Several types of passwords can be set on MS Office documents. They can be divided into two types: passwords, encrypting the document, and passwords that do not encrypt the document:
- The first type only includes one password. It is password to open the document which prevents the document from opening. Such password can be set in all MS Office documents.
- The second type comprises password for Visual Basic for Applications (VBA) projects, and a number of passwords restricting shared access to the document. These passwords are different for each MS Office application:
- For Microsoft Word – password to modify the document and Restrict Permission for Formatting and Editing.
- For Microsoft Excel – password to modify the document, password to protect worksheet, password to protect workbook, password to protect shared workbook.
- For Microsoft PowerPoint – password to modify the document.
Since there is no encryption for the passwords of the second type, there is no problem in removing them from the documents, which is well demonstrated in our Password-Find service. We believe that these types of passwords have been developed by Microsoft for convenient shared use of the document rather than for its protection.
Password to the open document
The only password securely protecting MS Office documents is a password to open the document. The protection technology is different for documents, saved in MS Office 97-2003 and in MS Office 2007-2010:
- In old versions of MS Office 97, 2000, a standard documents protection algorithm converts a password into a 40-bit key, in which the document is encrypted. Modern servers allow finding such a short key very quickly. The Password-Find service finds such a key instantly!
- For documents in MS Office XP, 2003, the default protection has remained the same as in MS Office 97 and 2000, but the user has received an opportunity to change protection (to choose a non-standard Crypto Service Provider) and to increase the length of the key. But the speed of password search in this case still remains quite high. That is why it is possible to retrieve long passwords within a reasonable timeframe using the supercomputer of the Password-Find service.
- Documents, saved in the new MS Office 2007, 2010, format, are well protected. A 128-bit key is used for document encryption and in order to lower the password search speed, this key is retrieved from the password by 50000 \ 100000 SHA1 conversions. Thanks to the special algorithm of Password-Find, it is possible to instantly remove protection from almost a half of all documents! For the rest of documents, Password-Find uses a specialized hardware combination (supercomputer) to find the original password set by the user. This hardware solution finds passwords 400 times faster than an average home computer. Using these two methods, Password-Find can unlock up to 80% of documents, saved in MS Office 2007 / 2010 format.