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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>14.4. sha — SHA-1 message digest algorithm — Python v2.6.6 documentation</title> <link rel="stylesheet" href="../_static/default.css" type="text/css" /> <link rel="stylesheet" href="../_static/pygments.css" type="text/css" /> <script type="text/javascript"> var DOCUMENTATION_OPTIONS = { URL_ROOT: '../', VERSION: '2.6.6', COLLAPSE_MODINDEX: false, FILE_SUFFIX: '.html', HAS_SOURCE: true }; </script> <script type="text/javascript" src="../_static/jquery.js"></script> <script type="text/javascript" src="../_static/doctools.js"></script> <link rel="search" type="application/opensearchdescription+xml" title="Search within Python v2.6.6 documentation" href="../_static/opensearch.xml"/> <link rel="author" title="About these documents" href="../about.html" /> <link rel="copyright" title="Copyright" href="../copyright.html" /> <link rel="top" title="Python v2.6.6 documentation" href="../index.html" /> <link rel="up" title="14. 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Cryptographic Services</a> »</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body"> <div class="section" id="module-sha"> <h1>14.4. <tt class="xref docutils literal"><span class="pre">sha</span></tt> — SHA-1 message digest algorithm<a class="headerlink" href="#module-sha" title="Permalink to this headline">¶</a></h1> <p class="deprecated"> <span class="versionmodified">Deprecated since version 2.5: </span>Use the <a title="Secure hash and message digest algorithms." class="reference external" href="hashlib.html#module-hashlib"><tt class="xref docutils literal"><span class="pre">hashlib</span></tt></a> module instead.</p> <p id="index-545">This module implements the interface to NIST’s secure hash algorithm, known as SHA-1. SHA-1 is an improved version of the original SHA hash algorithm. It is used in the same way as the <a title="RSA's MD5 message digest algorithm. (deprecated)" class="reference external" href="md5.html#module-md5"><tt class="xref docutils literal"><span class="pre">md5</span></tt></a> module: use <a title="sha.new" class="reference internal" href="#sha.new"><tt class="xref docutils literal"><span class="pre">new()</span></tt></a> to create an sha object, then feed this object with arbitrary strings using the <tt class="xref docutils literal"><span class="pre">update()</span></tt> method, and at any point you can ask it for the <em>digest</em> of the concatenation of the strings fed to it so far. SHA-1 digests are 160 bits instead of MD5’s 128 bits.</p> <dl class="function"> <dt id="sha.new"> <tt class="descclassname">sha.</tt><tt class="descname">new</tt><big>(</big><span class="optional">[</span><em>string</em><span class="optional">]</span><big>)</big><a class="headerlink" href="#sha.new" title="Permalink to this definition">¶</a></dt> <dd>Return a new sha object. If <em>string</em> is present, the method call <tt class="docutils literal"><span class="pre">update(string)</span></tt> is made.</dd></dl> <p>The following values are provided as constants in the module and as attributes of the sha objects returned by <a title="sha.new" class="reference internal" href="#sha.new"><tt class="xref docutils literal"><span class="pre">new()</span></tt></a>:</p> <dl class="data"> <dt id="sha.blocksize"> <tt class="descclassname">sha.</tt><tt class="descname">blocksize</tt><a class="headerlink" href="#sha.blocksize" title="Permalink to this definition">¶</a></dt> <dd>Size of the blocks fed into the hash function; this is always <tt class="docutils literal"><span class="pre">1</span></tt>. This size is used to allow an arbitrary string to be hashed.</dd></dl> <dl class="data"> <dt id="sha.digest_size"> <tt class="descclassname">sha.</tt><tt class="descname">digest_size</tt><a class="headerlink" href="#sha.digest_size" title="Permalink to this definition">¶</a></dt> <dd>The size of the resulting digest in bytes. This is always <tt class="docutils literal"><span class="pre">20</span></tt>.</dd></dl> <p>An sha object has the same methods as md5 objects:</p> <dl class="method"> <dt id="sha.sha.update"> <tt class="descclassname">sha.</tt><tt class="descname">update</tt><big>(</big><em>arg</em><big>)</big><a class="headerlink" href="#sha.sha.update" title="Permalink to this definition">¶</a></dt> <dd>Update the sha object with the string <em>arg</em>. Repeated calls are equivalent to a single call with the concatenation of all the arguments: <tt class="docutils literal"><span class="pre">m.update(a);</span> <span class="pre">m.update(b)</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">m.update(a+b)</span></tt>.</dd></dl> <dl class="method"> <dt id="sha.sha.digest"> <tt class="descclassname">sha.</tt><tt class="descname">digest</tt><big>(</big><big>)</big><a class="headerlink" href="#sha.sha.digest" title="Permalink to this definition">¶</a></dt> <dd>Return the digest of the strings passed to the <a title="sha.sha.update" class="reference internal" href="#sha.sha.update"><tt class="xref docutils literal"><span class="pre">update()</span></tt></a> method so far. This is a 20-byte string which may contain non-ASCII characters, including null bytes.</dd></dl> <dl class="method"> <dt id="sha.sha.hexdigest"> <tt class="descclassname">sha.</tt><tt class="descname">hexdigest</tt><big>(</big><big>)</big><a class="headerlink" href="#sha.sha.hexdigest" title="Permalink to this definition">¶</a></dt> <dd>Like <a title="sha.sha.digest" class="reference internal" href="#sha.sha.digest"><tt class="xref docutils literal"><span class="pre">digest()</span></tt></a> except the digest is returned as a string of length 40, containing only hexadecimal digits. This may be used to exchange the value safely in email or other non-binary environments.</dd></dl> <dl class="method"> <dt id="sha.sha.copy"> <tt class="descclassname">sha.</tt><tt class="descname">copy</tt><big>(</big><big>)</big><a class="headerlink" href="#sha.sha.copy" title="Permalink to this definition">¶</a></dt> <dd>Return a copy (“clone”) of the sha object. This can be used to efficiently compute the digests of strings that share a common initial substring.</dd></dl> <div class="admonition-see-also admonition seealso"> <p class="first admonition-title">See also</p> <dl class="last docutils"> <dt><a class="reference external" href="http://csrc.nist.gov/publications/fips/fips180-2/fips180-2withchangenotice.pdf">Secure Hash Standard</a></dt> <dd>The Secure Hash Algorithm is defined by NIST document FIPS PUB 180-2: <a class="reference external" href="http://csrc.nist.gov/publications/fips/fips180-2/fips180-2withchangenotice.pdf">Secure Hash Standard</a>, published in August 2002.</dd> <dt><a class="reference external" href="http://csrc.nist.gov/CryptoToolkit/tkhash.html">Cryptographic Toolkit (Secure Hashing)</a></dt> <dd>Links from NIST to various information on secure hashing.</dd> </dl> </div> </div> </div> </div> </div> <div class="sphinxsidebar"> <div class="sphinxsidebarwrapper"> <h4>Previous topic</h4> <p class="topless"><a href="md5.html" title="previous chapter">14.3. <tt class="docutils literal docutils literal docutils literal"><span class="pre">md5</span></tt> — MD5 message digest algorithm</a></p> <h4>Next topic</h4> <p class="topless"><a href="allos.html" title="next chapter">15. 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