# tor-hscrypto

`tor-hscrypto`: Basic cryptography used by onion services 

## Overview

This crate is part of
[Arti](https://gitlab.torproject.org/tpo/core/arti/), a project to
implement [Tor](https://www.torproject.org/) in Rust.

Onion services and the clients that connect to them need a few cryptographic
operations not used by the rest of Tor.  These include:

  * A set of key-blinding operations to derive short-term public keys 
    from long-term public keys.
  * An ad-hoc SHA3-based message authentication code.
  * Operations to encode and decode public keys as `.onion` addresses.
  * A set of operations to divide time into different "periods".  These periods
    are used as inputs to the DHT-style hash ring, and to the key-blinding
    operations.

This crate implements those operations, along with a set of wrapper types to
keep us from getting confused about the numerous keys and nonces used for the
onion services.

License: MIT OR Apache-2.0