](https://solokeys.com/v2)
Solo supports FIDO2 and U2F standards for strong two-factor authentication and password-less login, and it will protect you against phishing and other online attacks. With colored cases and multilingual guides we want to make secure login more personable and accessible to everyone around the globe.
This repo contains the Solo firmware, including implementations of FIDO2 and U2F (CTAP2 and CTAP) over USB and NFC. The main implementation is for STM32L432, but it is easily portable.
For development no hardware is needed, Solo also runs as a standalone application for Windows, Linux, and Mac OSX. If you like (or want to learn) hardware instead, you can run Solo on the NUCLEO-L432KC development board, or we make Solo for Hacker, an unlocked version of Solo that lets you customize its firmware.
# Security
Solo is based on the STM32L432 microcontroller. It offers the following security features.
- True random number generation to guarantee random keys.
- Security isolation so only simple & secure parts of code can handle keys.
- Flash protection from both external use and untrusted code segments.
- 256 KB of memory to support hardened crypto implementations and, later, additional features such as OpenPGP or SSH.
- No NDA needed to develop for.
# Solo for Hackers
Solo for Hacker is a special version of Solo that let you customize its firmware, for example you can change the LED color, and even build advanced applications.
Check out [solokeys.com](https://solokeys.com), for options on where to buy Solo. Solo Hacker can be converted to a secure version, but normal Solo cannot be converted to a Hacker version.
If you have a Solo for Hacker, here's how you can load your own code on it. You can find more details, including how to permanently lock it, in our [documentation](https://docs.solokeys.dev/building/). We support Python3.
For example, if you want to turn off any blue light emission, you can edit [`led_rgb()`](https://github.com/solokeys/solo/blob/master/targets/stm32l432/src/app.h#L48) and change `LED_INIT_VALUE`
to be a different hex color.
Then recompile, load your new firmware, and enjoy a different LED color Solo.
In the Hacker version, hardware is the same but the firmware is unlocked, so you can 1) load an unsigned application, or 2) entirely reflash the key. By contrast, in a regular Solo you can only upgrade to a firmware signed by SoloKeys, and flash is locked and debug disabled permanently.
Hacker Solo isn't really secure so you should only use it for development. An attacker with physical access to a Solo for Hacker can reflash it following the steps above, and even a malware on your computer could possibly reflash it.
## Checking out the code
```bash
git clone --recurse-submodules https://github.com/solokeys/solo
cd solo
```
If you forgot the `--recurse-submodules` while cloning, simply run `git submodule update --init --recursive`.
`make update` will also checkout the latest code on `master` and submodules.
## Checking out the code to build a specific version
You can checkout the code to build a specific version of the firmware with:
```
VERSION_TO_BUILD=2.5.3
git fetch --tags
git checkout ${VERSION_TO_BUILD}
git submodule update --init --recursive
```
## Installing the toolchain and applying updates
In order to compile ARM code, you need the ARM compiler and other things like bundling bootloader and firmware require the [solo1](https://github.com/solokeys/solo1-cli) python package. Check our [documentation](https://docs.solokeys.dev/) for details.
You can update your solokey after running `pip3 install solo1` with `solo1 key update` for the latest version. To apply a custom image use `solo1 program bootloader 
