- Public And Private Key Encryption
- Gpg Sign Public Key
- Gpg Generate Public And Private Key
- Gpg Generate Public And Private Key How It Works Videos
Feb 26, 2018 GPG is the Gnu Privacy Guard and it is an implementation of OpenPGP (Open Pretty Good Privacy). It is an encryption technique that was originally developed for use in. Use the gpg -list-secret-keys -keyid-format LONG command to list GPG keys for which you have both a public and private key. A private key is required for signing commits or tags. A private key is required for signing commits or tags. Jun 30, 2018 This is part 1 of this series. At the end of this post, you should be able to generate your own public/private keypair and a revocation certificate. This certificate is used to revoke your public/private keypair when your private key is compromised or you forget the passphrase for your private key. GPG can be used for encryption and for signing. Nov 14, 2019 GPG uses public key encryption wherein you create a key pair: one private or secret key you keep to yourself and one public key you share with your correspondents or the world. The important part of this two-key system is that neither key can be calculated by having the other.
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What is GnuPG?
GNU Privacy Guard (GnuPG), also known as GPG, is a tool for secure communication that was created by Werner Koch as Free Software under the GNU Project. GnuPG follows the OpenPGP protocol, which defines and standardizes all the necessary components involved in sending encrypted messages–signatures, private keys, and public key certificates. This piece of free software is notably used by journalists around the world to ensure that their sensitive email communication is kept secure and private.
GPG uses a combination of symmetric-key cryptography and public-key cryptography. Public key cryptography is likely already familiar to you since it is the recommended way to authenticate when SSHing in to your Linode. Public-key cryptography uses a key-pair system where any single user has a private and public key pair. The public key can be shared with anyone, while the private key should be protected and secret to maintain the integrity of the system.
This asymmetric cryptographic system is ideal for secure communication, because all it requires is that the sender of the message have a copy of the receiver’s public key before encrypting and sending the message. The recipient can then use their private key to decrypt the message. This means anyone can send you a secure message if they have a copy of your public key.
This guide shows how to create your own keypair, distribute the public key to a receiver, and encrypt and decrypt a message on Ubuntu 16.04 and 18.04.
Create GPG Keys
- Download and install the most recent version of the GPG command line tools for Ubuntu:
- Create a new primary keypair:Several prompts will appear before the keypair is generated:
- Select
(1) RSA and RSA (default)
for the type of key. - Enter
4096
for the key size. - Specify the duration the key should be valid in days, weeks, months, or years. For example,
1y
will set an expiration date of one year from the time of keypair creation. - Enter a name, email address, and comment to associate with the key pair. Any one of these three values can be used to identify the keypair for future use. Enter the desired information for each value and confirm when prompted.
- Provide a passphrase. The passphrase is used to unlock the private key, so it is important to ensure the passphrase is strong. Use a mix of alphanumeric characters.
Once you have responded to all prompts, the keypair will be generated. This may take a few minutes to generate depending on the key size that was chosen.If your system seems to hang at the following message:The system may require more entropy to generate the keypair, in a new shell session, install therng-utils
package:- Check and feed random data from an entropy source (e.g. hardware RNG device) to an entropy sink (e.g. kernel entropy pool) to provide the needed entropy for a secure keypair to be generated:
- Check the amount of entropy available on your Linode. The value should be somewhere near 3000 for keypair generation.
- Select
- Verify the keys on your public keyring:The example output contains two public keys:Each value in the list represents the following information:
- Public key:
pub
- Key size and type:
4096R
- Short key ID:
A11C0F78
- Creation date:
2018-08-02
- Expiration date:
[expires: 2018-09-01]
- User IDs:
exampleName2 (example comment) <[email protected]>
- Subkey:
sub
- Public key:
Throughout the remainder of this guide, the first public key will be used to encrypt our message. The output may vary slightly depending on the version of Ubuntu you are using.
Generate a Revocation Certificate
A revocation certificate is useful if you forget your passphrase or if your private key is somehow compromised. It is used to notify others that the public key is no longer valid. Create the revocation certificate immediately after generating your public key.
Generate a revocation certificate. Replace
[email protected]
with the email address associated with the public key:- A prompt will ask you to select a reason for the revocation and provide an optional description. The default reason is recommended.
- The revocation certificate will be saved to the current directory as a file named
revoke.asc
. Save the certificate to a safe location on a different system so that you can access it in case your key is compromised in the future.
Once you’ve revoked a public key it cannot be used to encrypt future messages to you. It can still be used to verify signatures that you made in the past and to decrypt past messages sent to you.
Exchange Public Keys
You will need to exchange public keys with someone in order to securely communicate with them. If you do not want to make your key available on a key server, you can exchange keys with someone directly by exporting your public key and sending them directly to the recipient.
Public And Private Key Encryption
Export Your Public Key
- Export the public key. Replace
public-key.gpg
with a desired name for the file and[email protected]
with the email address associated with your key’s user id:The file will save to the current directory. - Send the
public-key.gpg
file to the recipient in an email or copy and paste the contents of thepublic-key.gpg
file. - The recipient should import the public key and validate it in order to use it to decrypt a message sent by you.
Import and Validate a Public Key
You can add someone else’s public key to your public keyring by importing it. The user’s public key must first be sent to you, by email or some other format, before you can import it to your public key ring. When the key is imported you should verify the key by checking its fingerprint and then signing it.
Gpg Sign Public Key
- Once you’ve received the user’s public key and the
.gpg
file is saved to your Linode, import it to your public key ring. Replacepublic-key.gpg
with the file name of the public key you will import. If your file is saved somewhere other than the current directory, make sure you use the full path to the file: - Verify that the public key has been added to your public key ring:
- Check the key’s fingerprint:The output will resemble the followingAsk the owner of the public key to send you their public key’s fingerprint and verify that the fingerprint values match. If they match, you can be confident that the key you have added is a valid copy of the owner’s public key.
- When you have verified the public key’s fingerprint, sign the public key with your own key to officially validate it. Replace
[email protected]
with the associated email for the key you are validating:Enter your passphrase when prompted. - View the public key’s signatures to verify that your signature has been added:
- You can export the signature to the public key and then send the signed copy back to the owner of the public key to boost the key’s level of confidence for future users:Send the signed key to the public key owner via email so they can import the signature to their GPG database.
Submit Your Public Key to a Key Server
You can submit your public key to a GPG server to make it available to the general public. The GnuPG configuration file
~/.gnupg/gpg.conf
by default sets the key server as hkp://keys.gnupg.net
and provides examples of other key servers that can be used in the file’s comments. Since key servers around the globe synchronize their keys to each other it should not be necessary to change the default value set in the configuration file.- Find the long key ID for the public key you would like to send to the key server:You will see an output similar to the example. The long key ID is the value after the key size
4096R
in thepub
row. In the example the long key ID isC7277DE1A11C0F78
: - To send your public key to the default key server use the following command and replace
keyid
with your public key’s long key ID: - Anyone can request your public key from the key server with the following command:The public key will be added to the user’s trust database using the
trustdb.gpg
file.
Encrypt a Message
After you have obtained someone’s public keys, you can send them encrypted messages. When you are encrypting a message to send to someone, you are using their public key to encrypt the message. Only the holder of the corresponding private key will be able to decrypt the message.
To encrypt a message:
Replace
encrypted-doc.gpg
with a name for the encrypted version of your document, [email protected]
with the email associated with the public key of the encrypted message’s recipient, [email protected]
with your own public key’s associated email and doc-to-encrypt.txt
with the name of the document you will encrypt. If the document is not in the current directory, include the full path to the document.The extension
.gpg
is used for encrypted/binary data and .asc
or .sig
is used for detached or clearsign signatures. Including the --armor
flag will encrypt the message in plain text.Decrypt a Message
A message will need to have been encrypted with your public key for you to able to decrypt it with your private key. Ensure that anyone that will be sending you an encrypted message has a copy of your public key.
To decrypt a message:
Replace
decrypted-doc
with the name you want to assign to the decrypted message and doc-to-decrypt.gpg
with the name of the encrypted document. If the document is not in the current directory, include the full path to the document. Generate pem file from public key mac.More Information
You may wish to consult the following resources for additional information on this topic. While these are provided in the hope that they will be useful, please note that we cannot vouch for the accuracy or timeliness of externally hosted materials.
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After extending the expiry date of a GPG key you might have to copy your key to another machine to use the same key there. Here is how:
- Identify your private key:Example output:Remember the ID of your key (second column, after the slash, e.g. 'ABC12345'). If you have a 'sub' entry, you can ignore it.
- Run this command to export your key:
- Copy the key file to the other machine using a secure transport (
scp
is your friend). - To import, runIf the key already existed on the second machine, the import will fail saying 'Key already known'.
To force import, you will have to delete both the private and public key first (gpg --delete-keys
andgpg --delete-secret-keys
)
Gpg Generate Public And Private Key
Enigmail / GnuPG v2
Note that you probably also have gpg2 on your system which is backwards-compatible with gpg, but seems to manage a separate list of keys. When using Thunderbird with Enigmail, note that it uses version 2 and may be unable to see your private key after importing. To fix that, run
Gpg Generate Public And Private Key How It Works Videos
Restart Thunderbird afterwards.