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<?xml version="1.0" encoding="ascii"?>
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<a href="Crypto-module.html">Package Crypto</a> ::
<a href="Crypto.Signature-module.html">Package Signature</a> ::
Module PKCS1_v1_5
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<!-- ==================== MODULE DESCRIPTION ==================== -->
<h1 class="epydoc">Module PKCS1_v1_5</h1><p class="nomargin-top"></p>
<p>RSA digital signature protocol according to PKCS#1 v1.5</p>
<p>See <a class="rst-reference external" href="http://www.ietf.org/rfc/rfc3447.txt" target="_top">RFC3447</a> or the <a class="rst-reference external" href="http://www.rsa.com/rsalabs/node.asp?id=2125" target="_top">original RSA Labs specification</a>.</p>
<p>This scheme is more properly called <tt class="rst-docutils literal"><span class="pre">RSASSA-PKCS1-v1_5</span></tt>.</p>
<p>For example, a sender may authenticate a message using SHA-1 like
this:</p>
<blockquote>
<pre class="py-doctest">
<span class="py-prompt">>>> </span><span class="py-keyword">from</span> Crypto.Signature <span class="py-keyword">import</span> PKCS1_v1_5
<span class="py-prompt">>>> </span><span class="py-keyword">from</span> Crypto.Hash <span class="py-keyword">import</span> SHA
<span class="py-prompt">>>> </span><span class="py-keyword">from</span> Crypto.PublicKey <span class="py-keyword">import</span> RSA
<span class="py-prompt">>>></span>
<span class="py-prompt">>>> </span>message = <span class="py-string">'To be signed'</span>
<span class="py-prompt">>>> </span>key = RSA.importKey(open(<span class="py-string">'privkey.der'</span>).read())
<span class="py-prompt">>>> </span>h = SHA.new(message)
<span class="py-prompt">>>> </span>signer = PKCS1_v1_5.new(key)
<span class="py-prompt">>>> </span>signature = signer.sign(h)</pre>
</blockquote>
<p>At the receiver side, verification can be done using the public part of
the RSA key:</p>
<blockquote>
<pre class="py-doctest">
<span class="py-prompt">>>> </span>key = RSA.importKey(open(<span class="py-string">'pubkey.der'</span>).read())
<span class="py-prompt">>>> </span>h = SHA.new(message)
<span class="py-prompt">>>> </span>verifier = PKCS1_v1_5.new(key)
<span class="py-prompt">>>> </span><span class="py-keyword">if</span> verifier.verify(h, signature):
<span class="py-prompt">>>> </span> <span class="py-keyword">print</span> <span class="py-string">"The signature is authentic."</span>
<span class="py-prompt">>>> </span><span class="py-keyword">else</span>:
<span class="py-prompt">>>> </span> <span class="py-keyword">print</span> <span class="py-string">"The signature is not authentic."</span></pre>
</blockquote>
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<span class="summary-type"> </span>
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<a href="Crypto.Signature.PKCS1_v1_5.PKCS115_SigScheme-class.html" class="summary-name" onclick="show_private();">PKCS115_SigScheme</a><br />
This signature scheme can perform PKCS#1 v1.5 RSA signature or verification.
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<span class="summary-type"> </span>
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<td><span class="summary-sig"><a href="Crypto.Signature.PKCS1_v1_5-module.html#EMSA_PKCS1_V1_5_ENCODE" class="summary-sig-name" onclick="show_private();">EMSA_PKCS1_V1_5_ENCODE</a>(<span class="summary-sig-arg">hash</span>,
<span class="summary-sig-arg">emLen</span>)</span><br />
Implement the <tt class="rst-docutils literal"><span class="pre">EMSA-PKCS1-V1_5-ENCODE</span></tt> function, as defined
in PKCS#1 v2.1 (RFC3447, 9.2).</td>
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<span class="summary-type"> </span>
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<td><span class="summary-sig"><a href="Crypto.Signature.PKCS1_v1_5-module.html#new" class="summary-sig-name">new</a>(<span class="summary-sig-arg">key</span>)</span><br />
Return a signature scheme object <a href="Crypto.Signature.PKCS1_v1_5.PKCS115_SigScheme-class.html" class="link" onclick="show_private();">PKCS115_SigScheme</a> that
can be used to perform PKCS#1 v1.5 signature or verification.</td>
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<h3 class="epydoc"><span class="sig"><span class="sig-name">EMSA_PKCS1_V1_5_ENCODE</span>(<span class="sig-arg">hash</span>,
<span class="sig-arg">emLen</span>)</span>
</h3>
</td><td align="right" valign="top"
>
</td>
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<p>Implement the <tt class="rst-rst-docutils literal rst-docutils literal"><span class="pre">EMSA-PKCS1-V1_5-ENCODE</span></tt> function, as defined
in PKCS#1 v2.1 (RFC3447, 9.2).</p>
<p><tt class="rst-docutils literal"><span class="pre">EMSA-PKCS1-V1_5-ENCODE</span></tt> actually accepts the message <tt class="rst-docutils literal">M</tt> as input,
and hash it internally. Here, we expect that the message has already
been hashed instead.</p>
<dl class="fields">
<dt>Parameters:</dt>
<dd><ul class="nomargin-top">
<li><strong class="pname"><code>hash</code></strong> (hash object) - The hash object that holds the digest of the message being signed.</li>
<li><strong class="pname"><code>emLen</code></strong> (int) - The length the final encoding must have, in bytes.</li>
</ul></dd>
<dt>Returns:</dt>
<dd>An <tt class="rst-docutils literal">emLen</tt> byte long string that encodes the hash.</dd>
</dl>
<div class="fields"> <strong>Attention:</strong>
<ul class="nomargin-top">
<li>
the early standard (RFC2313) stated that <tt class="rst-docutils literal">DigestInfo</tt>
had to be BER-encoded. This means that old signatures
might have length tags in indefinite form, which
is not supported in DER. Such encoding cannot be
reproduced by this function.
</li>
<li>
the same standard defined <tt class="rst-docutils literal">DigestAlgorithm</tt> to be
of <tt class="rst-docutils literal">AlgorithmIdentifier</tt> type, where the PARAMETERS
item is optional. Encodings for <tt class="rst-docutils literal">MD2/4/5</tt> without
<tt class="rst-docutils literal">PARAMETERS</tt> cannot be reproduced by this function.
</li>
</ul>
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<h3 class="epydoc"><span class="sig"><span class="sig-name">new</span>(<span class="sig-arg">key</span>)</span>
</h3>
</td><td align="right" valign="top"
>
</td>
</tr></table>
Return a signature scheme object <a href="Crypto.Signature.PKCS1_v1_5.PKCS115_SigScheme-class.html" class="link" onclick="show_private();">PKCS115_SigScheme</a> that
can be used to perform PKCS#1 v1.5 signature or verification.
<dl class="fields">
<dt>Parameters:</dt>
<dd><ul class="nomargin-top">
<li><strong class="pname"><code>key</code></strong> (RSA key object) - The key to use to sign or verify the message. This is a <a href="Crypto.PublicKey.RSA-module.html" class="link">Crypto.PublicKey.RSA</a> object.
Signing is only possible if <em>key</em> is a private RSA key.</li>
</ul></dd>
</dl>
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