String Encrypt/Decrypt

Imports System
Imports System.Collections.Generic
Imports System.Linq
Imports System.Text
Imports System.Security.Cryptography
Imports System.IO

Namespace My

    Public Class strCrypto

        ' This constant string is used as a "salt" value for the PasswordDeriveBytes function calls.
        ' This size of the IV (in bytes) must = (keysize / 8).  Default keysize is 256, so the IV must be
        ' 32 bytes long.  Using a 16 character string here gives us 32 bytes when converted to a byte array.
        Private Const initVector As String = "r5dm5fgm24mfhfku"

        Private Const passPhrase As String = "yourpassphrase"

        ' email password encryption password
        ' This constant is used to determine the keysize of the encryption algorithm.
        Private Const keysize As Integer = 256

        Public Shared Function encryptString(ByVal plainText As String) As String
            'if the plaintext  is empty or null string just return an empty string
            If ((plainText = "")  _
                        OrElse (plainText Is Nothing)) Then
                Return ""
            End If
            Dim initVectorBytes() As Byte = Encoding.UTF8.GetBytes(initVector)
            Dim plainTextBytes() As Byte = Encoding.UTF8.GetBytes(plainText)
            Dim password As PasswordDeriveBytes = New PasswordDeriveBytes(passPhrase, Nothing)
            Dim keyBytes() As Byte = password.GetBytes((keysize / 8))
            Dim symmetricKey As RijndaelManaged = New RijndaelManaged
            symmetricKey.Mode = CipherMode.CBC
            Dim encryptor As ICryptoTransform = symmetricKey.CreateEncryptor(keyBytes, initVectorBytes)
            Dim memoryStream As MemoryStream = New MemoryStream
            Dim cryptoStream As CryptoStream = New CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write)
            cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length)
            cryptoStream.FlushFinalBlock
            Dim cipherTextBytes() As Byte = memoryStream.ToArray
            memoryStream.Close
            cryptoStream.Close
            Return Convert.ToBase64String(cipherTextBytes)
        End Function

        Public Shared Function decryptString(ByVal cipherText As String) As String
            'if the ciphertext is empty or null string just return an empty string
            If ((cipherText = "")  _
                        OrElse (cipherText Is Nothing)) Then
                Return ""
            End If
            Dim initVectorBytes() As Byte = Encoding.ASCII.GetBytes(initVector)
            Dim cipherTextBytes() As Byte = Convert.FromBase64String(cipherText)
            Dim password As PasswordDeriveBytes = New PasswordDeriveBytes(passPhrase, Nothing)
            Dim keyBytes() As Byte = password.GetBytes((keysize / 8))
            Dim symmetricKey As RijndaelManaged = New RijndaelManaged
            symmetricKey.Mode = CipherMode.CBC
            Dim decryptor As ICryptoTransform = symmetricKey.CreateDecryptor(keyBytes, initVectorBytes)
            Dim memoryStream As MemoryStream = New MemoryStream(cipherTextBytes)
            Dim cryptoStream As CryptoStream = New CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read)
            Dim plainTextBytes() As Byte = New Byte((cipherTextBytes.Length) - 1) {}
            Dim decryptedByteCount As Integer = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length)
            memoryStream.Close
            cryptoStream.Close
            Return Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount)
        End Function
    End Class
End Namespace