On-the-fly encryption

On-the-fly encryption (OTFE), also known as real-time encryption and transparent encryption, is a method used by some disk encryption software. "On-the-fly" refers to the fact that data is automatically encrypted or decrypted as it is loaded or saved. It is often used when the storage medium is portable or could be stolen, so that the data on the storage medium needs to be encrypted at all times.

With on-the-fly encryption, the files are accessible immediately after the key is provided, and the entire volume is typically mounted as if it were a physical drive, making the files just as accessible as any unencrypted ones. No data stored on an encrypted volume can be read (decrypted) without using the correct password/keyfile(s) or correct encryption keys. The entire file system within the volume is encrypted (including file names, folder names, file contents, and other meta-data).

To be transparent to the end user, on-the-fly encryption usually requires the use of device drivers to enable the encryption process. Although administrator access rights are normally required to install such drivers, encrypted volumes can typically be used by normal users without these rights.

In general, every method in which data is transparently encrypted on write and decrypted on read can be called on-the-fly encryption.

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