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janaFlag for United States of America

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How to change password of a file already within a ZIP file

Hi,

How can we change an existing password assigned to a file that is within WinZip compress & encrypt file.

The no-brainer is just extract and compress with new file, but we  are looking for changing without the need extracting.
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John
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Sometimes 7zip allows you to manipulate files within a zipped file without "extracting", although in truth it does still extract and re-archive. Either way, you might like to try 7zip and see if it will allow you to do it.
Z-zip extracts so if it allows you to save with a new password that would be as above: open, change, re-save
I suspect you're right John, however, the only difference I've found with 7z is that you can edit "on the go".

See:
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I understand, but it is using temporary files to do this. At least this is what it is doing on my machine.
Yes, I think my only point was that it may be slightly quicker than extract -> edit -> re-zip... I suspect I'm splitting hairs though! (I often do) :D
I was not worried about that, and it may be quicker, but you would need the password to open and then change the password upon save. So to the original question "can I change without opening" No, not really.
Just thought I'd throw it in there just in case it was an half way acceptable compromise:)
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My question is How can I change a password of a file already saved in a Zip file?
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IN your question as others pointed out, do you mean you have a zip archive that Contains other password protected zip files one of which you wish to change the password?

The other interpretation is the password protection on a file is from a different source.

John's an Chris's comment address adjusting a zip to have a different password, if your scenario is different, clarifying it could help or you will be left with the suggestions provided.

You might have/be using a reference to tar and other options where one could  extract a specific file, do what is needed and then reimport the changed file back into the archive replacing .......
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Hi, to your "...do you mean you have a zip archive that Contains other password protected zip files one of which you wish to change the password?", Yes! Exactly  what's needed!  FYI, the compression apps are WinZip and WinRar.
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How can I change a password of a file already saved in a Zip file?  You have to know the password, open it is some way (methods provided here), change the password and resave it.

Why can you not do this?
Chris, you are missing one item, the filename whose password shoukd change.

Rayluvs, how often do you have to do this?
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John, maybe you haven't quite grasped our question.  We can do this with no problem.  As a matter of fact, that is exactly what have been doing for years: extract and zip again but with new password.

However, we were looking for expert advice in changing password without doing this.  As the  question says:  "How to change password of a file already WITHIN a ZIP file" and further more we describe "...it's a no-brainer, is just extract and compress with new file, but we are looking for changing without the need extracting."

Hope this clears a bit what we are trying to accomplish.
I have grasped what you want and of course you can extract, resave with new password,

we are looking for changing without the need extracting."  <-- You cannot do this. Otherwise passwords  would be meaningless. If you could get my secure file you could change my password to yours and open it. How secure is that?
Your question is ambiguous in the following sense, do you have two layers of zip, the external functioning as an archive to password protected zip files within?
Use zip -l to see whether the outer zip only adds overlay.

The other option is to address this issue on the process that creates, password protects the files in the first place.
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Don't think I am getting thru.  Ok let's put this way:

A WinZip file has 3 password protected files compressed within it.

Each file can have a different password or the same password.

We want to change the password in 1 file or the 3 there on the fly within the actual WinZip file - don't want to unzip and zip again with a new password.

We want to do like we do in web sites or emails or any other web apps or desktop apps that has an option to "change" password: choose the option, change the password and that's it.  In Word and Excel and other similar desktop apps you just open the encrypted document, then save the same document with a different password.

The apps we use for compressing files are WinZip and WinRar.
I hear you loud and clear but you are not listening. YOU CANNOT DO THIS.
Here is an equivalent that hopefully clarifies,
You have three written pages sealed in an envelop, you want to change the content of one of the pages without opening the envelop.
As suggested either address the correction during the writing of the page before it is stuffed and sealed in an envelop.

Or open the envelop (extract) the password protected zips. Now look at whether programmatically you could access the password protected zip, to alter it to a new.

To change one's password, one has to login. Admin can reset a password of a user but that would remove user access to certain documents if present, EFS that relies on a password versus a certificate.
Just to expand, if you tried to open up a zip file (with your password zip files inside) in a text editor you would see serialised data which is machine readable only. What you are suggesting (which I concur with the others is not feasible)  is to be able to open a zip file in notepad edit some of the characters within it and then save it again. This won't work by the nature of serialisation, machine code, binary files or encryption.

The bottom line is, you can't do it without either you, or the machine extracting the data first.

Even if you were trying to use john the ripper to brute-force a password, it would still require unzipping applications to work.

Good luck! :)
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Thanx guys!
You're welcome! :)
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Chose Chris as assisted because we its great idea using some sort of script to ease the pain of doing the change.

Again, thanc guys.
You are very welcome and I was happy to help you.