Security Researcher Cracks Google's Widevine DRM (L3 Only)
Friday January 4, 2019. 11:00 AM , from Slashdot
The L3 protection level of Google's Widevine DRM technology has been cracked by a British security researcher who can now decrypt content transferred via DRM-protected multimedia streams. ZDNet's Catalin Cimpanu notes that while this 'sounds very cool,' it's not likely to fuel a massive piracy wave because 'the hack works only against Widevine L3 streams, and not L2 and L1, which are the ones that carry high-quality audio and video content.' From the report: Google designed its Widevine DRM technology to work on three data protection levels --L1, L2, and L3-- each usable in various scenarios. According to Google's docs, the differences between the three protection levels is as follows:
L1 - all content processing and cryptography operations are handled inside a CPU that supports a Trusted Execution Environment (TEE).
L2 - only cryptography operations are handled inside a TEE.
L3 - content processing and cryptography operations are (intentionally) handled outside of a TEE, or the device doesn't support a TEE
'Soooo, after a few evenings of work, I've 100% broken Widevine L3 DRM,' [British security researcher David Buchanan] said on Twitter. 'Their Whitebox AES-128 implementation is vulnerable to the well-studied DFA attack, which can be used to recover the original key. Then you can decrypt the MPEG-CENC streams with plain old ffmpeg.' Albeit Buchanan did not yet release any proof-of-concept code, it wouldn't help anyone if he did. In order to get the DRM-encrypted data blob that you want to decrypt, an attacker would still need 'the right/permission' to receive the data blob in the first place. If a Netflix pirate would have this right (being an account holder), then he'd most likely (ab)use it to pirate a higher-quality version of the content, instead of bothering to decrypt low-res video and lo-fi audio. The only advantage is in regards to automating the pirating process, but as some users have pointed out, this isn't very appealing in today's tech scene where almost all devices are capable of playing HD multimedia [1, 2].
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