Internet Engineering Task Force                           Y. Kadobayashi
Internet-Draft                                                     NAIST
Intended status: Informational                                   K. ANDO
Expires: September 4, 2014                                         BBsec
                                                            K. Kasamatsu
                                                                S. Kanno
                                                                NTT SOFT
                                                           March 3, 2014


            Use of S/MIME Encryption Function in Enterprises
                  draft-kadobayashi-smime-secureops-00

Abstract

   In this document, we provide a method for enterprises to utilize and
   operate the use of S/MIME to handle highly confidential information.

Status of This Memo

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   This Internet-Draft will expire on September 4, 2014.

Copyright Notice

   Copyright (c) 2014 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
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   include Simplified BSD License text as described in Section 4.e of




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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   2.  Decrease of anti-virus functionality on the e-mail server . .   2
     2.1.  Use of anti-virus function at S/MIME user agent . . . . .   3
     2.2.  Use of S/MIME at the Gateway  . . . . . . . . . . . . . .   3
   3.  Decreased monitoring of highly confidential e-mails that are
       sent and received . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Method for managing keys  . . . . . . . . . . . . . . . .   3
     3.2.  Accessing e-mails that have been decrypted  . . . . . . .   3
   4.  Importance of the management of expired certificates  . . . .   4
     4.1.  Use of Dual Key Pairs . . . . . . . . . . . . . . . . . .   4
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   7.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .   4
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   Use of the S/MIME encryption function within enterprises allows them
   to handle highly confidential information such as business critical
   information.  However, use of encryption, decreases the functionality
   of anti-virus software and creates the need to manage expired digital
   certificates.  In this document, we provide a method for enterprises
   to utilize and operate the use of S/MIME to handle highly
   confidential information.

1.1.  Requirements Language

   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 RFC 2119 [RFC2119].

2.  Decrease of anti-virus functionality on the e-mail server

   There is an issue where anti-virus software on e-mail servers may not
   properly function when encrypted e-mails are received.  The following
   issues are also seen when the anti-virus software does not function
   properly.




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2.1.  Use of anti-virus function at S/MIME user agent

   Using S/MIME at user agent(MUA), it is highly recommended that the S/
   MIME decrypted e-mails must be checked by anti-virus function
   immediately after the decryption.

2.2.  Use of S/MIME at the Gateway

   Using S/MIME at the Gateway is one way to work around the anti-virus
   issue.  By implementing S/MIME at the Gateway, viruses can be
   detected at the Gateway.  By storing and managing keys of senders at
   the Gateway, e-mails can be decrypted and scanned for viruses at the
   Gateway.

3.  Decreased monitoring of highly confidential e-mails that are sent
    and received

   Monitoring may decrease when sending highly confidential information,
   such as business information to a party outside of the organization.
   This issue differs from the issue where anti-virus functionality
   decreases, and an organization must consider that e-mails must be
   monitored when sending the e-mail (immediate monitoring) and e-mail
   contents must be monitored every so often after the e-mail has been
   sent (intermittent monitoring).

   For immediate monitoring, S/MIME at the Gateway introduced previously
   (3.1) can be used to maintain confidentiality outside of the
   organization and monitoring in accordance to organizational policies
   also becomes possible.  For intermittent monitoring, the following
   methods where keys are managed or decrypted e-mails are managed can
   be used.

3.1.  Method for managing keys

   When digital certificates are disposed, e-mails that were encrypted
   using that certificate cannot be decrypted, so you can choose to
   manage and maintain such digital certificates.  However, the
   disclosure of a private key for an expired digital certificate
   contains the same dangers as the disclosure of a private key for a
   valid digital certificate.  Keys can be managed by sharing keys or
   delegating management of the keys through the implementation of S/
   MIME at the Gateway.

3.2.  Accessing e-mails that have been decrypted

   Since the contents of encrypted e-mails cannot be read if the expired
   keys are not stored, decrypted e-mails can be stored in plaintext if
   expired keys are not managed and stored.  In this case, you may be



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   saving highly confidential information in plaintext, therefore access
   to such information must be managed properly.

4.  Importance of the management of expired certificates

   In order to be able to use encrypted e-mails into the future, you
   must store expired digital certificates of the senders.  Expired
   digital certificates may be leveraged for impersonation, so storage
   of these certificates must be done carefully, increasing the burden
   on the recipient.  To handle this issue, you can use the following
   technological measure in addition to the methods described in 4.1 and
   4.2.

4.1.  Use of Dual Key Pairs

   Key pairs that have expired should be disposed of as quickly as
   possible, but key pairs for encryption must be stored for an extended
   period of time for decryption purposes.  One can use separate key
   pairs for encryption and signing.  This allows a user to not have to
   change key pairs for encryption when the certificate has expired.

5.  Acknowledgements

   TBD.

6.  IANA Considerations

   This memo includes no request to IANA.

7.  Privacy Considerations

   TBD.

8.  Security Considerations

   TBD.

9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.








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9.2.  Informative References

   [RFC5750]  Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet
              Mail Extensions (S/MIME) Version 3.2 Certificate
              Handling", RFC 5750, January 2010.

   [RFC5751]  Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet
              Mail Extensions (S/MIME) Version 3.2 Message
              Specification", RFC 5751, January 2010.

Authors' Addresses

   Youki Kadobayashi
   Nara Institute of Science and Technology

   Email: youki-k@is.aist-nara.ac.jp


   Kazunori Ando
   BroadBand Security, Inc.

   Email: ando@bbsec.co.jp


   Kohei Kasamatsu
   NTT Software Corporation

   Email: kasamatsu.kohei@po.ntts.co.jp


   Satoru Kanno
   NTT Software Corporation

   Email: kanno.satoru@po.ntts.co.jp

















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