Updated: March 2009
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)
Visual Basic (Declaration)
<ComVisibleAttribute(True)> _
Public NotInheritable Class RNGCryptoServiceProvider _
Inherits RandomNumberGenerator
Dim instance As RNGCryptoServiceProvider
[ComVisibleAttribute(true)]
public sealed class RNGCryptoServiceProvider : RandomNumberGenerator
[ComVisibleAttribute(true)]
public ref class RNGCryptoServiceProvider sealed : public RandomNumberGenerator
public final class RNGCryptoServiceProvider extends RandomNumberGenerator
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.
Imports System
Imports System.IO
Imports System.Text
Imports System.Security.Cryptography
Class RNGCSP
' 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
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 new instance of the RNGCryptoServiceProvider.
Dim rngCsp As New RNGCryptoServiceProvider()
' 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
//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
{
// 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 new instance of the RNGCryptoServiceProvider.
RNGCryptoServiceProvider rngCsp = new RNGCryptoServiceProvider();
// 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.
using namespace System;
using namespace System::IO;
using namespace System::Text;
using namespace System::Security::Cryptography;
bool IsFairRoll(int roll, int 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;
}
int RollDice(int numberSides)
{
// Create a byte array to hold the random value.
array<Byte>^ randomNumber = gcnew array<Byte>(1);
// Create a new instance of the RNGCryptoServiceProvider.
RNGCryptoServiceProvider^ cryptoProvider =
gcnew RNGCryptoServiceProvider();
// Fill the array with a random value.
cryptoProvider->GetBytes(randomNumber);
// Convert the byte to an integer value to make the modulus operation
// easier.
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 (int)((randomNumber[0] % numberSides) + 1);
}
int main()
{
// Roll the dice 30 times and display
// the results to the console.
for (int i = 0; i < 30; i++)
{
Console::WriteLine(RollDice(6));
}
}
System..::.Object
System.Security.Cryptography..::.RandomNumberGenerator
System.Security.Cryptography..::.RNGCryptoServiceProvider
This type is thread safe.
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
.NET Framework
Supported in: 3.5, 3.0, 2.0, 1.1, 1.0
.NET Compact Framework
Supported in: 3.5, 2.0
Reference
Other Resources
Date | History | Reason |
|---|
March 2009
| Added Thread Safety section. |
Information enhancement.
|