# Features

## Security

* [ChaCha20-Poly1305](https://www.rfc-editor.org/rfc/rfc8439) for authenticated encryption, with the [padding fix](https://github.com/samuel-lucas6/kcChaCha20-Poly1305) for key commitment.
* [Argon2id](https://www.rfc-editor.org/rfc/rfc9106.html) for password-based key derivation.
* [BLAKE2b](https://www.rfc-editor.org/rfc/rfc7693) for hashing, keyed hashing, and key derivation.
* [X25519](https://www.rfc-editor.org/rfc/rfc7748) for key exchange.
* [Elligator 2](https://elligator.cr.yp.to/) for hiding ephemeral public keys.
* [Ed25519](https://www.rfc-editor.org/rfc/rfc8032) for digital signatures.

The [libsodium](https://doc.libsodium.org/) library is used for everything but Elligator2, which is from [Monocypher](https://monocypher.org/).

## Functionality

* Encrypt multiple files/directories with a passphrase, symmetric key, or asymmetric keys.
* Encrypt to multiple recipients for sender authenticated, one-way file sharing.
* Encrypted files are indistinguishable from random. File names can also be encrypted.
* Create and verify digital signatures, with support for an authenticated comment and prehashing.
* Small public keys. Private keys are encrypted for protection at rest.
* UNIX style passphrase entry and random passphrase generation.
* Pre-shared keys can be used for post-quantum secure key exchange.

## Privacy

* Kryptor runs locally on your computer. No personal data is ever collected or sent to anyone.​
* Kryptor runs offline unless you run the `-u|--update` command, which downloads [this](https://github.com/samuel-lucas6/Kryptor/blob/master/version.txt) text file and [this](https://github.com/samuel-lucas6/Kryptor/blob/master/version.txt.signature) signature file from GitHub. If you choose to let Kryptor install an update for you when prompted, the [latest release](https://github.com/samuel-lucas6/Kryptor/releases/latest) for your operating system and the associated signature file will also be downloaded from GitHub. You can read GitHub's Privacy Statement [here](https://docs.github.com/en/github/site-policy/github-privacy-statement).

{% hint style="info" %}
As of [v4.1.0](https://www.kryptor.co.uk/changelog#v4.1.0), the`-u|--update` option has been removed to be consistent with other command line tools. A package manager should be used instead if this is a concern.
{% endhint %}