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17 | <title>15.2 md5 -- MD5 message digest algorithm</title> | |
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55 | <H1><A NAME="SECTION0017200000000000000000"> | |
56 | 15.2 <tt class="module">md5</tt> -- | |
57 | MD5 message digest algorithm</A> | |
58 | </H1> | |
59 | ||
60 | <P> | |
61 | <A NAME="module-md5"></A> | |
62 | ||
63 | <P> | |
64 | This module implements the interface to RSA's MD5 message digest | |
65 | <a id='l2h-4820' xml:id='l2h-4820'></a> | |
66 | algorithm (see also Internet <a class="rfc" id='rfcref-92073' xml:id='rfcref-92073' | |
67 | href="http://www.faqs.org/rfcs/rfc1321.html">RFC 1321</a>). Its use is quite | |
68 | straightforward: use <tt class="function">new()</tt> to create an md5 object. | |
69 | You can now feed this object with arbitrary strings using the | |
70 | <tt class="method">update()</tt> method, and at any point you can ask it for the | |
71 | <i class="dfn">digest</i> (a strong kind of 128-bit checksum, | |
72 | a.k.a. ``fingerprint'') of the concatenation of the strings fed to it | |
73 | so far using the <tt class="method">digest()</tt> method. | |
74 | <a id='l2h-4821' xml:id='l2h-4821'></a> | |
75 | ||
76 | <P> | |
77 | For example, to obtain the digest of the string <code>'Nobody inspects | |
78 | the spammish repetition'</code>: | |
79 | ||
80 | <P> | |
81 | <div class="verbatim"><pre> | |
82 | >>> import md5 | |
83 | >>> m = md5.new() | |
84 | >>> m.update("Nobody inspects") | |
85 | >>> m.update(" the spammish repetition") | |
86 | >>> m.digest() | |
87 | '\xbbd\x9c\x83\xdd\x1e\xa5\xc9\xd9\xde\xc9\xa1\x8d\xf0\xff\xe9' | |
88 | </pre></div> | |
89 | ||
90 | <P> | |
91 | More condensed: | |
92 | ||
93 | <P> | |
94 | <div class="verbatim"><pre> | |
95 | >>> md5.new("Nobody inspects the spammish repetition").digest() | |
96 | '\xbbd\x9c\x83\xdd\x1e\xa5\xc9\xd9\xde\xc9\xa1\x8d\xf0\xff\xe9' | |
97 | </pre></div> | |
98 | ||
99 | <P> | |
100 | The following values are provided as constants in the module and as | |
101 | attributes of the md5 objects returned by <tt class="function">new()</tt>: | |
102 | ||
103 | <P> | |
104 | <dl><dt><b><tt id='l2h-4813' xml:id='l2h-4813'>digest_size</tt></b></dt> | |
105 | <dd> | |
106 | The size of the resulting digest in bytes. This is always | |
107 | <code>16</code>. | |
108 | </dd></dl> | |
109 | ||
110 | <P> | |
111 | md5 objects support the following methods: | |
112 | ||
113 | <P> | |
114 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
115 | <td><nobr><b><tt id='l2h-4814' xml:id='l2h-4814' class="function">new</tt></b>(</nobr></td> | |
116 | <td><var></var><big>[</big><var>arg</var><big>]</big><var></var>)</td></tr></table></dt> | |
117 | <dd> | |
118 | Return a new md5 object. If <var>arg</var> is present, the method call | |
119 | <code>update(<var>arg</var>)</code> is made. | |
120 | </dl> | |
121 | ||
122 | <P> | |
123 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
124 | <td><nobr><b><tt id='l2h-4815' xml:id='l2h-4815' class="function">md5</tt></b>(</nobr></td> | |
125 | <td><var></var><big>[</big><var>arg</var><big>]</big><var></var>)</td></tr></table></dt> | |
126 | <dd> | |
127 | For backward compatibility reasons, this is an alternative name for the | |
128 | <tt class="function">new()</tt> function. | |
129 | </dl> | |
130 | ||
131 | <P> | |
132 | An md5 object has the following methods: | |
133 | ||
134 | <P> | |
135 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
136 | <td><nobr><b><tt id='l2h-4816' xml:id='l2h-4816' class="method">update</tt></b>(</nobr></td> | |
137 | <td><var>arg</var>)</td></tr></table></dt> | |
138 | <dd> | |
139 | Update the md5 object with the string <var>arg</var>. Repeated calls are | |
140 | equivalent to a single call with the concatenation of all the | |
141 | arguments: <code>m.update(a); m.update(b)</code> is equivalent to | |
142 | <code>m.update(a+b)</code>. | |
143 | </dl> | |
144 | ||
145 | <P> | |
146 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
147 | <td><nobr><b><tt id='l2h-4817' xml:id='l2h-4817' class="method">digest</tt></b>(</nobr></td> | |
148 | <td><var></var>)</td></tr></table></dt> | |
149 | <dd> | |
150 | Return the digest of the strings passed to the <tt class="method">update()</tt> | |
151 | method so far. This is a 16-byte string which may contain | |
152 | non-ASCII characters, including null bytes. | |
153 | </dl> | |
154 | ||
155 | <P> | |
156 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
157 | <td><nobr><b><tt id='l2h-4818' xml:id='l2h-4818' class="method">hexdigest</tt></b>(</nobr></td> | |
158 | <td><var></var>)</td></tr></table></dt> | |
159 | <dd> | |
160 | Like <tt class="method">digest()</tt> except the digest is returned as a string of | |
161 | length 32, containing only hexadecimal digits. This may | |
162 | be used to exchange the value safely in email or other non-binary | |
163 | environments. | |
164 | </dl> | |
165 | ||
166 | <P> | |
167 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
168 | <td><nobr><b><tt id='l2h-4819' xml:id='l2h-4819' class="method">copy</tt></b>(</nobr></td> | |
169 | <td><var></var>)</td></tr></table></dt> | |
170 | <dd> | |
171 | Return a copy (``clone'') of the md5 object. This can be used to | |
172 | efficiently compute the digests of strings that share a common initial | |
173 | substring. | |
174 | </dl> | |
175 | ||
176 | <P> | |
177 | <div class="seealso"> | |
178 | <p class="heading">See Also:</p> | |
179 | ||
180 | <dl compact="compact" class="seemodule"> | |
181 | <dt>Module <b><tt class="module"><a href="module-sha.html">sha</a></tt>:</b> | |
182 | <dd>Similar module implementing the Secure Hash | |
183 | Algorithm (SHA). The SHA algorithm is considered a | |
184 | more secure hash. | |
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