Rfc2898DeriveBytes.IterationCount Property

Definition

Namespace:

System.Security.Cryptography

Assembly:

System.Security.Cryptography.dll

Source:

Rfc2898DeriveBytes.cs

Gets or sets the number of iterations for the operation.

public:
 property int IterationCount { int get(); void set(int value); };

public int IterationCount { get; set; }

member this.IterationCount : int with get, set

Public Property IterationCount As Integer

Property Value

Int32

The number of iterations for the operation.

Exceptions

ArgumentOutOfRangeException

The number of iterations is less than 1.

Examples

The following example shows how to use the IterationCount property to display the number of iterations used in the generation of the key. This code example is part of a larger example provided for the Rfc2898DeriveBytes class.

//The default iteration count is 1000 so the two methods use the same iteration count.
int myIterations = 1000;

try
{
   Rfc2898DeriveBytes ^ k1 = gcnew Rfc2898DeriveBytes( pwd1,salt1,myIterations );
   Rfc2898DeriveBytes ^ k2 = gcnew Rfc2898DeriveBytes( pwd1,salt1 );

   // Encrypt the data.
   Aes^ encAlg = Aes::Create();
   encAlg->Key = k1->GetBytes( 16 );
   MemoryStream^ encryptionStream = gcnew MemoryStream;
   CryptoStream^ encrypt = gcnew CryptoStream( encryptionStream,encAlg->CreateEncryptor(),CryptoStreamMode::Write );
   array<Byte>^utfD1 = (gcnew System::Text::UTF8Encoding( false ))->GetBytes( data1 );

   encrypt->Write( utfD1, 0, utfD1->Length );
   encrypt->FlushFinalBlock();
   encrypt->Close();
   array<Byte>^edata1 = encryptionStream->ToArray();
   k1->Reset();

   // Try to decrypt, thus showing it can be round-tripped.
   Aes^ decAlg = Aes::Create();
   decAlg->Key = k2->GetBytes( 16 );
   decAlg->IV = encAlg->IV;
   MemoryStream^ decryptionStreamBacking = gcnew MemoryStream;
   CryptoStream^ decrypt = gcnew CryptoStream( decryptionStreamBacking,decAlg->CreateDecryptor(),CryptoStreamMode::Write );

   decrypt->Write( edata1, 0, edata1->Length );
   decrypt->Flush();
   decrypt->Close();
   k2->Reset();

   String^ data2 = (gcnew 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}", k1->IterationCount );
      Console::WriteLine( "k2 iterations: {0}", k2->IterationCount );
   }

            //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.
                Aes encAlg = Aes.Create();
                encAlg.Key = k1.GetBytes(16);
                MemoryStream encryptionStream = new MemoryStream();
                CryptoStream encrypt = new CryptoStream(encryptionStream,
encAlg.CreateEncryptor(), CryptoStreamMode.Write);
                byte[] utfD1 = new System.Text.UTF8Encoding(false).GetBytes(
data1);

                encrypt.Write(utfD1, 0, utfD1.Length);
                encrypt.FlushFinalBlock();
                encrypt.Close();
                byte[] edata1 = encryptionStream.ToArray();
                k1.Reset();

                // Try to decrypt, thus showing it can be round-tripped.
                Aes decAlg = Aes.Create();
                decAlg.Key = k2.GetBytes(16);
                decAlg.IV = encAlg.IV;
                MemoryStream decryptionStreamBacking = new MemoryStream();
                CryptoStream decrypt = new CryptoStream(
decryptionStreamBacking, decAlg.CreateDecryptor(), CryptoStreamMode.Write);
                decrypt.Write(edata1, 0, edata1.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}", k1.IterationCount);
                    Console.WriteLine("k2 iterations: {0}", k2.IterationCount);
                }

'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 Aes = Aes.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 Aes = Aes.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

Remarks

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.

See also

• Cryptographic Services