(Excel) JWE using A256GCMKW

This example demonstrates creating a JCE with AES GCM key wrap.

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' This requires the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.


plaintext = "My text to enrypt"

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

' First build the JWE Protected Header: 

'         {
'             "alg": "A256GCMKW",
'             "kid": "18ec08e1-bfa9-4d95-b205-2b4dd1d4321d",
'             "tag": "kfPduVQ3T3H6vnewt--ksw",
'             "iv": "KkYT0GX_2jHlfqN_",
'             "enc": "A128CBC-HS256"
'         }

Dim jweProtHdr As Chilkat.JsonObject
Set jweProtHdr = Chilkat.NewJsonObject
Dim success As Boolean
success = jweProtHdr.AppendString("alg","A256GCMKW")
' kid is optional
success = jweProtHdr.AppendString("kid","18ec08e1-bfa9-4d95-b205-2b4dd1d4321d")
' tag is optional
success = jweProtHdr.AppendString("tag","kfPduVQ3T3H6vnewt--ksw")
success = jweProtHdr.AppendString("enc","A256GCM")
' the iv should be 16 random chars.
Dim prng As Chilkat.Prng
Set prng = Chilkat.NewPrng
success = jweProtHdr.AppendString("iv",prng.RandomString(16,True,True,True))
success = jwe.SetProtectedHeader(jweProtHdr)

Debug.Print "JWE Protected Header: "; jweProtHdr.Emit()
Debug.Print "--"

' Given that we have 256-bit AES, our key should be 32 bytes.
' The ascii string here is 32 bytes, therefore the 2nd arg is "ascii" to use these
' ascii chars directly as the key.

aesWrappingKey = "2baf4f730f5e4542b428593ef9cceb0e"
success = jwe.SetWrappingKey(0,aesWrappingKey,"ascii")

' Encrypt and return the JWE:

strJwe = jwe.Encrypt(plaintext,"utf-8")
If (jwe.LastMethodSuccess <> True) Then
    Debug.Print jwe.LastErrorText
    Exit Sub
End If

' Show the JWE we just created:
Debug.Print strJwe

' Decrypt the JWE that was just produced.
' 1) Load the JWE.
' 2) Set the AES wrapping key.
' 3) Decrypt.
Dim jwe2 As Chilkat.Jwe
Set jwe2 = Chilkat.NewJwe
success = jwe2.LoadJwe(strJwe)
If (success <> True) Then
    Debug.Print jwe2.LastErrorText
    Exit Sub
End If

' Set the AES wrap key.  Important to use "ascii"
success = jwe2.SetWrappingKey(0,aesWrappingKey,"ascii")

' Decrypt.

originalPlaintext = jwe2.Decrypt(0,"utf-8")
If (jwe2.LastMethodSuccess <> True) Then
    Debug.Print jwe2.LastErrorText
    Exit Sub
End If

Debug.Print "original text: "
Debug.Print originalPlaintext