(VB.NET) JWS Using HMAC SHA-256

Creates a JSON Web Signatures (JWS) using HMAC SHA-256.

Note: This example requires Chilkat v9.5.0.66 or greater.

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

' Note: This example requires Chilkat v9.5.0.66 or greater.

Dim success As Boolean

' First create the JWS Protected Header
Dim jwsProtHdr As New Chilkat.JsonObject
jwsProtHdr.AppendString("typ","JWT")
jwsProtHdr.AppendString("alg","HS256")
Debug.WriteLine("JWS Protected Header: " & jwsProtHdr.Emit())

' Output:
' JWS Protected Header: {"typ":"JWT","alg":"HS256"}


Dim jws As New Chilkat.Jws

' Set the HMAC key:
Dim hmacKey As String = "AyM1SysPpbyDfgZld3umj1qzKObwVMkoqQ-EstJQLr_T-1qS0gZH75aKtMN3Yj0iPS4hcgUuTwjAzZr1Z9CAow"
Dim signatureIndex As Integer = 0
jws.SetMacKey(signatureIndex,hmacKey,"base64url")

' Set the protected header:
jws.SetProtectedHeader(signatureIndex,jwsProtHdr)

' Set the payload.
Dim bIncludeBom As Boolean = False
Dim payloadStr As String = "In our village, folks say God crumbles up the old moon into stars."
jws.SetPayload(payloadStr,"utf-8",bIncludeBom)

' Create the JWS
' By default, the compact serialization is used.
Dim jwsCompact As String = jws.CreateJws()
If (jws.LastMethodSuccess <> True) Then
    Debug.WriteLine(jws.LastErrorText)
    Exit Sub
End If


Debug.WriteLine("JWS: " & jwsCompact)

' sample output:
' JWS: eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu.bsYsi8HJ0N6OqGI1hKQ9QQRNPxxA5qMpcHLtOvXatk8


' Now load the JWS, validate, and recover the original text.
Dim jws2 As New Chilkat.Jws

' Load the JWS.
success = jws2.LoadJws(jwsCompact)

' Set the MAC key used for validation.
signatureIndex = 0
jws2.SetMacKey(signatureIndex,hmacKey,"base64url")

' Validate the 1st (and only) signature at index 0..
Dim v As Integer = jws2.Validate(signatureIndex)
If (v < 0) Then
    ' Perhaps Chilkat was not unlocked or the trial expired..
    Debug.WriteLine("Method call failed for some other reason.")
    Debug.WriteLine(jws2.LastErrorText)
    Exit Sub
End If

If (v = 0) Then
    Debug.WriteLine("Invalid signature.  The MAC key was incorrect, the JWS was invalid, or both.")
    Exit Sub
End If


' If we get here, the signature was validated..
Debug.WriteLine("Signature validated.")

' Recover the original content:
Debug.WriteLine(jws2.GetPayload("utf-8"))

' Examine the protected header:
Dim joseHeader As Chilkat.JsonObject = jws2.GetProtectedHeader(signatureIndex)
If (jws2.LastMethodSuccess <> True) Then
    Debug.WriteLine("No protected header found at the given index.")
    Exit Sub
End If

joseHeader.EmitCompact = False

Debug.WriteLine("Protected (JOSE) header:")
Debug.WriteLine(joseHeader.Emit())


' Output:

' 	Signature validated.
' 	In our village, folks say God crumbles up the old moon into stars.
' 	Protected (JOSE) header:
' 	{ 
' 	  "typ": "JWT",
' 	  "alg": "HS256"
' 	}