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It is important to separate the use of passwords to set 
protections from use of a password to encrypt the document.  

Only "Save with Password" provides cryptographic security 
of the document.  

The "Save with Password" encryption is difficult to attack.  
The password is usually the weakest point and the password 
may fall to a variety of attacks that use pre-computed 
dictionaries of SHA1 digests and other brute-force 
techniques.  It is also possible that an attack may break 
the encryption without discovering the password itself.  
All of these attacks are believed to required great effort.  
In general, one should expect that a password used in 
"Save with Password" is not discoverable unless it is 
carelessly chosen or heavily reused.  

The harder the password is to attack, the harder it is
to recover, of course. 

In contrast, all of the protection settings are insecure.  

The protections are trivial to remove.  It can be done 
by any knowledgeable user with a Zip utility and an XML 
editor.  It is not necessary to know the password to 
remove the protection.  However, all passwords used in 
making protection settings should be considered compromised.  
That is because the document stores an SHA1 or other unsalted
 hash in "plain view" in the document.  These hashes are 
cracked with ease using conventional systems.  A password 
used to set a protection should not be used for any 
more-private purpose.  In particular, if the same passwords
 are used for protections on unencrypted documents and for 
saving with password (encryption), the encryption can be 
broken directly using the SHA1 digest from the protection 

Protection settings are on spreadsheet fields and sheets.  
There are protection settings on text as well.  The 
protection against altering change-tracking and the 
protection for keeping a document read-only are all of 
this kind.  The protection is useful for avoiding mistaken

It is easy for all of these protections to be removed, the
document altered, and the protections restored with the 
very same unlocking password without ever having to 
know the password.  

A digital signature can prevent the document from undetected
alterations, but that doesn't work for turnaround documents 
where some alterations are meant to be allowed.

There is more explanation of the use and risk of protections, 
and their removal, here:

A proposal for more-reliable security of protection passwords 
(but not the protections themselves) is before the

 - Dennis

-----Original Message-----
From: Dr. R. O Stapf [] 
Sent: Tuesday, October 16, 2012 06:30
Subject: Re: [libreoffice-users] Re: how to crack a PW in LO?

you are perfectly right about this!!!

On 16.10.2012 22:22, Andrew Douglas Pitonyak wrote:
Unless you have a lot of time to kill (days, weeks, months, etc), you are much better off not 
forgetting your password.

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