Network Working Group U. Koenig Internet-Draft J. Schallaboeck Intended status: Experimental Unabhaengiges Landeszentrum Expires: December 9, 2012 fuer Datenschutz Schleswig-Holstein June 07, 2012 Privacy Preferences for E-Mail Messages draft-koenig-privicons-04 Abstract This document proposes a syntax and semantics as an extension of the Internet Message Format (e-mail message) allowing a Sending User of an e-mail message to express his or her preference for how the message content is to be handled by the Receiving Users. For this purpose, semantics of sets of different character combinations ("Privicons") are described. These can syntactically be integrated either in the first-line of the body, in the subject line and/or in a dedicated header of any e-mail message. The Privicons icon set consists of six different icons. They will be machine-readable. The Privicons concept is partly borrowing its approach from the concept of emoticons. For example, to express that the content may be forwarded and even be published. The Sending User could use the Privicon "[>]", which may be followed by an additional explanations, such as "please share". Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on December 9, 2012. Copyright Notice Copyright (c) 2012 IETF Trust and the persons identified as the Koenig & Schallaboeck Expires December 9, 2012 [Page 1]
Internet-Draft Privicons June 2012 document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Koenig & Schallaboeck Expires December 9, 2012 [Page 2]
Internet-Draft Privicons June 2012 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Relations to other standards . . . . . . . . . . . . . . . 4 1.3. Terminology and Conventions . . . . . . . . . . . . . . . 5 2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 6 2.2. First-Line(s) of Message body . . . . . . . . . . . . . . 6 2.3. Subject Line . . . . . . . . . . . . . . . . . . . . . . . 7 2.4. Header . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.5. Footer . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.6. Authoritative or Parsing order - Conflicts . . . . . . . . 9 2.7. Syntax error . . . . . . . . . . . . . . . . . . . . . . . 9 2.8. HTML-Messages . . . . . . . . . . . . . . . . . . . . . . 9 3. Semantics . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.1. Privicons . . . . . . . . . . . . . . . . . . . . . . . . 10 3.1.1. [X] Keep private . . . . . . . . . . . . . . . . . . . 10 3.1.2. [/] Don't print . . . . . . . . . . . . . . . . . . . 10 3.1.3. [=] Delete after reading, I days or on date . . . . . 10 3.1.4. [-] No attribution . . . . . . . . . . . . . . . . . . 10 3.1.5. [o] Keep internal . . . . . . . . . . . . . . . . . . 11 3.1.6. [>] Please share . . . . . . . . . . . . . . . . . . . 11 3.2. Multiple Privicons . . . . . . . . . . . . . . . . . . . . 11 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 5. Security Considerations . . . . . . . . . . . . . . . . . . . 12 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 7. Normative References . . . . . . . . . . . . . . . . . . . . . 12 Appendix A. Example e-mail message . . . . . . . . . . . . . . . 13 Appendix B. Informative example requirements for e-mail message user agents . . . . . . . . . . . . . . . . . 14 B.1. User agent behaviour . . . . . . . . . . . . . . . . . . . 14 B.1.1. Terms . . . . . . . . . . . . . . . . . . . . . . . . 14 B.1.2. [X] Keep secret . . . . . . . . . . . . . . . . . . . 14 B.1.3. [/] Don't print . . . . . . . . . . . . . . . . . . . 15 B.1.4. [=] Delete after reading, I days or on date . . . . . 15 B.1.5. [-] No attribution . . . . . . . . . . . . . . . . . . 16 B.1.6. [o] Keep internal . . . . . . . . . . . . . . . . . . 16 B.1.7. [>] Please share . . . . . . . . . . . . . . . . . . . 16 B.2. Confirmation/Affirmation of preferences . . . . . . . . . 17 B.3. Transparency (OPTIONAL) . . . . . . . . . . . . . . . . . 17 Appendix C. Graphical Representation of the State Machine . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 Koenig & Schallaboeck Expires December 9, 2012 [Page 3]
Internet-Draft Privicons June 2012 1. Introduction 1.1. Overview Privicons describe a vocabulary of icons as an extension of the Internet Message Format (e-mail message) for users to indicate how their e-mail message should be treated. The icons are based on ASCII symbols so that they can appear as embedded graphics or plain text and include a variety of instructions such as "don't print," "internal use only," and "confidential". It is partly borrowing its approach from the concept of emoticons. For example to express, that the content can be forwarded and even be published, the Sending User could use the Privicon "[>]", which may be followed by an additional explanations, such as "please share". This document proposes a syntax (Section 2) and semantics (Section 3) allowing a Sending User of an e-mail message to express his or her preference for how the e-mail message content should be handled by the Receiving Users. For this purpose, semantics of sets of different character combinations ("Privicons") are described. These can syntactically be integrated either in the first-line of the body, in the subject line and/or in a dedicated header of any e-mail message. The Privicons icon set has six different icons. They will be machine-readable. Importantly, the user can override all requests transmitted by Privicons: The approach is grounded in reminder over hard-coded solutions that indiscriminately restrict speech. Therefore, the icons are merely asking the Receiving User of an e-mail to follow the Sending User's preference. Other than DRM oriented approaches, Privicons embraces the concept of code-based norms approach. This means, that the approach relies on social norms to be followed by the Receiving User, rather than technical enforcement mechanisms. However, technical means may be used to support this (for example, specifications see example e-mail message (Appendix B)). Note: The specific character combinations for each Privicon is currently undergoing user testing, it therefore might and will most certainly change during the progression of this draft. 1.2. Relations to other standards This specification extends [RFC5322] - Internet Message Format by defining certain syntax for the first-line(s) of the body, the subject line and an additional header field. Koenig & Schallaboeck Expires December 9, 2012 [Page 4]
Internet-Draft Privicons June 2012 1.3. Terminology and Conventions 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 [RFC2119]. o The term "User Agent" (often also Mail User Agent, UA, MUA) is used as defined in Section-2.3.3 in [RFC5321] o The terms "Sending User" and "Receiving User" are related to a user using the User Agent either sending or receiving an e-mail message. A Sending User is a user that sends an e-mail message to a Receiving User. A Receiving User is a user that receives an e-mail message from a Sending User. o The term "Line" is used as defined by SMTP Section-2.3.8 in [RFC5322] thereof o The term "full-date" is used as defined by Section-5.6 in [RFC3339]. o The term Privacy Preference describes the intention the user had when she has sent a specific e-mail message. It can be expressed with the Privicons described in this RFC. 2. Syntax In this section, the syntax if the Privicon e-mail extension is defined. For semantics (Section 3), please see next section. A User can indicate a Privacy Preference as lined out below in the following ways: o by making available selection of the Privicons, which SHOULD be provided by the user agent, o by inserting a Privicon in the subject line - by inserting a Privicon in the first-line of the body. An e-mail message fully compliant with this RFC will be called a Privicon Message, it o MUST contain a header (Section 2.4) with Privacy Preferences, o SHOULD contain subject (Section 2.3) with Privicon, o SHOULD have first-line (Section 2.2) and footer (Section 2.5) Koenig & Schallaboeck Expires December 9, 2012 [Page 5]
Internet-Draft Privicons June 2012 o and MAY generate an HTML version. The following section describes how the Privicon status of an e-mail message is determined, concerning the privacy preferences described in Overview (Section 1.1) 2.1. Definitions element1 | element2 Elements separated by a bar ("|") are alternatives, e.g., "yes | no" will accept yes or no. "literal" Quotation marks surround literal text. Unless stated otherwise, the text is case-insensitive. whitespace " " whatever Some arbitrary text. date Will be substituted by a "full-date", [RFC3339]. privicon = ("[X]"|"[/]"|"[=]"|"[=0]"|"[=I]"|"[=date]"|"[-]"|"[o]"|"[>]") - the Privicon token. It contains all valid Privicons, the Privicon icon set. I I will be substituted by an integer number >= 0. description Contains the description of the Privicon as defined in Semantics (Section 3). subject Is the e-mail message subject field, see [RFC5322]. CRLF Is the carriage return/line feed pair written in this document as "CRLF". A line is a series of characters that is delimited with the two characters carriage-return and line-feed; that is, the carriage return (CR) character (ASCII value 13) followed immediately by the line feed (LF) character (ASCII value 10), as described in section2.1 in [RFC5322] 2.2. First-Line(s) of Message body An indication of the Privacy Preference can be given in the first line of the body of an e-mail message. The expression MUST be followed by a text giving a short explanation the meaning of the expressions. It is RECOMMENDED to use the following text, although localization into other languages is also encouraged, albeit not lined out in this document. Koenig & Schallaboeck Expires December 9, 2012 [Page 6]
Internet-Draft Privicons June 2012 firstLine = privicon whitespace "-" whitespace description For example: [X] - Keep private [/] - Don't print [=] - Delete after reading [=0] - Delete after reading [=I] - Delete after I days [=date] - Delete on date [-] - No attribution [o] - Keep internal [>] - Please share After the first-line, a second line, with an additional privacy preference may follow if the combination (Section 3.2) is permitted. 2.3. Subject Line An indication of the Privacy Preference can be given in the beginning of a subject line of an e-mail message using the following expression: privicon whitespace subject or whatever whitespace privicon whitespace subject For example: [X] This is the subject of the e-mail message [/] This is the subject of the e-mail message [=] This is the subject of the e-mail message Koenig & Schallaboeck Expires December 9, 2012 [Page 7]
Internet-Draft Privicons June 2012 [=4] This is the subject of the e-mail message [=1980-01-01] This is the subject of the e-mail message [-] This is the subject of the e-mail message [o] This is the subject of the e-mail message [>] This is the subject of the e-mail message or Re: [X] This is the subject of the e-mail message Fwd: [/] This is the subject of the e-mail message 2.4. Header An indication of the Privacy Preference MAY be given in the header of an e-mail message, for this purpose the following field is defined, extending in section 3.6 in [RFC5322] the field definition, thereof. priviconfield = "Privicon:" whitespace privicon CRLF The possible values of the Privicon token are described in Definitions (Section 2.1) 2.5. Footer Separated by -- The Footer MAY be located within the signature as described in section 4.3 in [RFC3676] . It contains a paragraph that describes what the Sending User of the e-mail message intended when she chooses the selected Privicon. A clarification MAY be added that a conflict between header and first-line would lead to the first-line to be authoritative. footer = CRLF "-- " CRLF footertext footertext = firstLine CRLF description For example: Koenig & Schallaboeck Expires December 9, 2012 [Page 8]
Internet-Draft Privicons June 2012 -- [X] - Keep private The "Keep secret" Privicon asks the Receiving User to keep the received e-mail message secret. Note: Footnote may violates [RFC1855] Page4 - do not use more than 4 lines signature. The Footnote is just informative not authoritative 2.6. Authoritative or Parsing order - Conflicts When parsed, the authoritative order of the different elements is as follows: 1. first-line in body (Section 2.2) 2. subject (Section 2.3) 3. header (Section 2.4) If only one Privicon is found, it has always the same meaning, no matter if it is defined in first-line in body, subject or header. 2.7. Syntax error After syntax error, the most restrictive case is assumed. For example "Delete after ??? days" will be transformed into "Delete immediately") 2.8. HTML-Messages In HTML-Messages, the "Privicon" are OPTIONAL represented with graphical icons. Example icons can be found in Annex. Embedded icons MUST be included into the Message and MUST NOT be loaded from an Internet Server. This is important avoid a loss of privacy for the receiving user. It also causes in some cases problems with SSL- Encryption in web based e-mail message user agents (MUA). The graphical representation MUST contain the ASCII-Icon as Alternate-Text. If the "Privicon" is included in the First Line of Body, the "description" MUST also be displayed in next to the Privicon. Koenig & Schallaboeck Expires December 9, 2012 [Page 9]
Internet-Draft Privicons June 2012 3. Semantics 3.1. Privicons The Privicons icon set has six different icons. The meaning of the icons will be described in this section. It is important, that Privicons always just meant to be a nice way of asking somebody to do something. 3.1.1. [X] Keep private The "Keep private" Privicon asks the Receiving User to keep the received e-mail message private. 3.1.2. [/] Don't print The "Don't print" Privicon asks the Receiving User to not print the received e-mail message. 3.1.3. [=] Delete after reading, I days or on date The "Delete after reading/I days" Privicon asks the Receiving User to delete the e-mail message no later than a specified period. There are four different cases: 1. [=] delete after reading 2. [=0] delete after reading 3. [=I] delete after I days 4. [=date] delete on date "I" and "date" are defined in Terminology and Conventions (Section 1.3). 3.1.4. [-] No attribution The "No attribution" Privicon asks the Receiving User to not attribute, name or mention the original Sending User of the e-mail message in any kind. At the same time the Receiving User may quote, follow or paraphrase the content, facts and opinions voiced in the original e-mail message. In other words, the Receiving User is free to use the information received, but neither the identity nor the affiliation of the Sending User may be revealed. Koenig & Schallaboeck Expires December 9, 2012 [Page 10]
Internet-Draft Privicons June 2012 3.1.5. [o] Keep internal The "Keep internal" Privicon asks the Receiving User to present this e-mail message only to those people that are common friends, or otherwise part of a group of people are in a relation to both the Sending User and the Receiving User. Note that the judgement, whether a person belongs to this group is solely upon the Receiving User unless otherwise indicated by the Sending User. The "Keep internal" just indicates, that a Receiving User SHOULD give some further thought on which she is sending the e-mail message to, and that the Sending User does not want the e-mail message to be forwarded arbitrarily. 3.1.6. [>] Please share The "Please share" Privicon asks the Receiving User to share this e-mail message with everyone, as she likes. It may be supplemented by further instructions on licensing for clarifying the copyright status. 3.2. Multiple Privicons Possible: Y Impossible: N Does not apply: X As secondary option, potentially, and if first preference is overruled: +-----+-----+-----+-----+-----+-----+-----+ | | [X] | [/] | [=] | [-] | [o] | [>] | +-----+-----+-----+-----+-----+-----+-----+ | [X] | X | Y | Y | N | N | N | | [/] | Y | X | Y | Y | Y | Y | | [=] | Y | Y | X | Y | Y | N | | [-] | N | Y | Y | X | Y | Y | | [o] | N | N | Y | Y | X | N | | [>] | N | Y | N | Y | N | X | +-----+-----+-----+-----+-----+-----+-----+ Table 1: Matrix of all combinations of Privicons. Koenig & Schallaboeck Expires December 9, 2012 [Page 11]
Internet-Draft Privicons June 2012 4. IANA Considerations This document introduces a new field in the e-mail header, as described in the header (Section 2.4) section. 5. Security Considerations The extensions to the e-mail message Format described in this document does not change the fundamental nature of the SMTP service and hence does not create any new security exposures in and of itself. 6. Acknowledgements In alphabetical order: Andreas M. Braendhaugen, Designer, San Francisco Laurent Bussard, European Microsoft Innovation Center Ryan Calo, Stanford University Alissa Cooper, Oxford Internet Institute Ethan Forrest, Stanford University Marit Hansen, Unabhaengiges Landeszentrum fuer Datenschutz Schleswig-Holstein Alexey Melnikov, Isode Ulrich Pinsdorf, European Microsoft Innovation Center Thomas Roessler, W3C Max Senges, Google Inc. Hannes Tschofenig, Nokia Siemens Networks 7. Normative References [RFC1855] Hambridge, S., "Netiquette Guidelines", RFC 1855, October 1995. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Koenig & Schallaboeck Expires December 9, 2012 [Page 12]
Internet-Draft Privicons June 2012 Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3339] Klyne, G., Ed. and C. Newman, "Date and Time on the Internet: Timestamps", RFC 3339, July 2002. [RFC3461] Moore, K., "Simple Mail Transfer Protocol (SMTP) Service Extension for Delivery Status Notifications (DSNs)", RFC 3461, January 2003. [RFC3676] Gellens, R., "The Text/Plain Format and DelSp Parameters", RFC 3676, February 2004. [RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321, October 2008. [RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322, October 2008. Appendix A. Example e-mail message This is an example Privicon e-mail message (Figure 1). Message-ID: <4C3203D3.60109@ulikoenig.com> Date: Mon, 05 Jul 2010 23:59:00 +0200 From: Ulrich Koenig <rfc@ulikoenig.com> To: Jan Schallaboeck <uld62@datenschutzzentrum.de> Subject: [>] last update for Privicons RFC Privicon: [>] Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: quoted-printable [>] Please share Hey Jan, please check the IETF Website for our Privicons RFC! ;) best Ulrich --=20 [>] Please share The "Please share" Privicon asks the Receiving User to share this e-mail message with everyone she likes. Figure 1: Example of an e-mail message using a Privicon Koenig & Schallaboeck Expires December 9, 2012 [Page 13]
Internet-Draft Privicons June 2012 Appendix B. Informative example requirements for e-mail message user agents B.1. User agent behaviour This section gives developers of e-mail message user agents (MUA) or plug-ins for MUAs instructions how to integrate the Privicons in the client. An MUA implementing this RFC MUST enable the user at any time to overrule the received Privicon. The user SHOULD also be able to set a default for always overruling in her client. The rest of the instructions in this section are OPTIONAL. If the user agent displays an e-mail message that contains one or more Privicons it SHOULD display the icon and its meaning in a salient way. If the icon is displayed by the user agent it MAY hide the Privicon in Subject and Body of the e-mail message. The user agent MAY localise the explaining text. B.1.1. Terms confirm A confirm pop-up or any other visible notion that yields active interaction by the user (i.e. clicking a button). The user SHOULD be able to disable a part or all confirmations. inform A pop-up, or any other visible notion, that SHOULD yield confirmation. Such notification SHOULD be enabled by default. The user SHOULD be able to disable the notification by default. B.1.2. [X] Keep secret The "Keep private" Privicon asks the Receiving User to keep the received e-mail message secret. B.1.2.1. EVENT: Forward/Reply to third Person If the Receiving User wants to forward or reply-to the e-mail message to a third person, that is not the original Sending User, than the Receiving User MUST be informed, that she is going to violate the included Privicon and she MUST confirm that she is willing to do this before the e-mail message is sent. OPTIONAL: Transparency (Appendix B.3) applies. Koenig & Schallaboeck Expires December 9, 2012 [Page 14]
Internet-Draft Privicons June 2012 B.1.3. [/] Don't print B.1.3.1. EVENT: Printing e-mail message If the Receiving User wants to print the e-mail message, she MUST be informed that she is going to violate the included Privicon and she MUST confirm that she is willing to do this before printing is started. B.1.4. [=] Delete after reading, I days or on date B.1.4.1. EVENT: Closing Mail If the Receiving User closes the e-mail message, she MUST be informed, that the e-mail message SHOULD be deleted after X days. The user MUST confirm whenever she closes the e-mail message, hat the e-mail message is deleted immediately. The client SHOULD enable the user to choose a default option. Note: if e-mail messages are displayed in list mode, then the confirmation will be raised, when opening the next e-mail message. B.1.4.1.1. Option a) delete after reading The above confirmation MUST ask the user, whether o ignore, do not decide now, ask me again next time, o delete or move into a "to be deleted" folder, as indicated in the preferences or o ask again after a specified period. B.1.4.1.2. Option b) delete after X days The above confirmation MUST ask the user, whether o ignore, do not decide now, ask me again next time, o delete now, o delete after X days automatically or o ask me in X days. Koenig & Schallaboeck Expires December 9, 2012 [Page 15]
Internet-Draft Privicons June 2012 B.1.4.1.3. Option c) delete on date The above confirmation MUST ask the user, whether o ignore, do not decide now, ask me again next time, o delete now, o delete on date automatically or o ask me on date. B.1.5. [-] No attribution B.1.5.1. EVENT: reply, forward, store If the Receiving User wants to forward or reply to a third person or store the e-mail message, she MUST be informed, that the Sending User doesn't want to be mentioned and MUST confirm that she is willing to overrule the Sending Users wish or remove any occurrence of the Sending User in the e-mail message (Header and Body). The removal of the Sending User MAY be done by the user agent automatically. OPTIONAL: Transparency (Appendix B.3) applies. B.1.6. [o] Keep internal If the Receiving User has defined what "internal" means to her, the following rules in the "Keep internal" subsection only apply if at least one of the Receiving Users are not part of her internal definition. If the Receiving User wants to forward or reply the e-mail message to a third person, the user MUST be informed that she SHOULD check if the third person is really part of the group that the Sending User intended to be internal and MUST confirm that she really to send this e-mail message. OPTIONAL: Transparency (Appendix B.3) applies. B.1.7. [>] Please share The client SHOULD notice the user, that the content of the e-mail message can be published. If the Sending User has transmitted a license for publishing the content, it SHOULD also be displayed. Koenig & Schallaboeck Expires December 9, 2012 [Page 16]
Internet-Draft Privicons June 2012 B.2. Confirmation/Affirmation of preferences Note this may be for further versions, but might yield legal implications: Before opening the e-mail message containing a Privicon, the User Agent SHOULD inform the user what the user is asked to do with the option to reject the e-mail message. To reject an e-mail message means the Sending User is notified, that the e-mail message is rejected and has been deleted at User Agent's side before reading. Not to reject the e-mail message does not mean, that the receiving user accepts the requested conditions, see [RFC3461]. B.3. Transparency (OPTIONAL) If a Receiving User forwards or replies an e-mail message containing a Privicon to a third person, the original Sending User OPTIONAL get a copy via carbon copy or a blind carbon copy by default. The Receiving User MUST be able overrule this. She also SHOULD be able to disable the default sending of a copy in the user preferences. Appendix C. Graphical Representation of the State Machine There is a graphical representation of the Privicons, that MAY be used by MUAs, see Figure (Figure 2). In the PS/PDF version of this specification, the graphical representation of the Privicons can be found here. Figure 2: Graphical representation of the Privicons. Authors' Addresses Ulrich Koenig Unabhaengiges Landeszentrum fuer Datenschutz Schleswig-Holstein Duesternbrooker Weg 70 Kiel, Schleswig-Holstein 24105 Germany Phone: +49-431-988-1220 Fax: +49-431-988-1223 Email: rfc@ulikoenig.com URI: https://www.datenschutzzentrum.de Koenig & Schallaboeck Expires December 9, 2012 [Page 17]
Internet-Draft Privicons June 2012 Jan Schallaboeck Unabhaengiges Landeszentrum fuer Datenschutz Schleswig-Holstein Holstenstr. 98 Kiel, Schleswig-Holstein 24103 Germany Phone: +49-431-988-1220 Fax: +49-431-988-1223 Email: uld62@datenschutzzentrum.de URI: https://www.datenschutzzentrum.de Koenig & Schallaboeck Expires December 9, 2012 [Page 18]