(VB.NET) JWE using AES Key Wrap and AES_128_CBC_HMAC_SHA_256

This example duplicates the example A.3 in RFC 7516 for JSON Web Encryption (JWE).

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
Dim plaintext As String = "Live long and prosper."

Dim jwe As New Chilkat.Jwe

' First build the JWE Protected Header: {"alg":"A128KW","enc":"A128CBC-HS256"}
Dim jweProtHdr As New Chilkat.JsonObject
jweProtHdr.AppendString("alg","A128KW")
jweProtHdr.AppendString("enc","A128CBC-HS256")
jwe.SetProtectedHeader(jweProtHdr)

Debug.WriteLine("JWE Protected Header: " & jweProtHdr.Emit())
Debug.WriteLine("--")

' The example A.3 in RFC 7516 uses the following 128-bit AES key,
' specified in JWK (JSON Web Key) format:
'      {"kty":"oct",
'       "k":"GawgguFyGrWKav7AX4VKUg"
'      }
' This is just a way of saying: The key type ("kty") is 
' a bunch of octets ("k") in base64url encoding.
' We can simply set the AES wrapping key like this:
Dim aesWrappingKey As String = "GawgguFyGrWKav7AX4VKUg"
jwe.SetWrappingKey(0,aesWrappingKey,"base64url")

' Encrypt and return the JWE:
Dim strJwe As String = jwe.Encrypt(plaintext,"utf-8")
If (jwe.LastMethodSuccess <> True) Then
    Debug.WriteLine(jwe.LastErrorText)
    Exit Sub
End If


' Show the JWE we just created:
Debug.WriteLine(strJwe)


' Decrypt the JWE that was just produced.
' 1) Load the JWE.
' 2) Set the AES wrapping key.
' 3) Decrypt.
Dim jwe2 As New Chilkat.Jwe
success = jwe2.LoadJwe(strJwe)
If (success <> True) Then
    Debug.WriteLine(jwe2.LastErrorText)
    Exit Sub
End If

' Set the AES wrap key.
jwe2.SetWrappingKey(0,aesWrappingKey,"base64url")

' Decrypt.
Dim originalPlaintext As String = jwe2.Decrypt(0,"utf-8")
If (jwe2.LastMethodSuccess <> True) Then
    Debug.WriteLine(jwe2.LastErrorText)
    Exit Sub
End If


Debug.WriteLine("original text: ")
Debug.WriteLine(originalPlaintext)

' ---------------------------------------------------------------------------------
' It should also be possible to decrypt the JWE as shown in RFC 7516, Appendix A.3.7
' because it was produced using the same AES Wrap key.

Dim sbJwe As New Chilkat.StringBuilder
sbJwe.Append("eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.")
sbJwe.Append("6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ.")
sbJwe.Append("AxY8DCtDaGlsbGljb3RoZQ.")
sbJwe.Append("KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY.")
sbJwe.Append("U0m_YmjN04DJvceFICbCVQ")

success = jwe2.LoadJweSb(sbJwe)
If (success <> True) Then
    Debug.WriteLine(jwe2.LastErrorText)
    Exit Sub
End If


jwe2.SetWrappingKey(0,aesWrappingKey,"base64url")

' Decrypt.
originalPlaintext = jwe2.Decrypt(0,"utf-8")
If (jwe2.LastMethodSuccess <> True) Then
    Debug.WriteLine(jwe2.LastErrorText)
    Exit Sub
End If


Debug.WriteLine(originalPlaintext)