(Excel) 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.

' Create some plaintext to be encrypted.
' This example will demonstrate with and without DEFLATE (zip) compression.
Dim sbPlainText As Chilkat.StringBuilder
Set sbPlainText = Chilkat.NewStringBuilder

bCrLf = True

line = "Live long and prosper."
Dim success As Boolean
success = sbPlainText.AppendLine(line,bCrLf)
success = sbPlainText.AppendLine(line,bCrLf)
success = sbPlainText.AppendLine(line,bCrLf)
success = sbPlainText.AppendLine(line,bCrLf)

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

Dim jwe As Chilkat.Jwe
Set jwe = Chilkat.NewJwe

' 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 Chilkat.JsonObject
Set jweProtHdr = Chilkat.NewJsonObject
success = jweProtHdr.AppendString("alg","A128KW")
success = jweProtHdr.AppendString("enc","A128CBC-HS256")
success = jweProtHdr.AppendString("zip","DEF")
success = jwe.SetProtectedHeader(jweProtHdr)

' Set the AES key wrap key:

aesWrappingKey = "GawgguFyGrWKav7AX4VKUg"
success = jwe.SetWrappingKey(0,aesWrappingKey,"base64url")

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

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

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

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

' Show the uncompressed JWE:
Debug.Print sbJweUncompressed.GetAsString()
Debug.Print "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 Chilkat.Jwe
Set jwe2 = Chilkat.NewJwe
success = jwe2.LoadJweSb(sbJweCompressed)
If (success <> True) Then
    Debug.Print jwe2.LastErrorText
    Exit Sub
End If

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

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

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

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

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

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

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

Debug.Print "original text from uncompressed JWE: "
Debug.Print 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.
'