ISO/IEC 23001-7:2023

ISO/IEC JTC 1/SC 29
Date: 2021-10-29
ISO/IEC 23001-7:2021(E)
ISO/IEC JTC 1/SC 29/WG 3
Date: 2023-02-08
ISO/IEC FDIS 23001-7:2023(E)
ISO/IEC JTC 1/SC 29/WG 3
Secretariat: JISCJISC
Information technology — MPEG systems technologies — Part 7: Common
encryption in ISO base media file format files
Élément introductif — Élément central — Partie 7: Titre de la partie
Document type:
Document subtype:
Document stage:
Document language:

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Information technology — MPEG systems technologies — Part 7: Common encryption in
ISO base media file format files
Élément introductif — Élément central — Partie 7: Titre de la partie
Document type:
Document subtype:
Document stage:
Document language:

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ISO/IEC FDIS 23001-7:2023(E)
© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
© ISO/IEC 2023 – All rights reserved iii

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ISO/IEC FDIS 23001-7:2023(E)
Contents Page
Foreword . viivii
Introduction . ix Field Code Changed
1 Scope . 1x
2 Normative references . 11
3 Terms, definitions and abbreviated terms . 22
3.1 Terms and definitions . 22
3.2 Abbreviated terms . 33
4 Protection schemes . 33
4.1 Scheme type signalling . 33
4.2 Common encryption scheme types . 44
5 Overview of encryption metadata . 44
6 Encryption parameters shared by groups of samples . 5 Field Code Changed
7 Common encryption sample auxiliary information . 77
7.1 Definition . 77
7.2 Sample encryption information box for storage of sample auxiliary information . 9 Field Code Changed
7.2.1 Sample encryption box . 99
8 Box Definitionsdefinitions . 1212
Field Code Changed
8.1 Protection system specific header box . 12
8.1.1 Definition . 12
Field Code Changed
8.1.2 Syntax . 13
Field Code Changed
8.1.3 Semantics . 13
Field Code Changed
8.2 Track Encryption box . 14
Field Code Changed
8.2.1 Definition . 14
Field Code Changed
8.2.2 Syntax . 14
8.2.3 Semantics . 15 Field Code Changed
8.3 Item encryption box . 15
Field Code Changed
8.3.1 Definition . 15
Field Code Changed
8.3.2 Syntax . 16
Field Code Changed
8.3.3 Semantics . 17
Field Code Changed
8.4 Item auxiliary information box . 17
Field Code Changed
8.4.1 Definition . 17
8.4.2 Syntax . 18 Field Code Changed
8.4.3 Semantics . 18
Field Code Changed
Field Code Changed
9 Encryption of media data . 19
9.1 Field semantics . 19
Field Code Changed
9.2 Initialization vectors . 20
Field Code Changed
9.3 AES-CTR mode counter operation . 21
Field Code Changed
9.4 Full sample encryption . 21
Field Code Changed
9.4.1 General . 21
Field Code Changed
9.4.2 Full sample encryption using AES-CTR mode . 22
Field Code Changed
9.4.3 Full sample encryption using AES-CBC mode . 22
9.5 Subsample encryption . 2323
Field Code Changed
9.5.1 Definition (normative) . 2323
Field Code Changed
9.5.2 Subsample encryption of NAL structured video tracks . 2525
Field Code Changed
9.6 Pattern encryption . 3131
9.6.1 Definition . 3131
9.6.2 Example of pattern encryption applied to a video NAL unit . 32 Field Code Changed
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ISO/IEC FDIS 23001-7:2023(E)
9.7 Whole-block full sample encryption . 33 Field Code Changed
9.8 Content sensitive encryption . 33
Field Code Changed
9.8.1 Definition . 33
Field Code Changed
9.8.2 Content sensitive encryption applied to a video NAL unit . 3333
10 Protection scheme definitions . 34 Field Code Changed
10.1 'cenc' AES-CTR scheme . 34
Field Code Changed
10.2 'cbc1' AES-CBC scheme . 35
Field Code Changed
10.3 'cens' AES-CTR subsample pattern encryption scheme . 3636
10.4 'cbcs' AES-CBC subsample pattern encryption scheme . 3636
10.4.1 Definition . 3636
10.4.2 'cbcs' AES-CBC mode pattern encryption scheme application (Informative) . 3737
10.5 'sve1' AES-CTR sensitive encryption scheme . 3838
11 XML representation of Common Encryption parameters . 3838
11.1 IntroductionGeneral . 3838
11.2 Definition of the XML cenc:default_KID attribute and cenc:pssh element . 38 Field Code Changed
11.3 Use of the cenc:default_KID attribute and cenc:pssh element in DASH
ContentProtection Descriptor elements . 39 Field Code Changed
11.3.1 IntroductionGeneral . 3939
11.3.2 Addition of cenc:default_KID attributes in DASH ContentProtection Descriptors . 40 Field Code Changed
11.3.3 Addition of the cenc:pssh element in Protection System Specific UUID
ContentProtection Descriptors . 41 Field Code Changed
11.3.4 Example of two Content Protection Descriptors in an MPD . 4141
Annex A (normative) Content sensitive encryption scheme . 4343
A.1 Code-words containing bits selected for encryption for MPEG-4/AVC CAVLC . 43
A.1.1 General . 43
A.1.2 Slice QP Delta . 43
A.1.3 Macroblock type . 43
A.1.4 PCM sample Luma and Chroma . 45
A.1.5 Macroblock QP Delta . 45
A.1.6 Prediction Intra Luma . 45
A.1.7 Prediction Intra Chroma . 45
A.1.8 Motion prediction reference . 46
A.1.9 Motion prediction vector . 47
A.1.10 Trailing ones . 47
A.1.11 Level Suffix . 47
A.1.12 Total zeros . 47
A.1.13 Run Before . 48
A.2 Code-words containing bins selected for encryption for MPEG-4/AVC CABAC . 49
A.2.1 PCM sample Luma and Chroma . 49
A.2.2 Absolute value of coefficient level . 49
A.2.3 Motion prediction vector . 50
A.2.4 Sign of coefficient level . 51
A.3 Code-words containing bins selected for encryption MPEG-H/HEVC . 51
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ISO/IEC FDIS 23001-7:2023(E)
A.3.1 Motion vector difference . 51
A.3.2 Motion vector difference sign . 52
A.3.3 Delta QP sign syntax element . 52
A.3.4 Transform coefficient sign . 52
Bibliography . 5353
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ISO/IEC FDIS 23001-7:2023(E)
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 Directives, Part 2 (see
www.iso.org/directives or www.iec.ch/members_experts/refdocs).
Attention is drawnISO and IEC draw attention to the possibility that some of the elementsimplementation
of this document may beinvolve the subjectuse of (a) patent rights. ISO and IEC (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. 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 onof 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 the following
URL: Foreword - Supplementary informationwww.iso.org/iso/foreword.html. In the IEC, see
www.iec.ch/understanding-standards.
The committee responsible for thisThis document iswas prepared by Joint Technical Committee
ISO/IEC JTC 1, Information technology, Subcommittee SC 29, Coding of audio, picture, multimedia and
hypermedia information.
This thirdfourth edition cancels and replaces the secondthird edition (ISO/IEC 23001-7:20152016),
which has been technically revised.
It also incorporates the Amendment ISO/IEC 23001 consists of the following parts, under the general
title Information technology — MPEG systems technologies:-7:2016/Amd 1:2019.
— Part 1: Binary MPEG format for XML
— Part 2: Fragment request units
— Part 3: XML IPMP messages
— Part 4: Codec configuration representation
© ISO/IEC 2023 – All rights reserved vii

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ISO/IEC FDIS 23001-7:2023(E)
— Part 5: Bitstream Syntax Description Language (BSDL)
— Part 7: CommonThe main changes are as follows:
Addition of:
— item encryption in ISO base , which allows image items to use protection schemes defined for media
file format filestracks,
— Part 8: Coding-independent code points
— Part 9: Common encryption of MPEG-2 transport streams
— Part 10: Carriage of timed metadata metrics of media— support for multiple keys and IVs per
protected sample,
— 'sve1' sensitive encryption scheme, a codec-specific encryption scheme for which the encrypted
bitstream remains a valid decodable bitstream,
— improved selective encryption using sample groups
A list of all parts in the ISO base media file format
— Part 11: Energy-efficient media consumption (green metadata)
— Part 12: Sample variants in/IEC 23001 series can be found on the ISO base media file formatand IEC
websites.
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 www.iec.ch/national-
committees.
viii © ISO/IEC 2023 – All rights reserved

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ISO/IEC FDIS 23001-7:2023(E)
Introduction
Common Encryption specifies encryption and key mapping methods that enable decryption of the same
file using different Digital Rights Management (DRM) and key management systems. It defines encryption
algorithms and encryption related metadata necessary to decrypt the protected streams, yet it leaves the
details of rights mappings, key acquisition and storage, DRM content protection compliance rules, etc., up
to the DRM system or systems. For instance, DRM systems necessarily support identifying the decryption
key via stored key identifiers (KIDs), but how each DRM system protects and locates the KID identified
decryption key is left to a DRM-specific method.
DRM specific information such as licenses, rights, and license acquisition information can be stored in an
ISO Base Media file using a ProtectionSystemSpecificHeaderBox. Each instance of this box
stored in the file corresponds to one applicable DRM system identified by a well-known SystemID. DRM
licenses or license acquisition information need not be stored in the file in order to look up a separately
delivered key using a KID stored in the file and decrypt media samples using the encryption parameters
stored in each track.
The second edition of this document added XML representations of Common Encryption parameters for
delivery in XML documents, such as an MPEG DASH Media Presentation Description Documents (MPD).
The second edition also defined the 'cbc1' protection scheme using AES-CBC mode encryption.
The third edition added 'cbcs' and 'cens' protection schemes for pattern encryption, which encrypt
only a fraction of the data blocks within each video subsample protected. Pattern encryption reduces the
computational power required by devices to decrypt video tracks.
The additions in this fourth edition added:are listed in the Foreword.
item
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ISO/IEC FDIS 23001-7:2023(E)
Information technology — MPEG systems technologies — Part 7:
Common encryption, which allows image items to use protection
schemes defined for in ISO base media tracks,file format files
− support for multiple keys and IVs per protected sample,
− 'sve1' sensitive encryption scheme, a codec-specific encryption scheme for which the
encrypted bitstream remains a valid decodable bitstream,
− improved selective encryption using sample groups.

x © ISO/IEC 2023 – All rights reserved

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FINAL DRAFT INTERNATIONAL STANDARDFINAL ISO/IEC 23001-7:2021(E)ISO/IEC FDIS
DRAFT INTERNATIONAL STANDARD 23001-7:2023(E)

1 Scope
Part 7 of ISO/IEC 23001This document specifies common encryption formats for use in any file format
based on ISO/IEC 14496-12, ISO Base Media File Format. File, item, track, and track fragment metadata
is specified to enable multiple digital rights and key management systems (DRMs) to access the same
common encrypted file or stream. This document does not define a DRM system.
The AES-128 symmetric block cipher is used to encrypt elementary stream data contained in media
samples. Both AES counter mode (CTR) and Cipher Block Chaining (CBC) are specified in separate
protection schemes. Partial encryption using a pattern of encrypted and clear blocks is also specified in
separate protection schemes. The identification of encryption keys, initialization vector storage and
processing is specified for each scheme.
Subsample encryption is specified for NAL structured video, such as AVC and HEVC, to enable normal
processing and editing of video elementary streams prior to decryption.
An XML representation is specified for important common encryption information so that it can be
included in XML files as standard elements and attributes to enable interoperable license and key
management prior to media file download.
2 Normative references
The following documents, are referred to in wholethe text in such a way that some or in part, are
normatively referenced inall of their content constitutes requirements of 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.
ITU-T Rec.H.264 | ISO/IEC 14496--10, Information technology — Coding of audio-visual objects — Part
10: Advanced Video Coding
ISO/IEC 14496--12, Information technology — Coding of audio-visual objects — Part 12: ISO Base Media
File Format
ISO/IEC 14496--15, Information technology — Coding of audio-visual objects — Part 15: Carriage of
network abstraction layer (NAL) unit structured video in the ISO Base Media File Formatbase media file
format
ISO/IEC 23008--2, Information technology – Coding of audio-visual objects – Part 2: High Efficiency Video
Coding (HEVC)
ISO/IEC 23008--12, Information technology –— High efficiency coding and media delivery in
heterogeneous environments –— Part 12: Image File Format (HEIF)
IETF RFC 4122, A Universally Unique IDentifier (UUID) URN Namespace
FIPS-197, Advanced Encryption Standard, Federal Information Processing Standards Publication 197,
FIPS-197, http://www.nist.gov/https://www.nist.gov/
NIST Special Publication 800-38A, Recommendation of Block Cipher Modes of Operation, NIST, NIST
Special Publication 800-38A, http://www.nist.gov/https://www.nist.gov/
IETF RFC 4122, A Universally Unique IDentifier (UUID) URN Namespace, July 2005
1

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ISO/IEC FDIS 23001-7:2023(E)
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/
3.1.1
block
16-byte extent of sample data that may be encrypted or decrypted by AES-128 block cipher
Note 1 to entry: This is commonly known as a cipher block.
3.1.2
CENC SAI

sample auxiliary information associated with a sample and containing cryptographic information such as
initialization vector or subsample information

Note 1 to entry: The sample auxiliary information is defined in ISO/IEC 14496-12, and is not part of the sample data.

3.1.3
constant IV
initialization vector specified in a sample entry or sample group description that applies to all samples
and subsamples under that sample entry or mapped to that sample group

3.1.4
initialization vector
8 or 16-byte value used in combination with a key and a block to create the first cipher block in a chain,
and derive subsequent cipher blocks in a cipher block chain

3.1.5
NAL unit
syntax structure containing an indication of the type of data to follow and bytes containing that data in
the form of an RBSP interspersed as necessary with emulation prevention bytes

3.1.6
NAL structured video
video streams composed of NAL Units
Note 1 to entry: The carriage of NAL Units is specified in ISO/IEC 14496-15

3.1.7
2

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ISO/IEC FDIS 23001-7:2023(E)
protection scheme
encryption algorithm and information identified by the scheme_type in a SchemeTypeBox in a
ProtectionSchemeInfoBox

3.1.8
sample
media sample when the protection applies to media tracks, or the payload of an item when the protection
applies to items
Note 1 to entry: Media sample as defined in ISO/IEC 14496-12.
Note 2 to entry: Payload of an item as defined in ISO/IEC 14496-12.
3.1.9
selective encryption
change in the isProtected value of samples associated with the same sample description entry
Note 1 to entry: this This is achieved using CencSampleEncryptionInformationGroupEntry
sample groups.
3.1.10
subsample
byte range within a sample consisting of an unprotected part immediately followed by a protected part
3.2 Abbreviated terms
For the purposes of this International Standard, the following abbreviated terms apply.
AES Advanced Encryption Standard
AES-CTR AES Counter
AES-CBC AES Cipher-Block Chaining
AVC Advanced Video Coding as
...

FINAL
INTERNATIONAL ISO/IEC
DRAFT
STANDARD FDIS
23001-7
ISO/IEC JTC 1/SC 29
Information technology — MPEG
Secretariat: JISC
systems technologies —
Voting begins on:
2023-05-10
Part 7:
Voting terminates on:
Common encryption in ISO base media
2023-07-05
file format files
Technologies de l'information — Technologies des systèmes MPEG —
Partie 7: Cryptage commun des fichiers au format de fichier de
médias de la base ISO
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/IEC FDIS 23001-7:2023(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. © ISO/IEC 2023

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FINAL
INTERNATIONAL ISO/IEC
DRAFT
STANDARD FDIS
23001-7
ISO/IEC JTC 1/SC 29
Information technology — MPEG
Secretariat: JISC
systems technologies —
Voting begins on:
Part 7:
Voting terminates on:
Common encryption in ISO base media
file format files
Technologies de l'information — Technologies des systèmes MPEG —
Partie 7: Cryptage commun des fichiers au format de fichier de
médias de la base ISO
COPYRIGHT PROTECTED DOCUMENT
© ISO/IEC 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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.
RECIPIENTS OF THIS DRAFT ARE INVITED TO
ISO copyright office
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
CP 401 • Ch. de Blandonnet 8
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
CH-1214 Vernier, Geneva
DOCUMENTATION.
Phone: +41 22 749 01 11
IN ADDITION TO THEIR EVALUATION AS
Reference number
Email: copyright@iso.org
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
ISO/IEC FDIS 23001­7:2023(E)
Website: www.iso.org
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
Published in Switzerland
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN­
DARDS TO WHICH REFERENCE MAY BE MADE IN
ii
  © ISO/IEC 2023 – All rights reserved
NATIONAL REGULATIONS. © ISO/IEC 2023

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ISO/IEC FDIS 23001-7:2023(E)
Contents Page
Foreword .v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and abbreviated terms . 2
3.1 Terms and definitions . 2
3.2 Abbreviated terms . 3
4 Protection schemes . 3
4.1 Scheme type signalling . 3
4.2 Common encryption scheme types . 4
5 Overview of encryption metadata . 4
6 Encryption parameters shared by groups of samples . 4
7 Common encryption sample auxiliary information . 6
7.1 Definition . 6
7.2 Sample encryption information box for storage of sample auxiliary information . 7
7.2.1 Sample encryption box — Definition . 7
7.2.2 Syntax . . 8
7.2.3 Semantics . 8
8 Box definitions . 9
8.1 Protection system specific header box . 9
8.1.1 Definition . 9
8.1.2 Syntax . 10
8.1.3 Semantics . 10
8.2 Track Encryption box . 10
8.2.1 Definition . 10
8.2.2 Syntax . 11
8.2.3 Semantics . 11
8.3 Item encryption box. 11
8.3.1 Definition . 11
8.3.2 Syntax . .12
8.3.3 Semantics . 12
8.4 Item auxiliary information box.13
8.4.1 Definition .13
8.4.2 Syntax . .13
8.4.3 Semantics . 13
9 Encryption of media data .14
9.1 Field semantics . 14
9.2 Initialization vectors . 15
9.3 AES­CTR mode counter operation . 16
9.4 Full sample encryption . 16
9.4.1 General . 16
9.4.2 Full sample encryption using AES-CTR mode . 16
9.4.3 Full sample encryption using AES-CBC mode . 17
9.5 Subsample encryption . 17
9.5.1 Definition . 17
9.5.2 Subsample encryption of NAL structured video tracks . 18
9.6 Pattern encryption . 23
9.6.1 Definition .23
9.6.2 Example of pattern encryption applied to a video NAL unit . 24
9.7 Whole-block full sample encryption . 24
9.8 Content sensitive encryption . 24
iii
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ISO/IEC FDIS 23001-7:2023(E)
9.8.1 Definition . 24
9.8.2 Content sensitive encryption applied to a video NAL unit .25
10 Protection scheme definitions .26
10.1 'cenc' AES­CTR scheme . 26
10.2 'cbc1' AES­CBC scheme .26
10.3 'cens' AES-CTR subsample pattern encryption scheme . 27
10.4 'cbcs' AES-CBC subsample pattern encryption scheme . 27
10.4.1 Definition . 27
10.4.2 'cbcs' AES-CBC mode pattern encryption scheme application .28
10.5 'sve1' AES-CTR sensitive encryption scheme .29
11 XML representation of Common Encryption parameters .29
11.1 General .29
11.2 Definition of the XML cenc:default_KID attribute and cenc:pssh element.29
11.3 Use of the cenc:default_KID attribute and cenc:pssh element in DASH
ContentProtection Descriptor elements .30
11.3.1 General .30
11.3.2 Addition of cenc:default_KID attributes in DASH ContentProtection
Descriptors . 30
11.3.3 Addition of the cenc:pssh element in Protection System Specific UUID
ContentProtection Descriptors . 31
11.3.4 Example of two Content Protection Descriptors in an MPD . 31
Annex A (normative) Content sensitive encryption scheme .33
Bibliography .42
iv
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ISO/IEC FDIS 23001-7:2023(E)
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 non­governmental, 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. This document was drafted in
accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives or
www.iec.ch/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 www.iec.ch/understanding­standards.
This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information.
This fourth edition cancels and replaces the third edition (ISO/IEC 23001­7:2016), which has been
technically revised. It also incorporates the Amendment ISO/IEC 23001-7:2016/Amd 1:2019.
The main changes are as follows:
Addition of:
— item encryption, which allows image items to use protection schemes defined for media tracks,
— support for multiple keys and IVs per protected sample,
— 'sve1' sensitive encryption scheme, a codec-specific encryption scheme for which the encrypted
bitstream remains a valid decodable bitstream,
— improved selective encryption using sample groups
A list of all parts in the ISO/IEC 23001 series can be found on the ISO and IEC websites.
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
www.iec.ch/national­committees.
v
© ISO/IEC 2023 – All rights reserved

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ISO/IEC FDIS 23001-7:2023(E)
Introduction
Common Encryption specifies encryption and key mapping methods that enable decryption of the
same file using different Digital Rights Management (DRM) and key management systems. It defines
encryption algorithms and encryption related metadata necessary to decrypt the protected streams,
yet it leaves the details of rights mappings, key acquisition and storage, DRM content protection
compliance rules, etc., up to the DRM system or systems. For instance, DRM systems necessarily support
identifying the decryption key via stored key identifiers (KIDs), but how each DRM system protects and
locates the KID identified decryption key is left to a DRM-specific method.
DRM specific information such as licenses, rights, and license acquisition information can be stored in
an ISO Base Media file using a ProtectionSystemSpecificHeaderBox. Each instance of this box stored in
the file corresponds to one applicable DRM system identified by a well-known SystemID. DRM licenses
or license acquisition information need not be stored in the file in order to look up a separately delivered
key using a KID stored in the file and decrypt media samples using the encryption parameters stored in
each track.
The second edition of this document added XML representations of Common Encryption parameters
for delivery in XML documents, such as an MPEG DASH Media Presentation Description Documents
(MPD). The second edition also defined the 'cbc1' protection scheme using AES-CBC mode encryption.
The third edition added 'cbcs' and 'cens' protection schemes for pattern encryption, which encrypt
only a fraction of the data blocks within each video subsample protected. Pattern encryption reduces
the computational power required by devices to decrypt video tracks.
The additions in this fourth edition are listed in the Foreword.
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FINAL DRAFT INTERNATIONAL STANDARD ISO/IEC FDIS 23001-7:2023(E)
Information technology — MPEG systems technologies —
Part 7:
Common encryption in ISO base media file format files
1 Scope
This document specifies common encryption formats for use in any file format based on
ISO/IEC 14496-12. File, item, track, and track fragment metadata is specified to enable multiple digital
rights and key management systems (DRMs) to access the same common encrypted file or stream. This
document does not define a DRM system.
The AES-128 symmetric block cipher is used to encrypt elementary stream data contained in media
samples. Both AES counter mode (CTR) and Cipher Block Chaining (CBC) are specified in separate
protection schemes. Partial encryption using a pattern of encrypted and clear blocks is also specified
in separate protection schemes. The identification of encryption keys, initialization vector storage and
processing is specified for each scheme.
Subsample encryption is specified for NAL structured video, such as AVC and HEVC, to enable normal
processing and editing of video elementary streams prior to decryption.
An XML representation is specified for important common encryption information so that it can be
included in XML files as standard elements and attributes to enable interoperable license and key
management prior to media file download.
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.
ITU­T Rec.H.264 | ISO/IEC 14496­10, Information technology — Coding of audio-visual objects — Part 10:
Advanced Video Coding
ISO/IEC 14496­12, Information technology — Coding of audio-visual objects — Part 12: ISO Base Media
File Format
ISO/IEC 14496­15, Information technology — Coding of audio-visual objects — Part 15: Carriage of
network abstraction layer (NAL) unit structured video in the ISO base media file format
ISO/IEC 23008­2, Information technology – Coding of audio-visual objects – Part 2: High Efficiency Video
Coding (HEVC)
ISO/IEC 23008­12, Information technology — High efficiency coding and media delivery in heterogeneous
— Part 12: Image File Format (HEIF)
IETF RFC 4122, A Universally Unique IDentifier (UUID) URN Namespace
FIPS­197, Advanced Encryption Standard, Federal Information Processing Standards Publication 197,
https:// www .nist .gov/
NIST Special Publication 800­38A, Recommendation of Block Cipher Modes of Operation, https:// www
.nist .gov/
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ISO/IEC FDIS 23001-7:2023(E)
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1.1
block
16-byte extent of sample data that may be encrypted or decrypted by AES-128 block cipher
Note 1 to entry: This is commonly known as a cipher block.
3.1.2
CENC SAI
sample auxiliary information associated with a sample and containing cryptographic information such
as initialization vector or subsample information
Note 1 to entry: The sample auxiliary information is defined in ISO/IEC 14496-12, and is not part of the sample
data.
3.1.3
constant IV
initialization vector specified in a sample entry or sample group description that applies to all samples
and subsamples under that sample entry or mapped to that sample group
3.1.4
initialization vector
8 or 16-byte value used in combination with a key and a block to create the first cipher block in a chain,
and derive subsequent cipher blocks in a cipher block chain
3.1.5
NAL unit
syntax structure containing an indication of the type of data to follow and bytes containing that data in
the form of an RBSP interspersed as necessary with emulation prevention bytes
3.1.6
NAL structured video
video streams composed of NAL Units
Note 1 to entry: The carriage of NAL Units is specified in ISO/IEC 14496-15
3.1.7
protection scheme
encryption algorithm and information identified by the scheme_type in a SchemeTypeBox in a
ProtectionSchemeInfoBox
3.1.8
sample
media sample when the protection applies to media tracks, or the payload of an item when the
protection applies to items
Note 1 to entry: Media sample as defined in ISO/IEC 14496-12.
Note 2 to entry: Payload of an item as defined in ISO/IEC 14496-12.
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ISO/IEC FDIS 23001-7:2023(E)
3.1.9
selective encryption
change in the isProtected value of samples associated with the same sample description entry
Note 1 to entry: This is achieved using CencSampleEncryptionInformationGroupEntry sample groups.
3.1.10
subsample
byte range within a sample consisting of an unprotected part immediately followed by a protected part
3.2 Abbreviated terms
AES Advanced Encryption Standard
AES­CTR AES Counter
AES­CBC AES Cipher­Block Chaining
AVC Advanced Video Coding as specified in ISO/IEC 14496-10
CENC Common ENCryption
DRM Digital Rights Management
HEVC High Efficiency Video Coding as specified in ISO/IEC 23008-2
IV Initialization vector
NAL Network Abstraction Layer, as specified in ISO/IEC 14496-10 and ISO/IEC 23008-2
UUID Universally Unique Identifier
4 Protection schemes
4.1 Scheme type signalling
Scheme signalling shall conform to ISO/IEC 14496-12. For media tracks, as defined in ISO/IEC 14496-12,
the sample entry is transformed and a ProtectionSchemeInfoBox is added to the standard sample entry
in the SampleDescriptionBox to denote that a stream is protected. The ProtectionSchemeInfoBox shall
contain a SchemeTypeBox so that the scheme is identifiable. The SchemeTypeBox shall obey the following
additional constraints:
— The scheme_type field shall be set to a value equal to a four-character code defined in Clause 10.
— The scheme_version field shall be set to 0x00010000 (Major version 1, Minor version 0).
The ProtectionSchemeInfoBox shall also contain a SchemeInformationBox. For media tracks, the
SchemeInformationBox shall contain a TrackEncryptionBox, describing the default encryption
parameters for the track.
The schemes identify general classes of algorithms used to encrypt data. Implementations should not
rely solely on scheme_type and scheme_version to determine if they can process a file and should also
take into account:
— parameters associated with the scheme (e.g. the pattern in case of pattern encryption, or the size of
initialization vectors),
— use of CencSampleEncryptionInformationGroupEntry and the associated parameters (e.g. change in
isProtected, change in number and/or values of keys, change in size of initialization vectors),
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ISO/IEC FDIS 23001-7:2023(E)
— value of the field aux_info_type_parameter associated with CENC SAI,
— versions and flags of the SampleEncryptionBox box if present,
— versions of the ProtectionSystemSpecificHeaderBox and TrackEncryptionBox,
— support for, and values of versions and flags, of ItemEncryptionBox and ItemAuxiliaryInformationBox.
This document does not define brands nor profiles to restrict or recommend combinations of these
parameters. Derived specifications may restrict some of these aspects.
4.2 Common encryption scheme types
Five protection schemes are specified in this edition of Common Encryption. Each scheme uses syntax
and algorithms specified in Clause 5 to Clause 9, as constrained in Clause 10. They are the following:
a) 'cenc' – AES-CTR mode full sample and video NAL subsample encryption; see 10.1.
b) 'cbc1' – AES-CBC mode full sample and video NAL subsample encryption; see 10.2.
c) 'cens' – AES-CTR mode partial video NAL pattern encryption; see 10.3.
d) 'cbcs' – AES-CBC mode partial video NAL pattern encryption; see 10.4.
e) 'sve1' – AES-CTR content sensitive encryption, as defined in Annex A.
5 Overview of encryption metadata
The encryption metadata defined by Common Encryption can be categorized as fo
...