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<div class="section" id="module-sha">
<span id="sha-sha-1-message-digest-algorithm"></span><h1>14.4. <a class="reference internal" href="#module-sha" title="sha: NIST's secure hash algorithm, SHA. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">sha</span></code></a> — SHA-1 message digest algorithm<a class="headerlink" href="#module-sha" title="Permalink to this headline">¶</a></h1>
<div class="deprecated">
<p><span class="versionmodified deprecated">Deprecated since version 2.5: </span>Use the <a class="reference internal" href="hashlib.html#module-hashlib" title="hashlib: Secure hash and message digest algorithms."><code class="xref py py-mod docutils literal notranslate"><span class="pre">hashlib</span></code></a> module instead.</p>
</div>
<p id="index-0">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 class="reference internal" href="md5.html#module-md5" title="md5: RSA's MD5 message digest algorithm. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">md5</span></code></a> module: use <a class="reference internal" href="new.html#module-new" title="new: Interface to the creation of runtime implementation objects. (deprecated)"><code class="xref py py-func docutils literal notranslate"><span class="pre">new()</span></code></a> to create an sha
object, then feed this object with arbitrary strings using the <code class="xref py py-meth docutils literal notranslate"><span class="pre">update()</span></code>
method, and at any point you can ask it for the <em class="dfn">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">
<code class="descclassname">sha.</code><code class="descname">new</code><span class="sig-paren">(</span><span class="optional">[</span><em>string</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#sha.new" title="Permalink to this definition">¶</a></dt>
<dd><p>Return a new sha object. If <em>string</em> is present, the method call
<code class="docutils literal notranslate"><span class="pre">update(string)</span></code> is made.</p>
</dd></dl>
<p>The following values are provided as constants in the module and as attributes
of the sha objects returned by <a class="reference internal" href="new.html#module-new" title="new: Interface to the creation of runtime implementation objects. (deprecated)"><code class="xref py py-func docutils literal notranslate"><span class="pre">new()</span></code></a>:</p>
<dl class="data">
<dt id="sha.blocksize">
<code class="descclassname">sha.</code><code class="descname">blocksize</code><a class="headerlink" href="#sha.blocksize" title="Permalink to this definition">¶</a></dt>
<dd><p>Size of the blocks fed into the hash function; this is always <code class="docutils literal notranslate"><span class="pre">1</span></code>. This size
is used to allow an arbitrary string to be hashed.</p>
</dd></dl>
<dl class="data">
<dt id="sha.digest_size">
<code class="descclassname">sha.</code><code class="descname">digest_size</code><a class="headerlink" href="#sha.digest_size" title="Permalink to this definition">¶</a></dt>
<dd><p>The size of the resulting digest in bytes. This is always <code class="docutils literal notranslate"><span class="pre">20</span></code>.</p>
</dd></dl>
<p>An sha object has the same methods as md5 objects:</p>
<dl class="method">
<dt id="sha.sha.update">
<code class="descclassname">sha.</code><code class="descname">update</code><span class="sig-paren">(</span><em>arg</em><span class="sig-paren">)</span><a class="headerlink" href="#sha.sha.update" title="Permalink to this definition">¶</a></dt>
<dd><p>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: <code class="docutils literal notranslate"><span class="pre">m.update(a);</span>
<span class="pre">m.update(b)</span></code> is equivalent to <code class="docutils literal notranslate"><span class="pre">m.update(a+b)</span></code>.</p>
</dd></dl>
<dl class="method">
<dt id="sha.sha.digest">
<code class="descclassname">sha.</code><code class="descname">digest</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#sha.sha.digest" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the digest of the strings passed to the <a class="reference internal" href="#sha.sha.update" title="sha.sha.update"><code class="xref py py-meth docutils literal notranslate"><span class="pre">update()</span></code></a> method so far.
This is a 20-byte string which may contain non-ASCII characters, including null
bytes.</p>
</dd></dl>
<dl class="method">
<dt id="sha.sha.hexdigest">
<code class="descclassname">sha.</code><code class="descname">hexdigest</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#sha.sha.hexdigest" title="Permalink to this definition">¶</a></dt>
<dd><p>Like <a class="reference internal" href="#sha.sha.digest" title="sha.sha.digest"><code class="xref py py-meth docutils literal notranslate"><span class="pre">digest()</span></code></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.</p>
</dd></dl>
<dl class="method">
<dt id="sha.sha.copy">
<code class="descclassname">sha.</code><code class="descname">copy</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#sha.sha.copy" title="Permalink to this definition">¶</a></dt>
<dd><p>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.</p>
</dd></dl>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<dl class="simple">
<dt><a class="reference external" href="http://csrc.nist.gov/publications/fips/fips180-2/fips180-2withchangenotice.pdf">Secure Hash Standard</a></dt><dd><p>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.</p>
</dd>
<dt><a class="reference external" href="http://csrc.nist.gov/CryptoToolkit/tkhash.html">Cryptographic Toolkit (Secure Hashing)</a></dt><dd><p>Links from NIST to various information on secure hashing.</p>
</dd>
</dl>
</div>
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