(VB.NET) JWE with DEFLATE Compression

Demonstrates how to DEFLATE ("zip") compress the JWE payload prior to encryption.

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
' Create some plaintext to be encrypted.
' This example will demonstrate with and without DEFLATE (zip) compression.
Dim sbPlainText As New Chilkat.StringBuilder
Dim bCrLf As Boolean = True
Dim line As String = "Live long and prosper."
sbPlainText.AppendLine(line,bCrLf)
sbPlainText.AppendLine(line,bCrLf)
sbPlainText.AppendLine(line,bCrLf)
sbPlainText.AppendLine(line,bCrLf)

' The text to be encrypted:
Debug.WriteLine(sbPlainText.GetAsString())

Dim jwe As New Chilkat.Jwe

' Build the JWE Protected Header: {"alg":"A128KW","enc":"A128CBC-HS256","zip":"DEF"}
' The "zip":"DEF" parameter indicates that the plaintext payload should
' be compressed prior to encryption.
Dim jweProtHdr As New Chilkat.JsonObject
jweProtHdr.AppendString("alg","A128KW")
jweProtHdr.AppendString("enc","A128CBC-HS256")
jweProtHdr.AppendString("zip","DEF")
jwe.SetProtectedHeader(jweProtHdr)

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

' Encrypt and return the JWE in sbJweCompressed:
Dim sbJweCompressed As New Chilkat.StringBuilder
success = jwe.EncryptSb(sbPlainText,"utf-8",sbJweCompressed)
If (success <> True) Then
    Debug.WriteLine(jwe.LastErrorText)
    Exit Sub
End If


' Show the compressed JWE:
Debug.WriteLine(sbJweCompressed.GetAsString())
Debug.WriteLine("size of compressed JWE: " & sbJweCompressed.Length)

' Now create a JWE without compression.
jweProtHdr.Delete("zip")
' Make sure to update the shared protected header:
jwe.SetProtectedHeader(jweProtHdr)

Dim sbJweUncompressed As New Chilkat.StringBuilder
success = jwe.EncryptSb(sbPlainText,"utf-8",sbJweUncompressed)
If (success <> True) Then
    Debug.WriteLine(jwe.LastErrorText)
    Exit Sub
End If


' Show the uncompressed JWE:
Debug.WriteLine(sbJweUncompressed.GetAsString())
Debug.WriteLine("size of uncompressed JWE: " & sbJweUncompressed.Length)


' Decrypting is the same whether compression is used or not.
' The "zip" header in the JWE indicates that the payload should be 
' automatically decompressed (inflated) after decrypting.
Dim jwe2 As New Chilkat.Jwe
success = jwe2.LoadJweSb(sbJweCompressed)
If (success <> True) Then
    Debug.WriteLine(jwe2.LastErrorText)
    Exit Sub
End If

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

' Decrypt (also automatically decompresses).
Dim sbOriginalText As New Chilkat.StringBuilder
success = jwe2.DecryptSb(0,"utf-8",sbOriginalText)
If (success <> True) Then
    Debug.WriteLine(jwe2.LastErrorText)
    Exit Sub
End If


Debug.WriteLine("original text from compressed JWE: ")
Debug.WriteLine(sbOriginalText.GetAsString())

' -----------------------------------------------------------
' Do the same with the uncompressed JWE

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

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

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


Debug.WriteLine("original text from uncompressed JWE: ")
Debug.WriteLine(sbOriginalText.GetAsString())

' ------------------------------------------------
' The output of this example is:
' (Note: Your output data will be different because the content encryption key is randomly generated.)

' eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2IiwiemlwIjoiREVGIn0.xuW-pEAIdEUFnk10m8ocursvktO8Of9ByCCAt6LgKkkOtCWCUn1kQw.zpGj-9WVni3cQxyOuZbcGA.0hzP1myua3oYpUHwCIY_3edBUREbUpLaX6wYuJduOdI.Ppc6aEO3y3B8BJ1FKMPjlA
' size of compressed JWE: 212
' eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.N4KeyC7nnSFkieJOyE24_zKeuV_m7v5UKoJb1TgV4Yc_r2RzUPNvyA.6AEdyXSCKx-iMmUJyypSLg.QpixfyrwhGpmwUDp623viik4smPav7vwPLiC2r-V-jwnSfEH3mxWu6DbrIz3mixaqATwynmEBzVPxvS9jTXpSAGCnniib4_0WoPl3r_wF5tlsKOEe--jpNso-DKd1Tp8jJxj3JkFWt3IRnUUKGj17g.sBfDwFc5fzpaI-UW8-SW4g
' size of uncompressed JWE: 303
' original text from compressed JWE: 
' Live long and prosper.
' Live long and prosper.
' Live long and prosper.
' Live long and prosper.
' 
' original text from uncompressed JWE: 
' Live long and prosper.
' Live long and prosper.
' Live long and prosper.
' Live long and prosper.
'