Microsoft PlayReady Cryptography Weakness

Hello All,There is yet another attack possible against Protected Media Pathprocess beyond the one involving two global XOR keys [1]. The newattack may also result in the extraction of a plaintext content keyvalue.The attack has its origin in a white-box crypto [2] implementation.More specifically, one can devise plaintext content key from white-boxcrypto data structures of which goal is to make such a reconstructiondifficult / not possible. This alone breaks one of the main securityobjective of white-box cryptography which is to protect the secret key(unbreakability) [3].Contrary to the initial (XOR key) attack, the white-box crypto attackis not limited to the given narrow time window (white-box datastructures need to be present for the time of a movie decryption /playback). Fixing it might require a completely new approach /implementation (current one is obviously flawed).In that context, white-box crypto attack seems to be more severe thanthe XOR key one.Additionally, a cryptographic check proving that extracted key valuescorrespond to real keys has been conducted for Canal+ Online, Netflix,HBO Max, Amazon Prime Video and Sky Showtime.The check relies on a digital cryptographic signature verification.Such a signature is appended at the end of each license issued byPlayReady license server.The crypto check works as following:- plaintext value of a digital signature key encrypted through ECC isextracted from a Protected Media Path process- the extracted signature key is used to calculate the AES-CMAC valueof a binary licence XMR blob- the calculated signature value is checked against the signatureappended at the end of the issued license- correct AES-CMAC value implicates correct signature key (and correctcontent key)The above mechanism is also used by Microsoft to verify thecorrectness of decrypted content keys received from a license server.It relies on the fact that signature key is part of the same encryptedlicense blob as content key. Thus, successful extraction of asignature key implicates successful extraction of a content key.In the context of no confirmation / denial [4] from the platformsindicated above as being affected, the crypto check should constitutesufficient proof to support that claim alone.Thank you.Best Regards,Adam Gowdiak----------------------------------Security Explorations -AG Security Research Labhttps://security-explorations.com----------------------------------References:[1] Microsoft Warbird and PMP security research    https://security-explorations.com/microsoft-warbird-pmp.html[2] White-box cryptography, Wikipedia    https://en.wikipedia.org/wiki/White-box_cryptography[3] White-Box Security Notions for Symmetric Encryption Schemes    https://eprint.iacr.org/2013/523.pdf[4] Microsoft DRM Hack Could Allow Movie Downloads From PopularStreaming Services    https://www.securityweek.com/microsoft-drm-hacking-could-allow-movie-downloads-from-popular-streaming-services/