[thomastjeffery]

You don't need quantum computing. You just need a debugger. The user already has the encryption key, else they would not be able to see the content.

[bawolff]

Widevine has different levels. In level 1 & 2 the key is in a TPM.

Even for level3, i can only inagine that the amount of obfuscation must be pretty intense.