Generating entropy to create gpg keys

12 April 2020 - less than 1 min read time
Tags: entropy gpg spack

It’s been over a month under lockdown due to Covid-19. I try to spend my time being as productive as possible. However, I find myself unable to keep track of the progress I’m making given that I don’t document any of it. So, below is the first in a series of posts to keep a record of at least One New Thing I learn everyday.

Generating entropy to create gpg keys

While trying to create a new gpg key for a spack mirror, I found that it was taking way too long.

$ spack gpg create "Nithin Kumar" senthilkumar.16@osu.edu
$ spack gpg init

The reason it was taking so long was because there was not enough entropy in the system to generate the required number of bits. This entropy can be created by using the system actively. For eg., moving the mouse around a lot, having a lot of chrome tabs open, etc. Surely there should be a way to generate randomness by running background processes to simulate high cpu usage and high disk IO. After a little googling, I came across the below snippets which I could run parallely in other shells while the gpg key was being created.

1. Read/Write to a whole lot of files

Generate IO using any of the below two commands

$ (find / | xargs file) &> /dev/null &
$ dd if=/dev/zero of=/dev/null

2. Increase CPU utilization

Run the command as many times as the number of cores

$ yes > /dev/null &
$ killall yes

3. Using RNG

Install rng-tools based on the system you are running and launch it.

$ sudo apt-get install rng-tools
$ sudo yum install rng-tools
$ sudo rngd -r /dev/urandom

Once the gpg key has been generated kill any of these commands if you have pushed them to the background.