// EncryptionAlgorithm.cs
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// ------------------------------------------------------------------
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//
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// Copyright (c) 2009 Dino Chiesa
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// All rights reserved.
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//
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// This code module is part of DotNetZip, a zipfile class library.
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//
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// ------------------------------------------------------------------
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//
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// This code is licensed under the Microsoft Public License.
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// See the file License.txt for the license details.
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// More info on: http://dotnetzip.codeplex.com
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//
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// ------------------------------------------------------------------
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//
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// last saved (in emacs):
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// Time-stamp: <2009-October-21 17:24:45>
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//
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// ------------------------------------------------------------------
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//
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// This module defines the EncryptionAgorithm enum
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//
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//
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// ------------------------------------------------------------------
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namespace HH.WMS.Utils.Ionic.Zip
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{
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/// <summary>
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/// An enum that provides the various encryption algorithms supported by this
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/// library.
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/// </summary>
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///
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/// <remarks>
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///
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/// <para>
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/// <c>PkzipWeak</c> implies the use of Zip 2.0 encryption, which is known to be
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/// weak and subvertible.
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/// </para>
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///
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/// <para>
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/// A note on interoperability: Values of <c>PkzipWeak</c> and <c>None</c> are
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/// specified in <see
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/// href="http://www.pkware.com/documents/casestudies/APPNOTE.TXT">PKWARE's zip
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/// specification</see>, and are considered to be "standard". Zip archives
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/// produced using these options will be interoperable with many other zip tools
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/// and libraries, including Windows Explorer.
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/// </para>
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///
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/// <para>
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/// Values of <c>WinZipAes128</c> and <c>WinZipAes256</c> are not part of the Zip
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/// specification, but rather imply the use of a vendor-specific extension from
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/// WinZip. If you want to produce interoperable Zip archives, do not use these
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/// values. For example, if you produce a zip archive using WinZipAes256, you
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/// will be able to open it in Windows Explorer on Windows XP and Vista, but you
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/// will not be able to extract entries; trying this will lead to an "unspecified
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/// error". For this reason, some people have said that a zip archive that uses
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/// WinZip's AES encryption is not actually a zip archive at all. A zip archive
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/// produced this way will be readable with the WinZip tool (Version 11 and
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/// beyond).
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/// </para>
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///
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/// <para>
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/// There are other third-party tools and libraries, both commercial and
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/// otherwise, that support WinZip's AES encryption. These will be able to read
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/// AES-encrypted zip archives produced by DotNetZip, and conversely applications
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/// that use DotNetZip to read zip archives will be able to read AES-encrypted
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/// archives produced by those tools or libraries. Consult the documentation for
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/// those other tools and libraries to find out if WinZip's AES encryption is
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/// supported.
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/// </para>
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///
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/// <para>
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/// In case you care: According to <see
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/// href="http://www.winzip.com/aes_info.htm">the WinZip specification</see>, the
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/// actual AES key used is derived from the <see cref="ZipEntry.Password"/> via an
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/// algorithm that complies with <see
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/// href="http://www.ietf.org/rfc/rfc2898.txt">RFC 2898</see>, using an iteration
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/// count of 1000. The algorithm is sometimes referred to as PBKDF2, which stands
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/// for "Password Based Key Derivation Function #2".
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/// </para>
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///
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/// <para>
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/// A word about password strength and length: The AES encryption technology is
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/// very good, but any system is only as secure as the weakest link. If you want
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/// to secure your data, be sure to use a password that is hard to guess. To make
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/// it harder to guess (increase its "entropy"), you should make it longer. If
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/// you use normal characters from an ASCII keyboard, a password of length 20 will
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/// be strong enough that it will be impossible to guess. For more information on
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/// that, I'd encourage you to read <see
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/// href="http://www.redkestrel.co.uk/Articles/RandomPasswordStrength.html">this
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/// article.</see>
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/// </para>
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///
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/// <para>
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/// The WinZip AES algorithms are not supported with the version of DotNetZip that
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/// runs on the .NET Compact Framework. This is because .NET CF lacks the
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/// HMACSHA1 class that is required for producing the archive.
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/// </para>
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/// </remarks>
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public enum EncryptionAlgorithm
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{
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/// <summary>
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/// No encryption at all.
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/// </summary>
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None = 0,
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/// <summary>
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/// Traditional or Classic pkzip encryption.
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/// </summary>
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PkzipWeak,
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#if AESCRYPTO
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/// <summary>
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/// WinZip AES encryption (128 key bits).
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/// </summary>
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WinZipAes128,
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/// <summary>
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/// WinZip AES encryption (256 key bits).
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/// </summary>
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WinZipAes256,
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#endif
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/// <summary>
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/// An encryption algorithm that is not supported by DotNetZip.
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/// </summary>
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Unsupported = 4,
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// others... not implemented (yet?)
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}
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}
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