Install-Package OtpSharp -Version
dotnet add package OtpSharp --version
<PackageReference Include="OtpSharp" Version="" />
For projects that support PackageReference, copy this XML node into the project file to reference the package.
paket add OtpSharp --version
The NuGet Team does not provide support for this client. Please contact its maintainers for support.
#r "nuget: OtpSharp,"
#r directive can be used in F# Interactive, C# scripting and .NET Interactive. Copy this into the interactive tool or source code of the script to reference the package.
// Install OtpSharp as a Cake Addin
#addin nuget:?package=OtpSharp&version=

// Install OtpSharp as a Cake Tool
#tool nuget:?package=OtpSharp&version=
The NuGet Team does not provide support for this client. Please contact its maintainers for support.

This is an implementation of HOTP and TOTP which are commonly used for multi factor authentication by using a shared key between the client and the server to generate and verify one time use codes.  This library is capable of generating and verifying both TOTP and HOTP authentication codes.  The calculations in this library are known to be compatible with Google 2-Step Verification and consequently the Google Authenticator smartphone app.  It is also known to be able to generate codes for Amazon Web Services Multi Factor Authentication and Dropbox 2 step authentication.  It should work with any other service or client that is RFC compliant.

This library is released under an MIT license. No warranty is provided as to the correctness of the library and the consumer of the library assumes all risk for the use thereof, as per the MIT license.

Every effort has gone into implementing this library in accordance with the RFCs mentioned above. However it is up to the users of this library to read through the RFCs and ensure that this implementation is in accordance with the security procedures outlined therein.

The implementation includes the code calculation as well as simple verification. Persistence of the keys, secure key storage, ensuring that a single code can't be validated multiple times and other things are not a part of this library. Thus far those functions (and any others mentioned in the RFCs) are up to the consumer of this library.

For documentation please visit the project website.

NuGet packages (3)

Showing the top 3 NuGet packages that depend on OtpSharp:

Package Downloads

A simple enterprise content management system


Adds two factor authentication to an MVC project using google's authenticator. Relies on Microsoft's ASP.NET Identity service.


Bitskins.com C# .net API

GitHub repositories

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Version Downloads Last updated 595,981 11/16/2015 24,224 1/17/2015 13,497 7/13/2014 763 7/12/2014 2,691 10/25/2013 958 8/9/2013 886 7/29/2013 1,398 3/12/2013 859 3/12/2013 811 3/12/2013 813 3/11/2013 854 3/8/2013 883 3/2/2013
1.0.5 887 3/1/2013

1.3 Sign the assembly

1.2 extract base32 functionality into seperate nuget package (Base32). Implement FromUrl functionality

1.1 Change the Key api to no longer require returning the plaintext key. (will break any custom key implementations). Move the get URL from the Otp to a static Url type.

1.0.6 Change the computed values from ints to padded strings. (Breaking change but is a more appropriate API)

1.0.5 Change package name from OTP-Sharp to OtpSharp

1.0.4 Changed the Protected Key API to be more explicit (may break existing direct useage of the protected key)

The protected key no longer implicitly causes side effects (destroying the plaintext key provided must be done explicitly)

Added a time correction class with experimental NTP abilities.