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25 May 2009, 16:01

Adobe acts against Flash video stream recorder

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SourceForge, the open-source project host, has removed the pages of the rtmpdump stream-recording software from its network in response to a cease-and-desist notice from Adobe. The program uses the Real-Time Messaging Protocol (RTMP) to record not only streamed Flash media but also encrypted streams. Adobe added encryption to its proprietary protocol on introducing Flash Media Server 3 in order to prevent the recording of Flash content, and defined RTMPE (RMTP encrypted) for the purpose. Adobe takes the view that its copy protection can be circumvented by the RTMPE support incorporated in rtmpdump and, in its cease-and-desist notice, invokes the Digital Millennium Copyright Act to prevent the distribution of the software.

A recently published analysis of RTMPE comes to the conclusion that, although the algorithm "provides end-to-end secrecy in exactly the same way that SSL provides end-to-end secrecy, it provides no security and uses no authentication of any kind." Nowhere is a secret key, a password or even a pass phrase required in order to decrypt the content: only a 32-byte hash value plus the size of the SWF file and publicly exchanged information, specifically the last 32 bytes of the first response from the streaming server, are involved.

Following this line of argument, it could be concluded that RTMPE is only a proprietary streaming protocol with encrypted transmission. It seems at least questionable whether Adobe could call this a circumvention of copy protection and thus be in a position to invoke the DMCA and prevent distribution of the software.

At any rate, Adobe may have a little difficulty in giving an explanation to its clients – among them TV broadcasters and film studios – who are increasingly relying on RTMPE for the DRM-protected distribution of their content. And flvstreamer, an offshoot from rtmpdump, has now appeared on the scene; like other Flash stream recorders, it does without the problematic RTMPE.


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