Internet DRAFT - draft-kadobayashi-smime-secureops
draft-kadobayashi-smime-secureops
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
This Internet-Draft is submitted in full conformance with the
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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
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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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