(VB.NET) JWE Using Flattened JWE JSON Serialization

This example duplicates the example A.5 in RFC 7516 for JSON Web Encryption (JWE).

This example demonstrates using the flattened JWE JSON Serialization syntax. This example demonstrates the capability for encrypting the plaintext to a single recipient in a flattened JSON structure.

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: {"enc":"A128CBC-HS256"}
Dim jweProtHdr As New Chilkat.JsonObject
jweProtHdr.AppendString("enc","A128CBC-HS256")
jwe.SetProtectedHeader(jweProtHdr)

' We have a single recipient that uses AES Key Wrap to encrypt the CEK.
' 
'      {"alg":"A128KW","kid":"7"}

Dim jweRecipientHdr As New Chilkat.JsonObject
jweRecipientHdr.AppendString("alg","A128KW")
jweRecipientHdr.AppendString("kid","7")
Dim recipientIndex As Integer = 0
jwe.SetRecipientHeader(recipientIndex,jweRecipientHdr)

' Set the Shared Unprotected Header:  {"jku":"https://server.example.com/keys.jwks"}
Dim jweUnprotHdr As New Chilkat.JsonObject
jweUnprotHdr.AppendString("jku","https://server.example.com/keys.jwks")
jwe.SetUnprotectedHeader(jweUnprotHdr)

' Set the AES key wrapping key.
Dim aesWrappingKey As String = "GawgguFyGrWKav7AX4VKUg"
recipientIndex = 0
jwe.SetWrappingKey(recipientIndex,aesWrappingKey,"base64url")

' OK.. everything has been specified.
' Now encrypt.  
' Indicate that we prefer the flattened JSON serialization.
jwe.PreferFlattened = True
Dim strJwe As String = jwe.Encrypt(plaintext,"utf-8")
If (jwe.LastMethodSuccess <> True) Then
    Debug.WriteLine(jwe.LastErrorText)
    Exit Sub
End If


' The JWE is produced in the most compact form possible (a single line).
' Let's load it into a JSON object and examine in a non-compact pretty-printed format:
Dim jsonTemp As New Chilkat.JsonObject
jsonTemp.Load(strJwe)
jsonTemp.EmitCompact = False
Debug.WriteLine(jsonTemp.Emit())

' The JWE looks like this:
' (Note: Because of random values used in the encryption process, your encrypted results will be different.)

' 	{ 
' 	  "protected": "eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0",
' 	  "unprotected": { 
' 	    "jku": "https://server.example.com/keys.jwks"
' 	  },
' 	  "header": { 
' 	    "alg": "A128KW",
' 	    "kid": "7"
' 	  },
' 	  "encrypted_key": "FW7z9VxOvnF2ClicvUT4HTeqcdyh90C6qytfEFJsOb77FOwTfYrc3w",
' 	  "iv": "O6Ly5-eML3zTs-_fNX3D5Q",
' 	  "ciphertext": "Q8NLmeac9JhLh0CQPuG_7D9wVDb55eToCh0g5-FQ4M0",
' 	  "tag": "slzlo6-J9C7wSDF4dh_kBg"
' 	} 

' Now decrypt......................................

' First, load the JWE..
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..
recipientIndex = 0
jwe2.SetWrappingKey(recipientIndex,aesWrappingKey,"base64url")

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


Debug.WriteLine("original text decrypted with AES key wrap key: ")
Debug.WriteLine(originalPlaintext)

' ---------------------------------------------------------------------------------
' It should also be possible to decrypt the flattened JWE as shown in RFC 7516, Appendix A.5
' because it was produced using the same key.

Dim sbJwe As New Chilkat.StringBuilder

sbJwe.Append("{")
sbJwe.Append("""protected"":")
sbJwe.Append("""eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0"",")
sbJwe.Append("""unprotected"":")
sbJwe.Append("{""jku"":""https://server.example.com/keys.jwks""},")
sbJwe.Append("""header"":")
sbJwe.Append("{""alg"":""A128KW"",""kid"":""7""},")
sbJwe.Append("""encrypted_key"":")
sbJwe.Append("""6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ"",")
sbJwe.Append("""iv"":")
sbJwe.Append("""AxY8DCtDaGlsbGljb3RoZQ"",")
sbJwe.Append("""ciphertext"":")
sbJwe.Append("""KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY"",")
sbJwe.Append("""tag"":")
sbJwe.Append("""Mz-VPPyU4RlcuYv1IwIvzw""")
sbJwe.Append("}")

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


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

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


Debug.WriteLine("original text decrypted from published flattened JWE: ")
Debug.WriteLine(originalPlaintext)

' The output:

' original text decrypted with AES key wrap key: 
' Live long and prosper.
' original text decrypted from published flattened JWE: 
' Live long and prosper.