/doc/streams.md5.html

http://github.com/foodmike/PTypes · HTML · 76 lines · 71 code · 1 blank · 4 comment · 0 complexity · deaf447fff8f05e2c102c0a607a0eb46 MD5 · raw file 

    

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  4. <title>PTypes: streams: outmd5</title>
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  10. <p><a href="../index.html"><img src="title-21.png" width="253" height="39" alt="C++ Portable Types Library (PTypes) Version 2.1" border="0"></a> 
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  13. <p class="hpath"><a href="index.html">Top</a>: <a href="streams.html">Streams</a>: 
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  14. outmd5 </p>
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  15. <blockquote> 
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  16. <pre class="lang">#include &lt;pstreams.h&gt;
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  17. 

  18. class outmd5: outstm {
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  19.     outmd5();
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  20.     outmd5(outstm* outthru);
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  21.     string get_digest();
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  22.     const unsigned char* get_bindigest();
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  23. }
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  24. </pre>
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  26. <p>MD5, the message digest algorithm described in RFC 1321, computes a 128-bit 
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  27. sequence (sometimes called 'message digest', 'fingerprint' or 'MD5 checksum') 
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  28. from arbitrary data. As stated in RFC 1321, it is conjectured that it is computationally 
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  29. infeasible to produce two messages having the same message digest, or to produce 
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  30. any message having a given prespecified target message digest. MD5 can be viewed 
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  31. as a one-way encryption system and can be used, for example, to encrypt passwords 
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  32. in a password database.</p>
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  33. <p>The MD5 fingerprint is more often converted to so-called ASCII-64 form in order 
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  34. to conveniently store it in plain text environments and protocols. Thus, the 128-bit 
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  35. binary sequence becomes a 22-character text string consisting of letters, digits 
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  36. and two special symbols '.' and '/'. (Note that this is not the same as Base64 
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  37. encoding in MIME).</p>
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  38. <p>In order to compute a MD5 fingerprint you first create a stream object of type 
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  39. <span class="lang">outmd5</span> and then send data to it as if it was an ordinary 
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  40. output file or a socket stream. After you close the stream, you can obtain the 
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  41. fingerprint in ASCII-64 form using the object's <span class="lang">get_digest()</span> 
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  42. method.</p>
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  43. <p>The implementation of MD5 is derived from L. Peter Deutsch's work.</p>
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  44. <p>This class derives all public methods and properties from <a href="streams.iobase.html">iobase</a> 
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  45. and <a href="streams.outstm.html">outstm</a>, and in addition defines the following:</p>
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  46. <p><span class="def">outmd5::outmd5()</span> creates a bufferless MD5 stream.</p>
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  47. <p><span class="def">outmd5::outmd5(outstm* outthru)</span> creates a MD5 stream 
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  48. and attaches an output stream <span class="lang">outthru</span> to it. Everything 
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  49. sent to the MD5 stream will also be duplicated to <span class="lang">outthru</span>. 
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  50. You may want, for example, to attach <span class="lang">perr</span> to your MD5 
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  51. stream for debugging purposes.</p>
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  52. <p><span class="def">string outmd5::get_digest()</span> closes the stream and 
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  53. returns the computed fingerprint in text form (ASCII-64).</p>
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  54. <p><span class="def">const unsigned char* outmd5::get_bindigest()</span> closes 
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  55. the stream and returns a pointer to a 16-byte buffer with the binary MD5 fingerprint.</p>
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  56. <p><b>Example:</b></p>
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  57. <blockquote> 
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  58. <pre>
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  59. string cryptpw(string username, string password)
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  60. {
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  61.     outmd5 m;
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  62.     m.open();
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  63.     m.put(username);
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  64.     m.put(password);
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  65.     m.put(&quot;Banana with ketchup&quot;);
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  66.     return m.get_digest();
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  67. }
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  68. </pre>
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  69. </blockquote>
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  70. <p class="seealso">See also: <a href="streams.iobase.html">iobase</a>, <a href="streams.outstm.html">outstm</a> 
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  71. </p>
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