Network Working Group J. Peterson
Request for Comments: 3323 Neustar
Category: Standards Track November 2002
A Privacy Mechanism for the Session Initiation Protocol (SIP)
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
Abstract
This document defines new mechanisms for the Session Initiation
Protocol (SIP) in support of privacy. Specifically, guidelines are
provided for the creation of messages that do not divulge personal
identity information. A new "privacy service" logical role for
intermediaries is defined to answer some privacy requirements that
user agents cannot satisfy themselves. Finally, means are presented
by which a user can request particular functions from a privacy
service.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
3. Varieties of Privacy . . . . . . . . . . . . . . . . . . . 4
3.1 When is Privacy Necessary? . . . . . . . . . . . . . . . . 5
3.2 User-Provided Privacy . . . . . . . . . . . . . . . . . . 6
3.3 Network-Provided Privacy . . . . . . . . . . . . . . . . . 7
4. User Agent Behavior . . . . . . . . . . . . . . . . . . . 7
4.1 Constructing Private Messages . . . . . . . . . . . . . . 8
4.1.1 URIs, Display-Names and Privacy . . . . . . . . . . . . . 8
4.1.1.1 Display-Names . . . . . . . . . . . . . . . . . . . . . . 9
4.1.1.2 URI Usernames . . . . . . . . . . . . . . . . . . . . . . 9
4.1.1.3 URI Hostnames and IP Addresses . . . . . . . . . . . . . . 9
4.2 Expressing Privacy Preferences . . . . . . . . . . . . . . 11
4.3 Routing Requests to Privacy Services . . . . . . . . . . . 12
4.4 Routing Responses to Privacy Services . . . . . . . . . . 13
5. Privacy Service Behavior . . . . . . . . . . . . . . . . . 14
Peterson Standards Track [Page 1]
RFC 3323 Privacy Mechanism for SIP November 2002
5.1 Header Privacy . . . . . . . . . . . . . . . . . . . . . . 16
5.2 Session Privacy . . . . . . . . . . . . . . . . . . . . . 17
5.3 Applying User-Level Privacy Functions. . . . . . . . . . . 18
6. Security Considerations . . . . . . . . . . . . . . . . . 19
7. IANA Considerations . . . . . . . . . . . . . . . . . . . 19
Normative References . . . . . . . . . . . . . . . . . . . 20
Informative References . . . . . . . . . . . . . . . . . . 20
Author's Address . . . . . . . . . . . . . . . . . . . . . 21
Acknowledgments . . . . . . . . . . . . . . . . . . . . . 21
Full Copyright Statement . . . . . . . . . . . . . . . . . 22
1. Introduction
This document provides privacy requirements and mechanisms for the
Session Initiation Protocol (SIP).
Privacy is defined in this document as the withholding of the
identity of a person (and related personal information) from one or
more parties in an exchange of communications, specifically a SIP
dialog. These parties potentially include the intended
destination(s) of messages and/or any intermediaries handling these
messages. As identity is defined in this document, withholding the
identity of a user will, among other things, render the other parties
in the dialog unable to send new SIP requests to the user outside of
the context of the current dialog.
In SIP, identity is most commonly carried in the form of a SIP URI
and an optional display-name. A SIP address-of-record has a form
similar to an email address with a SIP URI scheme (for example,
sip:alice@atlanta.com). A display-name is a string containing a name
for the identified user (for example, "Alice"). SIP identities of
this form commonly appear in the To and From header fields of SIP
requests and responses. A user may have many identities that they
use in different contexts.
There are numerous other places in SIP messages in which identity-
related information can be revealed. For example, the Contact header
field contains a SIP URI, one that is commonly as revealing as the
address-of-record in the From. In some headers, the originating user
datatracker.ietf.org