# Password Protected Word Document



## Johnny Faster (Apr 25, 2005)

A friend recieved a password-protected Microsoft Word document via e-mail the other day and was unable to open it.

As I am the local "guru" on these matters, I am expected to solve this problem.

Looked at Word, played around with the features, ran Google searches and searched the MS Office database and found ZIP on how to open them.

Is this the best-kept secret in the world ?

The friend thinks she has the password, but we couldn't find any means of entering it in order to access the doc.

Could someone please help ?

Thanks in advance,

Johnny


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## ReeKorl (Mar 25, 2005)

In terms of brute forcing the file, it is possible, but anything over about a 6 character password is prohibitive - it takes logarithmically longer depending on password length. For example, a document a colleague needed opened should have had a 10 character password, but it wasn't what they thought is should be. The time estimate for brute-forcing the file was in excess of 320 years for a 10 char p/w!

On the internet there are sites which claim to be able to force or rainbow crack the passwords, however I have never attempted to use these considering the possible legality issues over it and the fact that the site would then have the data in the protected document, not to mention the fact that the cheapest service I could find was more than $30!

You say your friend thinks they have the password, but can't enter it. What do you mean by this? It should come up with a password prompt when opening it if it's password protected.


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## Johnny Faster (Apr 25, 2005)

*Exactly*



> It should come up with a password prompt when opening it if it's password protected.


When double-clicking the document, an error message comes up immediately saying something like "This document is password protected and cannot be opened.) (Or words to that effect, it was about a week ago since we tried to open it.

THAT was the issue. There was no opportunity given to input a password, nor could I find a way to "manually" force an input. So that's part of the answer I needed.

NOW the questions is "Why wasn't the password prompt brought up when the doc was opened ?"

Corrupt document ? Is there a setting in Word I can fiddle with ?

Thanks again,

Johnny


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## Squashman (Apr 14, 2005)

ReeKorl said:


> In terms of brute forcing the file, it is possible, but anything over about a 6 character password is prohibitive - it takes logarithmically longer depending on password length. For example, a document a colleague needed opened should have had a 10 character password, but it wasn't what they thought is should be. The time estimate for brute-forcing the file was in excess of 320 years for a 10 char p/w!.


I will have to disagree with your brute force calculation.


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## Volt-Schwibe (Jan 12, 2003)

i think reekorl is referring to the time involved in a human typing in all the possible passwords, including a-z and 0-9 x 10 digits = some number of decades at least.

it comes out to 3.656158440063e+015 on my calculator.



now, that number x the 15 seconds to enter the password, and see if it worked = 5.484237660094e+016 

turns out to be 1.523399350026e+013 hours, or 634749729177.6 days, or 1737850045.661 years.

hmm....

freakin scary.


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## ReeKorl (Mar 25, 2005)

Sorry, it was a 9 char password actually... the 10 char would have taken considerably longer. I've studied cryptography and cryptanalysis for about 8 years as a hobby, I do these calcs all the time. Here's a mean-time-to-solve (MTS) calc, just as proof of the difficulty of brute forcing these things.

OK, not including strange characters, the password character set is a-z, A-Z, 0-9 and a space. 63 characters total. This means there are a total of:

63^10 passwords = 984,930,291,881,790,849 <- That's a lot.

Even assuming a brute force program can handle 3,000,000 passwords a second (and that's being VERY generous to the system doing the cracking) this means it will take 

328,310,097,293 seconds to do the testing of every password (figures have been rounded down to lower integer)
= 5,471,834,954 minutes.
= 91,197,249 hours.
= 3,799,885 days.
= 10,410 years.

Now assuming the MTS is an average of _any_ password, this means that it will solve it in about half of the time to run through every password. Basically, you can expect a brute-force attack on a home computer to take about 5000 years to break a 10 character password if it's using the above character set.

If you calculate the MTS for a 1 char p/w, the a 2, then a 3, then up to as many as you want then plot them on a graph, it's an almost perfect log graph. This is why I never use a password that is smaller than 8 characters - the MTS is about 10.5 years for the character set I use. The only real way to break it open is to find a flaw in the cypher itself.

-EDIT

Sorry, got a bit carried away there, forgot why I was replying. On Johhny's problem... I'm not sure why that message is coming up, I've never seen that one before. Can you get the document resent, there's a possibility it's become corrupt somehow. If it still doesn't open, it might be a problem with the way the document is locked - try getting them to send it unprotected and in a password protected zipfile or suchlike.


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## ReeKorl (Mar 25, 2005)

OK, in respect to the pw/sec amount, here's a product for reference: http://unprotect-excel-password.password-studio.com/unlock/

They say 140,000+ pw/sec. That's a bit low on a very high end computer, so you could expect something in the region of 160,000 per second. Even so, it's not enough to make the time estimate drop by any real amount.

NOTE: This only refers to true brute force attacks, not hybrid dictionary/brute attacks, or 'smart' attacks. Also, this assumes the password is of a complexity to use the different character sets. even putting in an extra dot into your password will increase cracking time by a huge amount. Hybrid and smart attacks also rely on the password being similar to a dictionary word, such as 'P4ssword', so if your p/w is 'P3n8Ed Q' then you're likely to have quite a secure p/w.


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## Volt-Schwibe (Jan 12, 2003)

i knew my math was wrong,but i knew it was a lot longer than 300-400 years.

lol

so basically, either remember the password, or give up on it 

but i guess the real question is, if you might have to right password, where do you put it...

i have no clue what's going on, because there is a pop up that should prompt you to enter the password, and if it isn't, something may be corrupted, either within the file itself, or within the windows OS on that computer.


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## stevepayne (Nov 17, 2004)

It sounds like the file is protected so that you've only got 'read' access. To access the options to unprotect it in Word 2003, click on Tools > Protect Document... and this will bring up a menu on the right, which is where you can set passwords for various different protection levels.

As for cracking the password, I've no idea I'm afriad - other than checking that your colleague hasn't got an older version of the file without the protection (any backups?).

Hope this is of help.


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