jhurdlow / jwt

JWT (JSON Web Token) implementation for .NET 3.5+ (Public Domain)

JSON Web Token (JWT) Implementation for .NET

This library supports generating and decoding JSON Web Tokens.

Installation

The easiest way to install is via NuGet. See here. Else, you can download and compile it yourself.

Usage

Creating Tokens

var payload = new Dictionary<string, object>()
{
    { "claim1", 0 },
    { "claim2", "claim2-value" }
};
var secretKey = "GQDstcKsx0NHjPOuXOYg5MbeJ1XT0uFiwDVvVBrk";
string token = JWT.JsonWebToken.Encode(payload, secretKey, JWT.JwtHashAlgorithm.HS256);
Console.WriteLine(token);

Output will be: eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJjbGFpbTEiOjAsImNsYWltMiI6ImNsYWltMi12YWx1ZSJ9.8pwBI_HtXqI3UgQHQ_rDRnSQRxFL1SR8fbQoS-5kM5s

Verifying and Decoding Tokens

var token = "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJjbGFpbTEiOjAsImNsYWltMiI6ImNsYWltMi12YWx1ZSJ9.8pwBI_HtXqI3UgQHQ_rDRnSQRxFL1SR8fbQoS-5kM5s";
var secretKey = "GQDstcKsx0NHjPOuXOYg5MbeJ1XT0uFiwDVvVBrk";
try
{
    string jsonPayload = JWT.JsonWebToken.Decode(token, secretKey);
    Console.WriteLine(jsonPayload);
}
catch (JWT.SignatureVerificationException)
{
    Console.WriteLine("Invalid token!");
}

Output will be:

{"claim1":0,"claim2":"claim2-value"}

You can also deserialize the JSON payload directly to a .Net object with DecodeToObject:

var payload = JWT.JsonWebToken.DecodeToObject(token, secretKey) as IDictionary<string, object>;
Console.WriteLine(payload["claim2"]);

which will output:

claim2-value

exp claim

As described in the JWT RFC the exp "claim identifies the expiration time on or after which the JWT MUST NOT be accepted for processing." If an exp claim is present and is prior to the current time the token will fail verification. The exp (expiry) value must be specified as the number of seconds since 1/1/1970 UTC.

var unixEpoch = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
var now = Math.Round((DateTime.UtcNow - unixEpoch).TotalSeconds);
var payload = new Dictionary<string, object>()
{
    { "exp", now }
};
var secretKey = "GQDstcKsx0NHjPOuXOYg5MbeJ1XT0uFiwDVvVBrk";
string token = JWT.JsonWebToken.Encode(payload, secretKey, JWT.JwtHashAlgorithm.HS256);

string jsonPayload = JWT.JsonWebToken.Decode(token, secretKey); // JWT.SignatureVerificationException!

Configure JSON Serialization

By default JSON Serialization is done by System.Web.Script.Serialization.JavaScriptSerializer. To configure a different one first implement the IJsonSerializer interface.

public class CustomJsonSerializer : IJsonSerializer
{
    public string Serialize(object obj)
    {
        // Implement using favorite JSON Serializer
    }

    public T Deserialize<T>(string json)
    {
        // Implement using favorite JSON Serializer
    }
}

Next configure this serializer as the JsonSerializer.

JsonWebToken.JsonSerializer = new CustomJsonSerializer();