gpg: OpenPGP Encryption and Signing Tool

Overview

gpg protects data using public-key cryptography. It generates and manages pairs of private and public keys, allowing for secure exchange of file and email content. It supports strong encryption algorithms and is available on various operating systems.

Key Features

Public/private key pair generation and management
File and message encryption/decryption
Digital signature generation and verification
Public key sharing via key servers

Key Options

The gpg command offers numerous options for various tasks. Here are some of the most frequently used ones.

Key Management

Encryption and Decryption

Signing and Verification

Generated command:

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Description:

`gpg` Executes the command.

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Usage Examples

Here are some common examples of using gpg to generate keys, encrypt/decrypt files, and create/verify signatures.

Generate a New Key Pair

gpg --gen-key

Follow the interactive prompts to set the key type, size, expiration date, name, email, etc.

View Public Key List

gpg --list-keys

Check all public key information stored in your current keyring.

Encrypt File (Specify Recipient)

gpg --encrypt --recipient Alice secret.txt

Encrypts 'secret.txt' using the public key of the specified recipient (e.g., 'Alice'). The result is saved as 'secret.txt.gpg'.

Decrypt File

gpg --decrypt secret.txt.gpg

Decrypts the encrypted file 'secret.txt.gpg'. Requires your private key passphrase. The output is to standard output. You can save it to a file using the `--output` option.

Add Digital Signature to File

gpg --sign document.txt

Adds a signature to 'document.txt'. The signed file is created as 'document.txt.gpg'.

Verify Signed File

gpg --verify document.txt.gpg

Verifies the signature of 'document.txt.gpg'. The signer's public key must be in your keyring.

Export Public Key (ASCII Armor)

gpg --export --armor Alice > alice_pubkey.asc

Exports the public key of user ID 'Alice' in ASCII Armor format and saves it to 'alice_pubkey.asc'.

Installation

gpg is usually pre-installed on most Linux distributions or can be easily installed from standard repositories. Here are the installation commands for major distributions.

Debian/Ubuntu

sudo apt update && sudo apt install gnupg

Install gpg using the APT package manager.

RHEL/CentOS/Fedora

sudo dnf install gnupg

Install gpg using the YUM or DNF package manager.

Arch Linux

sudo pacman -S gnupg

Install gpg using the Pacman package manager.

Tips & Precautions

Tips and precautions for using gpg safely and efficiently. Pay special attention to key management and password security.

Use Strong Passphrases

Use a strong and memorable passphrase when generating keys. The passphrase is the key element protecting your private key.

Strong Passphrase: Minimum 12 characters, combination of uppercase, lowercase, numbers, and special characters.

Backup Your Private Key

Your private key is extremely important, so it's recommended to back it up to a secure offline storage (e.g., USB drive, encrypted external hard drive). If you lose your key, you cannot recover your encrypted data.

Backup Method: gpg --export-secret-keys --armor [USER_ID] > private_key.asc

Generate a Revocation Certificate

Immediately after generating a key, create and securely store a revocation certificate. This is used to invalidate the key if it is compromised or lost.

Generate Revocation Certificate: gpg --gen-revoke [USER_ID]

Utilize Key Servers

You can upload your public key to a key server, making it easily discoverable and usable by others. This facilitates public key exchange.

Upload to Key Server: gpg --send-keys [USER_ID]