(VB.NET UWP/WinRT) 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.

Chilkat Universal Windows Platform (UWP) / WinRT Downloads Chilkat for the Universal Windows Platform (UWP)

' 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.

Dim jwt As New Chilkat.Jwt

Dim token As String = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJodHRwOi8vZXhhbXBsZS5vcmciLCJzdWIiOiJKb2huIiwiYXVkIjoiaHR0cDovL2V4YW1wbGUuY29tIiwiaWF0IjoxNDYzNDMxODEyLCJuYmYiOjE0NjM0MzE4MTIsImV4cCI6MTQ2MzQzNTQxMn0.SHnMJ11qJH5pbp22YchT_9fL2HIx0koHiUHLG67_foU"

' First verify the signature.
' The password used to create this JWT was "secret".
Dim sigVerified As Boolean = jwt.VerifyJwt(token,"secret")
Debug.WriteLine("with correct password: " & sigVerified)

' Now try with a different password:
sigVerified = jwt.VerifyJwt(token,"secret2")
Debug.WriteLine("with incorrect password " & 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.
Dim leeway As Integer = 60
Dim bTimeValid As Boolean = jwt.IsTimeValid(token,leeway)
Debug.WriteLine("time constraints valid: " & bTimeValid)

' Now let's recover the original claims JSON (the payload).
Dim payload As String = 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.
Dim json As New Chilkat.JsonObject
Dim success As Boolean = json.Load(payload)
json.EmitCompact = False
Debug.WriteLine(json.Emit())

' We can recover the original JOSE header in the same way:
Dim joseHeader As String = 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())