Function: Blowfish Encrypt/Decrypt Strings

[Lorne]

The following pair of functions can be used with the Crypto plugin in AutoPlay Media Studio 5.0 Professional to blowfish encrypt and decrypt strings.

Note: The Crypto.BlowfishEncrypt and Crypto.BlowfishDecrypt actions only operate on files because blowfish-encrypted data can't be stored in a string without (the encrypted data contains characters that aren't valid string characters). The following two functions get around this limitation by using temporary text files and base64-encoding the encrypted versions so they can be read back in as strings.

-- Function: BlowfishEncryptString
-- Purpose: Blowfish encrypts a string by saving it to a
-- temporary file and then base-64 encoding the encrypted
-- version to get the encrypted data in string form.
-- Returns: The source string blowfish encrypted 
-- and base64 encoded, or "" if an error occurs.
function BlowfishEncryptString(SourceText, Key)

	-- I've tried to choose filenames that are unlikely to already exist ;)
	local tempsrc = _TempFolder.."\\ILoveMyMommysChicken.tempsrc";
	local tempenc = _TempFolder.."\\ILoveMyMommysChicken.tempenc";

	-- Write the source string out to a temporary file
	TextFile.WriteFromString(tempsrc, SourceText);

	-- Make sure the TextFile.WriteFromString action was successful
	-- (If an error occurred, display the error message in a dialog, clean up and abort)
	local error = Application.GetLastError();
	if (error ~= 0) then
		Dialog.Message("Error", _tblErrorMessages[error] , MB_OK, MB_ICONEXCLAMATION, MB_DEFBUTTON1);
		File.Delete(tempsrc);
		return "";
	end

	-- Now blowfish encrypt the file
	Crypto.BlowfishEncrypt(tempsrc, tempenc, Key);

	-- Make sure the Crypto.BlowfishEncrypt action was successful
	local error = Application.GetLastError();
	if (error ~=0) then
		Dialog.Message("Error", _tblErrorMessages[error] , MB_OK, MB_ICONEXCLAMATION, MB_DEFBUTTON1);
		File.Delete(tempsrc);
		File.Delete(tempenc);
		return "";
	end

	-- Now base64 encode the encrypted file and store it in a string
	local strEncoded = Crypto.Base64EncodeToString(tempenc);

	-- Make sure the Crypto.Base64EncodeToString action was successful
	error = Application.GetLastError();
	if (error ~=0) then
		Dialog.Message("Error", _tblErrorMessages[error], MB_OK, MB_ICONEXCLAMATION, MB_DEFBUTTON1);
		File.Delete(tempsrc);
		File.Delete(tempenc);
		return "";
	end	

	-- remove the temp files
	File.Delete(tempsrc);
	File.Delete(tempenc);
	
	return strEncoded;
end

-- Function: BlowfishDecryptString
-- Purpose: Blowfish decrypts a string that was encrypted
-- using the BlowfishEncryptString function.
-- Returns: The source string base64 decoded and blowfish 
-- decrypted, or "" if an error occurs.
function BlowfishDecryptString(SourceText, Key)

	-- I've tried to choose filenames that are unlikely to already exist ;)
	-- (If you're wondering, I have an Australian friend who says this constantly,
	-- I can't seem to get this out of my head today)
	local tempsrc = _TempFolder.."\\ILoveMyMommysChicken.tempsrc";
	local tempdec = _TempFolder.."\\ILoveMyMommysChicken.tempdec";

	-- base64 decode the string to a temp file
	Crypto.Base64DecodeFromString(SourceText, tempsrc);
	
	-- Make sure the Crypto.Base64DecodeFromString action was successful
	-- (If an error occurred, display the error message in a dialog, clean up and abort)
	local error = Application.GetLastError();
	if (error ~=0) then
		Dialog.Message("Error", _tblErrorMessages[error], MB_OK, MB_ICONEXCLAMATION, MB_DEFBUTTON1);
		File.Delete(tempsrc);
		return "";
	end	

	-- Now blowfish decrypt the file
	Crypto.BlowfishDecrypt(tempsrc, tempdec, Key);

	-- Make sure the Crypto.BlowfishDecrypt action was successful
	error = Application.GetLastError();
	if (error ~=0) then
		Dialog.Message("Error", _tblErrorMessages[error] , MB_OK, MB_ICONEXCLAMATION, MB_DEFBUTTON1);
		File.Delete(tempsrc);
		File.Delete(tempdec);
		return "";
	end

	-- Read the source string in from the temporary file
	local strDecrypted = TextFile.ReadToString(tempdec);
	
	-- Check if any errors occurred from calling the TextFile.ReadToString action.
	-- If an error occurred, display it's error message in a dialog message, clean up and abort.
	error = Application.GetLastError();
	if (error ~=0) then
		Dialog.Message("Error", _tblErrorMessages[error] , MB_OK, MB_ICONEXCLAMATION, MB_DEFBUTTON1);
		File.Delete(tempsrc);
		File.Delete(tempdec);
		return "";
	end

	-- remove the temp files
	File.Delete(tempsrc);
	File.Delete(tempdec);

	return strDecrypted;
end

I've attached a simple project that demonstrates how to use these two functions (and proves that they work ). The functions are contained in the Global Functions section and the code that uses them is in the On Click event for the "Test" button.

Requirements:

These functions and the example project require the Crypto plugin to be installed and enabled (go to Project > Plugins and make sure the "Crypto" item is checked).

Note also that these functions are only for use with AutoPlay Media Studio 5.0 Professional Edition. The Standard Edition does not support action plugins.