dcrypt

A utility library that wraps commonly-used cryptographic operations using OpenSSL's libcrypto API

IMPORTANT

This library was written for the education of the author and as such is absolutely NOT production-ready code!

Install

This library is targeted to Linux only and depends on libssl.

The Makefile uses the clang compiler and lld linker, but can be replaced with gcc and ld if LLVM tools are not installed.

To download and install, run

git clone https://github.com/ddddddeon/dcrypt.git
cd dcrypt
make
sudo make install

Usage

#include <assert.h>
#include <dcrypt.h>

#define KEY_LENGTH 4096

int main(int argc, char *argv[]) {
  // Generate a 4096-bit RSA key
  DCRYPT_PKEY *private_key = RSAGenerateKey(KEY_LENGTH);
  assert(private_key != NULL);

  // Write a private key to PEM-encoded file (private = true)
  bool written = RSAKeyToFile(private_key, "example_rsa", true);
  assert(written == true);

  // Write a public key to PEM-encoded file (private = false)
  written = RSAKeyToFile(private_key, "example_rsa.pub", false);
  assert(written == true);

  // Load a public or private key from PEM-encoded file
  DCRYPT_PKEY *public_key = RSAFileToKey("./example_rsa.pub", false);
  assert(public_key != NULL);

  // Convert a key to string
  unsigned char *public_key_string = RSAKeyToString(public_key, false);
  printf("%s\n", public_key_string);

  // Generate N random bytes
  unsigned char *message = GenerateRandomBytes(32);

  // Sign a message with the private key
  unsigned char *signature = RSASign((char *)message, private_key);
  assert(signature != NULL);

  // Verify a message with the public key
  bool verified = RSAVerify((char *)message, signature, public_key);
  assert(verified == true);

  // Encrypt a string with the public key
  unsigned char *ciphertext = RSAEncrypt("hello alice", public_key);

  // Decrypt a string with the private key
  unsigned char *plaintext = RSADecrypt(ciphertext, private_key);

  // hello alice
  printf("%s\n", plaintext);

  // Keys, byte arrays & signatures are allocated & must be freed by the caller
  DCRYPT_PKEY_free(private_key);
  DCRYPT_PKEY_free(public_key);
  free(message);
  free(signature);
  free(ciphertext);
  free(plaintext);
}

TODOs

• AES key creation
• Encrypt/Decrypt using AES key