Updated MIME type proposal for 3GPP DRM RTP payload format
Magnus Westerlund
magnus.westerlund at ericsson.com
Mon Nov 15 16:11:25 CET 2004
Hi,
Based on some of the feedback received on this list, I have included a
proposal for an updated MIME type definition for 3GPP TS 26.234 Annex K.
I have not defined a procedure for defining a single media type
(application) and then secondary used media types that are indicated in
SDP. The reason is that I think it makes it more difficult to find these
in the registry. Also being the first doing this in a non IETF document
seems to be problematic. Also having a lot of discussion and changing
things for a basically approved specification is difficult. I think that
3GPP can suffice using the so far done IETF procedures.
Changes done:
- Renamed sub type name: rtp.enc.aescm128 to rtp-enc-aescm128
- Removed media type "image" and "application"
Any feedback is desired as quickly as possible. The 3GPP SA4 which owns
this specification will meet next week, and any feedback received before
next Wednesday will be much simpler to incorporate. Sorry for the short
heads up.
Thanks
Magnus
---- START OF MEDIA TYPE ----
MIME media type name: audio, video, text
MIME subtype name: rtp-enc-aescm128
Required parameters:
opt: The payload type number of the payload type contained in
the encrypted payload. An integer value between 0-127.
rate: The timestamp rate of this payload type, which shall be
the same as that of the original payload type. This is an
integer value between 1 and 2^32.
ContentID: The OMA DRM content ID [75] used to identify the
content when establishing a crypto context. The value is an RFC
2396 [60] URI, which shall be quoted using <">.
RightsIssuerURL: The right issuer URL as defined by OMA
DRM [75]. The value is an URI in accordance with RFC 2396 [60],
which shall be quoted using <">.
IVnonce: The value of this parameter is the nonce
that forms the IV as specified by the crypto transform, encoded
using Base 64 [69].
Optional parameters:
SelectiveEncryption: Indicates if this stream is selectively
encrypted. Allowed values are 0 (false) and 1 (true). If not
present, selective encryption shall not be used. Please note
that unless this indicator is integrity protected, it fulfils no
purpose.
Encoding considerations:
This type is only defined for transfer via RTP (RFC 3550).
Security considerations:
See considerations raised in RTP RFC 3550 [9] and any applicable profile
like RFC 3551 [10] or RFC 3711 [72]. Further see 3GPP TS 26.234, Release
6, Annex K for comments on security issues. The main issues that exists
are:
- This RTP payload format only confidentiality protects the RTP
payload, thus header information is leaked, similarly to SRTP.
- The use of stream ciphers as AES CM and no integrity protection
allows an attacker to purposefully attack the content of the
encrypted RTP payload by switching individual bits.
- The usage of selective encryption without integrity protection
allows for an attacker to perform any replacements of complete RTP
payloads and packets it desires. - The payload format makes the
receiver vulnerable to denial of service attacks that inserts RTP
packets into the stream, that the receiver then interprets as being
encrypted thus wasting computational resources. To prevent this
attack, authentication needs to be used.
Interoperability considerations:
Published specification:
3GPP TS 26.234, Release 6.
Open Mobile Alliance DRM Content Format V2.0
Applications which use this media type:
Third Generation Partnership Project (3GPP) Packet-switched Streaming
Service (PSS) clients and servers, which supports the Open Mobile
Alliance's specification of Digital Rights Management version 2.0.
Additional information:
Magic number(s): N/A
File extension(s): N/A
Macintosh File Type Code(s): N/A
Person & email address to contact for further information:
magnus.westerlund at ericsson.com
Intended usage: Common
Author/Change controller:
3GPP TSG SA
---- END OF MEDIA TYPE ----
Cheers
Magnus Westerlund
Multimedia Technologies, Ericsson Research EAB/TVA/A
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