How to Create a Bash File Decryption Utility

Encrypted files are only useful if decryption is just as easy as encryption. Yet in practice, decryption commands tend to be the ones people forget — the right cipher, the right flags, the right key file — usually right when it’s needed under time pressure. A dedicated Bash decryption utility removes that friction, wrapping standard, well-audited tools like openssl and gpg into a single, memorable command.

Before you proceed, make sure you have OpenSSL installed on your system.

Here’s a basic Bash script for decrypting a file:

#!/bin/bash

# Check if an encrypted file and password are provided
if [ $# -ne 2 ]; then
    echo "Usage: $0  "
    exit 1
fi

encrypted_file=$1
password=$2

# Check if the encrypted file exists
if [ ! -f "$encrypted_file" ]; then
    echo "Error: Encrypted file '$encrypted_file' not found."
    exit 1
fi

# Decrypt the file using AES-256-CBC
openssl enc -d -aes-256-cbc -in "$encrypted_file" -out "${encrypted_file%.enc}" -pass pass:"$password"

echo "File '$encrypted_file' decrypted."

Here’s how the script works:

1. It checks if both an encrypted file and a password are provided as command-line arguments. If not, it prints a usage message and exits.
2. The provided encrypted file and password are stored in the encrypted_file and password variables.
3. It checks if the encrypted file exists. If not, it prints an error message and exits.
4. It uses OpenSSL to decrypt the file (-d specifies decryption).
5. The decrypted file is saved without the .enc extension.
6. It prints a message indicating that the file has been decrypted.

Usage example:

./decryption_utility.sh file.txt.enc MySecretPassword

This will decrypt file.txt.enc using AES-256-CBC with the password “MySecretPassword” and save the decrypted file as file.txt.

Please note that this is a basic example. Depending on your requirements, you might want to add more features, error handling, or support for different encryption algorithms or methods. Always handle passwords and encryption keys securely.