(.NET Core C#) Verify JWT Using HS256, HS384, or HS512

Demonstrates how to verify a JWT that was signed using HS256, HS384, or HS512. (HS256 is JWT's acronym for HMAC-SHA256.)

This example verifies the signature. It also does the following:

• Checks to see if the time constraints ("nbf" and "exp") are valid.
• Recovers the original JOSE header.
• Recovers the original claims JSON.

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// Demonstrates how to verify an HMAC JWT using a shared secret (password).

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

Chilkat.Jwt jwt = new Chilkat.Jwt();

string token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJodHRwOi8vZXhhbXBsZS5vcmciLCJzdWIiOiJKb2huIiwiYXVkIjoiaHR0cDovL2V4YW1wbGUuY29tIiwiaWF0IjoxNDYzNDMxODEyLCJuYmYiOjE0NjM0MzE4MTIsImV4cCI6MTQ2MzQzNTQxMn0.SHnMJ11qJH5pbp22YchT_9fL2HIx0koHiUHLG67_foU";

// First verify the signature.
// The password used to create this JWT was "secret".
bool sigVerified = jwt.VerifyJwt(token,"secret");
Debug.WriteLine("with correct password: " + Convert.ToString(sigVerified));

// Now try with a different password:
sigVerified = jwt.VerifyJwt(token,"secret2");
Debug.WriteLine("with incorrect password " + Convert.ToString(sigVerified));

// Let's see if the time constraints, if any, are valid.
// The above JWT was created on the afternoon of 16-May-2016, with an expiration of 1 hour.
// If the current system time is before the "nbf" time, or after the "exp" time,
// then IsTimeValid will return false/0.
// Also, we'll allow a leeway of 60 seconds to account for any clock skew.
// Note: If the token has no "nbf" or "exp" claim fields, then IsTimeValid is always true.
int leeway = 60;
bool bTimeValid = jwt.IsTimeValid(token,leeway);
Debug.WriteLine("time constraints valid: " + Convert.ToString(bTimeValid));

// Now let's recover the original claims JSON (the payload).
string payload = jwt.GetPayload(token);
// The payload will likely be in compact form:
Debug.WriteLine(payload);

// We can format for human viewing by loading it into Chilkat's JSON object
// and emit.
Chilkat.JsonObject json = new Chilkat.JsonObject();
bool success = json.Load(payload);
json.EmitCompact = false;
Debug.WriteLine(json.Emit());

// We can recover the original JOSE header in the same way:
string joseHeader = jwt.GetHeader(token);
// The payload will likely be in compact form:
Debug.WriteLine(joseHeader);

// We can format for human viewing by loading it into Chilkat's JSON object
// and emit.
success = json.Load(joseHeader);
json.EmitCompact = false;
Debug.WriteLine(json.Emit());