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Rfc2898DeriveBytes.IterationCount Property

Gets or sets the number of iterations for the operation.

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

'Declaration
Public Property IterationCount As Integer
'Usage
Dim instance As Rfc2898DeriveBytes
Dim value As Integer

value = instance.IterationCount

instance.IterationCount = value
/** @property */
public int get_IterationCount ()

/** @property */
public void set_IterationCount (int value)

public function get IterationCount () : int

public function set IterationCount (value : int)

Not applicable.

Property Value

The number of iterations for the operation.
Exception typeCondition

ArgumentOutOfRangeException

The number of iterations is less than 1.

Iteration count is the number of times an operation is performed. For this method, the count should be greater than zero. The minimum recommended number of iterations is 1000.

The following code example uses the Rfc2898DeriveBytes class to create two identical keys for the TripleDES class. It then encrypts and decrypts some data using the keys.

'The default iteration count is 1000 so the two methods use the same iteration count.
Dim myIterations As Integer = 1000
Try
    Dim k1 As New Rfc2898DeriveBytes(pwd1, salt1, myIterations)
    Dim k2 As New Rfc2898DeriveBytes(pwd1, salt1)
    ' Encrypt the data.
    Dim encAlg As TripleDES = TripleDES.Create()
    encAlg.Key = k1.GetBytes(16)
    Dim encryptionStream As New MemoryStream()
    Dim encrypt As New CryptoStream(encryptionStream, encAlg.CreateEncryptor(), CryptoStreamMode.Write)
    Dim utfD1 As Byte() = New System.Text.UTF8Encoding(False).GetBytes(data1)
    encrypt.Write(utfD1, 0, utfD1.Length)
    encrypt.FlushFinalBlock()
    encrypt.Close()
    Dim edata1 As Byte() = encryptionStream.ToArray()
    k1.Reset()

    ' Try to decrypt, thus showing it can be round-tripped.
    Dim decAlg As TripleDES = TripleDES.Create()
    decAlg.Key = k2.GetBytes(16)
    decAlg.IV = encAlg.IV
    Dim decryptionStreamBacking As New MemoryStream()
    Dim decrypt As New CryptoStream(decryptionStreamBacking, decAlg.CreateDecryptor(), CryptoStreamMode.Write)
    decrypt.Write(edata1, 0, edata1.Length)
    decrypt.Flush()
    decrypt.Close()
    k2.Reset()
    Dim data2 As String = New UTF8Encoding(False).GetString(decryptionStreamBacking.ToArray())

    If Not data1.Equals(data2) Then
        Console.WriteLine("Error: The two values are not equal.")
    Else
        Console.WriteLine("The two values are equal.")
        Console.WriteLine("k1 iterations: {0}", k1.IterationCount)
        Console.WriteLine("k2 iterations: {0}", k2.IterationCount)
    End If

//The default iteration count is 1000 so the two methods use the
//same iteration count.
int myIterations = 1000;
try {
    Rfc2898DeriveBytes k1 = new Rfc2898DeriveBytes(pwd1, salt1,
        myIterations);
    Rfc2898DeriveBytes k2 = new Rfc2898DeriveBytes(pwd1, salt1);
    // Encrypt the data.
    TripleDES encAlg = TripleDES.Create();
    encAlg.set_Key(k1.GetBytes(16));
    MemoryStream encryptionStream = new MemoryStream();
    CryptoStream encrypt = new CryptoStream(encryptionStream, 
        encAlg.CreateEncryptor(), CryptoStreamMode.Write);
    ubyte utfD1[] = (new System.Text.UTF8Encoding(false)).
        GetBytes(data1);
    encrypt.Write(utfD1, 0, utfD1.get_Length());
    encrypt.FlushFinalBlock();
    encrypt.Close();
    ubyte eData1[] = encryptionStream.ToArray();
    k1.Reset();
    // Try to decrypt, thus showing it can be round-tripped.
    TripleDES decAlg = TripleDES.Create();
    decAlg.set_Key(k2.GetBytes(16));
    decAlg.set_IV(encAlg.get_IV());
    MemoryStream decryptionStreamBacking = new MemoryStream();
    CryptoStream decrypt = new CryptoStream(decryptionStreamBacking, 
        decAlg.CreateDecryptor(), CryptoStreamMode.Write);
    decrypt.Write(eData1, 0, eData1.get_Length());
    decrypt.Flush();
    decrypt.Close();
    k2.Reset();
    String data2 = (new UTF8Encoding(false)).
        GetString(decryptionStreamBacking.ToArray());
    if (!(data1.Equals(data2))) {
        Console.WriteLine("Error: The two values are not equal.");
    }
    else {
        Console.WriteLine("The two values are equal.");
        Console.WriteLine("k1 iterations: {0}", (System.Int32)k1.
            get_IterationCount());
        Console.WriteLine("k2 iterations: {0}", (System.Int32)k2.
            get_IterationCount());
    }

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0
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