@thunderbird @Mozilla Glad you found it helpful!
If you don't speak french, I also made an english version of the tutorial here! https://jlai.lu/post/10859694
jlai.lu[Guide] 🔏 Digitally sign and send encrypted emails with S/MIME - jlai.luHeya, I found how you can digitally sign and encrypt emails! (It even gives them
a cool icon for others to see!), and I haven’t seen anything about it before so
I thought I’d share how I did it!
[https://jlai.lu/pictrs/image/c401e086-78e4-4404-ab77-cc78d24d2bab.png] Do you
also want to send encrypted emails and sign them? Just follow these few steps! #
But beforehand, let’s define some terms : - Signed email : Email with a valid
numerical signature. Anyone can read it and know it has not been modified since
it was sent. - Encrypted email : Email encrypted with the recipient’s public
key. They can decrypt it with their private key - S/MIME certificate : A .p12
file containing your private key (So keep it for yourself and don’t send it to
anyone!!) and your public key. Okay, now it’s time to… # Start the setup (Obtain
an S/MIME certificate) - You’ll need to ask to an authority for a certificate.
Personally I use Actalis [https://actalis.it/] because they give free
certificates for multiple email addresses, valid for a year (you need to redo
the setup every year). If you don’t want to use Actalis, more info is avilable
here [https://support.mozilla.org/kb/instructions-smime-certificate-using-csr].
- Don’t forget to put the website in english if you don’t understand italian. -
Go on the page to request an S/MIME certificate
[https://www.actalis.com/request-s-mime-certificate], create an account and
follow the setup. The verification email can take a little while (~2min) - When
the setup ends, you’ll have a valid certificate in your dashboard
[https://www.actalis.com/dashboard] (It can take a few minutes to appear if you
just verified it) that you can download, and a password that Actalis emailed you
to enable your certificate.
[https://jlai.lu/pictrs/image/23bb7d9c-a69e-4c50-af14-48060a1dc59b.png] #
Install the certificate - Download the .p12 file, then open it, type your
password, and leave the default options to install the certificate on your
device (Android or PC, on Android pick “For VPN and apps”). Don’t delete your
old one, so you can still decrypt old messages sent on the expired certificate -
Use an S/MIME compatible email client. On PC, there is Thunderbird
[https://thunderbird.net], on Android, FairEmail
[https://f-droid.org/fr/packages/eu.faircode.email/]. - In your email client
settings, importer the S/MIME certificate pofor signing AND encrypting your
messages. It changes depending on your client, so here it is for Thunderbird : -
In the top-right menu, go to Account settings, End-to-end encryption,
underS/MIME click on Manage S/MIME certificates, Import and pick your.p12 file.
Then, pick Select a certificate, and pick yours from the tab “Your
certificates”. An image is worth a thousand words (Sorry for the french)
[https://jlai.lu/pictrs/image/b01a8dff-9973-4672-875f-b14da4bc2178.png] Don’t
forget to check the box to sign and/or encrypt every message just below, if you
want! # Communicate with someone Once this is done, here is how you can
communicate… - …While signing your messages : > It’s easy, just click on “Sign”
before sending. Usually, email clients show a small medal next to your name to
show the email is signed. - …While encrypting your messages : > For that, you’ll
need your recipient’s public key. They needs to send you a signed message (not
encrypted, since you don’t have each other’s key at this point) where you can
get their public key from their signature, and add it to your email client,
which will allow you to encrypt messages you send to them. Then, send them a
signed email (you can encrypt it) so they can get your public key and add it to
their client, and then you’ll be able to exchange encrypted emails! I’m not an
expert and probably made a few mistakes, if you spot any please tell me in the
comments and I’ll try to fix the guide!