Differences

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--- pgp_workshop [2025/05/20 12:20] – [Signing and verifying signatures with OpenPGP] usera
+++ pgp_workshop [2026/07/16 12:37] (current) – [Signing and verifying signatures with OpenPGP] usera
@@ Line 1: / Line 1: @@
 ====== PGP Workshop ======
+<aside outline box>
+**Important note on PGP:** PGP has been more and more criticized in the security community over the years (see for example [[https://www.latacora.com/blog/2019/07/16/the-pgp-problem/|here]] and [[https://soatok.blog/2024/11/15/what-to-use-instead-of-pgp/| here]]) for its complexity and flawed design. Therefore, it is not really a good idea to use PGP for sending ourselves encrypted mails, as opposed to use Signal (until some other better protocol is ready). As PGP is still quite used for signing packages, it can still be a good idea to learn it for verifying those packages.
+</aside>
 Here is a small tutorial for getting started with this protocol named Pretty Good Privacy (PGP), an asymmetric cryptographic tool that allows to have end to end encrypted mails despite using very mainstream services like gmail, outlook, etc. You will find several names around, like GPG, PGP, OpenPGP. I will use them interchangeably as they basically refer to the same thing.
@@ Line 167: / Line 171: @@
 The way it is done is the following:
-  - The file is **[[hashed|hashed]]** (see the paragraph below).
+  - The file is **[[hashed|hashed]]**.
   - This hashed file is encrypted with your private key
   - The result is added at the end of your file, giving a **signed** file.
@@ Line 173: / Line 177: @@
 Actually, in most case you will do both: signing (with your private key) then encrypting (with the public key of someone else). The person receiving the message will decrypt it with their private key, and then extract the signature and verify it with your public key.
+==== First step if you only set up Thunderbird with PGP so far ====
+If you were on Windows and set up your keys with Kleopatra, the command line gpg tool will already know those keys. However, if you used the PGP key manager from thunderbird, it is different. You will therefore have to copy all your keys from the thunderbird key manager to the keys that are known by the gpg command line tool.
+This is how to do it. First, go to the key manager, select your own key, that you will use to sign things with, and click on File->Backup Secret Key to File, then find a location on your computer (you will be asked for a passphrase for this, please use a [[diceware|good one]])
+Then, open a command line, navigate to the directory where your secret key file is located and enter:
+<code>
+gpg --import [filename]
+</code>
+where [filename] is the name of this secret key file. you then need to tell the gpg command tool to use this key as a default signing key. This is done by the command:
+<code>
+echo 'default-key:0:"[fingerprint]' | gpgconf --change-options gpg
+</code>
+where [fingerprint] is the fingerprint of your key. You can find it with the command:
+<code>
+gpg --fingerprint [NAME]
+</code>
+where [NAME] can be a small part of your mail address: gpg is cleaver enough to do a search among your keys and guess which one is the closest.
+You are then ready to sign files and keys !
 ==== Checking the integrity of a downloaded file ====
@@ Line 248: / Line 280: @@
 GPG is a lot based on the trust that you are talking to the right person. Therefore, to tell to the whole world that you trust some public key, you should **sign the public keys** of other people.
+=== Note if you used Thunderbird and not Kleopatra ===
+To sign a key, you need to use the command line gpg, so as said before, if you used Kleopatra to generate your keys, you are good to go, as the gpg tool will already know your keys. However, if you used Thunderbird, you need to copy the keys you want to sign. This is how you do it.
+  - First, go to the PGP key manager in Thunderbird
+  - Select the public key you want to sign, then right click and click on Export public key to file and select a location on your computer
+  - Open a command line, navigate to the folder where your file is and enter ''%%gpg --import [FILENAME]%%'', where [FILENAME] is the file you exported the public key to
+  - repeat the operaton for each key you want to sign
+=== The actual Key signing ===
 This is how to do it (as recommended [[https://gist.github.com/F21/b0e8c62c49dfab267ff1d0c6af39ab84|here]]):
   - Alice (you) get the public key of Bob
-  - Alice sign it with her private key: <code>gpg --sign-key [key_id]</code> where <code>[key_id]</code> is the fingerprint of the Bob public key. In the process you will be asked to check that the fingerprint match with the key of the other person, which you should do in a secure channel, or in person, with the person owning the key.
+  - Alice sign it with her private key: ''%%gpg --sign-key [key_id]%%'' where ''%%[key_id]%%'' is the fingerprint of the Bob public key. In the process you will be asked to check that the fingerprint match with the key of the other person, which you should do in a secure channel, or in person, with the person owning the key. Note: you can at every time look at all signatures on a key with the command: ''%%gpg --list-sig [NAME]%%'', with [NAME] being for example part of the mail address associated with the key.
-  - Alice exports, then encrypts the signed key with Bob public key, with the following command: <code>gpg --armor --export [key_id] | gpg --sign --encrypt -r [key_id] > [filename]</code>, where <code>[key_id]</code> is the fingerprint of Bob public key and <code>[filename]</code>is the output filename
+  - Alice exports, then encrypts the signed key with Bob public key, with the following command: <code>gpg --armor --export [key_id] | gpg --sign --encrypt -r [key_id] > [filename]</code>, where ''%%[key_id]%%'' is the fingerprint of Bob public key and ''%%[filename]%%'' is the output filename. Note: you can alternatively, since you already configured your mails for this, just export the key with ''%%gpg --armor --export [key_id] > [filename]%%'', and attach it to a mail encrypted with your mail client.
   - Alice emails the key to Bob using the mail address associated with the key
-  - Bob receives it, then decrypt it with his private key and import it: <code>gpg --decrypt [filename]</code> and then <code>gpg --import [filename_decrypted]</code>
+  - Bob receives it, then decrypt it with his private key and import it: ''%%gpg --decrypt [filename]%%'' and then ''%%gpg --import [filename_decrypted]%%''
-  - He can then send it to a keyserver, containing Alice signature: <code>gpg --send_keys [key_id]</code>
+  - He can then send it to a keyserver, containing Alice signature: ''%%gpg --send_keys [key_id]%%''