ISO/IEC 20648:2016

INTERNATIONAL ISO/IEC
STANDARD 20648
First edition
2016-03-01
Information technology — TLS
specification for storage systems
Technologies de l’information — Spécification TLS pour systèmes de
stockage
Reference number
©
ISO/IEC 2016
© ISO/IEC 2016, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO/IEC 2016 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 2
5 Overview and concepts . 3
5.1 General . 3
5.2 Storage specifications . 3
5.3 Overview of TLS . 4
5.3.1 TLS Background . . . 4
5.3.2 TLS functionality . 4
5.3.3 Summary of cipher suites. 4
5.3.4 X.509 digital certificates . 5
6 Requirements . 5
6.1 TLS protocol requirements . 5
6.2 Cipher suites . 6
6.2.1 Required cipher suites for interoperability . 6
6.2.2 Recommended cipher suites for enhanced security . 6
6.3 Digital certificates. 7
7 Guidance for the implementation and use of TLS in data storage .7
7.1 Digital certificates. 7
7.1.1 Certificate model . 7
7.1.2 Chain of trust . 8
7.1.3 Certificate lifecycle . 8
7.1.4 Revocation . 8
7.2 Security awareness . 8
7.3 Cipher suites . 9
7.4 Using TLS with HTTP . 9
7.5 Use of pre-shared keys . 9
Bibliography .11
© ISO/IEC 2016 – All rights reserved iii

Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
members of ISO or IEC participate in the development of International Standards through technical
committees established by the respective organization to deal with particular fields of technical
activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international
organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the
work. In the field of information technology, ISO and IEC have established a joint technical committee,
ISO/IEC JTC 1.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for
the different types of document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject
of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent
rights. Details of any patent rights identified during the development of the document will be in the
Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT), see the following URL: Foreword — Supplementary information.
ISO/IEC 20648 was prepared by the Storage Networking Industry Association (SNIA) [as TLS
Specification for Storage Systems, Version 1.0.1] and was adopted, under the PAS procedure, by Joint
Technical Committee ISO/IEC JTC 1, Information technology, in parallel with its approval by the national
bodies of ISO and IEC. The content of ISO/IEC 20648 and SNIA TLS Specification for Storage Systems
Version 1.0.1 is identical.
iv © ISO/IEC 2016 – All rights reserved

Introduction
Within Information and Communications Technology (CT), one of the best defenses against
telecommunications attacks is to deploy security services implemented with mechanisms specified
in standards that are thoroughly vetted in the public domain and rigorously tested by third party
laboratories, by vendors, and by users of commercial off-the-shelf products. Three services that
most often address network user security requirements are confidentiality, message integrity and
authentication.
The Internet Engineering Task Force (IETF) with its Transport Layer Security (TLS) has a standard that
is able to prevent tampering, message forgery, and eavesdropping by encrypting data units, or segments,
from one end of the transport layer to the other. In addition, TLS is application protocol independent,
which means higher-level protocols like HTTP can layer on top of the TLS protocol transparently.
Additional details beyond the basic TLS protocol specification are necessary to ensure both security
and interoperability. This specification provides that detail in the form of specific requirements and
guidance for using Transport Layer Security (TLS) in conjunction with storage systems.
© ISO/IEC 2016 – All rights reserved v

INTERNATIONAL STANDARD ISO/IEC 20648:2016(E)
Information technology — TLS specification for storage
systems
1 Scope
This specification details the requirements for use of the Transport Layer Security (TLS) protocol in
conjunction with data storage technologies. The requirements set out in this specification are intended
to facilitate secure interoperability of storage clients and servers as well as non-storage technologies
that may have similar interoperability needs.
This specification is relevant to anyone involved in owning, operating or using data storage devices.
This includes senior managers, acquirers of storage product and service, and other non-technical
managers or users, in addition to managers and administrators who have specific responsibilities
for information security and/or storage security, storage operation, or who are responsible for an
organization’s overall security program and security policy development. It is also relevant to anyone
involved in the planning, design and implementation of the architectural aspects of storage security.
2 Normative references
The following referenced documents, in whole or in part, are normatively referenced in this document
and are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO/IEC 27000, Information technology — Security techniques — Information security management
systems — Overview and vocabulary
IETF RFC 5280, Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL)
Profile, IETF, 2008
IETF RFC 5246, The Transport Layer Security (TLS) Protocol Version 1.2, IETF, 2008
IETF RFC 5746, Transport Layer Security (TLS) Renegotiation Indication Extension, IETF, 2010
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 27000 and the
following apply.
3.1
cipher suite
named combination of authentication, encryption, and message authentication code algorithms used to
negotiate the security settings for a network connection
Note 1 to entry: Cipher suites are typically used with the Transport Layer Security (TLS) and the Secure Sockets
Layer (SSL) network protocols.
3.2
digital certificate
data structure signed with a digital signature that is based on a public key and which asserts that the
key belongs to a subject identified in the structure
© ISO/IEC 2016 – All rights reserved 1

3.3
perfect forward secrecy
security condition in which a leaving entity cannot obtain any subsequent shared secret keys
[SOURCE: ISO/IEC 11770-5:2011, 3.24]
3.4
proxy
intermediary that acts as both a server and a client for the purpose of making requests on behalf of
other clients
3.5
self-signed certificate
digital certificate (3.2) that is signed by the same entity whose identity it certifies
Note 1 to entry: A self-signed certificate is one signed with its own private key.
3.6
security strength
a number associated with the amount of work (i.e. the number of operations) that is required to break a
cryptographic algorithm or system
Note 1 to entry: Security strength is specified in bits, and is a specific value from the set {80, 112, 128, 192, 256}.
b
A security strength of b bits means that of the order of 2 operations are required to break the system.
[SOURCE: ISO/IEC 9797-2:2011, 3.14]
4 Symbols and abbreviated terms
3DES Triple Data Encryption Standard
AED Authenticated Encryption with Additional Data
AES Advanced Encryption Standard
CA Certificate Authority
CBC Cipher Block Chaining
CDMI Cloud Data Management Interface
CRL Certificate Revocation List
CRLDP CRL Distribution Point
DER Distinguished Encoding Rules
DHE Ephemeral Diffie-Hellman
DSA Digital Signature Algor
...