[12074] | 1 | // EncryptionAlgorithm.cs
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| 2 | // ------------------------------------------------------------------
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| 3 | //
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| 4 | // Copyright (c) 2009 Dino Chiesa
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| 5 | // All rights reserved.
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| 6 | //
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| 7 | // This code module is part of DotNetZip, a zipfile class library.
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| 8 | //
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| 9 | // ------------------------------------------------------------------
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| 10 | //
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| 11 | // This code is licensed under the Microsoft Public License.
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| 12 | // See the file License.txt for the license details.
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| 13 | // More info on: http://dotnetzip.codeplex.com
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| 14 | //
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| 15 | // ------------------------------------------------------------------
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| 16 | //
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| 17 | // last saved (in emacs):
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| 18 | // Time-stamp: <2009-October-21 17:24:45>
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| 19 | //
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| 20 | // ------------------------------------------------------------------
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| 21 | //
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| 22 | // This module defines the EncryptionAgorithm enum
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| 23 | //
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| 24 | //
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| 25 | // ------------------------------------------------------------------
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| 26 |
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| 27 |
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| 28 | namespace OfficeOpenXml.Packaging.Ionic.Zip
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| 29 | {
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| 30 | /// <summary>
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| 31 | /// An enum that provides the various encryption algorithms supported by this
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| 32 | /// library.
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| 33 | /// </summary>
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| 34 | ///
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| 35 | /// <remarks>
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| 36 | ///
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| 37 | /// <para>
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| 38 | /// <c>PkzipWeak</c> implies the use of Zip 2.0 encryption, which is known to be
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| 39 | /// weak and subvertible.
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| 40 | /// </para>
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| 41 | ///
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| 42 | /// <para>
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| 43 | /// A note on interoperability: Values of <c>PkzipWeak</c> and <c>None</c> are
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| 44 | /// specified in <see
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| 45 | /// href="http://www.pkware.com/documents/casestudies/APPNOTE.TXT">PKWARE's zip
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| 46 | /// specification</see>, and are considered to be "standard". Zip archives
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| 47 | /// produced using these options will be interoperable with many other zip tools
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| 48 | /// and libraries, including Windows Explorer.
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| 49 | /// </para>
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| 50 | ///
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| 51 | /// <para>
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| 52 | /// Values of <c>WinZipAes128</c> and <c>WinZipAes256</c> are not part of the Zip
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| 53 | /// specification, but rather imply the use of a vendor-specific extension from
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| 54 | /// WinZip. If you want to produce interoperable Zip archives, do not use these
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| 55 | /// values. For example, if you produce a zip archive using WinZipAes256, you
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| 56 | /// will be able to open it in Windows Explorer on Windows XP and Vista, but you
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| 57 | /// will not be able to extract entries; trying this will lead to an "unspecified
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| 58 | /// error". For this reason, some people have said that a zip archive that uses
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| 59 | /// WinZip's AES encryption is not actually a zip archive at all. A zip archive
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| 60 | /// produced this way will be readable with the WinZip tool (Version 11 and
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| 61 | /// beyond).
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| 62 | /// </para>
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| 63 | ///
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| 64 | /// <para>
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| 65 | /// There are other third-party tools and libraries, both commercial and
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| 66 | /// otherwise, that support WinZip's AES encryption. These will be able to read
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| 67 | /// AES-encrypted zip archives produced by DotNetZip, and conversely applications
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| 68 | /// that use DotNetZip to read zip archives will be able to read AES-encrypted
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| 69 | /// archives produced by those tools or libraries. Consult the documentation for
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| 70 | /// those other tools and libraries to find out if WinZip's AES encryption is
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| 71 | /// supported.
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| 72 | /// </para>
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| 73 | ///
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| 74 | /// <para>
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| 75 | /// In case you care: According to <see
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| 76 | /// href="http://www.winzip.com/aes_info.htm">the WinZip specification</see>, the
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| 77 | /// actual AES key used is derived from the <see cref="ZipEntry.Password"/> via an
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| 78 | /// algorithm that complies with <see
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| 79 | /// href="http://www.ietf.org/rfc/rfc2898.txt">RFC 2898</see>, using an iteration
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| 80 | /// count of 1000. The algorithm is sometimes referred to as PBKDF2, which stands
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| 81 | /// for "Password Based Key Derivation Function #2".
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| 82 | /// </para>
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| 83 | ///
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| 84 | /// <para>
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| 85 | /// A word about password strength and length: The AES encryption technology is
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| 86 | /// very good, but any system is only as secure as the weakest link. If you want
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| 87 | /// to secure your data, be sure to use a password that is hard to guess. To make
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| 88 | /// it harder to guess (increase its "entropy"), you should make it longer. If
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| 89 | /// you use normal characters from an ASCII keyboard, a password of length 20 will
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| 90 | /// be strong enough that it will be impossible to guess. For more information on
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| 91 | /// that, I'd encourage you to read <see
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| 92 | /// href="http://www.redkestrel.co.uk/Articles/RandomPasswordStrength.html">this
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| 93 | /// article.</see>
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| 94 | /// </para>
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| 95 | ///
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| 96 | /// <para>
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| 97 | /// The WinZip AES algorithms are not supported with the version of DotNetZip that
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| 98 | /// runs on the .NET Compact Framework. This is because .NET CF lacks the
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| 99 | /// HMACSHA1 class that is required for producing the archive.
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| 100 | /// </para>
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| 101 | /// </remarks>
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| 102 | internal enum EncryptionAlgorithm
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| 103 | {
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| 104 | /// <summary>
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| 105 | /// No encryption at all.
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| 106 | /// </summary>
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| 107 | None = 0,
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| 108 |
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| 109 | /// <summary>
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| 110 | /// Traditional or Classic pkzip encryption.
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| 111 | /// </summary>
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| 112 | PkzipWeak,
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| 113 |
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| 114 | #if AESCRYPTO
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| 115 | /// <summary>
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| 116 | /// WinZip AES encryption (128 key bits).
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| 117 | /// </summary>
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| 118 | WinZipAes128,
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| 119 |
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| 120 | /// <summary>
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| 121 | /// WinZip AES encryption (256 key bits).
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| 122 | /// </summary>
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| 123 | WinZipAes256,
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| 124 | #endif
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| 125 |
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| 126 | /// <summary>
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| 127 | /// An encryption algorithm that is not supported by DotNetZip.
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| 128 | /// </summary>
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| 129 | Unsupported = 4,
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| 130 |
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| 131 |
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| 132 | // others... not implemented (yet?)
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| 133 | }
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| 134 |
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| 135 | }
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