# challenge-response
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`challenge-response` is a Rust library for performing [challenge-response](https://wiki.archlinux.org/index.php/yubikey#Function_and_Application_of_Challenge-Response) operations (hashing and encryption) using security keys like the YubiKey and the OnlyKey.
## Examples
Code examples for performing a challenge-response (both HMAC and OTP) as well as configuring a device can be found in the [examples/](https://github.com/louib/challenge-response/tree/master/examples) directory.
## Current features
- [HMAC-SHA1 Challenge-Response](https://datatracker.ietf.org/doc/html/rfc2104)
- [Yubico OTP Challenge-Response encryption](https://docs.yubico.com/yesdk/users-manual/application-otp/yubico-otp.html)
- Challenge-Response configuration
## Supported devices
- YubiKey 2.2 and later
- OnlyKey (**untested**)
- NitroKey (**untested**)
## Usage
Add this to your `Cargo.toml`
```toml
[dependencies]
challenge_response = "0"
```
### nusb backend (EXPERIMENTAL)
You can enable the experimental [nusb](https://crates.io/crates/nusb) backend by adding the following to your `Cargo.toml` manifest:
```toml
[dependencies]
challenge_response = { version = "0", default-features = false, features = ["nusb"] }
```
The `nusb` backend has the advantage of not depending on `libusb`, thus making it easier to add
`challenge_response` to your dependencies.
> [!NOTE]
> The `nusb` feature is not available on Windows. If configured, the library will default to using the `rusb` backend instead.
## Credits
This library was originally a fork of the [yubico_manager](https://crates.io/crates/yubico_manager) library.
## License
MIT or Apache-2.0