RNGCryptoServiceProvider Class

Definition

Caution

RNGCryptoServiceProvider is obsolete. To generate a random number, use one of the RandomNumberGenerator static methods instead.

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

public sealed class RNGCryptoServiceProvider : System.Security.Cryptography.RandomNumberGenerator
[System.Obsolete("RNGCryptoServiceProvider is obsolete. To generate a random number, use one of the RandomNumberGenerator static methods instead.", DiagnosticId="SYSLIB0023", UrlFormat="https://aka.ms/dotnet-warnings/{0}")]
public sealed class RNGCryptoServiceProvider : System.Security.Cryptography.RandomNumberGenerator
[System.Runtime.InteropServices.ComVisible(true)]
public sealed class RNGCryptoServiceProvider : System.Security.Cryptography.RandomNumberGenerator
Inheritance
RNGCryptoServiceProvider
Attributes

Examples

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);
        }
        rngCsp.Dispose();
    }

    // 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];
        do
        {
            // Fill the array with a random value.
            rngCsp.GetBytes(randomNumber);
        }
        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;
    }
}

Remarks

Important

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.

Constructors

RNGCryptoServiceProvider()

Initializes a new instance of the RNGCryptoServiceProvider class.

RNGCryptoServiceProvider(Byte[])

Initializes a new instance of the RNGCryptoServiceProvider class.

RNGCryptoServiceProvider(CspParameters)

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

RNGCryptoServiceProvider(String)

Initializes a new instance of the RNGCryptoServiceProvider class.

Methods

Dispose()

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

(Inherited from RandomNumberGenerator)
Dispose(Boolean)

When overridden in a derived class, releases the unmanaged resources used by the RandomNumberGenerator and optionally releases the managed resources.

(Inherited from RandomNumberGenerator)
Equals(Object)

Determines whether the specified object is equal to the current object.

(Inherited from Object)
Finalize()

Frees resources used by the RNGCryptoServiceProvider class.

GetBytes(Byte[], Int32, Int32)

Fills the specified byte array with a cryptographically strong random sequence of values starting at a specified index for a specified number of bytes.

GetBytes(Byte[], Int32, Int32)

Fills the specified byte array with a cryptographically strong random sequence of values.

(Inherited from RandomNumberGenerator)
GetBytes(Byte[])

Fills an array of bytes with a cryptographically strong sequence of random values.

GetBytes(Span<Byte>)

Fills a span with cryptographically strong random bytes.

GetBytes(Span<Byte>)

Fills a span with cryptographically strong random bytes.

(Inherited from RandomNumberGenerator)
GetHashCode()

Serves as the default hash function.

(Inherited from Object)
GetNonZeroBytes(Byte[])

Fills an array of bytes with a cryptographically strong sequence of random nonzero values.

GetNonZeroBytes(Span<Byte>)

Fills a byte span with a cryptographically strong random sequence of nonzero values.

GetNonZeroBytes(Span<Byte>)

Fills a byte span with a cryptographically strong random sequence of nonzero values.

(Inherited from RandomNumberGenerator)
GetType()

Gets the Type of the current instance.

(Inherited from Object)
MemberwiseClone()

Creates a shallow copy of the current Object.

(Inherited from Object)
ToString()

Returns a string that represents the current object.

(Inherited from Object)

Applies to

Product Versions (Obsolete)
.NET Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5 (6, 7, 8, 9)
.NET Framework 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 2.0, 2.1

Thread Safety

This type is thread safe.

See also