AutoIt

Decrypt 256-bit AES GCM Produced by Something Unknown

See more Encryption Examples

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

Local $bSuccess = False

; 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): 
Local $sKeyBase64 = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"

; IV (Base64Url):
Local $sIvBase64Url = "xrvaINMLqotAbWRK"

; ciphertext (base64url):
Local $sCipherBase64Url = "RtGNAS-zQOxSB8W0HfqJjCoyt9KgImW_l-HjVC40hOOl-RNfRF3hzDIT1kvFVF8i_KX9XmqAftb6lyq-jLCEc_MSgqt3q1ixv3Ez4SbS3G5e3qGzLwxIMi2sCt00aDNwK2ipsJ4aw8s7ePPnl4oY-y1st9rwCWR0rrgEZwS9jmS4uJWGPn9K3jbKRnMslznDbtFLNJctMVXBTP-cv47JelxLCBOQSlK29rMuEFrhHR_VQrPq6gtZaBVSXZSYT0XOklp7nu9mVhrMCRtBCC5oiu5MPE5JYx4ANo3hUY7_NyQl2bpn9GfRXrdvqRGE-gy2upj-cDkm0t_tV8xmYge9DBQTH3B_4BGl2qTk_o-m7pEmKkS8XSdQhGcuFlykqrkE8SzB5I8esfzWOM0pwxbz0H_VaylKYHY="

$oCrypt = ObjCreate("Chilkat.Crypt2")

$oCrypt.CryptAlgorithm = "aes"
$oCrypt.CipherMode = "gcm"
$oCrypt.KeyLength = 256

$bSuccess = $oCrypt.SetEncodedAad("random","ascii")
$oCrypt.SetEncodedKey $sKeyBase64,"base64"
$oCrypt.SetEncodedIV $sIvBase64Url,"base64url"

; The cipher text contains the 16-byte auth tag at the end.
; get it separately..
$oBdEncrypted = ObjCreate("Chilkat.BinData")
$oBdAuthTag = ObjCreate("Chilkat.BinData")
$bSuccess = $oBdEncrypted.AppendEncoded($sCipherBase64Url,"base64url")

Local $iNumBytes = $oBdEncrypted.NumBytes
Local $sAuthTagHex = $oBdEncrypted.GetEncodedChunk($iNumBytes - 16,16,"hex")

ConsoleWrite("Auth tag in hex: " & $sAuthTagHex & @CRLF)

$bSuccess = $oBdAuthTag.AppendEncoded($sAuthTagHex,"hex")
$oBdEncrypted.RemoveChunk($iNumBytes - 16,16)

; Use this special value to tell Chilkat to ignore the auth tag.
$bSuccess = $oCrypt.SetEncodedAuthTag("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF","hex")

; Decrypt
$oCrypt.EncodingMode = "base64"
Local $sOriginalText = $oCrypt.DecryptStringENC($oBdEncrypted.GetEncoded("base64"))
If ($oCrypt.LastMethodSuccess = False) Then
    ConsoleWrite($oCrypt.LastErrorText & @CRLF)
Else
    ConsoleWrite($sOriginalText & @CRLF)
    ConsoleWrite("Success." & @CRLF)
EndIf

; Decrypted text