JavaCrypt

A small command-line tool for RSA file encryption, decryption, key generation, and plain file copying.

Note: v1.0.4 (commit c9121e8) is the release submitted as my Abitur exam project. Everything after that is just bugfixes and small adjustments.

Install Java

The only thing you need to install yourself is a JDK (11 or newer).

• Debian: sudo apt update && sudo apt install default-jdk
• Arch: sudo pacman -S jdk-openjdk
• Mac (Homebrew): brew install openjdk
• Windows (winget): winget install EclipseAdoptium.Temurin.21.JDK

Build

This project uses Maven together with the Maven Wrapper, so you don't need to install Maven yourself - the wrapper downloads it for you on first run.

./mvnw package      # Linux / Mac
mvnw.cmd package    # Windows

This produces target/JavaCrypt.jar.

Usage

java -jar target/JavaCrypt.jar -genkeys [priv_keyfile] [pub_keyfile]
java -jar target/JavaCrypt.jar -encrypt [pub_keyfile] [ifile] [ofile]
java -jar target/JavaCrypt.jar -decrypt [priv_keyfile] [ifile] [ofile]
java -jar target/JavaCrypt.jar -copy [ifile] [ofile]

Generate Keys

Generates an RSA key pair and writes it to the given files, in Java's own serialized object format (not a standard PEM/DER format, so it's only readable by JavaCrypt itself).

java -jar target/JavaCrypt.jar -genkeys priv.key pub.key

Encrypt a File

Encrypts a file using a public key.

java -jar target/JavaCrypt.jar -encrypt pub.key file.txt file.enc

Decrypt a File

Decrypts a file using the matching private key.

java -jar target/JavaCrypt.jar -decrypt priv.key file.enc file.dec

Copy a File

A plain file copy, without any encryption.

java -jar target/JavaCrypt.jar -copy file.txt file_copy.txt

Full Example

An end-to-end walkthrough, from a fresh clone to a verified encrypt/decrypt roundtrip:

./mvnw package

java -jar target/JavaCrypt.jar -genkeys priv.key pub.key
# Private key file: priv.key
# Public key file:  pub.key

echo "Hello World" > test.txt

java -jar target/JavaCrypt.jar -encrypt pub.key test.txt test_encrypt.txt
# Number of bytes transferred: 128

java -jar target/JavaCrypt.jar -decrypt priv.key test_encrypt.txt test_decrypt.txt
# Number of bytes transferred: 128

cat test_decrypt.txt
# Hello World

License

GPLv3