Brandon Rozek

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PhD Student @ RPI studying Automated Reasoning in AI and Linux Enthusiast.

GPG Keygen

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3 minute reading time

GPG keys have a variety of different uses from sending encrypted emails to verifying git commits. Here I’ll show how to create a public/private key-pair. This post assumes you have the gpg client installed.

Type the following command

gpg --full-gen-key

This will then show

gpg (GnuPG) 2.2.12; Copyright (C) 2018 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Please select what kind of key you want:
   (1) RSA and RSA (default)
   (2) DSA and Elgamal
   (3) DSA (sign only)
   (4) RSA (sign only)
Your selection? 1

I generally recommend selecting the default option. As cryptography standards change, I would expect the options presented to you to differ from my selection screen.

RSA keys may be between 1024 and 4096 bits long.
What keysize do you want? (3072) 4096
Requested keysize is 4096 bits

For keysizes, the bigger the more secure. The tradeoff is in the time it takes to perform the cryptographic operations. Since I rarely encrypted very large inputs, I went for the highest available option as the encryption time to me is negligable.

Please specify how long the key should be valid.
         0 = key does not expire
      <n>  = key expires in n days
      <n>w = key expires in n weeks
      <n>m = key expires in n months
      <n>y = key expires in n years
Key is valid for? (0) 1y

I highly recommend that you set an expiration date. Not only does this allow for the key to become invalid if you happen to lose your private key, it also announces to the wider world that you actually use your GPG key.

I try to set my key expiration dates to be a year out.

Key expires at Mon 11 Apr 2021 06:42:01 PM EDT
Is this correct? (y/N) y

As a quick sanity check, it’ll provide the date that the key will expire.

GnuPG needs to construct a user ID to identify your key.

Real name: Brandon Rozek
Email address:
Comment: Git

All the fields are optional. Fill them in as you wish.

You selected this USER-ID:
    "Brandon Rozek (Git)"
Change (N)ame, (C)omment, (E)mail or (O)kay/(Q)uit? O

Another sanity check, to ensure that you set your user information correctly. Keep in mind that this information is included in plaintext as part of your public key.

We need to generate a lot of random bytes. It is a good idea to perform
some other action (type on the keyboard, move the mouse, utilize the
disks) during the prime generation; this gives the random number
generator a better chance to gain enough entropy.

Do as it says, start going crazy.

gpg: key IFMWDHXYSKTICHSE marked as ultimately trusted
public and secret key created and signed.

pub   rsa4096 2020-04-11 [SC] [expires: 2021-04-11]
uid                      Brandon Rozek (Git)
sub   rsa4096 2020-04-11 [E] [expires: 2021-04-11]

Congratulations, you now have a GPG key set.

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