Office 2010: two times more secure

July 28th, 2009 by Andrey Malyshev

We are waiting for release of new Microsoft office suite – Office 2010. Right now Microsoft has only technical preview of new Office; this preview has been leaked from Microsoft and everyone can download it with the help of torrent trackers. We’ve got a copy of Office 2010 and analysed its (new) password protection.

Starting from Office 2007, Microsoft used password protection system called ECMA-376, developed by ECMA International. This standard is open and everyone can write ECMA-376 based protection which will be accepted by Microsoft Office. The standard allows to select hash and encryption algorithms as well as the number of hash rounds (up to 10 millions is allowed).

In Office 2007, ECMA-376 with SHA-1 hash and AES-128 encryption is implemented. The number of hash rounds is 50000 that makes password recovery really difficult and slow. Office 2010 also uses SHA-1 and AES-128, but the number of hash rounds is now 100000. Therefore password recovery for new Office files will be two times slower.

Here is a diagram of password recovery speed for Office 2007:

To get a speed for Office 2010, simply divide these values to 2. We’ll get about 175 pps on Core2 6600 and about 8750 pps on Tesla S1070.

Why don’t increase the number of hash rounds to 10 millions ? Security is really important but it always affects usability. The hash is calculating to verify a password and when each document block is decrypted. If we add hash rounds – the document decryption time is increased. If a document is opening in MS Office during one hour – its unacceptable despite of high security.

Anyway – Office 2010 documents will be more secure than Office 2007 ones. And the new encryption has backward compatibility – all Office 2010 documents can be opened in Office 2007. 


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3 Responses to “Office 2010: two times more secure”

  1. KARPOLAN says:

    Если есть возможность открывать старым офисом, может можно и пароли пребирать там же? :)

  2. If new files can be opened in old office, may be it is possible to recover passwords right there? :)

    Well, password recovery is being done not in the Office itself, but in AOPR, of course :) . And as far as the number of hash rounds is doubled, the speed will be exactly two times lower anyway.

  3. Henk says:

    could you please give me more information about the security of password protection in office 2010
    how easily is a password cracked by a professional hacker?

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