A content key (CK) to decrypt a piece of encrypted content is obtained encrypted according to a public key of a licensor (PU-L) to result in (PU-L(CK)). (PU-L(CK)) is obscured according to (PU-L) and a value R to result in Obs (PU-L(CK)), and Obs (PU-L(CK)) is sent to the licensor, which applies a private key (PR-L) corresponding to (PU-L) to Obs (PU-L(CK)) to result in Obs (CK) as an obscured version of (CK). Obs (CK) is received from the licensor; and (CK) is obtained from Obs (CK) based on applying R thereto. The licensor cannot identify from Obs (PU-L(CK)) or from Obs (CK) the encrypted content or the content key (CK) from which the encrypted content may be identified.