(Excel) JWE with Binary Data

Demonstrates how to create a JWE that contains a binary payload (such as a JPG image).

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.

' Load a JPG file that will be the JWE payload.
Dim jpgBytes As Chilkat.BinData
Set jpgBytes = Chilkat.NewBinData
success = jpgBytes.LoadFile("qa_data/jpg/starfish.jpg")
' Make sure your app checks the success/failure of the call to LoadFile..
Debug.Print "Original JPG size = "; jpgBytes.NumBytes

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

Dim jweProtHdr As Chilkat.JsonObject
Set jweProtHdr = Chilkat.NewJsonObject
Dim success As Boolean
success = jweProtHdr.AppendString("alg","A128KW")
success = jweProtHdr.AppendString("enc","A128CBC-HS256")
success = jwe.SetProtectedHeader(jweProtHdr)


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

' Encrypt and return the JWE in sbJwe:
Dim sbJwe As Chilkat.StringBuilder
Set sbJwe = Chilkat.NewStringBuilder
success = jwe.EncryptBd(jpgBytes,sbJwe)
If (success <> True) Then
    Debug.Print jwe.LastErrorText
    Exit Sub
End If

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

' ---------------------------------------------------------
' Decrypt to get the original JPG file..

Dim jwe2 As Chilkat.Jwe
Set jwe2 = Chilkat.NewJwe
success = jwe2.LoadJweSb(sbJwe)
If (success <> True) Then
    Debug.Print jwe2.LastErrorText
    Exit Sub
End If

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

' Decrypt.
Dim jpgOriginal As Chilkat.BinData
Set jpgOriginal = Chilkat.NewBinData
success = jwe2.DecryptBd(0,jpgOriginal)
If (success <> True) Then
    Debug.Print jwe2.LastErrorText
    Exit Sub
End If

Debug.Print "Decrypted JPG size = "; jpgOriginal.NumBytes

' Save the decrypted JPG to a file.
success = jpgOriginal.WriteFile("qa_output/jwe_decrypted_starfish.jpg")

Debug.Print "success = "; success

' The output of this program, when tested, was:
' Original JPG size = 6229
' eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.9YFz_wteV ... 7Et3hKhpxnKEXw
' size of JWE: 8473
' Decrypted JPG size = 6229
' success = True