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International
Standard
ISO/IEC 20648
Second edition
Information technology — TLS
2024-07
specification for storage systems
Technologies de l'information — Spécification TLS pour systèmes
de stockage
Reference number
© ISO/IEC 2024
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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© ISO/IEC 2024 – All rights reserved
ii
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 . 4
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 . 5
5.3.4 X.509 digital certificates . 6
5.3.5 Quantum computing and TLS . 7
6 Requirements . 7
6.1 TLS protocol requirements . 7
6.2 Cipher suites . 7
6.2.1 Required cipher suites for interoperability with TLS 1.2 . 7
6.2.2 Recommended cipher suites for enhanced security with TLS 1.2 . 8
6.2.3 Recommended cipher suites and extensions with TLS 1.3 . 9
6.3 Digital certificates . 9
6.3.1 Certificate profile requirements . 9
6.3.2 Certificate validity and path validation requirements . 10
6.3.3 Certificate encoding requirements . 10
6.4 Compression methods . 10
7 Guidance for the implementation and use of TLS in data storage . 11
7.1 Digital certificates . 11
7.1.1 Certificate model . 11
7.1.2 Chain of trust . 11
7.1.3 Certificate lifecycle . 11
7.1.4 Revocation . 11
7.2 Security awareness. 12
7.3 Cipher suites . 12
7.4 Using TLS with HTTP . 12
7.5 Use of pre-shared keys . 12
Bibliography . 14
© ISO/IEC 2024 – 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.
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 (see www.iso.org/directives or /members_experts/refdocs).
ISO and IEC draw attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO and IEC take no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO and IEC had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that this may
not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents and https://patents.iec.ch. ISO and IEC shall not be held responsible for identifying any or all
such patent rights.
Any trade name used in this document is information given for the convenience of users and does not constitute an
endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions related
to conformity assessment, as well as information about ISO's adherence to the World Trade Organization (WTO)
principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html. In the IEC, see
/understanding-standards.
This document was prepared by SNIA (as TLS Specification for Storage Systems, Version 2.1) and drafted in
accordance with its editorial rules. It was adopted, under the JTC 1 PAS procedure, by Joint Technical Committee
ISO/IEC JTC 1, Information technology.
This second edition cancels and replaces the first edition (ISO/IEC 20648:2016), which has been technically
revised.
The main changes are as follows:
— a statement has been added regarding the relevance of ISO/IEC 20648 to Datagram Transport Layer Security
(DTLS) implementations;
— a statement has been added regarding quantum computing and TLS;
— a statement has been added encouraging the use of TLS 1.3;
— a recommendation has been added to guard against replay attacks on zero round-trip time (0-RTT) for TLS
version 1.3;
— the recommended cipher suites have been aligned with the RFC 7525 recommendations on forward secrecy;
— the requirements concerning 112 bits of security strength have been changed to 128 bits of security strength;
— the requirements for the maximum certificate validity period have been changed from 3 years to 398 days;
— the requirements associated with the ECDSA signature certificate have been clarified;
— a requirement has been added for including the TLS 1.3 extension for pre-shared key (PSK) support.
Any feedback or questions on this document should be directed to the user’s national standards body. A complete
listing of these bodies can be found at www.iso.org/members.html and /national-committees.
© ISO/IEC 2024 – All rights reserved
iv
Introduction
Within information and communications technology, one of the best defences 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 supports
preventing 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 the Hypertext Transfer Protocol (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 document provides detail in the form of specific requirements and guidance for using TLS in
conjunction with storage systems.
© ISO/IEC 2024 – All rights reserved
v
International Standard ISO/IEC 20648:2024(en)
Information technology —TLS specification for storage systems
1 Scope
This document details the requirements for use of the Transport Layer Security (TLS) protocol in conjunction with
data storage technologies. The requirements set out in this document are intended to facilitate secure
interoperability of storage clients and servers as well as non-storage technologies that may have similar
interoperability needs.
This document is relevant to anyone involved in owning, operating or using data storage devices. This includes
senior managers, acquirers of storage products 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 documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. 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, May 2008
IETF RFC 5246, The Transport Layer Security (TLS) Protocol Version 1.2, IETF, August 2008
IETF RFC 5746, Transport Layer Security (TLS) Renegotiation Indication Extension, IETF, February 2010
IETF RFC 8446, The Transport Layer Security (TLS) Protocol Version 1.3, IETF, August 2018
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 (TL
...