.NET YubiKey SDK

The SDK allows you to integrate the YubiKey and its applications into your .NET-based application or library.

SDK documentation

The documentation for the .NET YubiKey SDK is split into two main sections:

A user's manual that describes the concepts that you will encounter while working with the SDK and the YubiKey. It provides a general outline of how to use the SDK. Tutorials and walk-throughs can be found here as well.
API Documentation is where detailed descriptions of the classes and interfaces of the SDK reside.

Supported platforms

Modern .NET supports more than just Microsoft Windows, and so do we. Support for macOS is built in, and has been tested on both Intel and Apple Silicon (i.e. M1) platforms. (Apple Silicon is supported through Rosetta 2.) We also support common Linux distributions such as Debian, Ubuntu, RHEL, and CentOS. Other distros may still work, but they have not been tested by the SDK team.

Future distribution and platform support will be driven by customer interest.

This SDK targets .NET Standard 2.0, allowing for a wide reach of .NET platforms. See this page for more information on what .NET implementations support .NET Standard 2.0. Note that while this SDK may build with Xamarin and Mono, only the Windows and macOS operating systems are supported at this time. Additionally, while .NET Framework 4.6.x is listed as implementing Standard 2.0, this is not entirely true. The SDK relies on certain cryptographic functionality that is defined in the standard but not actually implemented in Framework 4.6.x.

Supported YubiKey applications

The YubiKey is a versatile security key that supports numerous standards and protocols. This SDK offers full support for integrating with Yubico OTP, along with the OATH, PIV, and FIDO U2F standards.

OTP

Yubico OTP is a simple yet strong authentication mechanism that is supported by all YubiKeys out of the box. Yubico OTP can be used as the second factor in a 2-factor authentication scheme or on its own, providing 1-factor authentication.

OATH

The Initiative for Open Authentication (OATH) is an organization that specifies two open one-time password standards: HMAC OTP (HOTP), and the more familiar Time-based OTP (TOTP). Read more about OATH here.

PIV

Personal Identity Verification (PIV), or FIPS 201, is a US government standard. It enables RSA signing and encryption, along with ECC signing and key agreement operations using a private key stored on a smart card (such as the YubiKey 5).

PIV is primarily used for non-web applications. It has built-in support under Windows and can be used on macOS as well.

FIDO U2F

U2F is an open authentication standard that enables keychain devices, mobile phones and other devices to securely access any number of web-based services - instantly and with no drivers or client software needed. U2F was created by Google and Yubico, with contribution from NXP, and is today hosted by the open-authentication industry consortium FIDO Alliance. The technical specifications were launched in late 2014, including native support in Google Accounts and Chrome, and have since resulted in a thriving ecosystem of hardware, software and service providers.

FIDO2

FIDO2 is the "second generation" of the FIDO open authentication standard. It is similar to U2F in that implementations allow instant secure access to web-based services, with no drivers or client software needed. FIDO2 was created by the FIDO Alliance -- a consortium of dozens of tech and other companies as well as government organizations from around the world -- along with the W3C (World Wide Web Consortium). The technical specifications for FIDO2 were launched in 2018. Today, many browsers and mobile platforms support FIDO2.

YubiHSM Auth

YubiHSM Auth is a YubiKey CCID application that stores the long-lived credentials used to establish secure sessions with a YubiHSM 2. The secure session protocol is based on Secure Channel Protocol 3 (SCP03). YubiHSM Auth is supported by YubiKey firmware version 5.4.3.

YubiHSM Auth uses hardware to protect these long-lived credentials. In addition to providing robust security for the YubiHSM Auth application itself, this hardware protection subsequently increases the security of the default password-based solution for YubiHSM 2's authentication.