(PowerBuilder) Decrypt 256-bit AES GCM Produced by Something Unknown

Demonstrates how to decrypt something produced elsewhere (unknown) with 256-bit AES GCM.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

integer li_rc
string ls_KeyBase64
string ls_IvBase64Url
string ls_CipherBase64Url
oleobject loo_Crypt
integer li_Success
oleobject loo_BdEncrypted
oleobject loo_BdAuthTag
integer li_NumBytes
string ls_AuthTagHex
string ls_OriginalText

// This example assumes the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

// We have the following to decrypt:

// Key (Base64): 
ls_KeyBase64 = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"

// IV (Base64Url):
ls_IvBase64Url = "xrvaINMLqotAbWRK"

// ciphertext (base64url):
ls_CipherBase64Url = "RtGNAS-zQOxSB8W0HfqJjCoyt9KgImW_l-HjVC40hOOl-RNfRF3hzDIT1kvFVF8i_KX9XmqAftb6lyq-jLCEc_MSgqt3q1ixv3Ez4SbS3G5e3qGzLwxIMi2sCt00aDNwK2ipsJ4aw8s7ePPnl4oY-y1st9rwCWR0rrgEZwS9jmS4uJWGPn9K3jbKRnMslznDbtFLNJctMVXBTP-cv47JelxLCBOQSlK29rMuEFrhHR_VQrPq6gtZaBVSXZSYT0XOklp7nu9mVhrMCRtBCC5oiu5MPE5JYx4ANo3hUY7_NyQl2bpn9GfRXrdvqRGE-gy2upj-cDkm0t_tV8xmYge9DBQTH3B_4BGl2qTk_o-m7pEmKkS8XSdQhGcuFlykqrkE8SzB5I8esfzWOM0pwxbz0H_VaylKYHY="

loo_Crypt = create oleobject
// Use "Chilkat_9_5_0.Crypt2" for versions of Chilkat < 10.0.0
li_rc = loo_Crypt.ConnectToNewObject("Chilkat.Crypt2")
if li_rc < 0 then
    destroy loo_Crypt
    MessageBox("Error","Connecting to COM object failed")
    return
end if

loo_Crypt.CryptAlgorithm = "aes"
loo_Crypt.CipherMode = "gcm"
loo_Crypt.KeyLength = 256

li_Success = loo_Crypt.SetEncodedAad("random","ascii")
loo_Crypt.SetEncodedKey(ls_KeyBase64,"base64")
loo_Crypt.SetEncodedIV(ls_IvBase64Url,"base64url")

// The cipher text contains the 16-byte auth tag at the end.
// get it separately..
loo_BdEncrypted = create oleobject
// Use "Chilkat_9_5_0.BinData" for versions of Chilkat < 10.0.0
li_rc = loo_BdEncrypted.ConnectToNewObject("Chilkat.BinData")

loo_BdAuthTag = create oleobject
// Use "Chilkat_9_5_0.BinData" for versions of Chilkat < 10.0.0
li_rc = loo_BdAuthTag.ConnectToNewObject("Chilkat.BinData")

li_Success = loo_BdEncrypted.AppendEncoded(ls_CipherBase64Url,"base64url")

li_NumBytes = loo_BdEncrypted.NumBytes
ls_AuthTagHex = loo_BdEncrypted.GetEncodedChunk(li_NumBytes - 16,16,"hex")

Write-Debug "Auth tag in hex: " + ls_AuthTagHex

li_Success = loo_BdAuthTag.AppendEncoded(ls_AuthTagHex,"hex")
loo_BdEncrypted.RemoveChunk(li_NumBytes - 16,16)

// Use this special value to tell Chilkat to ignore the auth tag.
li_Success = loo_Crypt.SetEncodedAuthTag("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF","hex")

// Decrypt
loo_Crypt.EncodingMode = "base64"
ls_OriginalText = loo_Crypt.DecryptStringENC(loo_BdEncrypted.GetEncoded("base64"))
if loo_Crypt.LastMethodSuccess = 0 then
    Write-Debug loo_Crypt.LastErrorText
else
    Write-Debug ls_OriginalText
    Write-Debug "Success."
end if

// Decrypted text


destroy loo_Crypt
destroy loo_BdEncrypted
destroy loo_BdAuthTag