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<title>RSA_private_encrypt</title>
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<ul id="index">
<li><a href="#NAME">NAME</a></li>
<li><a href="#SYNOPSIS">SYNOPSIS</a></li>
<li><a href="#DESCRIPTION">DESCRIPTION</a></li>
<li><a href="#RETURN-VALUES">RETURN VALUES</a></li>
<li><a href="#SEE-ALSO">SEE ALSO</a></li>
<li><a href="#COPYRIGHT">COPYRIGHT</a></li>
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<h1 id="NAME">NAME</h1>
<p>RSA_private_encrypt, RSA_public_decrypt - low-level signature operations</p>
<h1 id="SYNOPSIS">SYNOPSIS</h1>
<pre><code> #include <openssl/rsa.h>
int RSA_private_encrypt(int flen, unsigned char *from,
unsigned char *to, RSA *rsa, int padding);
int RSA_public_decrypt(int flen, unsigned char *from,
unsigned char *to, RSA *rsa, int padding);</code></pre>
<h1 id="DESCRIPTION">DESCRIPTION</h1>
<p>These functions handle RSA signatures at a low-level.</p>
<p>RSA_private_encrypt() signs the <b>flen</b> bytes at <b>from</b> (usually a message digest with an algorithm identifier) using the private key <b>rsa</b> and stores the signature in <b>to</b>. <b>to</b> must point to <b>RSA_size(rsa)</b> bytes of memory.</p>
<p><b>padding</b> denotes one of the following modes:</p>
<dl>
<dt id="RSA_PKCS1_PADDING">RSA_PKCS1_PADDING</dt>
<dd>
<p>PKCS #1 v1.5 padding. This function does not handle the <b>algorithmIdentifier</b> specified in PKCS #1. When generating or verifying PKCS #1 signatures, <a href="../man3/RSA_sign.html">RSA_sign(3)</a> and <a href="../man3/RSA_verify.html">RSA_verify(3)</a> should be used.</p>
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<dt id="RSA_NO_PADDING">RSA_NO_PADDING</dt>
<dd>
<p>Raw RSA signature. This mode should <i>only</i> be used to implement cryptographically sound padding modes in the application code. Signing user data directly with RSA is insecure.</p>
</dd>
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<p>RSA_public_decrypt() recovers the message digest from the <b>flen</b> bytes long signature at <b>from</b> using the signer's public key <b>rsa</b>. <b>to</b> must point to a memory section large enough to hold the message digest (which is smaller than <b>RSA_size(rsa) - 11</b>). <b>padding</b> is the padding mode that was used to sign the data.</p>
<h1 id="RETURN-VALUES">RETURN VALUES</h1>
<p>RSA_private_encrypt() returns the size of the signature (i.e., RSA_size(rsa)). RSA_public_decrypt() returns the size of the recovered message digest.</p>
<p>On error, -1 is returned; the error codes can be obtained by <a href="../man3/ERR_get_error.html">ERR_get_error(3)</a>.</p>
<h1 id="SEE-ALSO">SEE ALSO</h1>
<p><a href="../man3/ERR_get_error.html">ERR_get_error(3)</a>, <a href="../man3/RSA_sign.html">RSA_sign(3)</a>, <a href="../man3/RSA_verify.html">RSA_verify(3)</a></p>
<h1 id="COPYRIGHT">COPYRIGHT</h1>
<p>Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.</p>
<p>Licensed under the OpenSSL license (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <a href="https://www.openssl.org/source/license.html">https://www.openssl.org/source/license.html</a>.</p>
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