Some embodiments provide convenient auto-authentication for user data on a primary device, while still providing a significant level of security, by taking advantage of existing security and cryptographic measures used to communicate with a secondary device. The primary device of some embodiments encrypts the user data on the primary device using a cryptographic key based on a set of keys received from the secondary device. In some embodiments, the primary device encrypts authentication data, or a local key generated from the authentication data, using a remote key received from the secondary device, and encrypts the user data with the local key. In some embodiments, the keys received from the secondary device are an existing set of keys for establishing an encrypted channel of communication for transmitting digital rights management (DRM) protected content according to a DRM protection scheme.