Described is a technique for securely verifying access rights to a media file stored on a user device. By verifying the access rights to the media file, a server may provide access to a licensed version of the media from a media library in a remote location such as server for a cloud-based service. When a media file is confirmed to be available in a media library, a cryptographic a hash function that incorporates a random value or “salt” is used to verify that a user is in possession of an entire media file. Accordingly, the techniques described herein improve the security for verifying that a user is in possession of a media file by preventing the use of pre-calculated hashes.