(Visual Basic 6.0) 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 Long

' First create the JWS Protected Header
Dim jwsProtHdr As New ChilkatJsonObject
success = jwsProtHdr.AppendString("typ","JWT")
success = jwsProtHdr.AppendString("alg","HS256")
Debug.Print "JWS Protected Header: " & jwsProtHdr.Emit()

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

Dim jws As New ChilkatJws

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

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

' Set the payload.
Dim bIncludeBom As Long
bIncludeBom = 0
Dim payloadStr As String
payloadStr = "In our village, folks say God crumbles up the old moon into stars."
success = jws.SetPayload(payloadStr,"utf-8",bIncludeBom)

' Create the JWS
' By default, the compact serialization is used.
Dim jwsCompact As String
jwsCompact = jws.CreateJws()
If (jws.LastMethodSuccess <> 1) Then
    Debug.Print jws.LastErrorText
    Exit Sub
End If

Debug.Print "JWS: " & jwsCompact

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

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

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

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

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

If (v = 0) Then
    Debug.Print "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.Print "Signature validated."

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

' Examine the protected header:
Dim joseHeader As ChilkatJsonObject
Set joseHeader = jws2.GetProtectedHeader(signatureIndex)
If (jws2.LastMethodSuccess <> 1) Then
    Debug.Print "No protected header found at the given index."
    Exit Sub
End If

joseHeader.EmitCompact = 0

Debug.Print "Protected (JOSE) header:"
Debug.Print 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"
' 	}