Excel Passwords
Excel files often are password protected because they include sensitive financial data. In my experience, twice as many Excel files as Word files have lost passwords.
What types of Excel passwords are there, and how should you go about recovering your Excel file if you have lost your password? Read on to find out more.
Excel uses several types of passwords, including VBA passwords (for protecting macros). VBA passwords are covered elsewhere. The other types of passwords used in Excel include the file open password, file reservation password and hidden worksheet passwords.
File reservation or worksheet passwords are not secure and are more for protecting data from deletion than for privacy. To recover the password, you can purchase a simple Excel password recovery program, and it will get you in immediately.
File open passwords prior to version 97 are not secure, and can be readily recovered. Again, you need simply purchase Excel password recovery software that supports your version (see our article on selecting software for help with this).
However, a password protected 97, 2000, 2003 or 2007 later file can only be opened by either trying every possible password (which could take a long time). In the case of Excel 97, 2000 and 2003 (the latter with default encryption, not cryptographic service providers encryption), the best way is to search for the correct encryption key and using this to decrypt the file without the password.
How does this work? Well there are 2^40 possible RC4 keys, since the key length is 40 bits. There are also some shortcuts. A modern PC can search through these keys in a few days. With more specialised and expensive software with faster hardware, or a commercial recovery service such as Decryptum it can be recovered in seconds. Once you have the encryption key, you no longer need the password to unlock the file.
If you have a file that can be recovered (before Excel 2007), this is the best way. If you have an Excel 2003 file with secure encryption (this can be selected as a special option when you are saving the file with a password) or Excel 2007 file, you’ll need software that tries all the possible passwords, character by character.
If you haven’t chosen a dictionary word, this could take a long time, so it is a good idea to have software that allows you to enter a mask. For example, you might remember that the password starts with an “A” and is 7 characters long, and ends with a number. This immediately reduces the number of characters that need to be search through.
No matter what version of Excel you are using, there is software or recovery services available that make the job of finding your lost password a bit easier and will allow you to retrieve your lost data.
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