randpw — Secure Random Password Generator in C

randpw is a simple and secure command-line tool for generating high-entropy, cryptographically strong passwords using the Linux kernel’s getrandom() syscall. Built in C with no external dependencies, it ensures reliability and speed while minimizing bias in password generation.

🔐 Features

• 📏 Customizable password length (8–999 characters)
• 🔁 16-bit entropy per character (bias-minimized)
• 🔒 Uses /dev/urandom via getrandom() syscall
• ⚡ Extremely fast and dependency-free
• 🧬 High-entropy character set (includes special characters)

Usage/Example

$ randpw
dN7jL#iCpwFt-Q9yMkZA5B?fuwvGeLhO
$ randpw -n 64
fQAKGL4F_1OJyA4epw4ZjD1nW9BFAg3UWEboVQ1LbeM6bn2NSoPi5-rqbpZJ9e#X
$ randpw --help
A simple and secure command-line tool for generating random, high-entropy passwords using /dev/urandom.
Usage: randpw [option]

Options:
    -h, --help         print randpw command line options (currently set)
    -v, --version      print randpw version
    -n, --length       length of the generated password (default: 32)

Installation

Clone the repository:

git clone https://github.com/pr00x/randpw.git
cd randpw

Build and install the binary:

sudo make install

Uninstallation

To remove the installed binary, run:

sudo make uninstall

To remove the compiled binary file from the source directory, run:

sudo make clean

Uninstall and clean in one command:

sudo make clean uninstall

🔐 Security Considerations

• Uses getrandom() instead of reading from /dev/urandom manually, ensuring no file descriptors or blocking.
• Employs 16-bit entropy per character to minimize modulo bias.

🧠 How It Works

1. The program requests 2 * n bytes from getrandom(), where n is the desired password length.
2. For each password character, it consumes 16 bits (2 bytes) to get a high-entropy number.
3. That number is mapped to a character in the allowed charset via modulo operation.
4. The password is printed to standard output.

Author

@prox

Contributing

Contributions are welcome! Please create a pull request or submit an issue for any feature requests or bug reports.

License

This project is licensed under the MIT License. See the LICENSE file for details.