Support for Rclone Crypt client-side encryption scheme

[dkocher]

The encryption is a secret-key encryption (also called symmetric key encryption) algorithm, where a password (or pass phrase) is used to generate real encryption key. The password can be supplied by user, or you may chose to let rclone generate one. It will be stored in the configuration file, in a lightly obscured form. If you are in an environment where you are not able to keep your configuration secured, you should add configuration encryption as protection. As long as you have this configuration file, you will be able to decrypt your data. Without the configuration file, as long as you remember the password (or keep it in a safe place), you can re-create the configuration and gain access to the existing data. You may also configure a corresponding remote in a different installation to access the same data. See below for guidance to changing password.

Encryption uses cryptographic salt, to permute the encryption key so that the same string may be encrypted in different ways. When configuring the crypt remote it is optional to enter a salt, or to let rclone generate a unique salt. If omitted, rclone uses a built-in unique string. Normally in cryptography, the salt is stored together with the encrypted content, and do not have to be memorized by the user. This is not the case in rclone, because rclone does not store any additional information on the remotes. Use of custom salt is effectively a second password that must be memorized.

File content encryption is performed using NaCl SecretBox, based on XSalsa20 cipher and Poly1305 for integrity. Names (file- and directory names) are also encrypted by default, but this has some implications and is therefore possible to be turned off.

https://rclone.org/crypt/