(Visual Basic 6.0) 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 Long
Dim plaintext As String
plaintext = "Live long and prosper."

Dim jwe As New ChilkatJwe

' First build the JWE Protected Header: {"enc":"A128CBC-HS256"}
Dim jweProtHdr As New ChilkatJsonObject
success = jweProtHdr.AppendString("enc","A128CBC-HS256")
success = 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 ChilkatJsonObject
success = jweRecipientHdr.AppendString("alg","A128KW")
success = jweRecipientHdr.AppendString("kid","7")
Dim recipientIndex As Long
recipientIndex = 0
success = jwe.SetRecipientHeader(recipientIndex,jweRecipientHdr)

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

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

' OK.. everything has been specified.
' Now encrypt.  
' Indicate that we prefer the flattened JSON serialization.
jwe.PreferFlattened = 1
Dim strJwe As String
strJwe = jwe.Encrypt(plaintext,"utf-8")
If (jwe.LastMethodSuccess <> 1) Then
    Debug.Print 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 ChilkatJsonObject
success = jsonTemp.Load(strJwe)
jsonTemp.EmitCompact = 0
Debug.Print 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 ChilkatJwe
success = jwe2.LoadJwe(strJwe)
If (success <> 1) Then
    Debug.Print jwe2.LastErrorText
    Exit Sub
End If

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

' Decrypt
Dim originalPlaintext As String
originalPlaintext = jwe2.Decrypt(recipientIndex,"utf-8")
If (jwe2.LastMethodSuccess <> 1) Then
    Debug.Print jwe2.LastErrorText
    Exit Sub
End If

Debug.Print "original text decrypted with AES key wrap key: "
Debug.Print 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 ChilkatStringBuilder

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

success = jwe2.LoadJweSb(sbJwe)
If (success <> 1) Then
    Debug.Print jwe2.LastErrorText
    Exit Sub
End If

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

originalPlaintext = jwe2.Decrypt(recipientIndex,"utf-8")
If (jwe2.LastMethodSuccess <> 1) Then
    Debug.Print jwe2.LastErrorText
    Exit Sub
End If

Debug.Print "original text decrypted from published flattened JWE: "
Debug.Print 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.