hybrid_keyscrypt.sh - Asymmetric Encryption Tool

This script provides a simple command-line tool for asymmetric encryption and decryption using OpenSSL. It encrypts files with AES256 with a randomly generated secret key, which is then encrypted with an RSA public key (~/.ssh/id_rsa by default). The encrypted file and the encrypted secret key are combined into a single output file.

Why?

I wrote this initially to learn about openssl. The idea was that files could be stored encrypted and secured with ~/.ssh/id_rsa, so if secret files were accidently included in an archive, it wouldn't matter as long as ~/.ssh/id_rsa wasn't.

This is not a robust, production ready script. The current path workspace is geared more for testing than everyday use. It could be modified to use a temporary directory, but care should be taken to make sure any intermediate files are securely removed after use.

Prerequisites

OpenSSL installed and available in your system's PATH.
RSA key pair (public and private keys).

Usage

./hybrid_keycrypt.sh [encrypt filename (public_keyfile) | decrypt filename (private_keyfile)]

Encrypt

To encrypt a file, use the encrypt or -e option followed by the file to encrypt and optionally the public key file.

./hybrid_keycrypt.sh encrypt <filename> [public_keyfile]

<filename>: The file you want to encrypt.
[public_keyfile]: The public key file to use for encryption (default: ~/.ssh/id_rsa).

Decrypt

To decrypt a file, use the decrypt or -d option followed by the encrypted file and optionally the private key file.

./hybrid_keycrypt.sh decrypt <filename.enc> [private_keyfile]

<filename.enc>: The encrypted file to decrypt.
[private_keyfile]: The private key file to use for decryption (default: ~/.ssh/id_rsa).

Decrypt and Display Only

To decrypt a file and display the contents without saving, use the -- option after the filename.

./hybrid_keycrypt.sh decrypt <filename.enc> --

Example

Encrypt a file (assumes ~/.ssh/id_rsa exists):

./hybrid_keycrypt.sh encrypt myfile.txt

Decrypt a file (uses alternative RSA keypair):

./hybrid_keycrypt.sh decrypt myfile.txt.enc ~/.ssh/id_rsa_file_encryption

Notes

The script automatically cleans up temporary files after encryption or decryption.
Look at the filenames used under the finish function and make sure no files in the current path use those filenames.
Ensure your RSA keys are properly configured and accessible.

bsharper/hybridkeycrypt