jasleen1/csprng

A small C & C++ library to use the OS's Crytpgraphically Secure Pseudo-Random Number Generator

duthomhas::CSPRNG

CSPRNG is a small library that uses your Operating System’s native Cryptographically-Secure Pseudo-Random Number Generator.

It is a superior replacement for the clunky, ill-designed std::random_device. It won’t throw. It won’t give you non-CS random numbers. It won’t pretend to tell you anything about entropy. It just works.

C++

Using it couldn’t be simpler:

#include <iostream>
#include <duthomhas/csprng.hpp>

int main()
{
  duthomhas::csprng rng;
  std::cout << rng() << "\n";

Want a double?

  double e;
  std::cout << rng( e )        << "\n";
  std::cout << rng( double() ) << "\n";

Or an array/string/vector/whatever?

  char r[ 20 ];
  rng( r );
  
  auto s = rng( std::string( 20, 0 ) );
  auto v = rng( std::vector <int> ( 20 ) );
  
  int* xs = rng( new int[ 20 ], 20 );
  int* vs = rng( malloc( 20*sizeof(int) ), 20*sizeof(int) );

Perhaps you’d just like to have a proper std::seed_seq for your Mersenne Twister?

  duthomhas::csprng seed;
  std::mt19937 rng( seed.sseq );

But wait, I’m using C

Still easy.

#include <stdio.h>
#include <duthomhas/csprng.h>

int main()
{
  CSPRNG rng = csprng_create( rng );        // Constructor
  if (!rng)
  {
    fprintf( stderr, "%s\n", "No CSPRNG! Fooey!" );
    return 1;
  }
  
  long n = csprng_get_int( rng );           // Get an int
  
  double f;                                 // Get a double
  csprng_get( rng, &f, sizeof(f) );
  
  int xs[ 20 ];                             // Get an array
  csprng_get( rng, xs, sizeof(xs) );
  
  void* p = malloc(20);                     // et cetera
  csprng_get( rng, p, 20 );
  free( p );
  
  rng = csprng_destroy( rng );              // Destructor
  return 0;
}

See the examples in the ~test/ subdirectory for more.

Installing

This is such a small library, it works just fine if all you do is copy everything found in the ~source/ directory to your program’s source directory.

Directory of myprogram/source:

  duthomhas/       ←   copied from ~csprng/source/
  csprng.cpp       ←   copied from ~csprng/source/
  myprogram.cpp    ←   your program code
  ...              ←   anything else in your program’s source directory

Compile the csprng.cpp file along with your code. Make sure to add your program’s directory to the compiler’s include path. (If you are using C, everything is the same except files end in .c and .h instead of .cpp and .hpp.) Command-line examples:

• g++ myprogram.cpp csprng.cpp -I.

• cl /EHsc myprogram.cpp csprng.cpp /I.

If you would prefer a static library you can do that too. See below for more.

Design Rationale

CSPRNG was not designed to be “header only” for one important reason: namespace pollution. Using the OS facility requires pulling a lot of symbols from OS-headers, some of which are disruptive if you aren’t aware of them.

This also makes it easy to modularize the C and C++ parts of the code.

Test / Examples

To compile the examples you will need three things:

1. Have CMake version 3.1 or later.
2. Have Tcl/Tk Wish interpreter version 8.6 or later.
3. Initialize your command line properly for your compiler.

Once you have your command shell open and ready to compile, change to the ~csprng/ directory, and run the BUILD script:

BUILD               (Windows)
wish BUILD          (Linux)

To clean up, type

BUILD clean         (Windows)
wish BUILD clean    (Linux)

You can use CMake directly if you wish. Please read the CMakeFiles.txt file for how to use it.

Static Linkage

If you really want a static library (libcsprng.a or csprng.lib), build the examples with static linkage. When done you will find the static library in the appropriate lib directory. Copy that to your compiler’s correct lib directory, and copy the ~csprng/source/duthomhas directory to your compiler’s include directory (so that it is include/duthomhas). Thereafter you can link normally with your program, for example:

g++ ... my_foo.cpp ... -lcsprng

License

Copyright 2017 Michael Thomas Greer
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.)