tor-hscrypto

tor-hscrypto: Basic cryptography used by onion services

Overview

This crate is part of Arti, a project to implement Tor 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.
• Proof of work schemes for resisting denial of service attacks

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.

Compile-time features

• memquota-memcost -- implement tor_memquota::HasMemoryCost for many types. (Does not actually force compiling in memory quota tracking; that's memquota in tor-memquota and higher-level crates.)

• ope -- support for Order Preserving Encryption

• full -- Enable all features above.

Experimental and unstable features

Note that the APIs enabled by these features are NOT covered by semantic versioning[^1] guarantees: we might break them or remove them between patch versions.

• pow-v1 -- Tor Hidden Services Proof of Work (v1 scheme only)

• pow-full -- Tor Hidden Services Proof of Work (metafeature, enables all non-experimental schemes: currently, implies only pow-v1).

• experimental: Enable all the above experimental features.

[^1]: Remember, semantic versioning is what makes various cargo features work reliably. To be explicit: if you want cargo update to only make safe changes, then you cannot enable these features.

License

MIT OR Apache-2.0

When the pow feature is used, we link with LGPL licensed dependencies.