RNGCryptoServiceProvider Class

Definition

public ref class RNGCryptoServiceProvider sealed : 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[System.Obsolete("RNGCryptoServiceProvider is obsolete.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

public sealed class RNGCryptoServiceProvider : System.Security.Cryptography.RandomNumberGenerator

[System.Runtime.InteropServices.ComVisible(true)]
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System.Obsolete("RNGCryptoServiceProvider is obsolete.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}")>]
type RNGCryptoServiceProvider = class
 inherit RandomNumberGenerator

type RNGCryptoServiceProvider = class
 inherit RandomNumberGenerator

[<System.Runtime.InteropServices.ComVisible(true)>]
type RNGCryptoServiceProvider = class
 inherit RandomNumberGenerator

Public NotInheritable Class RNGCryptoServiceProvider
Inherits RandomNumberGenerator

Inheritance

Object

RandomNumberGenerator

RNGCryptoServiceProvider

Attributes

ObsoleteAttribute ComVisibleAttribute

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;
 }
}

'The following sample uses the Cryptography class to simulate the roll of a dice.
Imports System.IO
Imports System.Text
Imports System.Security.Cryptography



Class RNGCSP
 Private Shared rngCsp As New RNGCryptoServiceProvider()
 ' Main method.
 Public Shared Sub Main()
 Const totalRolls As Integer = 25000
 Dim results(5) As Integer

 ' Roll the dice 25000 times and display
 ' the results to the console.
 Dim x As Integer
 For x = 0 To totalRolls
 Dim roll As Byte = RollDice(System.Convert.ToByte(results.Length))
 results((roll - 1)) += 1
 Next x
 Dim i As Integer

 While i < results.Length
 Console.WriteLine("{0}: {1} ({2:p1})", i + 1, results(i), System.Convert.ToDouble(results(i)) / System.Convert.ToDouble(totalRolls))
 i += 1
 End While
 rngCsp.Dispose()
 End Sub


 ' This method simulates a roll of the dice. The input parameter is the
 ' number of sides of the dice.
 Public Shared Function RollDice(ByVal numberSides As Byte) As Byte
 If numberSides <= 0 Then
 Throw New ArgumentOutOfRangeException("NumSides")
 End If 
 ' Create a byte array to hold the random value.
 Dim randomNumber(0) As Byte
 Do
 ' Fill the array with a random value.
 rngCsp.GetBytes(randomNumber)
 Loop While Not IsFairRoll(randomNumber(0), numberSides)
 ' Return the random number mod the number
 ' of sides. The possible values are zero-
 ' based, so we add one.
 Return System.Convert.ToByte(randomNumber(0) Mod numberSides + 1)

 End Function


 Private Shared Function IsFairRoll(ByVal roll As Byte, ByVal numSides As Byte) As Boolean
 ' 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.
 Dim fullSetsOfValues As Integer = [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

 End Function 'IsFairRoll
End Class

Remarks

Thread Safety

This type is thread safe.

See also

• Cryptographic Services