1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
|
<?xml version="1.0" encoding="ascii"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<title>Crypto.Cipher.DES</title>
<link rel="stylesheet" href="epydoc.css" type="text/css" />
<script type="text/javascript" src="epydoc.js"></script>
</head>
<body bgcolor="white" text="black" link="blue" vlink="#204080"
alink="#204080">
<!-- ==================== NAVIGATION BAR ==================== -->
<table class="navbar" border="0" width="100%" cellpadding="0"
bgcolor="#a0c0ff" cellspacing="0">
<tr valign="middle">
<!-- Home link -->
<th> <a
href="Crypto-module.html">Home</a> </th>
<!-- Tree link -->
<th> <a
href="module-tree.html">Trees</a> </th>
<!-- Index link -->
<th> <a
href="identifier-index.html">Indices</a> </th>
<!-- Help link -->
<th> <a
href="help.html">Help</a> </th>
<!-- Project homepage -->
<th class="navbar" align="right" width="100%">
<table border="0" cellpadding="0" cellspacing="0">
<tr><th class="navbar" align="center"
><a href="http://www.pycrypto.org/">PyCrypto.org</a></th>
</tr></table></th>
</tr>
</table>
<table width="100%" cellpadding="0" cellspacing="0">
<tr valign="top">
<td width="100%">
<span class="breadcrumbs">
<a href="Crypto-module.html">Package Crypto</a> ::
<a href="Crypto.Cipher-module.html">Package Cipher</a> ::
Module DES
</span>
</td>
<td>
<table cellpadding="0" cellspacing="0">
<!-- hide/show private -->
<tr><td align="right"><span class="options"
>[<a href="frames.html" target="_top">frames</a
>] | <a href="Crypto.Cipher.DES-module.html"
target="_top">no frames</a>]</span></td></tr>
</table>
</td>
</tr>
</table>
<!-- ==================== MODULE DESCRIPTION ==================== -->
<h1 class="epydoc">Module DES</h1><p class="nomargin-top"></p>
<p>DES symmetric cipher</p>
<p>DES <a class="rst-reference external" href="http://en.wikipedia.org/wiki/Data_Encryption_Standard" target="_top">(Data Encryption Standard)</a> is a symmetric block cipher standardized
by <a class="rst-reference external" href="http://csrc.nist.gov/publications/fips/fips46-3/fips46-3.pdf" target="_top">NIST</a> . It has a fixed data block size of 8 bytes.
Its keys are 64 bits long, even though 8 bits were used for integrity (now they
are ignored) and do not contribute to securty.</p>
<p>DES is cryptographically secure, but its key length is too short by nowadays
standards and it could be brute forced with some effort.</p>
<p>DES should not be used for new designs. Use <a href="Crypto.Cipher.AES-module.html" class="link">AES</a>.</p>
<p>As an example, encryption can be done as follows:</p>
<blockquote>
<pre class="py-doctest">
<span class="py-prompt">>>> </span><span class="py-keyword">from</span> Crypto.Cipher <span class="py-keyword">import</span> DES3
<span class="py-prompt">>>> </span><span class="py-keyword">from</span> Crypto <span class="py-keyword">import</span> Random
<span class="py-prompt">>>></span>
<span class="py-prompt">>>> </span>key = b<span class="py-string">'Sixteen byte key'</span>
<span class="py-prompt">>>> </span>iv = Random.new().read(DES3.block_size)
<span class="py-prompt">>>> </span>cipher = DES3.new(key, DES3.MODE_OFB, iv)
<span class="py-prompt">>>> </span>plaintext = b<span class="py-string">'sona si latine loqueris '</span>
<span class="py-prompt">>>> </span>msg = iv + cipher.encrypt(plaintext)</pre>
</blockquote>
<!-- ==================== CLASSES ==================== -->
<a name="section-Classes"></a>
<table class="summary" border="1" cellpadding="3"
cellspacing="0" width="100%" bgcolor="white">
<tr bgcolor="#70b0f0" class="table-header">
<td align="left" colspan="2" class="table-header">
<span class="table-header">Classes</span></td>
</tr>
<tr>
<td width="15%" align="right" valign="top" class="summary">
<span class="summary-type"> </span>
</td><td class="summary">
<a href="Crypto.Cipher.DES.DESCipher-class.html" class="summary-name">DESCipher</a><br />
DES cipher object
</td>
</tr>
</table>
<!-- ==================== FUNCTIONS ==================== -->
<a name="section-Functions"></a>
<table class="summary" border="1" cellpadding="3"
cellspacing="0" width="100%" bgcolor="white">
<tr bgcolor="#70b0f0" class="table-header">
<td align="left" colspan="2" class="table-header">
<span class="table-header">Functions</span></td>
</tr>
<tr>
<td width="15%" align="right" valign="top" class="summary">
<span class="summary-type"> </span>
</td><td class="summary">
<table width="100%" cellpadding="0" cellspacing="0" border="0">
<tr>
<td><span class="summary-sig"><a href="Crypto.Cipher.DES-module.html#new" class="summary-sig-name">new</a>(<span class="summary-sig-arg">key</span>,
<span class="summary-sig-arg">*args</span>,
<span class="summary-sig-arg">**kwargs</span>)</span><br />
Create a new DES cipher</td>
<td align="right" valign="top">
</td>
</tr>
</table>
</td>
</tr>
</table>
<!-- ==================== VARIABLES ==================== -->
<a name="section-Variables"></a>
<table class="summary" border="1" cellpadding="3"
cellspacing="0" width="100%" bgcolor="white">
<tr bgcolor="#70b0f0" class="table-header">
<td align="left" colspan="2" class="table-header">
<span class="table-header">Variables</span></td>
</tr>
<tr>
<td width="15%" align="right" valign="top" class="summary">
<span class="summary-type"> </span>
</td><td class="summary">
<a name="MODE_ECB"></a><span class="summary-name">MODE_ECB</span> = <code title="1">1</code><br />
Electronic Code Book (ECB). See <a href="Crypto.Cipher.blockalgo-module.html#MODE_ECB" class="link">blockalgo.MODE_ECB</a>.
</td>
</tr>
<tr>
<td width="15%" align="right" valign="top" class="summary">
<span class="summary-type"> </span>
</td><td class="summary">
<a name="MODE_CBC"></a><span class="summary-name">MODE_CBC</span> = <code title="2">2</code><br />
Cipher-Block Chaining (CBC). See <a href="Crypto.Cipher.blockalgo-module.html#MODE_CBC" class="link">blockalgo.MODE_CBC</a>.
</td>
</tr>
<tr>
<td width="15%" align="right" valign="top" class="summary">
<span class="summary-type"> </span>
</td><td class="summary">
<a name="MODE_CFB"></a><span class="summary-name">MODE_CFB</span> = <code title="3">3</code><br />
Cipher FeedBack (CFB). See <a href="Crypto.Cipher.blockalgo-module.html#MODE_CFB" class="link">blockalgo.MODE_CFB</a>.
</td>
</tr>
<tr>
<td width="15%" align="right" valign="top" class="summary">
<span class="summary-type"> </span>
</td><td class="summary">
<a name="MODE_PGP"></a><span class="summary-name">MODE_PGP</span> = <code title="4">4</code><br />
This mode should not be used.
</td>
</tr>
<tr>
<td width="15%" align="right" valign="top" class="summary">
<span class="summary-type"> </span>
</td><td class="summary">
<a name="MODE_OFB"></a><span class="summary-name">MODE_OFB</span> = <code title="5">5</code><br />
Output FeedBack (OFB). See <a href="Crypto.Cipher.blockalgo-module.html#MODE_OFB" class="link">blockalgo.MODE_OFB</a>.
</td>
</tr>
<tr>
<td width="15%" align="right" valign="top" class="summary">
<span class="summary-type"> </span>
</td><td class="summary">
<a name="MODE_CTR"></a><span class="summary-name">MODE_CTR</span> = <code title="6">6</code><br />
CounTer Mode (CTR). See <a href="Crypto.Cipher.blockalgo-module.html#MODE_CTR" class="link">blockalgo.MODE_CTR</a>.
</td>
</tr>
<tr>
<td width="15%" align="right" valign="top" class="summary">
<span class="summary-type"> </span>
</td><td class="summary">
<a name="MODE_OPENPGP"></a><span class="summary-name">MODE_OPENPGP</span> = <code title="7">7</code><br />
OpenPGP Mode. See <a href="Crypto.Cipher.blockalgo-module.html#MODE_OPENPGP" class="link">blockalgo.MODE_OPENPGP</a>.
</td>
</tr>
<tr>
<td width="15%" align="right" valign="top" class="summary">
<span class="summary-type"> </span>
</td><td class="summary">
<a name="block_size"></a><span class="summary-name">block_size</span> = <code title="8">8</code><br />
Size of a data block (in bytes)
</td>
</tr>
<tr>
<td width="15%" align="right" valign="top" class="summary">
<span class="summary-type"> </span>
</td><td class="summary">
<a name="key_size"></a><span class="summary-name">key_size</span> = <code title="8">8</code><br />
Size of a key (in bytes)
</td>
</tr>
</table>
<!-- ==================== FUNCTION DETAILS ==================== -->
<a name="section-FunctionDetails"></a>
<table class="details" border="1" cellpadding="3"
cellspacing="0" width="100%" bgcolor="white">
<tr bgcolor="#70b0f0" class="table-header">
<td align="left" colspan="2" class="table-header">
<span class="table-header">Function Details</span></td>
</tr>
</table>
<a name="new"></a>
<div>
<table class="details" border="1" cellpadding="3"
cellspacing="0" width="100%" bgcolor="white">
<tr><td>
<table width="100%" cellpadding="0" cellspacing="0" border="0">
<tr valign="top"><td>
<h3 class="epydoc"><span class="sig"><span class="sig-name">new</span>(<span class="sig-arg">key</span>,
<span class="sig-arg">*args</span>,
<span class="sig-arg">**kwargs</span>)</span>
</h3>
</td><td align="right" valign="top"
>
</td>
</tr></table>
Create a new DES cipher
<dl class="fields">
<dt>Parameters:</dt>
<dd><ul class="nomargin-top">
<li><strong class="pname"><code>key</code></strong> (byte string) - The secret key to use in the symmetric cipher.
It must be 8 byte long. The parity bits will be ignored.</li>
<li><strong class="pname"><code>mode</code></strong> (a <em>MODE_*</em> constant) - The chaining mode to use for encryption or decryption.
Default is <a href="Crypto.Cipher.DES-module.html#MODE_ECB" class="link">MODE_ECB</a>.</li>
<li><p><strong class="pname"><code>IV</code></strong> (byte string) - The initialization vector to use for encryption or decryption.</p>
<p>It is ignored for <a href="Crypto.Cipher.DES-module.html#MODE_ECB" class="link">MODE_ECB</a> and <a href="Crypto.Cipher.DES-module.html#MODE_CTR" class="link">MODE_CTR</a>.</p>
<p>For <a href="Crypto.Cipher.DES-module.html#MODE_OPENPGP" class="link">MODE_OPENPGP</a>, IV must be <a href="Crypto.Cipher.DES-module.html#block_size" class="link">block_size</a> bytes long for encryption
and <a href="Crypto.Cipher.DES-module.html#block_size" class="link">block_size</a> +2 bytes for decryption (in the latter case, it is
actually the <em>encrypted</em> IV which was prefixed to the ciphertext).
It is mandatory.</p>
<p>For all other modes, it must be <a href="Crypto.Cipher.DES-module.html#block_size" class="link">block_size</a> bytes longs. It is optional and
when not present it will be given a default value of all zeroes.</p></li>
<li><strong class="pname"><code>counter</code></strong> (callable) - (<em>Only</em> <a href="Crypto.Cipher.DES-module.html#MODE_CTR" class="link">MODE_CTR</a>). A stateful function that returns the next
<em>counter block</em>, which is a byte string of <a href="Crypto.Cipher.DES-module.html#block_size" class="link">block_size</a> bytes.
For better performance, use <a href="Crypto.Util.Counter-module.html" class="link" onclick="show_private();">Crypto.Util.Counter</a>.</li>
<li><strong class="pname"><code>segment_size</code></strong> (integer) - (<em>Only</em> <a href="Crypto.Cipher.DES-module.html#MODE_CFB" class="link">MODE_CFB</a>).The number of bits the plaintext and ciphertext
are segmented in.
It must be a multiple of 8. If 0 or not specified, it will be assumed to be 8.</li>
</ul></dd>
<dt>Returns:</dt>
<dd>an <a href="Crypto.Cipher.DES.DESCipher-class.html" class="link">DESCipher</a> object</dd>
</dl>
</td></tr></table>
</div>
<br />
<!-- ==================== NAVIGATION BAR ==================== -->
<table class="navbar" border="0" width="100%" cellpadding="0"
bgcolor="#a0c0ff" cellspacing="0">
<tr valign="middle">
<!-- Home link -->
<th> <a
href="Crypto-module.html">Home</a> </th>
<!-- Tree link -->
<th> <a
href="module-tree.html">Trees</a> </th>
<!-- Index link -->
<th> <a
href="identifier-index.html">Indices</a> </th>
<!-- Help link -->
<th> <a
href="help.html">Help</a> </th>
<!-- Project homepage -->
<th class="navbar" align="right" width="100%">
<table border="0" cellpadding="0" cellspacing="0">
<tr><th class="navbar" align="center"
><a href="http://www.pycrypto.org/">PyCrypto.org</a></th>
</tr></table></th>
</tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" width="100%%">
<tr>
<td align="left" class="footer">
Generated by Epydoc 3.0.1 on Thu May 24 09:02:36 2012
</td>
<td align="right" class="footer">
<a target="mainFrame" href="http://epydoc.sourceforge.net"
>http://epydoc.sourceforge.net</a>
</td>
</tr>
</table>
<script type="text/javascript">
<!--
// Private objects are initially displayed (because if
// javascript is turned off then we want them to be
// visible); but by default, we want to hide them. So hide
// them unless we have a cookie that says to show them.
checkCookie();
// -->
</script>
</body>
</html>
|
