I assume you mean the private keys would be on the player?
This would work until somebody manages to do a memory dump of one of the players and posts the private key on the internet.
Even if you were to re-encrypt the data for each individual player (manufacture each with a different key) you still have the problem that one DRM free copy can multiply quickly via bittorrent etc.
The most practical solution would be to have players that will only play DRM protected medium and require hardware circumvention on each individual player to bypass that and hope that this is more effort than it is worth to potential pirates.
This would work until somebody manages to do a memory dump of one of the players and posts the private key on the internet.
Even if you were to re-encrypt the data for each individual player (manufacture each with a different key) you still have the problem that one DRM free copy can multiply quickly via bittorrent etc.
The most practical solution would be to have players that will only play DRM protected medium and require hardware circumvention on each individual player to bypass that and hope that this is more effort than it is worth to potential pirates.