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 NotInheritable Class RNGCryptoServiceProvider
	Inherits 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.
Imports System
Imports System.IO
Imports System.Text
Imports System.Security.Cryptography

    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
    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
            ' Fill the array with a random value.
        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

.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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