Tillitis TKey

Introduction

The Tillitis TKey is a new kind of USB security token. What makes the TKey unique is that it allows a user to load and run applications on the device, while still providing security. This allow for open-ended, flexible usage. Given the right application, the TKey can support use cases such as SSH login, Ed25519 signing, Root of Trust, FIDO2, TOTP, Passkey, and more.

During the load operation, the device measures the application (calculates a cryptographic hash digest over it) before running it on the open hardware security processor. This measurement is similar to TCG DICE.

Each TKey device contains a Unique Device Secret (UDS), which together with the application measurement, and an optional User-Supplied Secret (USS), is used to derive key material unique to each application. This guarantees that if the integrity of the application loaded onto the device has been tampered with, the correct keys needed for an authentication will not be generated.

Key derivation with a User-Supplied Secret allows users to build and load their own apps, while ensuring that each app loaded will have its own cryptographic identity, and can also be used for authentication towards different services.

The TKey platform is based around a 32-bit RISC-V processor and has 128 KB of RAM. The current firmware is designed to load an app that is up to 100 KB in size, and gives it a stack of 28 KB. A smaller app may move itself in memory to get larger continuous memory.

All of the TKey software, firmware, FPGA Verilog source code, schematics and PCB design files are open source. Like all trustworthy security software and hardware should be. This in itself makes it different, as other security tokens utilize at least some closed source hardware for its security-critical operations.

The TK1 PCB, the first implementation of the TKey.

Documentation

Getting started

• tillitis-key1-apps repository, with apps and host programs for using the TKey
• Quickstart to initial programming of the TKey (only required for the DevKit)
• Toolchain setup
• Release Notes

In-depth technical information

• System Description
• Threat Model
• Framing Protocol
• Boards
• Boards
• FPGA
• Software
• QEMU (branch tk1 in separate repository)

Note that development is ongoing. For example, changes might be made to the measuring and derivation of key material, causing the public/private keys of a signer app to change. To avoid unexpected changes, please use a tagged release. Read the Release Notes to keep up to date with changes and new releases.

About this repository

This repository contains hardware, software and utilities written as part of the TKey. It is structured as monolithic repository, or "monorepo", where all components live in one repository.

Licensing

See LICENSES for more information about the projects' licenses.

All contributors must adhere to the Developer Certificate of Origin.