Protected content distribution is accomplished by a first entity
generating a set of asymmetric key pairs, creating a plurality of sets of
private keys by selecting a combination of private keys from the set of
asymmetric key pairs for each created set, and distributing the sets of
private keys to playback devices. A second entity produces protected
content including encrypted content and a public key media key block,
encrypts a symmetric content key with each public key in the set of
asymmetric key pairs to form the public key media key block and encrypts
a content title with the symmetric content key to form the encrypted
content. A playback device stores one set of private keys, receives the
protected content, and decrypts and plays the content title stored in the
protected content when a selected one of the set of private keys stored
by the playback device successfully decrypts the encrypted symmetric
content key stored in the public key media key block of the received
protected content.