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source: trunk/HeuristicLab.ExtLibs/HeuristicLab.EPPlus/4.0.3/EPPlus-4.0.3/Packaging/DotNetZip/EncryptionAlgorithm.cs @ 18191

Last change on this file since 18191 was 12074, checked in by sraggl, 10 years ago

#2341: Added EPPlus-4.0.3 to ExtLibs

File size: 5.3 KB
Line 
1// EncryptionAlgorithm.cs
2// ------------------------------------------------------------------
3//
4// Copyright (c)  2009 Dino Chiesa
5// All rights reserved.
6//
7// This code module is part of DotNetZip, a zipfile class library.
8//
9// ------------------------------------------------------------------
10//
11// This code is licensed under the Microsoft Public License.
12// See the file License.txt for the license details.
13// More info on: http://dotnetzip.codeplex.com
14//
15// ------------------------------------------------------------------
16//
17// last saved (in emacs):
18// Time-stamp: <2009-October-21 17:24:45>
19//
20// ------------------------------------------------------------------
21//
22// This module defines the EncryptionAgorithm enum
23//
24//
25// ------------------------------------------------------------------
26
27
28namespace OfficeOpenXml.Packaging.Ionic.Zip
29{
30    /// <summary>
31    /// An enum that provides the various encryption algorithms supported by this
32    /// library.
33    /// </summary>
34    ///
35    /// <remarks>
36    ///
37    /// <para>
38    ///   <c>PkzipWeak</c> implies the use of Zip 2.0 encryption, which is known to be
39    ///   weak and subvertible.
40    /// </para>
41    ///
42    /// <para>
43    ///   A note on interoperability: Values of <c>PkzipWeak</c> and <c>None</c> are
44    ///   specified in <see
45    ///   href="http://www.pkware.com/documents/casestudies/APPNOTE.TXT">PKWARE's zip
46    ///   specification</see>, and are considered to be "standard".  Zip archives
47    ///   produced using these options will be interoperable with many other zip tools
48    ///   and libraries, including Windows Explorer.
49    /// </para>
50    ///
51    /// <para>
52    ///   Values of <c>WinZipAes128</c> and <c>WinZipAes256</c> are not part of the Zip
53    ///   specification, but rather imply the use of a vendor-specific extension from
54    ///   WinZip. If you want to produce interoperable Zip archives, do not use these
55    ///   values.  For example, if you produce a zip archive using WinZipAes256, you
56    ///   will be able to open it in Windows Explorer on Windows XP and Vista, but you
57    ///   will not be able to extract entries; trying this will lead to an "unspecified
58    ///   error". For this reason, some people have said that a zip archive that uses
59    ///   WinZip's AES encryption is not actually a zip archive at all.  A zip archive
60    ///   produced this way will be readable with the WinZip tool (Version 11 and
61    ///   beyond).
62    /// </para>
63    ///
64    /// <para>
65    ///   There are other third-party tools and libraries, both commercial and
66    ///   otherwise, that support WinZip's AES encryption. These will be able to read
67    ///   AES-encrypted zip archives produced by DotNetZip, and conversely applications
68    ///   that use DotNetZip to read zip archives will be able to read AES-encrypted
69    ///   archives produced by those tools or libraries.  Consult the documentation for
70    ///   those other tools and libraries to find out if WinZip's AES encryption is
71    ///   supported.
72    /// </para>
73    ///
74    /// <para>
75    ///   In case you care: According to <see
76    ///   href="http://www.winzip.com/aes_info.htm">the WinZip specification</see>, the
77    ///   actual AES key used is derived from the <see cref="ZipEntry.Password"/> via an
78    ///   algorithm that complies with <see
79    ///   href="http://www.ietf.org/rfc/rfc2898.txt">RFC 2898</see>, using an iteration
80    ///   count of 1000.  The algorithm is sometimes referred to as PBKDF2, which stands
81    ///   for "Password Based Key Derivation Function #2".
82    /// </para>
83    ///
84    /// <para>
85    ///   A word about password strength and length: The AES encryption technology is
86    ///   very good, but any system is only as secure as the weakest link.  If you want
87    ///   to secure your data, be sure to use a password that is hard to guess.  To make
88    ///   it harder to guess (increase its "entropy"), you should make it longer.  If
89    ///   you use normal characters from an ASCII keyboard, a password of length 20 will
90    ///   be strong enough that it will be impossible to guess.  For more information on
91    ///   that, I'd encourage you to read <see
92    ///   href="http://www.redkestrel.co.uk/Articles/RandomPasswordStrength.html">this
93    ///   article.</see>
94    /// </para>
95    ///
96    /// <para>
97    ///   The WinZip AES algorithms are not supported with the version of DotNetZip that
98    ///   runs on the .NET Compact Framework.  This is because .NET CF lacks the
99    ///   HMACSHA1 class that is required for producing the archive.
100    /// </para>
101    /// </remarks>
102    internal enum EncryptionAlgorithm
103    {
104        /// <summary>
105        /// No encryption at all.
106        /// </summary>
107        None = 0,
108
109        /// <summary>
110        /// Traditional or Classic pkzip encryption.
111        /// </summary>
112        PkzipWeak,
113
114#if AESCRYPTO
115        /// <summary>
116        /// WinZip AES encryption (128 key bits).
117        /// </summary>
118        WinZipAes128,
119
120        /// <summary>
121        /// WinZip AES encryption (256 key bits).
122        /// </summary>
123        WinZipAes256,
124#endif
125
126        /// <summary>
127        /// An encryption algorithm that is not supported by DotNetZip.
128        /// </summary>
129        Unsupported = 4,
130
131
132        // others... not implemented (yet?)
133    }
134
135}
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