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.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.