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I know this question has been asked before but I am trying to get to the bottom of this. I am trying to encrypt a number of files in a zip file using some sort of decent encryption mechanism. By decent, I mean an algorithm that is either AES256 or upwards and a strong password.

I cannot find what the best way to do this is. More specifically, what algorithm does zip use when the -e switch is used. Also, I have tried 7z that some people recommend but again it is unclear what algorithm is used when a standard zip file is created and not a 7z file.

I have done some digging but I am unable to reach a conclusion - any help would be more than appreciated.

P.s. I can not use GPG or Truecrypt - the file has to be a zip file for various reasons. Briefly, this is because the file will be send electronically and people at the other end a) do not know how to use any of these programs b) will attempt to open the file using winzip. Under no circumstances do I want to send the data insecure but I do wish to send it in a manner which the recipient can use it easily.

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If your users are not technically skilled enough to use anything other than winzip, It will probably be much easier to attack the incompetence of your users (phishing, trojans or keyloggers, dumpster diving, social engineering) than to break the encryption. – b0fh Jul 27 '10 at 17:44
up vote 0 down vote accepted

Well 7zip uses AES256, has excellent compression ratio & can generate self extracting files. Other archivers with strong encryption would be FreeArc(AES/Blowfish/Twofish/Serpent)

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I don't know the proper name of the encryption but the one used by 7zip for zip files is named ZipCrypto (in the Windows version this name is written in the encryption combobox). As far as I know 7zip can use AES256 for zip files too, but that way other may not be able to decompress it. At least not with WinZip or the Windows default 'compressed folders'.

So if you have lame e-mail partners, you have to stick with lame encryption. Try to update your users. :)

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