#comments-start
File Encryptor/Decryptor. This code simply combines both functions into a single usable app.
Have removed all but AES-256 encryption methods.
Original code can be below at the following links:

Encrypt Function: https://www.autoitscript.com/autoit3/docs/libfunctions/_Crypt_EncryptFile.htm
Decrypt Function: https://www.autoitscript.com/autoit3/docs/libfunctions/_Crypt_DecryptFile.htm

Compiled binary can be found at: https://bitbucket.org/TheChiefMeat/file-encryptor-decryptor/downloads/File%20Encryptor-Decryptor.zip
#comments-end

#include <ComboConstants.au3>
#include <Crypt.au3>
#include <GUIConstantsEx.au3>
#include <MsgBoxConstants.au3>
#include <StringConstants.au3>

$PortableGUI = GUICreate("File Encryptor/Decryptor", 320, 100, -1, -1, True)
$Encrypt = GUICtrlCreateButton("Encrypt", 20, 15, 130, 40)
$Decrypt = GUICtrlCreateButton("Decrypt", 165, 15, 130, 40)
GUISetState(@SW_SHOW)

	While 1
		Switch GUIGetMsg()
			Case $GUI_EVENT_CLOSE
				ExitLoop
			Case $Encrypt
			GUIDelete($PortableGUI)
			Encrypt()
			Case $Decrypt
			GUIDelete($PortableGUI)
			Decrypt()
		EndSwitch
	WEnd

Func Encrypt()
    Local $iAlgorithm = $CALG_AES_256

    Local $hGUI = GUICreate("File Encrypter", 425, 100)
    Local $idSourceInput = GUICtrlCreateInput("", 5, 5, 200, 20)
    Local $idSourceBrowse = GUICtrlCreateButton("...", 210, 5, 35, 20)

    Local $idDestinationInput = GUICtrlCreateInput("", 5, 30, 200, 20)
    Local $idDestinationBrowse = GUICtrlCreateButton("...", 210, 30, 35, 20)

    GUICtrlCreateLabel("Password:", 5, 60, 200, 20)
    Local $idPasswordInput = GUICtrlCreateInput("", 5, 75, 200, 20)

    Local $idCombo = GUICtrlCreateCombo("", 210, 75, 100, 20, $CBS_DROPDOWNLIST)
    GUICtrlSetData($idCombo, "AES (256bit)", "AES (256bit)")
    Local $idEncrypt = GUICtrlCreateButton("Encrypt", 355, 70, 65, 25)
    GUISetState(@SW_SHOW, $hGUI)

    Local $sDestinationRead = "", $sFilePath = "", $sPasswordRead = "", $sSourceRead = ""
    While 1
        Switch GUIGetMsg()
            Case $GUI_EVENT_CLOSE
                ExitLoop

            Case $idSourceBrowse
                $sFilePath = FileOpenDialog("Select a file to encrypt.", "", "All files (*.*)") ; Select a file to encrypt.
                If @error Then
                    ContinueLoop
                EndIf
                GUICtrlSetData($idSourceInput, $sFilePath) ; Set the inputbox with the filepath.

            Case $idDestinationBrowse
                $sFilePath = FileSaveDialog("Save the file as ...", "", "All files (*.*)") ; Select a file to save the encrypted data to.
                If @error Then
                    ContinueLoop
                EndIf
                GUICtrlSetData($idDestinationInput, $sFilePath) ; Set the inputbox with the filepath.

            Case $idCombo ; Check when the combobox is selected and retrieve the correct algorithm.
                Switch GUICtrlRead($idCombo) ; Read the combobox selection.

                    Case "AES (256bit)"
                        $iAlgorithm = $CALG_AES_256
					EndSwitch

            Case $idEncrypt
                $sSourceRead = GUICtrlRead($idSourceInput) ; Read the source filepath input.
                $sDestinationRead = GUICtrlRead($idDestinationInput) ; Read the destination filepath input.
                $sPasswordRead = GUICtrlRead($idPasswordInput) ; Read the password input.
                If StringStripWS($sSourceRead, $STR_STRIPALL) <> "" And StringStripWS($sDestinationRead, $STR_STRIPALL) <> "" And StringStripWS($sPasswordRead, $STR_STRIPALL) <> "" And FileExists($sSourceRead) Then ; Check there is a file available to encrypt and a password has been set.
                    If _Crypt_EncryptFile($sSourceRead, $sDestinationRead, $sPasswordRead, $iAlgorithm) Then ; Encrypt the file.
                        MsgBox($MB_SYSTEMMODAL, "Success", "Operation succeeded.")
                    Else
                        Switch @error
                            Case 1
                                MsgBox($MB_SYSTEMMODAL, "Error", "Failed to create the key.")
                            Case 2
                                MsgBox($MB_SYSTEMMODAL, "Error", "Couldn't open the source file.")
                            Case 3
                                MsgBox($MB_SYSTEMMODAL, "Error", "Couldn't open the destination file.")
                            Case 4 Or 5
                                MsgBox($MB_SYSTEMMODAL, "Error", "Encryption error.")
                        EndSwitch
                    EndIf
                Else
                    MsgBox($MB_SYSTEMMODAL, "Error", "Please ensure the relevant information has been entered correctly.")
                EndIf
        EndSwitch
    WEnd

    GUIDelete($hGUI) ; Delete the previous GUI and all controls.
	EXIT
EndFunc   ;==>Example

Func Decrypt()
    Local $iAlgorithm = $CALG_AES_256

    Local $hGUI = GUICreate("File Decrypter", 425, 100)
    Local $idSourceInput = GUICtrlCreateInput("", 5, 5, 200, 20)
    Local $idSourceBrowse = GUICtrlCreateButton("...", 210, 5, 35, 20)

    Local $idDestinationInput = GUICtrlCreateInput("", 5, 30, 200, 20)
    Local $idDestinationBrowse = GUICtrlCreateButton("...", 210, 30, 35, 20)

    GUICtrlCreateLabel("Password:", 5, 60, 200, 20)
    Local $idPasswordInput = GUICtrlCreateInput("", 5, 75, 200, 20)

    Local $idCombo = GUICtrlCreateCombo("", 210, 75, 100, 20, $CBS_DROPDOWNLIST)
    GUICtrlSetData($idCombo, "AES (256bit)", "AES (256bit)")
    Local $idDecrypt = GUICtrlCreateButton("Decrypt", 355, 70, 65, 25)
    GUISetState(@SW_SHOW, $hGUI)

    Local $sDestinationRead = "", $sFilePath = "", $sPasswordRead = "", $sSourceRead = ""
    While 1
        Switch GUIGetMsg()
            Case $GUI_EVENT_CLOSE
                ExitLoop

            Case $idSourceBrowse
                $sFilePath = FileOpenDialog("Select a file to decrypt.", "", "All files (*.*)") ; Select a file to decrypt.
                If @error Then
                    ContinueLoop
                EndIf
                GUICtrlSetData($idSourceInput, $sFilePath) ; Set the inputbox with the filepath.

            Case $idDestinationBrowse
                $sFilePath = FileSaveDialog("Save the file as ...", "", "All files (*.*)") ; Select a file to save the decrypted data to.
                If @error Then
                    ContinueLoop
                EndIf
                GUICtrlSetData($idDestinationInput, $sFilePath) ; Set the inputbox with the filepath.

            Case $idCombo ; Check when the combobox is selected and retrieve the correct algorithm.
                Switch GUICtrlRead($idCombo) ; Read the combobox selection.
                    Case "AES (256bit)"
                        $iAlgorithm = $CALG_AES_256
					EndSwitch

            Case $idDecrypt
                $sSourceRead = GUICtrlRead($idSourceInput) ; Read the source filepath input.
                $sDestinationRead = GUICtrlRead($idDestinationInput) ; Read the destination filepath input.
                $sPasswordRead = GUICtrlRead($idPasswordInput) ; Read the password input.
                If StringStripWS($sSourceRead, $STR_STRIPALL) <> "" And StringStripWS($sDestinationRead, $STR_STRIPALL) <> "" And StringStripWS($sPasswordRead, $STR_STRIPALL) <> "" And FileExists($sSourceRead) Then ; Check there is a file available to decrypt and a password has been set.
                    If _Crypt_DecryptFile($sSourceRead, $sDestinationRead, $sPasswordRead, $iAlgorithm) Then ; Decrypt the file.
                        MsgBox($MB_SYSTEMMODAL, "Success", "Operation succeeded.")
                    Else
                        Switch @error
                            Case 1
                                MsgBox($MB_SYSTEMMODAL, "Error", "Failed to create the key.")
                            Case 2
                                MsgBox($MB_SYSTEMMODAL, "Error", "Couldn't open the source file.")
                            Case 3
                                MsgBox($MB_SYSTEMMODAL, "Error", "Couldn't open the destination file.")
                            Case 4 Or 5
                                MsgBox($MB_SYSTEMMODAL, "Error", "Decryption error.")
                        EndSwitch
                    EndIf
                Else
                    MsgBox($MB_SYSTEMMODAL, "Error", "Please ensure the relevant information has been entered correctly.")
                EndIf
        EndSwitch
    WEnd

    GUIDelete($hGUI) ; Delete the previous GUI and all controls.
	EXIT
EndFunc   ;==>Example