What is `$6$rounds=` when running Passlib with Python?
<p>I'm generating SHA-512 encoded password keys with Python's <code>Passlib</code>'s command.</p>

<p><code>python -c "from passlib.hash import sha512_crypt; import getpass; print sha512_crypt.encrypt(getpass.getpass())"</code></p>

<p>This is per Ansible documentation: <a href="http://docs.ansible.com/ansible/faq.html#how-do-i-generate-crypted-passwords-for-the-user-module" rel="nofollow">http://docs.ansible.com/ansible/faq.html#how-do-i-generate-crypted-passwords-for-the-user-module</a>).</p>

<p>It prompts for a password, which I input. And then it returns the key.</p>

<p>Regardless of the password I input, all keys created begin with <code>$6$rounds=...</code></p>

<p>What does this mean? Is this part of the key?</p>

<p>This indicates to the schema for the used algorithm. In the case of <code>sha512_crypt</code> <code>6</code> indicates <code>sha512</code> and <code>rounds=x</code> indicate the number of rounds to compute the hash. </p>

<p>Also current <code>NIST</code> standards suggest <code>pbkdf2_sha256</code> for password hashing.</p>

python encryption passlib