Encrypting assets on the fly using a per-consumer symmetric key would be prohibitively expensive, so I'm sure the media is stored pre-encrypted using a shared s

Encrypting assets on the fly using a per-consumer symmetric key would be prohibitively expensive, so I'm sure the media is stored pre-encrypted using a shared symmetric key. It only really matters that this key is unique per package, not per user, because once even a single user can compromise the trusted execution environment and extract either the key or the plain video stream, that piece of content is now pirated anyway. So, key reuse against the same content probably isn't really a major part of the threat model - this attacker could share the key with others, but they might as well share the decrypted content instead.