Excel Password Recovery

Microsoft Excel documents can utilize three passwords:

1.        Password to open

2.        Password to modify

3.        Protect sheet or Protect workbook

Password to open

The Password to open requires a user to enter a password to view the document.

When the user sets a Password to open, the entire Microsoft Excel document is encrypted with the RC4 stream cipher.

Password to modify

The Password to modify requires a user to enter a password to make changes to the document.

When a user sets a Password to modify, the password is stored inside the Microsoft Excel document. The password can be viewed or changed with a hex editor.

Protect sheet or Protect workbook

The Protect sheet or Protect workbook password requires the user to enter a password to unprotect the either the worksheet or the workbook.

When a user sets a Protect sheet or Protect workbook password, the 32-bit password hash is stored in the document. The password hash can be viewed or changed with a hex editor.

Applying passwords in Microsoft Excel

To apply a Password to open or a Password to modify to a Microsoft Excel document, click <File>, <Save As>, <Tools>, <General Options>.

If you select <Advanced> you can select which encryption algorithm you wish to use and what key length you wish to use with that algorithm.

Supported algorithms are:

1.        Weak Encryption (XOR)

2.        Office 97/2000 Compatible

3.        RC4, Microsoft Base Cryptographic Provider v1.0

4.        RC4, Microsoft Base DSS and Diffie-Hellman Cryptographic Provider

5.        RC4, Microsoft DH SChannel Cryptographic Provider

6.        RC4, Microsoft Enhanced Cryptographic Provider v1.0

7.        RC4, Microsoft Enhanced DSS and Diffie-Hellman Cryptographic Provider

8.        RC4, Microsoft Enhanced RSA and AES Cryptographic Provider (Prototype)

9.        RC4, Microsoft RSA SChannel Cryptographic Provider

10.     RC4, Microsoft Strong Cryptographic Provider

11.     The default is "Office 97/2000 Compatible" -- however even Microsoft states that this is not recommended!

To apply a Protect sheet or Protect workbook password to a Microsoft Excel document, click <Tools>, <Protection>.

Microsoft Excel Password Recovery

It is possible simply to edit the Password to modify with a hex editor. It is also possible to edit the hash of the Protect sheet or Protect workbook password.

The Password to open can be attacked with a dictionary attack or a brute force attack.

Several programs, with widely varying capabilities, are available to help you recover a lost Microsoft Excel password:

1.        Elcomsoft Advanced Office XP Password Recovery

2.        AccessData Password Recovery Toolkit

3.        AccentSoft Excel Password Recovery

4.        xlcrack