Teach you how to generate complex passwords and check password strength in Linux

In this tutorial, we will explore how to generate complex passwords and check password strength.

Generate complex password

Strong passwords should be a mix of letters, numbers, and symbols. Another requirement is not to use known words, birthdays, or names, as these are vulnerable to dictionary attacks.

So how many characters should the password contain? There isn't really a definite answer, but more than 16 characters is a good choice. Therefore, if your system has OpenSSL or GPG installed, you can use these tools to generate passwords. For example, below we useGPGto generate a password:

[root@localhost ~]# gpg --gen-random --armor 2 12 zXVKRoB0/V4BN9QG

If you don’t want special characters, you can use thesedcommand to filter them out:

[root@localhost ~]# gpg --gen-random --armor 2 12|sed 's/[^a-zA-Z0-9]//g' n4ciIlRLkLTkzwg

The above uses the--gen-randomoption to randomly generate characters. Use the--armoroption to generate ASCII characters. The following option 2 can use three options[0][1][2], which indicates the quality level. The last number represents the character length.

Same, we can useOpenSSLto generate passwords:

[root@localhost ~]# openssl rand -base64 12 QIrH/PLXqzmLuI/a

Similarly, you can also use thesedcommand to filter out special characters:

[root@localhost ~]# openssl rand -base64 12| sed 's/[^a-zA-Z0-9]//g' lXIg4cKLCLVvsi

Check password strength

Now that we have our password, it's time to see if it passes the test: Is your password strong enough? To determine if the password is strong enough, we will use thecracklibtool installed in Centos8.

[root@localhost ~]# yum -y install cracklib

Let’s test a simple password first:

[root@localhost ~]# echo "a1b2c5" | cracklib-check a1b2c5: it is based on a dictionary word

What if we use ordinary words?

[root@localhost ~]# echo "Administrator"|cracklib-check Administrator: it is based on a dictionary word

The output of the above two passwords also prompts that they can be found in the dictionary.

Let’s test a generated password to see how strong it is:

[root@localhost ~]# openssl rand -base64 12 | cracklib-check VdBlmvIgGY4ehWly: OK

You can see that the password is OK.

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