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I have a password-protected ZIP file that contains a single file. Also I have the same file outside the archive in a plain version. I know for sure that this is the same file. Is it possible to determine the password used for this archive?

To be clear, I want to know the actual password used for the ZIP file; I'm not trying to simply gain access to the ZIP file's content without knowing the password.

My question is not answered by this proposed duplicate question. That question deals with accessing the ZIP file without knowing the password. I am trying to compute the password leveraging the fact I have the same file inside and outside the archive.

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    In theory, yes. You would need to compress the file with every possible password, then bytecompare both files. When its an identical file, the password used to create that archive should work on the other one too. Of course, the archive options would need to be the same.
    – LPChip
    Commented Apr 7, 2017 at 20:58
  • The file you've extracted has no information about the archive it came from. As for cracking a Zip password, there's a ton of info out there (and on SU) about attempting it.
    – Ƭᴇcʜιᴇ007
    Commented Apr 7, 2017 at 20:58
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    Possible duplicate of Is it feasible to crack ZIP passwords? and/or How to crack a password protected zip file
    – Ƭᴇcʜιᴇ007
    Commented Apr 7, 2017 at 21:03
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    So you say I know for sure that this is the same file then why do you even need to access the zip encrypted or password protected file within it?
    – Vomit IT - Chunky Mess Style
    Commented Apr 7, 2017 at 21:41
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    @ModeratorImpersonator because I have other data encrypted with the same password.
    – pbies
    Commented Apr 7, 2017 at 22:18

2 Answers 2

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Your answer is "it depends" and "probably not". Apparently ZIP files support different types of encryption, and the ability to reverse engineer the password would be dependent on the type of encryption.

Probably the most popular encryption will be a variant of AES encryption, and it is generally accepted as being unbreakable in reality - and indeed, most suitable decent encryption methods will share this attribute.

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    The most popular variant is in fact ZipCrypto, because it is the only one universally supported. Everything else is effectively proprietary.
    – Daniel B
    Commented Apr 10, 2017 at 6:23
  • The closest answer is here: crypto.stackexchange.com/questions/19716/…
    – pbies
    Commented Aug 4, 2017 at 19:42
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There is program called pkcrack which could be useful here. But after searching for a password with it, nothing has been found. It taken half an hour and no result.

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