creative-chaos.dev

Using GnuPG (GPG) in the terminal to send and receive messages and encrypted files involves several steps. Here is a basic guide to help you get started.

1. Install GnuPG

Make sure you have GnuPG installed on your system. You can check by running:

gpg --version

If it’s not installed, you can install it using your package manager. For example, on Debian-based systems:

sudo apt-get install gnupg

or arch-based systems:

sudo pacman -S gnupg

2. Generate a Key Pair

If you haven’t already created a GPG key pair, you can do so with:

gpg --full-generate-key

Follow the prompts to select the key type, key size, expiration date, and to enter your user ID and passphrase.

3. Export Your Public Key

To share your public key with others, you can export it:

gpg --export -a "Your Name" > publickey.asc

Replace “Your Name” with the name or email associated with your key.

4. Import a Public Key

To send an encrypted message to someone, you need their public key. If you receive a public key file (e.g., friendkey.asc), import it using:

gpg --import friendkey.asc

5. Encrypt a Message

To encrypt a message for a recipient, you can use:

echo "Your secret message" | gpg --encrypt --armor -r "Recipient Name" > message.asc

Replace “Recipient Name” with the name or email associated with the recipient’s public key. The –armor option creates an ASCII-armored output.

6. Decrypt a Message

To decrypt a message you received, use:

gpg --decrypt message.asc

You will be prompted for your passphrase if the message is encrypted with your public key.

7. Encrypt a File

To encrypt a file, use:

gpg --encrypt -r "Recipient Name" file.txt

This will create an encrypted file named file.txt.gpg.

8. Decrypt a File

To decrypt an encrypted file, use:

gpg --decrypt file.txt.gpg > decrypted_file.txt

9. Sending Encrypted Files

You can send the encrypted file (file.txt.gpg) via email or any other file transfer method. Only the recipient with the corresponding private key can decrypt it.

10. Additional Commands List Keys: To see the keys you have, use:

gpg --list-keys

Delete a Key: To delete a key, use:

gpg --delete-key "Key Name"

Conclusion

This guide provides a basic overview of sending and receiving messages and files using GnuPG in the terminal. For more advanced features and options, refer to the GnuPG documentation or use man gpg in the terminal for more details.

Last time, we exported our public key. As my key expired I created a new pair.

Now, we will list our secrets key, where we can see our key ID. We remember, it’s the last 8 characters of the string.

Note: You should never publish your private key! It’s top secret!

– I’m just doing this here for demonstration purposes (anyway, I replaced this key with random numbers).

gpg --list-secret-keys
[keyboxd]
---------
sec   rsa4096 2024-08-22 [SC]
      7B865B1FB3B2731D4414F4A9319CA618681215D8
uid           [ultimate] Chaot (Test) <creative-chaos.dev@proton.me>
ssb   rsa4096 2024-08-22 [E]

Then we export the private key to a file. You will be prompted to type in your password.

gpg --armor --export-secret-keys 681215D8 > privatekey.asc

Here’s the privatekey.asc file. Keep it secure and never give it away. Don’t confuse it with your public key.

cat privatekey.asc 
-----BEGIN PGP PRIVATE KEY BLOCK-----

iQdGBGbGlVYBEAC9ttwIXe2jr+fCJd1XVTR6fK3+IeVbyqbgMFlY/dQj6zWnuqzx
nl0be+MuCBg9exdY1Xis68mmpZWALWx92lcdGQE8njqKi/RCO37qBHE7AuV02y59
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=Tl9U
-----END PGP PRIVATE KEY BLOCK-----

Now we know our key pair and will already be able to encrypt a file.

We’ll create a file named message.txt. I’ll use vim for it. Alternatively you can use nano. But nano has different commands than vim.

vim message.txt

Vim: In Vim, we’ll have to enable the ‘insert’-mode by typing ‘i’.

# This is just a comment. You should type i and then press enter.

Vim: Now I can insert some text, by typing in the keyboard.

Hello Bob,
how are you?
Kind Regards, 
Alice.
~
~
~
~
-- INSERT --

Vim: Now I press ESC-button to exit the insert mode.

# This is just a comment. You should press ESC to exit insert mode.

Vim: As we left insert mode, we can now save and exit, by typing ‘:wq’

# This is just a comment. You should press :wq and ENTER to exit insert mode.

Hello Bob,
how are you?
Kind Regards, 
Alice.
~
~
~
~
:wq

Now we left vim.

We can check our message.txt with the cat command:

cat message.txt

This will be the output:

cat message.txt
Hello Bob,
how are you?
Kind Regards, 
Alice.

Now we want to encrypt the message.txt file.

gpg --encrypt --recipient creative-chaos.dev@proton.me message.txt

This will create an encrypted file called message.txt.gpg. We can check it with the cat command. The contents are not meant to be human-readable, that’s why it looks strange. As I want to test the encryption I type in my mail adress, but if you want to send the message to someone else you should use their resp. the recipient’s mail.

cat message.txt.gpg
�
 Z�WJT:�TEvj(䡞B!�.q�ʣC&PI����8|�|U���#��9y��N�(P�l.IG���Ђ,D��s.xXj
                                                                   �nwɷ�v�.T�*z����XCJ&�yY	lcThjr<�l���+|�@w�4b���".������n��U�	�9�+
8�f����I�BE�th
qo!-����$W.ߩ9
      �d���^*OeaL�O5Uc�(�k�k�WBZ'�qO�3�[f]�"k���K��⩲�㌲/
�{��:��Eyw>���c�#���@@2=l�
���
   j�ݍ�ڍZn���[
              ��!& ׇ��9,�#*2Y�T�%�$����g�>�;ҷyF���jـf4��m���:�<�h�ו����+�5o�2�#����-�mȹ��]�N�<�?�d���Rn%%8�fdOU[3�]����=9�W�ԙ���`��z*����$tl0��;�*�~"�ڛR�?�v4��0���PEk�;^;�H�w	�%|���9���P�4�%/��`k�Ĭ4���d�b7t1T�}�$,*fg��;��G8/�T��N������ﭛ��86���&v����s���T����@F���q����x���)�����5�

So let’s decrypt this file with the command:

gpg --decrypt message.txt.gpg > decrypted_file.txt

You will be prompted to type in your password.

gpg --decrypt message.txt.gpg > decrypted_file.txt
gpg: encrypted with rsa4096 key, ID 1E5AAA7F574A543A, created 2024-08-22
      "Chaot (Test) <creative-chaos.dev@proton.me>"

Now we check our decrypted file with the cat command:

cat decrypted_file.txt

Will show this output:

cat decrypted_file.txt
Hello Bob, 
how are you?
Kind Regards

Now you know how to encrypt and decrypt files.

Oh, I forgot to mention that you should import your communication partner’s public keys beforehand.

---

To verify and sign a GPG key from a recipient that you have imported into your GnuPG keyring, you can follow these steps:

Step 1: Import the Recipient’s Key

If you haven’t already imported the recipient’s key, you can do so with the following command:

gpg --import /path/to/recipient-key.gpg

or

gpg --import /path/to/keyfile.asc

Or using a keyserver. You can import a key directly from a keyserver using the recipient’s email address or key ID. This is useful for obtaining public keys that have been shared publicly. Use the following command:

gpg --keyserver keyserver.ubuntu.com --recv-keys <key-id>

Or using the Web Key Directory (WKD). If the recipient’s key is available in a Web Key Directory, you can use the following command to locate and import it:

gpg --locate-keys recipient@example.com

Or Importing from a Clipboard

If you have copied the key to your clipboard (for example, from a website or email), you can paste it into a file and then import it. For example you can use nano or vim.

Step 2: List Keys

To verify that the key has been imported successfully, you can list the keys in your keyring:

gpg --list-keys

Step 3: Verify the Key

Before signing the key, you should verify the key’s authenticity. This typically involves checking the key’s fingerprint and ensuring that it matches what the recipient has provided. You can check the fingerprint with:

gpg --fingerprint recipient@example.com

Make sure to compare the displayed fingerprint with the one provided by the recipient through a trusted channel (e.g., in person, over a secure chat, etc.).

Step 4: Sign the Key

If you are satisfied that the key is legitimate and you trust the recipient, you can sign their key. To do this, use the following command:

gpg --sign-key recipient@example.com

This command will prompt you to confirm that you want to sign the key. You may also be asked to enter your passphrase if your private key is protected.

Step 5: Verify the Signature

After signing the key, you can verify that the signature has been added successfully by listing the key again:

gpg --list-sigs recipient@example.com

You should see your signature listed alongside the recipient’s key.

Step 6: Export the Signed Key (Optional)

If you want to share the signed key with others or upload it to a keyserver, you can export the signed key:

gpg --export -a recipient@example.com > signed-key.asc

Step 7: Upload the Signed Key to a Keyserver (Optional)

If you want to upload the signed key to a keyserver so that others can see your signature, you can do so with:

gpg --send-keys recipient@example.com

By following these steps, you can verify and sign a GPG key from a recipient, enhancing the trustworthiness of the key in the web of trust.

---

To upload your GPG key to a keyserver, you can follow these steps:
Step 1: Identify Your Key

First, you need to identify the key you want to upload. You can list your keys with the following command:

gpg --list-keys

This will display all the keys in your keyring along with their key IDs.

Step 2: Choose a Keyserver

You can choose from various keyservers to upload your key. Some popular keyservers include:

# keyserver.ubuntu.com
# pgp.mit.edu
# keys.openpgp.org
# pgp.key-server.io

Step 3: Upload Your Key

Once you have identified the key you want to upload and chosen a keyserver, you can use the following command to upload your key:

gpg --keyserver keyserver.ubuntu.com --send-keys

Replace with the actual key ID or email address associated with your key. For example:

gpg --keyserver keyserver.ubuntu.com --send-keys ABCD1234

Step 4: Verify the Upload

After uploading your key, you can verify that it has been successfully uploaded by searching for it on the keyserver. You can do this using the following command:

gpg --keyserver keyserver.ubuntu.com --search-keys your-email@example.com

This will search for your key using your email address. If it appears in the results, the upload was successful.

By following these steps, you can successfully upload your GPG key to a keyserver, making it available for others to find and use.

In the end, GnuPG is used to encrypt files. When it comes to emails, consider that metadata is also transmitted, which can reveal information about the sender, recipient, and the time of communication. There is an ongoing discussion about which is better – email encryption or messengers with encryption. Since email encryption is rarely used, messengers are more practical. Therefore, my idea for a client titled ‘Pretty-Nice-Privacy’. However, I am still in the conceptual phase.

Using a keyserver for managing and distributing GPG keys can be convenient, but there are several security concerns to consider:

1. Privacy and Anonymity:

• Public Exposure: Keys uploaded to a keyserver are generally public. This means that anyone can search for and retrieve your key, along with any associated user IDs (like your email address). If you are concerned about privacy, consider whether you want your key and associated information to be publicly accessible.
• Email Address Exposure: If your key is associated with an email address, that email address becomes publicly visible, which could lead to spam or targeted attacks.

2. Key Integrity:

• Key Spoofing: There is a risk that someone could upload a malicious key that impersonates you. If users do not verify the key’s fingerprint or check for signatures from trusted sources, they might inadvertently trust a fraudulent key.
• Lack of Trust: Keyservers do not inherently verify the authenticity of the keys they host. Users must rely on their own verification processes (e.g., checking fingerprints, using a web of trust).

3. Keyserver Reliability:

• Downtime and Availability: Keyservers can experience downtime or become unavailable, which may hinder your ability to retrieve keys when needed.
• Data Loss: If a keyserver is compromised or experiences data loss, keys may be lost or corrupted.

4. Key Revocation:

• Revocation Issues: If you revoke a key, it may take time for the revocation to propagate across all keyservers. Users may still find and use the old key until the revocation is fully recognized.
• Stale Keys: Users may encounter outdated or stale keys that have not been updated or removed from the keyserver.

5. Man-in-the-Middle Attacks:

• Key Interception: If a user retrieves a key from a keyserver without verifying its fingerprint, they may be vulnerable to man-in-the-middle attacks, where an attacker could provide a malicious key instead of the legitimate one.

6. Keyserver Trustworthiness:

• Trust in Keyserver Operators: Users must trust the operators of the keyserver to manage the keys securely. If the keyserver is compromised, it could lead to unauthorized access to keys or other sensitive information.

7. Legal and Regulatory Concerns:

• Data Retention and Compliance: Depending on the jurisdiction, keyservers may be subject to data retention laws or regulations that could impact user privacy.

Mitigation Strategies

To mitigate these concerns, consider the following best practices:

• Verify Key Fingerprints: Always verify the fingerprint of a key through a trusted channel before trusting it.
• Use Multiple Keyservers: Consider using multiple keyservers to increase redundancy and availability.
• Limit Personal Information: If privacy is a concern, consider using a pseudonym or limiting the personal information associated with your key.
• Regularly Update and Revoke Keys: Keep your keys up to date and promptly revoke any keys that are no longer in use or have been compromised.
• Educate Users: Encourage users to understand the importance of verifying keys and the potential risks associated with using keyservers.

You should be aware of these security concerns and taking appropriate precautions, so you can use keyservers more safely and effectively.