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This article is about how to use cenc encryption. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

Universal encryption format CENC is an encryption format based on ISO/IEC14496-12. CENC defines two encryption methods: full sample encryption and sub-sample encryption. Full sample encryption encrypts the whole sample as a complete unit; the sample in sub-sample encryption is divided into one or more subsample, each subsample is alternately composed of unencrypted region and encrypted region, all encrypted regions in Sample are regarded as a logically continuous block, and the increase of counter value has nothing to do with switching NAL units.

CENC encryption mechanism

CENC encryption replaces sampleentry as follows:

1. Add ProtectionSchemeInformationBox ('sinf') to each track to identify the content as encrypted.

2. ProtectionSchemeInformationBox ('sinf') contains SchemeTypeBox (' schm'): defines the corresponding encryption algorithm, where scheme_type defines the encryption type and scheme_version defines the schema version. In CENC encryption:

The pattern type scheme_type='cenc',CENC is encrypted by AES-CTR algorithm

Mode version scheme_version=0 x 00010000.

3. ProtectionSchemeInformationBox ('sinf') should include SchemeInformationBox (' schi').

4. SchemeInformationBox ('schi') contains TrackEncryptionBox (' tenc'): describes the encryption parameters of the track.

The relevant parameters defined in the CENC universal encryption format are included in the following box:

1. Information related to the scheme of the content protection system, such as license and authorization acquisition information, is included in ProtectionSystemSpecificHeaderBox ('pssh').

2. The encryption parameters for each track (including KID, initialization vector, encryption flag bits) are included in TrackEncryptionBox ('tenc').

3. The encryption parameters for samplesgroups (including KID, initialization vector, encryption flag bits) are included in SampleGroupDescriptionBox ('sgpd').

4. The encryption parameters of individual sample (including initialization vector, subsample encrypted data) are included in the additional information of the sample, which is referenced by SampleAuxiliaryInformationSizesBox ('saiz') and SampleAuxiliaryInformationOffsetsBox (' saio').

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