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I put some files into an encrypted archive with Secure Zip (was using a computer at another organization) and emailed them to some people. None of them have Secure Zip (nor do I on any of my own computers) and none of us can open them. Neither 7zip nor Winzip can open these archives.

Is SecureZip's encryption method completely proprietary? Do any other tools support it?

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ZIP file encryption is always proprietary. There is no standard to encrypt zip files.

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If you mean standard in the strictest, sense, then I don't think ZIP is a standard at all. However, the format is well-documented, and WinZip has published documentation on how its AES extension works: I know for a fact that 7zip can decode a WinZip AES archive. I was surprised that SecureZip apparently invented their own method. Apparently AES-256 isn't good enough for them. – mehaase Jan 9 '13 at 17:31

SecureZip supports a number of encryption options including passphrase and certificate based encryption as well as as FIPS 140 mode for government needs. It depends on how you encrypted it AES-256, AES192, AES128 or 3DES168. Winzip should be able to decrypt it as long as a compatible encryption method was used.

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