Request for reviewing audio, vidoe, text/rtp-enc-aescm128

[Magnus Westerlund]

This is a request to review the media types:
audio/rtp-enc-aescm128
video/rtp-enc-aescm128
text/rtp-enc-aescm128

These have been requested by 3GPP SA4 to be registered in the standards 
tree by the IESG following the SDO rules in RFC 4288. The type 
registration is present in Technical Specification 26.234 in section 
K.1.4.1:
http://www.3gpp.org/ftp/Specs/archive/26_series/26.234/26234-670.zip

It is reproduced below for your information. The full media format is 
specified in Annex K of above specification. The registration template 
has been present in the document for a while and follows the template in 
RFC 2048. If that is a problem it can be fixed, however it will take 
some months. I therefore would also like to receive any further comments 
in that case.

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 
fulfills 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

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Thanks

Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVA/A
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S-164 80 Stockholm, Sweden | mailto: magnus.westerlund at ericsson.com