ISMACryp
Encyclopedia
The ISMA Encryption and Authentication, Version 1.1 specification (or ISMACryp) specifies encryption
and message authentication
services for MPEG-4
over RTP
streams. It was defined by the Internet Streaming Media Alliance
and published on September 15, 2006.
The ISMA Encryption and Authentication, Version 2.0 specifies content encryption, message authentication (integrity) services, an RTP payload
format and a file format for pre-encrypted content for ISMA 1.0, ISMA 2.0 and more generally any media that can be stored as elementary stream
in an ISO base media file format
(ISO/IEC 14496-12). The specification was published on 15 November 2007. ISMACryp specification defined extensions over the ISO base media file format, which were registered by the registration authority for code-points in "MP4 Family" files. The ISMACryp 2.0 specification in an informative "Annex F" provides guidelines on how ISMACryp can be used together with the key and rights management system of OMA DRM
v2 (Open Mobile Alliance DRM
). The Packetized OMA DRM Content Format is almost based on ISMACryp format.
There are two alternatives to ISMACryp, SRTP
and IPsec
, that can also be used to provide service and content protection. The difference between the three is at what level encryption is done. Whereas ISMACryp encrypts MPEG-4 access units (that are in the RTP payload), SRTP encrypts the whole RTP payload, and IPsec encrypts packets at network level.
The ISMACryp specification does not mandate a cipher but AES
in Counter Mode, the default encryption and authentication
transform in the specification, is the de facto cipher used by ISMACryp implementations.
Encryption
In cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information...
and message authentication
Authentication
Authentication is the act of confirming the truth of an attribute of a datum or entity...
services for MPEG-4
MPEG-4
MPEG-4 is a method of defining compression of audio and visual digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group under the formal standard ISO/IEC...
over RTP
Real-time Transport Protocol
The Real-time Transport Protocol defines a standardized packet format for delivering audio and video over IP networks. RTP is used extensively in communication and entertainment systems that involve streaming media, such as telephony, video teleconference applications, television services and...
streams. It was defined by the Internet Streaming Media Alliance
Internet Streaming Media Alliance
The Internet Streaming Media Alliance was Founded in December 2000, by Apple Computer, Cisco Systems, IBM, Kasenna, Philips, and Sun Microsystems. It is a non-profit corporation whose mission is to accelerate the market adoption of open standards for streaming and progressive download of rich...
and published on September 15, 2006.
The ISMA Encryption and Authentication, Version 2.0 specifies content encryption, message authentication (integrity) services, an RTP payload
format and a file format for pre-encrypted content for ISMA 1.0, ISMA 2.0 and more generally any media that can be stored as elementary stream
Elementary stream
An elementary stream as defined by MPEG communication protocol is usually the output of an audio or video encoder. ES contains only one kind of data, e.g. audio, video or closed caption. An elementary stream is often referred to as "elementary", "data", "audio", or "video" bitstreams or streams...
in an ISO base media file format
ISO base media file format
ISO base media file format defines a general structure for time-based multimedia files such as video and audio. It is used as the basis for other media file formats...
(ISO/IEC 14496-12). The specification was published on 15 November 2007. ISMACryp specification defined extensions over the ISO base media file format, which were registered by the registration authority for code-points in "MP4 Family" files. The ISMACryp 2.0 specification in an informative "Annex F" provides guidelines on how ISMACryp can be used together with the key and rights management system of OMA DRM
OMA DRM
OMA DRM is a Digital Rights Management system invented by the Open Mobile Alliance, whose members represent mobile phone manufacturers , mobile system manufacturers , mobile phone network operators OMA DRM is a Digital Rights Management (DRM) system invented by the Open Mobile Alliance, whose...
v2 (Open Mobile Alliance DRM
Digital rights management
Digital rights management is a class of access control technologies that are used by hardware manufacturers, publishers, copyright holders and individuals with the intent to limit the use of digital content and devices after sale. DRM is any technology that inhibits uses of digital content that...
). The Packetized OMA DRM Content Format is almost based on ISMACryp format.
There are two alternatives to ISMACryp, SRTP
Secure Real-time Transport Protocol
The Secure Real-time Transport Protocol defines a profile of RTP , intended to provide encryption, message authentication and integrity, and replay protection to the RTP data in both unicast and multicast applications...
and IPsec
IPsec
Internet Protocol Security is a protocol suite for securing Internet Protocol communications by authenticating and encrypting each IP packet of a communication session...
, that can also be used to provide service and content protection. The difference between the three is at what level encryption is done. Whereas ISMACryp encrypts MPEG-4 access units (that are in the RTP payload), SRTP encrypts the whole RTP payload, and IPsec encrypts packets at network level.
The ISMACryp specification does not mandate a cipher but AES
Advanced Encryption Standard
Advanced Encryption Standard is a specification for the encryption of electronic data. It has been adopted by the U.S. government and is now used worldwide. It supersedes DES...
in Counter Mode, the default encryption and authentication
transform in the specification, is the de facto cipher used by ISMACryp implementations.
See also
- RTPReal-time Transport ProtocolThe Real-time Transport Protocol defines a standardized packet format for delivering audio and video over IP networks. RTP is used extensively in communication and entertainment systems that involve streaming media, such as telephony, video teleconference applications, television services and...
- SRTPSecure Real-time Transport ProtocolThe Secure Real-time Transport Protocol defines a profile of RTP , intended to provide encryption, message authentication and integrity, and replay protection to the RTP data in both unicast and multicast applications...
- IPsecIPsecInternet Protocol Security is a protocol suite for securing Internet Protocol communications by authenticating and encrypting each IP packet of a communication session...
- Internet Streaming Media AllianceInternet Streaming Media AllianceThe Internet Streaming Media Alliance was Founded in December 2000, by Apple Computer, Cisco Systems, IBM, Kasenna, Philips, and Sun Microsystems. It is a non-profit corporation whose mission is to accelerate the market adoption of open standards for streaming and progressive download of rich...
(ISMA)
External links
- ISMA Technical Specifications
- ISMA Encryption and Authentication Version 1.1
- DVB-H handheld video content protection with ISMA Encryption
- OpenIPMP - open source software for DRM including ISMACryp