RNGCryptoServiceProvider Class
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RNGCryptoServiceProvider Class


Implements a cryptographic Random Number Generator (RNG) using the implementation provided by the cryptographic service provider (CSP). This class cannot be inherited.

Namespace:   System.Security.Cryptography
Assembly:  mscorlib (in mscorlib.dll)


public sealed class RNGCryptoServiceProvider : RandomNumberGenerator


Initializes a new instance of the RNGCryptoServiceProvider class.


Initializes a new instance of the RNGCryptoServiceProvider class.


Initializes a new instance of the RNGCryptoServiceProvider class with the specified parameters.


Initializes a new instance of the RNGCryptoServiceProvider class.


When overridden in a derived class, releases all resources used by the current instance of the RandomNumberGenerator class.(Inherited from RandomNumberGenerator.)


Determines whether the specified object is equal to the current object.(Inherited from Object.)


Fills an array of bytes with a cryptographically strong sequence of random values.(Overrides RandomNumberGenerator.GetBytes(Byte[]).)

System_CAPS_pubmethodGetBytes(Byte[], Int32, Int32)

Fills the specified byte array with a cryptographically strong random sequence of values.(Inherited from RandomNumberGenerator.)


Serves as the default hash function. (Inherited from Object.)


Fills an array of bytes with a cryptographically strong sequence of random nonzero values.(Overrides RandomNumberGenerator.GetNonZeroBytes(Byte[]).)


Gets the Type of the current instance.(Inherited from Object.)


Returns a string that represents the current object.(Inherited from Object.)


This type implements the IDisposable interface. When you have finished using the type, you should dispose of it either directly or indirectly. To dispose of the type directly, call its Dispose method in a try/catch block. To dispose of it indirectly, use a language construct such as using (in C#) or Using (in Visual Basic). For more information, see the “Using an Object that Implements IDisposable” section in the IDisposable interface topic.

The following code example shows how to create a random number with the RNGCryptoServiceProvider class.

//The following sample uses the Cryptography class to simulate the roll of a dice.

using System;
using System.IO;
using System.Text;
using System.Security.Cryptography;

class RNGCSP
    private static RNGCryptoServiceProvider rngCsp = new RNGCryptoServiceProvider();
    // Main method.
    public static void Main()
        const int totalRolls = 25000;
        int[] results = new int[6];

        // Roll the dice 25000 times and display
        // the results to the console.
        for (int x = 0; x < totalRolls; x++)
            byte roll = RollDice((byte)results.Length);
            results[roll - 1]++;
        for (int i = 0; i < results.Length; ++i)
            Console.WriteLine("{0}: {1} ({2:p1})", i + 1, results[i], (double)results[i] / (double)totalRolls);

    // This method simulates a roll of the dice. The input parameter is the
    // number of sides of the dice.

    public static byte RollDice(byte numberSides)
        if (numberSides <= 0)
            throw new ArgumentOutOfRangeException("numberSides");

        // Create a byte array to hold the random value.
        byte[] randomNumber = new byte[1];
            // Fill the array with a random value.
        while (!IsFairRoll(randomNumber[0], numberSides));
        // Return the random number mod the number
        // of sides.  The possible values are zero-
        // based, so we add one.
        return (byte)((randomNumber[0] % numberSides) + 1);

    private static bool IsFairRoll(byte roll, byte numSides)
        // There are MaxValue / numSides full sets of numbers that can come up
        // in a single byte.  For instance, if we have a 6 sided die, there are
        // 42 full sets of 1-6 that come up.  The 43rd set is incomplete.
        int fullSetsOfValues = Byte.MaxValue / numSides;

        // If the roll is within this range of fair values, then we let it continue.
        // In the 6 sided die case, a roll between 0 and 251 is allowed.  (We use
        // < rather than <= since the = portion allows through an extra 0 value).
        // 252 through 255 would provide an extra 0, 1, 2, 3 so they are not fair
        // to use.
        return roll < numSides * fullSetsOfValues;

.NET Framework
Available since 1.1
Available since 2.0
Windows Phone Silverlight
Available since 7.0

This type is thread safe.

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