Home Forums .NET libraries Xceed Zip & Real-Time Zip for .NET PKWare can’t decrypt XCeed AES zip file

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    #19822 |

    I need to encrypt zip files with 256bit AES. We bought Xceed Zip for .NET because it claimed “Industry standard compatibility” for AES. However, upon attempting to unzip a file I discovered it doesn’t work. Only PKWare Zip Reader can decrypt the files, not PKZip itself. We need that because client’s need to automate the decryption of our files. I’m a little confused because I can decrypt PKWare encrypted files with no issue using Winzip, but not vice versa.

    Is this a known issue? Are there any plans to make XCeed encrypted files decryptable by PKZip?

    Imported from legacy forums. Posted by Greg (had 4660 views)

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    No, this is not a known issue. I created an archive with the following code:

    <code>
    AbstractFile zipFile = new DiskFile( @”D:\AESSecureArchive.zip” );

    ZipArchive archive = new ZipArchive( zipFile );

    AbstractFile textFile = new DiskFile( @”D:\Test.txt” );

    archive.DefaultEncryptionMethod = EncryptionMethod.WinZipAes;
    archive.DefaultEncryptionStrength = 256;

    archive.DefaultEncryptionPassword = “Soleil”;

    textFile.CopyTo( archive, true );
    </code>

    I was able to open the archive with Winzip, our tools and PKWare’s ZipReader.
    The algorithm to decrypt and decompress should be the same from ZipReader to PKZip. If it does not work, you should contact PKWare technical support (as they should be compatible with their PKWare ZipReader).

    Imported from legacy forums. Posted by CharlesB (had 256 views)

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    Actually PKWare for Windows works fine, but PKWare for the mainframe(zOS) does not. I realize this not really an issue for XCeed, but any direction you could give would be greatly appreciated. I have to send AES encrypted zip files to an agency of the federal government and PKWare is being very evasive as to why SecureZip for the mainframe will not unzip files created by WinZip, or XCeed Zip for .Net (I think they are trying to lock everyone in to using SecureZip). Is there a difference in the headers of the files that might cause a problem? I already have the blueprint edition of Zip for .Net, but if you could help me out on this, you would have a customer for life for all your products.

    Imported from legacy forums. Posted by Jason (had 272 views)

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    After looking at SecureZip, it seems that the AES Encryption is not the same as Winzip:
    <a href=”http://www.pkware.com/documents/productcollateral/SecureZIPCompMatrixPress-1.pdf”&gt; http://www.pkware.com/documents/productcollateral/SecureZIPCompMatrixPress-1.pdf</a&gt;

    The odd behavior here is that we are able to open files (encrypted with AES) created by SecureZip, but the opposite does not seem to work. Strangely, the archive created by Xceed Zip are much more simpler than the one created by SecureZip (if advanced features are used).

    Also, a note from <a href=”http://en.wikipedia.org/wiki/ZIP_(file_format) “> wikipedia </a>suggests that PKWARE SecureZIP is not using the same AES encryption as Winzip (and Xceed Zip):

    “PKWARE SecureZIP uses another format that enables AES Encryption, Digital Certificate (X.509) Encryption, Filename Encryption, File Authentication.[3] “

    Imported from legacy forums. Posted by CharlesB (had 340 views)

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    Charles,
    Thanks for the prompt reply. Is there any way to work around this behavior with the Blueprint version, so that I can create my compressed files using Xceed Zip (and have SecureZip for the mainframe be able to read them)? Or, am I stuck writing a batch file for SecureZip? I am encrypting using 256 bit AES encryption with a passphrase. SecureZip for Windows can read a file encrypted by Xceed Zip in this fashion, but the mainframe version cannot. I am hoping that there is some small difference between the two formats causing the problem.

    Imported from legacy forums. Posted by Jason (had 724 views)

    Xceed Support
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    We support Winzip AES encryption. Even with the Blueprint edition, you cannot modify the AES encryption algorithm that we are using.

    You should contact PKWare’s support as it is their issue.

    Imported from legacy forums. Posted by CharlesB (had 5538 views)

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