To encrypt your workbook and set a password to open it:
- Click the Microsoft Office Button , point to Prepare, and then click Encrypt Document.
- In the Password box, type a password, and then click OK.
You can type up to 255 characters. By default, this feature uses AES 128-bit advanced encryption. Encryption is a standard method used to help make your file more secure.
- In the Reenter password box, type the password again, and then click OK.
- To save the password, save the file.