ISO/IEC 23001-7:2016/Amd 1:2019

INTERNATIONAL ISO/IEC
STANDARD 23001-7
Third edition
2016-02-15
AMENDMENT 1
2019-09
Information technology — MPEG
systems technologies —
Part 7:
Common encryption in ISO base media
file format files
AMENDMENT 1: AES-CBC-128 and key
rotation
Technologies de l'information — Technologies des systèmes MPEG —
Partie 7: Cryptage commun des fichiers au format de fichier de médias
de la base ISO
AMENDEMENT 1: AES-CBC-128 et rotation des clés
Reference number
ISO/IEC 23001-7:2016/Amd.1:2019(E)
©
ISO/IEC 2019
ISO/IEC 23001-7:2016/Amd.1:2019(E)

© ISO/IEC 2019
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ISO/IEC 23001-7:2016/Amd.1:2019(E)

Foreword
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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.
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ISO/IEC 23001-7:2016/Amd.1:2019(E)
Information technology — MPEG systems technologies —
Part 7:
Common encryption in ISO base media file format files
AMENDMENT 1: AES-CBC-128 and key rotation

Clause 2
Add the following new normative references:
ISO/IEC 23008-2, Information technology — High efficiency coding and media delivery in heterogeneous
environments — Part 2: High efficiency video coding
ISO/IEC 23008-12, Information technology — High efficiency coding and media delivery in heterogeneous
environments — Part 12: Image File Format (HEIF)

3.1
Insert a new 3.1.8 and renumber current 3.1.8 as 3.1.9:
3.1.8
sample
media sample when the protection applies to media tracks, or payload of an item when the protection
applies to items
Note 1 to entry: Media sample as defined in 14496-12.
Note 2 to entry: Payload of an item as defined in 14496-12.

4.2
Add the following item to the list:
e) ‘sve1’ – AES-CTR content sensitive encryption, as defined in Annex A.
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ISO/IEC 23001-7:2016/Amd.1:2019(E)

Clause 6
In paragraph 4, replace:
{
unsigned int(8)   reserved = 0;
unsigned int(4)   crypt_byte_block;
unsigned int(4)   skip_byte_block;
unsigned int(8)   isProtected;
unsigned int(8)   Per_Sample_IV_Size;
unsigned int(8)[16] KID;
if (Per_Sample_IV_Size == 0) {
unsigned int(8)  constant_IV_size;
unsigned int(8)[constant_IV_size] constant_IV;
}
}
with
{
unsigned int(1)   multi_key_flag;
unsigned int(7)   reserved = 0;
unsigned int(4)   crypt_byte_block;
unsigned int(4)   skip_byte_block;
unsigned int(8)   isProtected;
if (multi_key_flag == 1) {
unsigned int(16)   key_count;
} else {
key_count = 1;
}
for (i=1; i <= key_count; i++) {
unsigned int(8)   Per_Sample_IV_Size;
unsigned int(8)[16] KID;
if (Per_Sample_IV_Size == 0) {
unsigned int(8)  constant_IV_size;
unsigned int(8)[constant_IV_size] constant_IV;
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ISO/IEC 23001-7:2016/Amd.1:2019(E)

}
}
}
Clause 6
Add a new item to the list in paragraph 5 (insert before semantics of isProtected):
— multi_key_flag indicates that the multiple key version of the sample group description is used. If
this flag is set, multiple keys will be described for this sample group description entry; otherwise, a
single key is described for this sample group description entry.
Add a new item to the list in paragraph 5 (insert after semantics of isProtected):
— key_count indicates the number of keys that may apply to a sample associated to this sample group
description entry. It is not required that a sample associated with this sample group description
entry uses all the keys described.

7.1
Replace the sample auxiliary information in paragraph 3 with:
aligned(8) class CencSampleAuxiliaryDataFormat
{
if (aux_info_type_parameter==0) {
unsigned int(Per_Sample_IV_Size*8) InitializationVector;
if (sample_info_size > Per_Sample_IV_Size ) {
unsigned int(16) subsample_count;
{
unsigned int(16) BytesOfClearData;
unsigned int(32) BytesOfProtectedData;
} [subsample_count ]
}
} else if (aux_info_type_parameter == 1) {
unsigned int(16) multi_IV_count;
for (i=1; i <= multi _IV_count; i++) {
unsigned int(8) multi_subindex_IV;
unsigned int(Per_Sample_IV_Size*8) IV;
}
unsigned int(32) subsample_count;
{
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ISO/IEC 23001-7:2016/Amd.1:2019(E)

unsigned int(16) multi_subindex;
unsigned int(16) BytesOfClearData;
unsigned int(32) BytesOfProtectedData;
} [subsample_count]
}
}
Following the sample auxiliary information, add the following at the end of the 'where' list (after
semantics of BytesOfProtectedData):
multi_IV_count indicates the number of entries in the initialization vector loop;
multi_subindex_IV indicates the index of the associated key entry, where value one is the first entry,
in the associated list; if this data is read for the processing of a track sample, the associated list is
the ’seig’ sample group description entry associated with this sample; otherwise (this data is
read for the processing of an item), the associated list is the list of key definitions in the ‘ienc’
item property of this item. The associated key entry shall have a Per_Sample_IV_Size different
from 0, i.e. key entries using constant IV shall not be present in this loop. If this data is read for
the processing of a track sample and aux_info_type_parameter is set to 1, the associated ‘seig’
sample group description entry shall have the multi_key_flag set to 1;
IV indicates the initialization vector to be used for the first block of protected data for the
associated key entry;
multi_subindex indicates the index of the associated key entry, where value one is the first entry,
in the associated list (see multi_subindex_IV) for the following run of encrypted data.

7.2.2
Replace the content of 7.2.2 with the following:
aligned(8) class SampleEncryptionBox extends FullBox(‘senc’, version, flags)
{
unsigned int(32) sample_count;
{
if (version==0) {
unsigned int(Per_Sample_IV_Size*8) InitializationVector;
if (flags & 0x000002) {
unsigned int(16) subsample_count;
{
unsigned int(16) BytesOfClearData;
unsigned int(32) BytesOfProtectedData;
} [subsample_count ]
}
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} else if (version==1) {
unsigned int(16) multi_IV_count;
for (i=1; i <= multi _IV_count; i++) {
unsigned int(8) multi_subindex_IV;
unsigned int(Per_Sample_IV_Size*8) IV;
}
unsigned int(32) subsample_count;
{
unsigned int(16) multi_subindex;
unsigned int(16) BytesOfClearData;
unsigned int(32) BytesOfProtectedData;
} [subsample_count]
}
}[ sample_count ]
}
7.2.3
Add the following to the list of semantics:
— multi_IV_count, multi_subindex_IV, IV and multi_subindex SHALL conform to the definition
specified in Clause 7.
8.1.1
Replace
Container:  Movie (‘moov’) or Movie Fragment (‘moof’)
with
Container: Movie (‘moov’) or Movie Fragment (‘moof’) or ‘meta’ if no Movie (‘moov’)

8.2
Add the following new subclauses after 8.2:
8.3  Item encryption box
8.3.1  Definition
Box Type: `ienc’
Container: Item Properties Box
Mandatory (per item): Yes for protected items using schemes defined in this document
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ISO/IEC 23001-7:2016/Amd.1:2019(E)

Quantity (per item): At most one associated with any item
Quantity: Zero or one
Items as defined in ISO/IEC 14496-12 may be protected using the schemes defined in this document. In
this case, such items shall have an associated ItemEncryptionBox property and an associated auxiliary
item with an aux_info_type matching the protection scheme used, as defined in 8.4. The payload of that
auxiliary item shall be exactly one CencSampleAuxiliaryDataFormat as defined in 7.1.
The ItemEncryptionBox contains default values for the isProtected flag, Per_Sample_IV_Size, and KID
for the item. In the case where pattern-based encryption is in effect, it supplies the pattern and when
Constant IVs are in use, it supplies the Constant IV. These values are used as the encryption parameters
for the item in this meta box. For files with only one key for all items, this property box allows the basic
encryption parameters to be specified once for all items instead of being repeated per item.
Items sharing this property are always protected; consequently, the default value for isProtected field
(see 9.1) is 1.
If the value Per_Sample_IV_Size is 0, then the constant_IV_size for all items that use these settings
SHALL be present. A Constant IV SHALL NOT be used with counter-mode encryption.
ItemEncryptionBox properties shall be marked as essential in ItemPropertyAssociation.
NOTE The version field of the ItemEncryptionBox is set to a value greater than zero when the pattern
encryption defined in 9.6 is used and to zero otherwise.
8.3.2  Syntax
aligned(8) class ItemEncryptionBox extends ItemFullProperty(‘ienc’, version, flags=0)
{
unsigned int(8) reserved = 0;
if (version==0) {
unsigned int(8) reserved = 0;
} else { // version is 1 or greater
unsigned int(4) crypt_byte_block;
unsigned int(4) skip_byte_block;
}
unsigned int(8) num_keys;
for (i=1; i<= num_keys; i++) {
unsigned int(8) Per_Sample_IV_Size;
unsigned int(8)[16] KID;
if (Per_Sample_IV_Size == 0) {
unsigned int(8) constant_IV_size;
unsigned int(8)[ constant_IV_size] constant_IV;
}
}
}
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8.3.3  Semantics
version SHALL be zero unless pattern-based encryption is in use, whereupon it SHALL be 1.
crypt_byte_block specifies the count of the encrypted blocks in the protection pattern, where each
block is of size 16-bytes, for items associated with this key entry. See 9.1 for further details.
skip_byte_block specifies the count of the unencrypted blocks in the protection pattern for items
associated with this key entry. See the skip_byte_block field in 9.1 for further details.
num_keys indicates the number of key definition entries.
Per_Sample_IV_Size is the initialization vector size in bytes for items associated with this key entry.
See the Per_Sample_IV_Size field in 9.1 for further details.
KID is the key identifier used for items associated with this key entry. See the KID field in 9.1 for further
details.
constant_IV_size is the size of a initialization vector for items associated with this key entry.
constant_IV, if present, is the initialization vector for items associated with this key entry. See the
constant_IV field in 9.1 for further details.
8.4  Item auxiliary information box
8.4.1  Definition
Box Type: `iaux’
Container: Item Properties Box
Mandatory (per item): Yes for protected items using schemes defined in this document
Quantity (per item): At most one associated with any item
Quantity: Zero or one
An item may have some auxiliary information associated, similarly to sample of a track having auxiliary
sample information. This information is usually declared through item properties and associations; it
can also be declared through auxiliary information items, to allow sharing the auxiliary info between
items and samples th
...