This repository implements the RSA algorithm in C, with arbitarily large integers. The implementation uses a custom bigint library to handle large key sizes.
The library is header-only, and can be included in any C project.
It has support for generating keys and encrypting/decrypting messages.
To use the library, first include it in your C file.
#include "rsa.h"Then, generate a public/private key pair using the generate_key_pair function.
int main() {
bigint p1 = bigint_from_string("61");
bigint p2 = bigint_from_string("53");
bigint n, t, e, d;
generate_key_pair(p1, p2, &n, &t, &e, &d);
printf("Public key: ");
bigint_print(e);
printf("\nPrivate key: ");
bigint_print(d);
return 0;
}Then, use the encrypt_text and decrypt_text functions to encrypt and decrypt messages.
int main() {
bigint p1 = bigint_from_string("61");
bigint p2 = bigint_from_string("53");
bigint n, t, e, d;
generate_key_pair(p1, p2, &n, &t, &e, &d);
printf("Public key: ");
bigint_print(e);
printf("\nPrivate key: ");
bigint_print(d);
char message[] = "Hello, world!";
bigint *encrypted = encrypt_text(message, e, n);
char *decrypted = decrypt_text(encrypted, strlen(message), d, n);
printf("\nEncrypted: ");
for (int i = 0; i < strlen(message); i++) {
bigint_print(encrypted[i]);
printf(" ");
}
printf("\nDecrypted: %s\n", decrypted);
return 0;
}To build your program with the RSA library, simply add it to your include path, along with the bigint header file, and link against the C standard library.
gcc -I path/to/rsa -I path/to/bigint main.c -o mainTo build with CMake, you can use a CMakeLists.txt file like the following:
cmake_minimum_required(VERSION 3.0)
# Create a new project
project(HelloWorld)
# Add an executable
add_executable(HelloWorld main.c)
include_directories(path/to/rsa)
include_directories(path/to/bigint)Alternatively, you can use FetchContent to download the RSA and Bigint repositories and include them in your project.
# Import the library from the git repo
include(FetchContent)
FetchContent_Declare(
rsa
GIT_REPOSITORY https://github.com/adam-mcdaniel/rsa
GIT_TAG main
)
FetchContent_MakeAvailable(rsa)
# Include the header only library
include_directories(${rsa_SOURCE_DIR})
# Do the same for the bigint project
FetchContent_Declare(
bigint
GIT_REPOSITORY https://github.com/adam-mcdaniel/bigint
GIT_TAG main
)
FetchContent_MakeAvailable(bigint)
# Include the header only library
include_directories(${bigint_SOURCE_DIR})This project is licensed under the MIT License - see the LICENSE file for details.