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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="#OPTIONS">OPTIONS</a></li>
 <li><a href="#NOTES">NOTES</a></li>
 <li><a href="#SEE-ALSO">SEE ALSO</a></li>
 <li><a href="#COPYRIGHT">COPYRIGHT</a></li>
</ul>

openssl-genrsa, genrsa - generate an RSA private key

<h1 id="SYNOPSIS">SYNOPSIS</h1>

openssl genrsa [-help] [-out filename] [-passout arg] [-aes128] [-aes192] [-aes256] [-aria128] [-aria192] [-aria256] [-camellia128] [-camellia192] [-camellia256] [-des] [-des3] [-idea] [-f4] [-3] [-rand file...] [-writerand file] [-engine id] [-primes num] [numbits]

<h1 id="DESCRIPTION">DESCRIPTION</h1>

The genrsa command generates an RSA private key.

<h1 id="OPTIONS">OPTIONS</h1>

<dl>

Print out a usage message.

</dd>
<dt id="out-filename">-out filename</dt>
<dd>

Output the key to the specified file. If this argument is not specified then standard output is used.

</dd>
<dt id="passout-arg">-passout arg</dt>
<dd>

The output file password source. For more information about the format of arg see <a href="../man1/openssl.html">&quot;Pass Phrase Options&quot; in openssl(1)</a>.

</dd>
<dt id="aes128--aes192--aes256--aria128--aria192--aria256--camellia128--camellia192--camellia256--des--des3--idea">-aes128, -aes192, -aes256, -aria128, -aria192, -aria256, -camellia128, -camellia192, -camellia256, -des, -des3, -idea</dt>
<dd>

These options encrypt the private key with specified cipher before outputting it. If none of these options is specified no encryption is used. If encryption is used a pass phrase is prompted for if it is not supplied via the -passout argument.

</dd>
<dt id="F4--3">-F4|-3</dt>
<dd>

The public exponent to use, either 65537 or 3. The default is 65537.

</dd>
<dt id="rand-file">-rand file...</dt>
<dd>

A file or files containing random data used to seed the random number generator. Multiple files can be specified separated by an OS-dependent character. The separator is ; for MS-Windows, , for OpenVMS, and : for all others.

</dd>
<dt id="writerand-file">[-writerand file]</dt>
<dd>

Writes random data to the specified file upon exit. This can be used with a subsequent -rand flag.

</dd>
<dt id="engine-id">-engine id</dt>
<dd>

Specifying an engine (by its unique id string) will cause genrsa to attempt to obtain a functional reference to the specified engine, thus initialising it if needed. The engine will then be set as the default for all available algorithms.

</dd>
<dt id="primes-num">-primes num</dt>
<dd>

Specify the number of primes to use while generating the RSA key. The num parameter must be a positive integer that is greater than 1 and less than 16. If num is greater than 2, then the generated key is called a &#39;multi-prime&#39; RSA key, which is defined in RFC 8017.

</dd>
<dt id="numbits">numbits</dt>
<dd>

The size of the private key to generate in bits. This must be the last option specified. The default is 2048 and values less than 512 are not allowed.

</dd>
</dl>

<h1 id="NOTES">NOTES</h1>

RSA private key generation essentially involves the generation of two or more prime numbers. When generating a private key various symbols will be output to indicate the progress of the generation. A . represents each number which has passed an initial sieve test, + means a number has passed a single round of the Miller-Rabin primality test, * means the current prime starts a regenerating progress due to some failed tests. A newline means that the number has passed all the prime tests (the actual number depends on the key size).

Because key generation is a random process the time taken to generate a key may vary somewhat. But in general, more primes lead to less generation time of a key.

<a href="../man1/gendsa.html">gendsa(1)</a>

<h1 id="COPYRIGHT">COPYRIGHT</h1>

Licensed under the OpenSSL license (the &quot;License&quot;). 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>.

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