/*

Spec:

Generate 6 random numbers between 1 and 59, printed in ascending order and no duplicates. Creative licence beyond this is permitted. Can be in any non-obscure language.

​

Comments:

for most applications I would use:

​

Random r = new Random();

 int x= r.Next(1,60);

As this is a lottery and there's potentially millions of pounds at stake I wouldn't trust it, expecially given that it has a bug in it's current implementation:

​

https://connect.microsoft.com/VisualStudio/feedback/details/634761/system-random-serious-bug#tabs

​

Instead I have used System.Security.Cryptography RandomNumberGenerator GetBytes() to get 32 bits of Crytograpgically secure random entropy.

​

I had to reinvent the wheel a little bit to convert the entropy into a random number within a range. I think that it's been worth it as the code is highly reusable.

​

*/

​

using System;

using System.Collections.Generic;

using System.Security.Cryptography;

​

public class Program

{

    const int LOTTERY_MAX = 60;

    SHA256 Sha256 = SHA256.Create();

    public static void Main()

    {   

        RandomNumberGenerator rng = RandomNumberGenerator.Create(); 

        SHA256 sha256 = SHA256.Create();

        byte[] random = new Byte[32];

        rng.GetBytes(random);   

        Console.WriteLine("my Rand:         " +  BitConverter.ToString(random));

        Console.WriteLine("my Commitment:   " + BitConverter.ToString(sha256.ComputeHash(random)));

        List<byte[]> seeds = new List<byte[]>

        {

            new Byte[] {0x01, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},

            new Byte[] {0x10, 0x01, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},

            new Byte[] {0x10, 0x00, 0x10, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},

            new Byte[] {0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},

        };

        byte[] combinedSeed = new Byte[32]{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};

        for(int i = 0; i < 32; i++)

        {

            foreach(byte[] seed in seeds)

            {

                combinedSeed[i] ^= seed[i];

            }

        }

        Console.WriteLine("my out:      " +  BitConverter.ToString(combinedSeed));

        Console.WriteLine(RandomNumbers.Rand(combinedSeed, 1, 59)); 

        /*

        for(int i = 0 ; i < 1000; i++)

        {

            rng.GetBytes(random);           

            RandomNumbers.Rand(random, 1, (uint.MaxValue / 3)+2);

        }

        /*

        rng.GetBytes(random);           

        Console.WriteLine(RandomNumbers.Rand(random, 1, 5));

        rng.GetBytes(random);           

        Console.WriteLine(RandomNumbers.Rand(random, 1, 5));

        rng.GetBytes(random);           

        Console.WriteLine(RandomNumbers.Rand(random, 1, 5));

        rng.GetBytes(random);           

        Console.WriteLine(RandomNumbers.Rand(random, 1, 5));

        rng.GetBytes(random);           

        Console.WriteLine(RandomNumbers.Rand(random, 1, 5));

        rng.GetBytes(random);           

        Console.WriteLine(RandomNumbers.Rand(random, 1, 5));

        rng.GetBytes(random);           

        Console.WriteLine(RandomNumbers.Rand(random, 1, 5));

        rng.GetBytes(random);           

        Console.WriteLine(RandomNumbers.Rand(random, 1, 5));

        Console.WriteLine("woop");

        Console.WriteLine(RandomNumbers.Rand(Convert.FromBase64String("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA="), 1, uint.MaxValue - 256));

        Console.WriteLine(RandomNumbers.Rand(Convert.FromBase64String("A/AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA="), 1, uint.MaxValue - 256));

        Console.WriteLine(RandomNumbers.Rand(Convert.FromBase64String("AA/AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA="), 1, uint.MaxValue - 256));

        Console.WriteLine(RandomNumbers.Rand(Convert.FromBase64String("AAA/AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA="), 1, uint.MaxValue - 256));

        Console.WriteLine(RandomNumbers.Rand(Convert.FromBase64String("AAAA/AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA="), 1, uint.MaxValue - 256));

        Console.WriteLine(RandomNumbers.Rand(Convert.FromBase64String("AAAAA/A/AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA/A="), 1, uint.MaxValue - 256));

        Console.WriteLine(RandomNumbers.Rand(Convert.FromBase64String("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA/AA="), 1, uint.MaxValue - 256));

        Console.WriteLine(RandomNumbers.Rand(Convert.FromBase64String("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA="), 1, uint.MaxValue - 256));

        Console.WriteLine(RandomNumbers.Rand(Convert.FromBase64String("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA/AAA="), 1, uint.MaxValue - 256));

        Console.WriteLine(RandomNumbers.Rand(Convert.FromBase64String("AAAAAAAAAAAAAAAAAAA/A/A/A/A/AAAAAAAAAAAAAAA="), 1, uint.MaxValue - 256));

        Console.WriteLine(RandomNumbers.Rand(Convert.FromBase64String("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA/AAA="), 1, uint.MaxValue - 256));

        Console.WriteLine(RandomNumbers.Rand(Convert.FromBase64String("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA//="), 1, uint.MaxValue - 256));

​

        SortedSet<uint> lotteryNumbers = new SortedSet<uint>();

        for(int i = 0; i < 6; i++)

        {

            uint newNum;

            do

            {

                newNum = RandomNumbers.Rand(1, LOTTERY_MAX);    

            } while(lotteryNumbers.Contains(newNum));

            lotteryNumbers.Add(newNum);

        }

        Console.WriteLine(string.Join(", ", lotteryNumbers));

        */

    }

}

​

///<summary>

/// Generates a seeded cryptographically secure random positive integer whithin number within ranges.

///</summary>

public static class RandomNumbers

{

    static RandomNumberGenerator rng = RandomNumberGenerator.Create();  

    static SHA256 sha256 = SHA256.Create();

    ///<summary>

    ///Returns a cryptographically secure random uint.

    ///</summary>

    ///<returns>

    ////Returns uint >= 0 and <= uint.MaxValue.

    ////</returns>

    public static uint Rand(byte[] seed)

    {       

        return BitConverter.ToUInt32(seed, 0);

    }

​

    ///<summary>

    ///Returns a cryptographically secure random uint.

    ///</summary>

    ///<param name = "max">Upper exclusive bound for the random integer</param>

    ///<returns>

    ////Returns uint >= 0 and < max.

    ////</returns>

    public static uint Rand(byte[] seed, uint max)

    {

        if(max == 0)

            throw new ArgumentOutOfRangeException("max", "max must be greater than 0");

        uint rand;

        while (true)

        {

            rand = Rand(seed);

            //If no bias is present, break. See http://stackoverflow.com/a/10984975

            if (rand < (uint.MaxValue - uint.MaxValue % max))

                break;

            //otherwise mutate the seed and try again

            seed = sha256.ComputeHash(seed);

        }

        return rand % max;

    }

​

    ///<summary>

    ///Returns a cryptographically secure random uint.

    ///</summary>

    ///<param name = "min">Lower inclusive bound for the random integer</param>

    ///<param name = "max">Upper exclusive bound for the random integer</param> 

    ///<returns>

    ////Returns uint >= min and < max.

    ////</returns>

    public static uint Rand(byte[] seed, uint min, uint max)

    {

        if(min >= max)

            throw new ArgumentOutOfRangeException("min", "max must be greater than min");

        return min + Rand(seed, max - min);

    }

}