Patent ID: 8397076

Claim:
A method for resetting a password at a second device from a first device, the password being used to encrypt a content protection key K to provide a first encrypted content protection key at the second device, the content protection key K also being encrypted by a key encryption key L to provide a second encrypted content protection key at the second device, the key encryption key L being generated from a private key b stored at the first device, an elliptic curve point P, and a private key d, such that L=dbP, and wherein a public key D=dP is stored by the second device, and d is not stored at either the first device or the second device, the method comprising the first device: transmitting a new password to the second device; receiving a public key D′ from the second device, wherein the public key D′ is derived from a key value r and the elliptic curve point P; generating a public key L′ from the private key b and the public key D′; and transmitting to the second device the public key L′, wherein transmitting enables the second device to derive the key encryption key L, decrypt the second encrypted content protection key, derive a new content protection key, and encrypt the new content protection key using the new password to provide a new first encrypted content protection key; generating a public key B 1 from a private key b 1 and an elliptic curve point P 1 ; and transmitting to the second device the public key B 1 , wherein transmitting enables the second device to derive a new key encryption key M from the public key B 1 , a private key d 1 , and a public key D 1 generated using the private key d 1 ; destroy the private key d 1 ; and encrypt the new password using the new key encryption key M.