Official resource for passwd or /etc/shadow indicating the encryption algorithm applied with its respective starting pattern by OS version?

Ubuntu
1

Hello friends

For academic purposes I am analyzing the /etc/shadow file at Ubuntu Desktop 22.04.

I did do realize for this 22.04 that for any user created through the adduser command - which behind the scenes is used the passwd command - the /etc/shadow file always shows the encrypted password for those users starting with $y$j9T$.

Now, this machine came from two full upgrades, 18.04 and 20.04, where the first user created from the beginning of the installation (18.04) has his encrypted password starting with $6$. It in the /etc/shadow file

Question

  • Is there an official resource for either the passwd command or /etc/shadow file indicating the encryption algorithm applied with its respective starting pattern according the OS version?

Something like (invalid data of course)

Ubuntu Desktop 18.04 - md5    - $6$
Ubuntu Desktop 20.04 - sha256 - $csdf$
Ubuntu Desktop 22.04 - bcrypt - $y$j9T$
2

There’s, of course, always its manpage…