mingw/html/lib/Digest/MD5.html

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  13 <big><strong><span class="block">&nbsp;Digest::MD5 - Perl interface to the MD5 Algorithm</span></strong></big>
  14 </td></tr>
  15 </table>
  16
  17 <p><a name="__index__"></a></p>
  18 <!-- INDEX BEGIN -->
  19
  20 <ul>
  21
  22         <li><a href="#name">NAME</a></li>
  23         <li><a href="#synopsis">SYNOPSIS</a></li>
  24         <li><a href="#description">DESCRIPTION</a></li>
  25         <li><a href="#functions">FUNCTIONS</a></li>
  26         <li><a href="#methods">METHODS</a></li>
  27         <li><a href="#examples">EXAMPLES</a></li>
  28         <li><a href="#see_also">SEE ALSO</a></li>
  29         <li><a href="#copyright">COPYRIGHT</a></li>
  30         <li><a href="#authors">AUTHORS</a></li>
  31 </ul>
  32 <!-- INDEX END -->
  33
  34 <hr />
  35 <p>
  36 </p>
  37 <h1><a name="name">NAME</a></h1>
  38 <p>Digest::MD5 - Perl interface to the MD5 Algorithm</p>
  39 <p>
  40 </p>
  41 <hr />
  42 <h1><a name="synopsis">SYNOPSIS</a></h1>
  43 <pre>
  44  # Functional style
  45  use Digest::MD5 qw(md5 md5_hex md5_base64);</pre>
  46 <pre>
  47  $digest = md5($data);
  48  $digest = md5_hex($data);
  49  $digest = md5_base64($data);</pre>
  50 <pre>
  51  # OO style
  52  use Digest::MD5;</pre>
  53 <pre>
  54  $ctx = Digest::MD5-&gt;new;</pre>
  55 <pre>
  56  $ctx-&gt;add($data);
  57  $ctx-&gt;addfile(*FILE);</pre>
  58 <pre>
  59  $digest = $ctx-&gt;digest;
  60  $digest = $ctx-&gt;hexdigest;
  61  $digest = $ctx-&gt;b64digest;</pre>
  62 <p>
  63 </p>
  64 <hr />
  65 <h1><a name="description">DESCRIPTION</a></h1>
  66 <p>The <code>Digest::MD5</code> module allows you to use the RSA Data Security
  67 Inc. MD5 Message Digest algorithm from within Perl programs.  The
  68 algorithm takes as input a message of arbitrary length and produces as
  69 output a 128-bit ``fingerprint'' or ``message digest'' of the input.</p>
  70 <p>Note that the MD5 algorithm is not as strong as it used to be.  It has
  71 since 2005 been easy to generate different messages that produce the
  72 same MD5 digest.  It still seems hard to generate messages that
  73 produce a given digest, but it is probably wise to move to stronger
  74 algorithms for applications that depend on the digest to uniquely identify
  75 a message.</p>
  76 <p>The <code>Digest::MD5</code> module provide a procedural interface for simple
  77 use, as well as an object oriented interface that can handle messages
  78 of arbitrary length and which can read files directly.</p>
  79 <p>
  80 </p>
  81 <hr />
  82 <h1><a name="functions">FUNCTIONS</a></h1>
  83 <p>The following functions are provided by the <code>Digest::MD5</code> module.
  84 None of these functions are exported by default.</p>
  85 <dl>
  86 <dt><strong><a name="item_md5"><code>md5($data,...)</code></a></strong>
  87
  88 <dd>
  89 <p>This function will concatenate all arguments, calculate the MD5 digest
  90 of this ``message'', and return it in binary form.  The returned string
  91 will be 16 bytes long.</p>
  92 </dd>
  93 <dd>
  94 <p>The result of md5(``a'', ``b'', ``c'') will be exactly the same as the
  95 result of md5(``abc'').</p>
  96 </dd>
  97 </li>
  98 <dt><strong><a name="item_md5_hex"><code>md5_hex($data,...)</code></a></strong>
  99
 100 <dd>
 101 <p>Same as md5(), but will return the digest in hexadecimal form. The
 102 length of the returned string will be 32 and it will only contain
 103 characters from this set: '0'..'9' and 'a'..'f'.</p>
 104 </dd>
 105 </li>
 106 <dt><strong><a name="item_md5_base64"><code>md5_base64($data,...)</code></a></strong>
 107
 108 <dd>
 109 <p>Same as md5(), but will return the digest as a base64 encoded string.
 110 The length of the returned string will be 22 and it will only contain
 111 characters from this set: 'A'..'Z', 'a'..'z', '0'..'9', '+' and
 112 '/'.</p>
 113 </dd>
 114 <dd>
 115 <p>Note that the base64 encoded string returned is not padded to be a
 116 multiple of 4 bytes long.  If you want interoperability with other
 117 base64 encoded md5 digests you might want to append the redundant
 118 string ``=='' to the result.</p>
 119 </dd>
 120 </li>
 121 </dl>
 122 <p>
 123 </p>
 124 <hr />
 125 <h1><a name="methods">METHODS</a></h1>
 126 <p>The object oriented interface to <code>Digest::MD5</code> is described in this
 127 section.  After a <code>Digest::MD5</code> object has been created, you will add
 128 data to it and finally ask for the digest in a suitable format.  A
 129 single object can be used to calculate multiple digests.</p>
 130 <p>The following methods are provided:</p>
 131 <dl>
 132 <dt><strong><a name="item_new">$md5 = Digest::MD5-&gt;new</a></strong>
 133
 134 <dd>
 135 <p>The constructor returns a new <code>Digest::MD5</code> object which encapsulate
 136 the state of the MD5 message-digest algorithm.</p>
 137 </dd>
 138 <dd>
 139 <p>If called as an instance method (i.e. $md5-&gt;new) it will just reset the
 140 state the object to the state of a newly created object.  No new
 141 object is created in this case.</p>
 142 </dd>
 143 </li>
 144 <dt><strong><a name="item_reset">$md5-&gt;reset</a></strong>
 145
 146 <dd>
 147 <p>This is just an alias for $md5-&gt;new.</p>
 148 </dd>
 149 </li>
 150 <dt><strong><a name="item_clone">$md5-&gt;clone</a></strong>
 151
 152 <dd>
 153 <p>This a copy of the $md5 object. It is useful when you do not want to
 154 destroy the digests state, but need an intermediate value of the
 155 digest, e.g. when calculating digests iteratively on a continuous data
 156 stream.  Example:</p>
 157 </dd>
 158 <dd>
 159 <pre>
 160     my $md5 = Digest::MD5-&gt;new;
 161     while (&lt;&gt;) {
 162         $md5-&gt;add($_);
 163         print &quot;Line $.: &quot;, $md5-&gt;clone-&gt;hexdigest, &quot;\n&quot;;
 164     }</pre>
 165 </dd>
 166 </li>
 167 <dt><strong><a name="item_add">$md5-&gt;<code>add($data,...)</code></a></strong>
 168
 169 <dd>
 170 <p>The $data provided as argument are appended to the message we
 171 calculate the digest for.  The return value is the $md5 object itself.</p>
 172 </dd>
 173 <dd>
 174 <p>All these lines will have the same effect on the state of the $md5
 175 object:</p>
 176 </dd>
 177 <dd>
 178 <pre>
 179     $md5-&gt;add(&quot;a&quot;); $md5-&gt;add(&quot;b&quot;); $md5-&gt;add(&quot;c&quot;);
 180     $md5-&gt;add(&quot;a&quot;)-&gt;add(&quot;b&quot;)-&gt;add(&quot;c&quot;);
 181     $md5-&gt;add(&quot;a&quot;, &quot;b&quot;, &quot;c&quot;);
 182     $md5-&gt;add(&quot;abc&quot;);</pre>
 183 </dd>
 184 </li>
 185 <dt><strong><a name="item_addfile">$md5-&gt;<code>addfile($io_handle)</code></a></strong>
 186
 187 <dd>
 188 <p>The $io_handle will be read until EOF and its content appended to the
 189 message we calculate the digest for.  The return value is the $md5
 190 object itself.</p>
 191 </dd>
 192 <dd>
 193 <p>The <a href="#item_addfile"><code>addfile()</code></a> method will <code>croak()</code> if it fails reading data for some
 194 reason.  If it croaks it is unpredictable what the state of the $md5
 195 object will be in. The <a href="#item_addfile"><code>addfile()</code></a> method might have been able to read
 196 the file partially before it failed.  It is probably wise to discard
 197 or reset the $md5 object if this occurs.</p>
 198 </dd>
 199 <dd>
 200 <p>In most cases you want to make sure that the $io_handle is in
 201 <a href="file://C|\msysgit\mingw\html/pod/perlfunc.html#item_binmode"><code>binmode</code></a> before you pass it as argument to the <a href="#item_addfile"><code>addfile()</code></a> method.</p>
 202 </dd>
 203 </li>
 204 <dt><strong><a name="item_add_bits">$md5-&gt;add_bits($data, $nbits)</a></strong>
 205
 206 <dt><strong>$md5-&gt;<code>add_bits($bitstring)</code></strong>
 207
 208 <dd>
 209 <p>Since the MD5 algorithm is byte oriented you might only add bits as
 210 multiples of 8, so you probably want to just use <a href="#item_add"><code>add()</code></a> instead.  The
 211 <a href="#item_add_bits"><code>add_bits()</code></a> method is provided for compatibility with other digest
 212 implementations.  See <a href="file://C|\msysgit\mingw\html/lib/Digest.html">the Digest manpage</a> for description of the arguments
 213 that <a href="#item_add_bits"><code>add_bits()</code></a> take.</p>
 214 </dd>
 215 </li>
 216 <dt><strong><a name="item_digest">$md5-&gt;digest</a></strong>
 217
 218 <dd>
 219 <p>Return the binary digest for the message.  The returned string will be
 220 16 bytes long.</p>
 221 </dd>
 222 <dd>
 223 <p>Note that the <a href="#item_digest"><code>digest</code></a> operation is effectively a destructive,
 224 read-once operation. Once it has been performed, the <code>Digest::MD5</code>
 225 object is automatically <a href="#item_reset"><code>reset</code></a> and can be used to calculate another
 226 digest value.  Call $md5-&gt;clone-&gt;digest if you want to calculate the
 227 digest without resetting the digest state.</p>
 228 </dd>
 229 </li>
 230 <dt><strong><a name="item_hexdigest">$md5-&gt;hexdigest</a></strong>
 231
 232 <dd>
 233 <p>Same as $md5-&gt;digest, but will return the digest in hexadecimal
 234 form. The length of the returned string will be 32 and it will only
 235 contain characters from this set: '0'..'9' and 'a'..'f'.</p>
 236 </dd>
 237 </li>
 238 <dt><strong><a name="item_b64digest">$md5-&gt;b64digest</a></strong>
 239
 240 <dd>
 241 <p>Same as $md5-&gt;digest, but will return the digest as a base64 encoded
 242 string.  The length of the returned string will be 22 and it will only
 243 contain characters from this set: 'A'..'Z', 'a'..'z', '0'..'9', '+'
 244 and '/'.</p>
 245 </dd>
 246 <dd>
 247 <p>The base64 encoded string returned is not padded to be a multiple of 4
 248 bytes long.  If you want interoperability with other base64 encoded
 249 md5 digests you might want to append the string ``=='' to the result.</p>
 250 </dd>
 251 </li>
 252 </dl>
 253 <p>
 254 </p>
 255 <hr />
 256 <h1><a name="examples">EXAMPLES</a></h1>
 257 <p>The simplest way to use this library is to import the <a href="#item_md5_hex"><code>md5_hex()</code></a>
 258 function (or one of its cousins):</p>
 259 <pre>
 260     use Digest::MD5 qw(md5_hex);
 261     print &quot;Digest is &quot;, md5_hex(&quot;foobarbaz&quot;), &quot;\n&quot;;</pre>
 262 <p>The above example would print out the message:</p>
 263 <pre>
 264     Digest is 6df23dc03f9b54cc38a0fc1483df6e21</pre>
 265 <p>The same checksum can also be calculated in OO style:</p>
 266 <pre>
 267     use Digest::MD5;
 268
 269     $md5 = Digest::MD5-&gt;new;
 270     $md5-&gt;add('foo', 'bar');
 271     $md5-&gt;add('baz');
 272     $digest = $md5-&gt;hexdigest;
 273
 274     print &quot;Digest is $digest\n&quot;;</pre>
 275 <p>With OO style you can break the message arbitrary.  This means that we
 276 are no longer limited to have space for the whole message in memory, i.e.
 277 we can handle messages of any size.</p>
 278 <p>This is useful when calculating checksum for files:</p>
 279 <pre>
 280     use Digest::MD5;</pre>
 281 <pre>
 282     my $file = shift || &quot;/etc/passwd&quot;;
 283     open(FILE, $file) or die &quot;Can't open '$file': $!&quot;;
 284     binmode(FILE);</pre>
 285 <pre>
 286     $md5 = Digest::MD5-&gt;new;
 287     while (&lt;FILE&gt;) {
 288         $md5-&gt;add($_);
 289     }
 290     close(FILE);
 291     print $md5-&gt;b64digest, &quot; $file\n&quot;;</pre>
 292 <p>Or we can use the addfile method for more efficient reading of
 293 the file:</p>
 294 <pre>
 295     use Digest::MD5;</pre>
 296 <pre>
 297     my $file = shift || &quot;/etc/passwd&quot;;
 298     open(FILE, $file) or die &quot;Can't open '$file': $!&quot;;
 299     binmode(FILE);</pre>
 300 <pre>
 301     print Digest::MD5-&gt;new-&gt;addfile(*FILE)-&gt;hexdigest, &quot; $file\n&quot;;</pre>
 302 <p>Perl 5.8 support Unicode characters in strings.  Since the MD5
 303 algorithm is only defined for strings of bytes, it can not be used on
 304 strings that contains chars with ordinal number above 255.  The MD5
 305 functions and methods will croak if you try to feed them such input
 306 data:</p>
 307 <pre>
 308     use Digest::MD5 qw(md5_hex);</pre>
 309 <pre>
 310     my $str = &quot;abc\x{300}&quot;;
 311     print md5_hex($str), &quot;\n&quot;;  # croaks
 312     # Wide character in subroutine entry</pre>
 313 <p>What you can do is calculate the MD5 checksum of the UTF-8
 314 representation of such strings.  This is achieved by filtering the
 315 string through <code>encode_utf8()</code> function:</p>
 316 <pre>
 317     use Digest::MD5 qw(md5_hex);
 318     use Encode qw(encode_utf8);</pre>
 319 <pre>
 320     my $str = &quot;abc\x{300}&quot;;
 321     print md5_hex(encode_utf8($str)), &quot;\n&quot;;
 322     # 8c2d46911f3f5a326455f0ed7a8ed3b3</pre>
 323 <p>
 324 </p>
 325 <hr />
 326 <h1><a name="see_also">SEE ALSO</a></h1>
 327 <p><a href="file://C|\msysgit\mingw\html/lib/Digest.html">the Digest manpage</a>,
 328 <a href="file://C|\msysgit\mingw\html/Digest/MD2.html">the Digest::MD2 manpage</a>,
 329 <a href="file://C|\msysgit\mingw\html/Digest/SHA1.html">the Digest::SHA1 manpage</a>,
 330 <a href="file://C|\msysgit\mingw\html/Digest/HMAC.html">the Digest::HMAC manpage</a></p>
 331 <p><em>md5sum(1)</em></p>
 332 <p>RFC 1321</p>
 333 <p><a href="http://en.wikipedia.org/wiki/MD5">http://en.wikipedia.org/wiki/MD5</a></p>
 334 <p>The paper ``How to Break MD5 and Other Hash Functions'' by Xiaoyun Wang
 335 and Hongbo Yu.</p>
 336 <p>
 337 </p>
 338 <hr />
 339 <h1><a name="copyright">COPYRIGHT</a></h1>
 340 <p>This library is free software; you can redistribute it and/or
 341 modify it under the same terms as Perl itself.</p>
 342 <pre>
 343  Copyright 1998-2003 Gisle Aas.
 344  Copyright 1995-1996 Neil Winton.
 345  Copyright 1991-1992 RSA Data Security, Inc.</pre>
 346 <p>The MD5 algorithm is defined in RFC 1321. This implementation is
 347 derived from the reference C code in RFC 1321 which is covered by
 348 the following copyright statement:</p>
 349 <dl>
 350 <dt>
 351 <dd>
 352 <p>Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All
 353 rights reserved.</p>
 354 </dd>
 355 <dd>
 356 <p>License to copy and use this software is granted provided that it
 357 is identified as the ``RSA Data Security, Inc. MD5 Message-Digest
 358 Algorithm'' in all material mentioning or referencing this software
 359 or this function.</p>
 360 </dd>
 361 <dd>
 362 <p>License is also granted to make and use derivative works provided
 363 that such works are identified as ``derived from the RSA Data
 364 Security, Inc. MD5 Message-Digest Algorithm'' in all material
 365 mentioning or referencing the derived work.</p>
 366 </dd>
 367 <dd>
 368 <p>RSA Data Security, Inc. makes no representations concerning either
 369 the merchantability of this software or the suitability of this
 370 software for any particular purpose. It is provided ``as is''
 371 without express or implied warranty of any kind.</p>
 372 </dd>
 373 <dd>
 374 <p>These notices must be retained in any copies of any part of this
 375 documentation and/or software.</p>
 376 </dd>
 377 </li>
 378 </dl>
 379 <p>This copyright does not prohibit distribution of any version of Perl
 380 containing this extension under the terms of the GNU or Artistic
 381 licenses.</p>
 382 <p>
 383 </p>
 384 <hr />
 385 <h1><a name="authors">AUTHORS</a></h1>
 386 <p>The original <code>MD5</code> interface was written by Neil Winton
 387 (<code>N.Winton@axion.bt.co.uk</code>).</p>
 388 <p>The <code>Digest::MD5</code> module is written by Gisle Aas &lt;<a href="mailto:gisle@ActiveState.com">gisle@ActiveState.com</a>&gt;.</p>
 389 <table border="0" width="100%" cellspacing="0" cellpadding="3">
 390 <tr><td class="block" style="background-color: #cccccc" valign="middle">
 391 <big><strong><span class="block">&nbsp;Digest::MD5 - Perl interface to the MD5 Algorithm</span></strong></big>
 392 </td></tr>
 393 </table>
 394
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