Redaction of Potentially Sensitive Data from Mail Abuse Reports
RFC 6590

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Internet Engineering Task Force (IETF)                      J. Falk, Ed.
Request for Comments: 6590                                   Return Path
Category: Standards Track                              M. Kucherawy, Ed.
ISSN: 2070-1721                                                Cloudmark
                                                              April 2012

    Redaction of Potentially Sensitive Data from Mail Abuse Reports

Abstract

   Email messages often contain information that might be considered
   private or sensitive, per either regulation or social norms.  When
   such a message becomes the subject of a report intended to be shared
   with other entities, the report generator may wish to redact or elide
   the sensitive portions of the message.  This memo suggests one method
   for doing so effectively.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6590.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   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.

Falk & Kucherawy             Standards Track                    [Page 1]
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Table of Contents

   1. Introduction ....................................................2
   2. Key Words .......................................................3
   3. Recommended Practice ............................................3
   4. Transformation Mechanisms .......................................4
   5. Security Considerations .........................................5
      5.1. General ....................................................5
      5.2. Digest Collisions ..........................................5
      5.3. Information Not Redacted ...................................5
   6. Privacy Considerations ..........................................6
   7. References ......................................................6
      7.1. Normative References .......................................6
      7.2. Informative References .....................................6
   Appendix A. Example ................................................7
   Appendix B. Acknowledgements .......................................8

1.  Introduction

   The Abuse Reporting Format [ARF] defines a message format for sending
   reports of abuse in the messaging infrastructure, with an eye toward
   automating both the generation and consumption of those reports.

   For privacy considerations, it might be the policy of a report
   generator to anonymize, or obscure, portions of the report that might
   identify an end user who caused the report to be generated.  This has
   come to be known in feedback loop parlance as "redaction".  Precisely
   how this is done is unspecified in [ARF], as it will generally be a
   matter of local policy.  That specification does admonish generators
   against being too overzealous with this practice, as obscuring too
   much data makes the report non-actionable.

   Previous redaction practices, such as replacing local-parts of
   addresses with a uniform string like "xxxxxxxx", frustrated any kind
   of prioritizing or grouping of reports.  This memo presents a
   practice for conducting redaction in a manner that allows a report
   receiver to detect that two reports were caused by the same end user,
   without revealing the identity of that user.  That is, the report
   receiver can use the redacted string, such as an obscured email
   address, to determine that two such unredacted strings were
   identical; the reports originally contained the same address.

Falk & Kucherawy             Standards Track                    [Page 2]
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   Generally, it is assumed that the recipient-identifying fields of a
   message, when copied into a report, are to be obscured to protect the