Constructors: NewRfc2898DeriveBytes

Initializes a new instance of the Rfc2898DeriveBytes class using a password, a salt or salt size, and number of iterations to derive the key.

Parameters

Return Values

Remarks

The salt size must be 8 bytes or larger and the iteration count must be greater than zero. The minimum recommended number of iterations is 1000.

RFC 2898 includes methods for creating a key and initialization vector (IV) from a password and salt. You can use PBKDF2, a password-based key derivation function, to derive keys using a pseudo-random function that allows keys of virtually unlimited length to be generated. The Rfc2898DeriveBytes class can be used to produce a derived key from a base key and other parameters. In a password-based key derivation function, the base key is a password and the other parameters are a salt value and an iteration count.

Exceptions

Exception	Condition
ArgumentException	The specified salt size is smaller than 8 bytes or the iteration count is less than 1.
ArgumentNullException	The password or salt is an unitialized array.

Examples

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.

Public Sub Main()
    Const Pwd1 As String = "Simple Password"
    Dim Salt1(8) As Byte
    Dim RngCsp As New RNGCryptoServiceProvider
    
    RngCsp.GetBytes Salt1
    
    ' Data1 can be a string or contents of a file.
    Const Data1 As String = "Some test data"
    
    ' The default iteration count is 1000 so the two methods use the same iteration count.
    Const MyIterations As Long = 1000
    
    On Error GoTo Catch
    
    Dim K1 As Rfc2898DeriveBytes
    Dim K2 As Rfc2898DeriveBytes
    
    Set K1 = NewRfc2898DeriveBytes(Pwd1, Salt1, MyIterations)
    Set K2 = NewRfc2898DeriveBytes(Pwd1, Salt1)
    
    ' Encrypt the data.
    Dim EncAlg As TripleDES
    Dim EncryptionStream As New MemoryStream
    Dim Encrypt As CryptoStream
    Dim UtfD1() As Byte
    
    Set EncAlg = TripleDES.Create()
    EncAlg.Key = K1.GetBytes(16)
    Set Encrypt = NewCryptoStream(EncryptionStream, EncAlg.CreateEncryptor(), CryptoStreamMode.WriteMode)
    UtfD1 = NewUTF8Encoding(False).GetBytes(Data1)
    
    Encrypt.WriteBlock UtfD1, 0, CorArray.Length(UtfD1)
    Encrypt.FlushFinalBlock
    Encrypt.CloseStream
    
    Dim EData1() As Byte
    EData1 = EncryptionStream.ToArray()
    K1.Reset

    ' Try to decrypt, thus showing it can be round-tripped.
    Dim DecAlg As TripleDES
    Dim DecryptionStreamBacking As New MemoryStream
    Dim Decrypt As CryptoStream
        
    Set DecAlg = TripleDES.Create()
    DecAlg.Key = K2.GetBytes(16)
    DecAlg.IV = EncAlg.IV
    
    Set Decrypt = NewCryptoStream(DecryptionStreamBacking, DecAlg.CreateDecryptor(), CryptoStreamMode.WriteMode)
    Decrypt.WriteBlock EData1, 0, CorArray.Length(EData1)
    Decrypt.Flush
    Decrypt.CloseStream
    K2.Reset
    
    Dim Data2 As String
    Data2 = NewUTF8Encoding(False).GetString(DecryptionStreamBacking.ToArray())

    If Data1 <> Data2 Then
        Debug.Print "Error: The two values are not equal."
    Else
        Debug.Print "The two values are equal."
        Debug.Print CorString.Format("K1 iterations: {0}", K1.IterationCount)
        Debug.Print CorString.Format("K2 iterations: {0}", K2.IterationCount)
    End If

    Exit Sub

Catch:
    Dim Ex As Exception
    
    Catch Ex, Err
    Debug.Print Ex.ToString
End Sub

' This example code produces the following output.
'
'    The two values are equal.
'    K1 iterations: 1000
'    K2 iterations: 1000

NewRfc2898DeriveBytes

Parameters

Return Values

Remarks

Exceptions

Examples

See Also