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7/31/2019 As NZS ISO IEC 18033.4-2006 Information Technology - Security Techniques - Encryption Algorithms Stream Ciphe

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AS/NZS ISO/IEC 18033.4:2006ISO/IEC 18033-4:2005

Australian/New Zealand Standard

Information technologySecuritytechniquesEncryption algorithms

Part 4: Stream ciphers

AS/NZS

ISO/IEC18033.4:2006


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AS/NZS ISO/IEC 18033.4:2006

This Joint Australian/New Zealand Standard was prepared by Joint TechnicalCommittee IT-012, Information Systems, Security and Identification. It wasapproved on behalf of the Council of Standards Australia on 31 March 2006 and onbehalf of the Council of Standards New Zealand on 16 June 2006.This Standard was published on 10 July 2006.

The following are represented on Commit tee IT-012:

Attorney Generals Department

Australia Post

Australian Association of Permanent Building Societies

Australian Bankers Association

Australian Chamber of Commerce and Industry

Australian Electrical and Electronic Manufacturers Association

Australian Information Industry Association

Certification Forum of AustraliaConsumers Federation of Australia

Department of Defence (Australia)

Department of Social Welfare New Zealand

Government Communications Security Bureau, New Zealand

Internet Industry Association

NSW Police Service

New Zealand Defence Force

Reserve Bank of Australia

Keeping Standards up-to-date

Standards are living documents which reflect progress in science, technology andsystems. To maintain their currency, all Standards are periodically reviewed, andnew editions are published. Between editions, amendments may be issued.Standards may also be withdrawn. It is important that readers assure themselvesthey are using a current Standard, which should include any amendments whichmay have been published since the Standard was purchased.

Detailed information about joint Australian/New Zealand Standards can be found byvisiting the Standards Web Shop at www.standards.com.au or Standards NewZealand web site at www.standards.co.nz and looking up the relevant Standard inthe on-line catalogue.

Alternatively, both organizations publish an annual printed Catalogue with fulldetails of all current Standards. For more frequent listings or notification ofrevisions, amendments and withdrawals, Standards Australia and Standards NewZealand offer a number of update options. For information about these services,users should contact their respective national Standards organization.

We also welcome suggestions for improvement in our Standards, and especiallyencourage readers to notify us immediately of any apparent inaccuracies orambiguities. Please address your comments to the Chief Executive of eitherStandards Australia or Standards New Zealand at the address shown on the backcover.

This Standard was issued in draft form for comment as DR 06035.


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AS/NZS ISO/IEC 18033.4:2006

Australian/New Zealand StandardInformation technologySecuritytechniquesEncryption algorithms

Part 4: Stream ciphers

COPYRIGHT

Standards Australia/Standards New Zealand

All rights are reserved. No part of this work may be reproduced or copied in any form or byany means, electronic or mechanical, including photocopying, without the written

permission of the publisher.

Jointly published by Standards Australia, GPO Box 476, Sydney, NSW 2001 and Standards

New Zealand, Private Bag 2439, Wellington 6020

ISBN 0 7337 7594 2

First published as AS/NZS ISO/IEC 18033.4:2006.


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ii

PREFACE

This Standard was prepared by the Joint Standards Australia/Standards New Zealand Committee

IT-012, Information Systems, Security and Identification.

This Standard is identical with, and has been reproduced from ISO/IEC 18033-4:2005,

Information technologySecurity techniquesEncryption algorithmsPart 4: Stream ciphers.

The objective of this Standard is to provide the Information Security programming and

development community with clear guidance to the selection and implementation of appropriate

encryption algorithms.

This Standard is Part 4 of AS/NZS ISO/IEC 18033, Information technologySecurity

techniquesEncryption Algorithms, which when complete will consist of the following:

Part 1: General

Part 2: Asymmetric ciphers

Part 3: Block ciphers

Part 4: Stream ciphers (this Standard)

The terms normative and informative are used to define the application of the annex to

which they apply. A normative annex is an integral part of a standard, whereas an informative

annex is only for information and guidance.

As this Standard is reproduced from an international standard, the following applies:

(a) Its number appears on the cover and title page while the international standard number

appears only on the cover.

(b) In the source text this part of ISO/IEC 18033 should read this Australian/New Zealand

Standard.(c) A full point substitutes for a comma when referring to a decimal marker.

Reference to International Standard Australian/New Zealand Standard

ISO/IEC AS/NZS

18033 Information technologySecurity

techniquesEncryption algorithms

18033 Information technologySecurity

techniquesEncryption algorithms

18033-1 Part 1: General 18033.1 Part 1: General

18033-3 Part 3: Block ciphers 18033.3 Part 3: Block ciphers


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ii i

CONTENTS

Page

1 Scope ..................................................................................................................................................... 1

2 Normative references ........................................................................................................................... 1

3 Terms and definitions........................................................................................................................... 1

4 Symbols and abbreviated terms.......................................................................................................... 44.1 Left-truncation of bits........................................................................................................................... 54.2 Shift operation....................................................................................................................................... 64.3 Variable I(k) ........................................................................................................................................... 6

5 General models for stream ciphers .................................................................................................... 65.1 Keystream generators.......................................................................................................................... 65.1.1 Synchronous keystream generators .................................................................................................. 6

5.1.2 Self-synchronizing keystream generators ......................................................................................... 65.2 Output functions................................................................................................................................... 75.2.1 Binary-additive output function .......................................................................................................... 75.2.2 MULTI-S01 output function.................................................................................................................. 8

6 Constructing keystream generators from block ciphers................................................................ 106.1 Modes of a block cipher for a synchronous keystream generator................................................ 106.1.1 OFB mode............................................................................................................................................ 116.1.2 CTR mode ............................................................................................................................................ 116.2 Mode of a block cipher for a self-synchronizing keystream generator ........................................ 126.2.1 CFB mode ............................................................................................................................................ 12

7 Dedicated keystream generators ...................................................................................................... 137.1 MUGI keystream generator ................................................................................................................ 13

7.1.1 Initialization function Init.................................................................................................................... 147.1.2 Next-state function Next..................................................................................................................... 157.1.3 Keystream function Strm ................................................................................................................... 157.1.4 Function1 .......................................................................................................................................... 157.1.5 Function1........................................................................................................................................... 167.1.6 Function F............................................................................................................................................ 167.1.7 Function SR.......................................................................................................................................... 177.1.8 Function M........................................................................................................................................... 187.2 SNOW 2.0 keystream generator ........................................................................................................ 187.2.1 Initialization function Init.................................................................................................................... 197.2.2 Next-state function Next..................................................................................................................... 207.2.3 Keystream function Strm ................................................................................................................... 217.2.4 Function T............................................................................................................................................ 21

7.2.5 Multiplications ofin finite field arithmetic..................................................................................... 227.2.6 Multiplications of

1in finite field arithmetic................................................................................. 22

7.2.7 Function FSM(x, y, z) ......................................................................................................................... 23

Annex A (informative) Examples..................................................................................................................... 24A.1 Operations over the finite field GF(2

n) .............................................................................................. 24

A.2 Example for MUGI ............................................................................................................................... 24A.2.1 Key, initialization vector, and keystream triplets ............................................................................ 24A.2.2 Sample internal states........................................................................................................................ 24A.3 Example for SNOW 2.0 ....................................................................................................................... 30A.3.1 128-bit key............................................................................................................................................ 30A.3.2 256-bit key............................................................................................................................................ 34


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iv

Page

Annex B (informative) Security information ................................................................................................. 39B.1 Security levels of stream ciphers...................................................................................................... 39B.1.1 Security-efficiency trade-off in MULTI-S01 ...................................................................................... 40B.2 Implementation examples of dedicated keystream generators..................................................... 40Annex C (normative) Object identifiers.......................................................................................................... 41Bibliography..................................................................................................................................................... 43


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1

AUSTRALIAN/NEW ZEALAND STANDARD

1 Scope

This part of ISO/IEC 18033 specifies stream cipher algorithms. A stream cipher is an encryption mechanismthat uses a keystream to encrypt a plaintext in bitwise or block-wise manner. There are two types of streamcipher: a synchronous stream cipher, in which the keystream is only generated from the secret key (and aninitialization vector) and a self-synchronizing stream cipher, in which the keystream is generated from the

secret key and some past ciphertexts (and an initialization vector). Typically the encryption operation is theadditive bitwise XOR operation between a keystream and the message. This part of ISO/IEC 18033 describesboth pseudorandom number generators for producing keystream, and output functions for stream ciphers.

The algorithms specified in this part of ISO/IEC 18033 have been assigned object identifiers in accordance withISO/IEC 9834. The list of assigned object identifiers is given in Annex C. Any change to the specificationof the algorithms resulting in a change of functional behaviour will result in a change of the object identifierassigned to the algorithm.

NOTE 1 In applications where a combination of algorithms is being used, or when an algorithm is parameterized by thechoice of a combination of other algorithms, the combination may be specified as a sequence of object identifiers.Alternatively, the object identifiers of lower layer algorithms may be included in the parameter field of the higher layeralgorithm's identifier structure. For example, the object identifier of a block cipher could be included as a parameter in the

algorithm identifier structure for a keystream generator. The algorithm identifier structure is defined in ISO/IEC 9594-8.

NOTE 2 The encoding of object identifiers is application dependent.

3.1big-endian

a method of storage of multi-byte numbers with the most significant bytes at the lowest memory addresses.

[ISO/IEC 10118-1: 2000]

Information technology Security techniques Encryptionalgorithms

Part 4:Stream ciphers

2 Normative references

The following referenced documents are indispensable for the application of this document. For datedreferences, only the edition cited applies. For undated references, the latest edition of the referenceddocument (including any amendments) applies.

ISO/IEC 18033-1, Information technology Security techniques Encryption algorithms Part 1: General

ISO/IEC 18033-3, Information technology Security techniques Encryption algorithms Part 3: Blockciphers

For the purposes of this document, the terms and definitions given in ISO/IEC 18033-1 and the followingapply.

3 Terms and definitions

COPYRIGHT


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