cgoldie: A C Implementation of the X448 Key Exchange Algorithm

cgoldie is a lightweight, portable, and secure implementation of the X448 key exchange cryptographic algorithm, designed to be highly performant and suitable for certification.

Features

• Portability: Written in portable C99, without dynamic memory allocation.
• Security: Uses only constant-time operations, making it resistant to all avoidable side-channel attacks.
• Performance: Can achieve over 700 key agreements per second on a laptop CPU.
• Certifications: Designed to pass cryptographic certifications by implementing self-tests and zeroizing all intermediate values.
• Self-tests: Provides embedded test vectors to ensure correct execution of operations.

Requirements

• Randomness: You must provide your own secure random numbers. Refer to BSI's AIS-31 guidelines for more information.

Usage

For detailed instructions, refer to the big comment in the source file here.

Example

Here’s a simple example of how to use the cgoldie library in your project:

#include "cgoldie.h"

// ...

cgoldie(shared_secret, private_key, public_key);
cgoldie(out, private_key, public_key);
    if (0 != memcmp(out, kat_sm_1o, 56)) {
        printf("This was unexpected\n");
        return 2;
    }

int main() {
    uint8_t private_key[56], public_key[56], shared_secret[56];
    cgoldie_keygen(private_key, public_key); // Generate keys
    cgoldie_keyexchange(shared_secret, private_key, public_key); // Exchange keys
    return 0;
}

Repository Files

• cgoldie.c: Main implementation.
• cgoldie.h: Optional header file that defines the public functions.
• kats.py: Python script that generates the embedded test vectors.
• test_main.c: Entry point of the test program.
• testall.sh: Bash script that runs all tests with various compilation options.

Status

This project is considered complete and is no longer actively developed.

License

This project is public domain. You can use, modify, and distribute it without any restrictions.