(Classic ASP) 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.

plaintext = "Live long and prosper."

' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.Jwe")
set jwe = Server.CreateObject("Chilkat.Jwe")

' First build the JWE Protected Header: {"enc":"A128CBC-HS256"}
' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.JsonObject")
set jweProtHdr = Server.CreateObject("Chilkat.JsonObject")
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"}

' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.JsonObject")
set jweRecipientHdr = Server.CreateObject("Chilkat.JsonObject")
success = jweRecipientHdr.AppendString("alg","A128KW")
success = jweRecipientHdr.AppendString("kid","7")
recipientIndex = 0
success = jwe.SetRecipientHeader(recipientIndex,jweRecipientHdr)

' Set the Shared Unprotected Header:  {"jku":"https://server.example.com/keys.jwks"}
' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.JsonObject")
set jweUnprotHdr = Server.CreateObject("Chilkat.JsonObject")
success = jweUnprotHdr.AppendString("jku","https://server.example.com/keys.jwks")
success = jwe.SetUnprotectedHeader(jweUnprotHdr)

' Set the AES key wrapping key.
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
strJwe = jwe.Encrypt(plaintext,"utf-8")
If (jwe.LastMethodSuccess <> 1) Then
    Response.Write "<pre>" & Server.HTMLEncode( jwe.LastErrorText) & "</pre>"
    Response.End
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:
' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.JsonObject")
set jsonTemp = Server.CreateObject("Chilkat.JsonObject")
success = jsonTemp.Load(strJwe)
jsonTemp.EmitCompact = 0
Response.Write "<pre>" & Server.HTMLEncode( jsonTemp.Emit()) & "</pre>"

' 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..
' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.Jwe")
set jwe2 = Server.CreateObject("Chilkat.Jwe")
success = jwe2.LoadJwe(strJwe)
If (success <> 1) Then
    Response.Write "<pre>" & Server.HTMLEncode( jwe2.LastErrorText) & "</pre>"
    Response.End
End If

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

' Decrypt
originalPlaintext = jwe2.Decrypt(recipientIndex,"utf-8")
If (jwe2.LastMethodSuccess <> 1) Then
    Response.Write "<pre>" & Server.HTMLEncode( jwe2.LastErrorText) & "</pre>"
    Response.End
End If

Response.Write "<pre>" & Server.HTMLEncode( "original text decrypted with AES key wrap key: ") & "</pre>"
Response.Write "<pre>" & Server.HTMLEncode( originalPlaintext) & "</pre>"

' ---------------------------------------------------------------------------------
' 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.

' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.StringBuilder")
set sbJwe = Server.CreateObject("Chilkat.StringBuilder")

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
    Response.Write "<pre>" & Server.HTMLEncode( jwe2.LastErrorText) & "</pre>"
    Response.End
End If

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

originalPlaintext = jwe2.Decrypt(recipientIndex,"utf-8")
If (jwe2.LastMethodSuccess <> 1) Then
    Response.Write "<pre>" & Server.HTMLEncode( jwe2.LastErrorText) & "</pre>"
    Response.End
End If

Response.Write "<pre>" & Server.HTMLEncode( "original text decrypted from published flattened JWE: ") & "</pre>"
Response.Write "<pre>" & Server.HTMLEncode( originalPlaintext) & "</pre>"

' 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.

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