in the exact usage of origid other than the UUID format as a globally unique identifier representing the originator of the call to whatever granularity the PASSporT signer determines is sufficient for the ability to trace the original origination point of the call. There will likely be best practices documents that more precisely guide it’s usage in real deployments.

The use of the ‘shaken’ PASSporT type and the claims ‘attest’ and ‘origid’ are formally defined in for usage in SIP aligned with the use of the identity header defined in .

The order of the claim keys MUST follow the rules of Section 9; the claim keys MUST appear in lexicographic order. Therefore, the claim keys discussed in this document appear in the PASSporT Payload in the following order, attest dest iat orig origid

This document defines a new PASSporT extension. The considerations related to the security of the PASSporT object itself are the same as those described in . defines how to compare the values of the "dest", "orig" and "iat" claims against fields in a SIP containing a PASSporT as part of validating that request. The values of the new "attest" and "origid" claims added by this extension are not used in such a validation step. They are not compared to fields in the SIP message. Instead, they simply carry additional information from the signer to the consumer of the PASSport. This new information shares the same integrity protection and non-repudiation properties as the base claims in the PASSporT.

This specification requests that the IANA add two new claims to the JSON Web Token Claims registry as defined in . Claim Name: “attest” Claim Description: Attestation level as defined in SHAKEN framework Change Controller: IESG Specification Document(s): [RFCThis] Claim Name: “origid” Claim Description: Originating Identifier as defined in SHAKEN framework Change Controller: IESG Specification Document(s): [RFCThis]

This specification requests that the IANA add a new entry to the Personal Assertion Token (PASSporT) Extensions registry for the type “shaken” which is specified in [RFCThis].

The authors would like to thank those that helped review and contribute to this document including specific contributions from Jon Peterson, Russ Housley, and Andrew Jurczak. The authors would like acknowledge the work of the ATIS/SIP Forum IP-NNI Task Force to develop the concepts behind this document.

The baseline security mechanisms in the Session Initiation Protocol (SIP) are inadequate for cryptographically assuring the identity of the end users that originate SIP requests, especially in an interdomain context. This document defines a mechanism for securely identifying originators of SIP requests. It does so by defining a SIP header field for conveying a signature used for validating the identity and for conveying a reference to the credentials of the signer.This document obsoletes RFC 4474. This document defines a method for creating and validating a token that cryptographically verifies an originating identity or, more generally, a URI or telephone number representing the originator of personal communications. The Personal Assertion Token, PASSporT, is cryptographically signed to protect the integrity of the identity of the originator and to verify the assertion of the identity information at the destination. The cryptographic signature is defined with the intention that it can confidently verify the originating persona even when the signature is sent to the destination party over an insecure channel. PASSporT is particularly useful for many personal-communications applications over IP networks and other multi-hop interconnection scenarios where the originating and destination parties may not have a direct trusted relationship. In order to prevent the impersonation of telephone numbers on the Internet, some kind of credential system needs to exist that cryptographically asserts authority over telephone numbers. This document describes the use of certificates in establishing authority over telephone numbers, as a component of a broader architecture for managing telephone numbers as identities in protocols like SIP. This specification defines a Uniform Resource Name namespace for UUIDs (Universally Unique IDentifier), also known as GUIDs (Globally Unique IDentifier). A UUID is 128 bits long, and can guarantee uniqueness across space and time. UUIDs were originally used in the Apollo Network Computing System and later in the Open Software Foundation\'s (OSF) Distributed Computing Environment (DCE), and then in Microsoft Windows platforms.This specification is derived from the DCE specification with the kind permission of the OSF (now known as The Open Group). Information from earlier versions of the DCE specification have been incorporated into this document. [STANDARDS-TRACK] JSON Web Token (JWT) is a compact, URL-safe means of representing claims to be transferred between two parties. The claims in a JWT are encoded as a JSON object that is used as the payload of a JSON Web Signature (JWS) structure or as the plaintext of a JSON Web Encryption (JWE) structure, enabling the claims to be digitally signed or integrity protected with a Message Authentication Code (MAC) and/or encrypted. ATIS/SIP Forum NNI Task Group In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. This document describes Session Initiation Protocol (SIP), an application-layer control (signaling) protocol for creating, modifying, and terminating sessions with one or more participants. These sessions include Internet telephone calls, multimedia distribution, and multimedia conferences. [STANDARDS-TRACK]