Disk encryption software
Disk encryption generally refers to wholesale encryption that operates on an entire volume mostly transparently to the user, the system, and applications. This is generally distinguished from file-level encryption that operates by user invocation on a single file or group of files, and which requires the user to decide which specific files should be encrypted. Disk encryption usually includes all aspects of the disk, including directories, so that an adversary cannot determine content, name or size of any file. It is well suited to portable devices such as laptop computers and thumb drives which are particularly susceptible to being lost or stolen. If used properly, someone finding a lost device cannot penetrate actual data, or even know what files might be present.
File hosting service
Secret key encryption is sometimes referred to as zero knowledge, meaning that only the user has the encryption key needed to decrypt the data. Since data is encrypted using the secret key, identical files encrypted with different keys will be different. To be truly zero knowledge, the file hosting service must not be able to store the user's passwords or see their data even with physical access to the servers. For this reason, secret key encryption is considered the highest level of access security in cloud storage. This form of encryption is rapidly gaining popularity, with companies such as SpiderOak being entirely zero knowledge file storage and sharing.