Crypt

Imports System.IO
Imports System.Text
Imports System.Security.Cryptography

Public Class Form1

    Private Sub cmdEncrypt_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdEncrypt.Click
        txtCipherText.Text = Encrypt(txtPlainText.Text, txtPassPhrase.Text, "s@1tValue", "SHA1", 2, "@1B2c3D4e5F6g7H8", 256)
    End Sub

    Private Sub cmdDecrypt_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdDecrypt.Click
        txtPlainText.Text = Decrypt(txtCipherText.Text, txtPassPhrase.Text, "s@1tValue", "SHA1", 2, "@1B2c3D4e5F6g7H8", 256)
    End Sub

    Private Function Encrypt(ByVal plainText As String, ByVal passPhrase As String, ByVal saltValue As String, ByVal hashAlgorithm As String, ByVal passwordIterations As Integer, ByVal initVector As String, ByVal keySize As Integer) As String

        Dim initVectorBytes As Byte()
        initVectorBytes = Encoding.ASCII.GetBytes(initVector)

        Dim saltValueBytes As Byte()
        saltValueBytes = Encoding.ASCII.GetBytes(saltValue)

        Dim plainTextBytes As Byte()
        plainTextBytes = Encoding.UTF8.GetBytes(plainText)

        Dim password As Rfc2898DeriveBytes = New Rfc2898DeriveBytes(passPhrase, saltValueBytes, passwordIterations)
        Dim keyBytes As Byte()
        keyBytes = password.GetBytes(CInt(keySize / 8))

        Dim symmetricKey As RijndaelManaged
        symmetricKey = New RijndaelManaged()
        symmetricKey.Mode = CipherMode.CBC

        Dim encryptor As ICryptoTransform
        encryptor = symmetricKey.CreateEncryptor(keyBytes, initVectorBytes)

        Dim memoryStream As MemoryStream
        memoryStream = New MemoryStream()

        Dim cryptoStream As CryptoStream
        cryptoStream = New CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write)
        cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length)
        cryptoStream.FlushFinalBlock()

        Dim cipherTextBytes As Byte()
        cipherTextBytes = memoryStream.ToArray()
        memoryStream.Close()
        cryptoStream.Close()

        Dim cipherText As String
        cipherText = Convert.ToBase64String(cipherTextBytes)
        Encrypt = cipherText

    End Function

    Private Function Decrypt(ByVal cipherText As String, ByVal passPhrase As String, ByVal saltValue As String, ByVal hashAlgorithm As String, ByVal passwordIterations As Integer, ByVal initVector As String, ByVal keySize As Integer) As String

        On Error Resume Next

        Dim initVectorBytes As Byte()
        initVectorBytes = Encoding.ASCII.GetBytes(initVector)

        Dim saltValueBytes As Byte()
        saltValueBytes = Encoding.ASCII.GetBytes(saltValue)

        Dim cipherTextBytes As Byte()
        cipherTextBytes = Convert.FromBase64String(cipherText)

        Dim password As Rfc2898DeriveBytes = New Rfc2898DeriveBytes(passPhrase, saltValueBytes, passwordIterations)
        Dim keyBytes As Byte()
        keyBytes = password.GetBytes(CInt(keySize / 8))

        Dim symmetricKey As RijndaelManaged
        symmetricKey = New RijndaelManaged()
        symmetricKey.Mode = CipherMode.CBC

        Dim decryptor As ICryptoTransform
        decryptor = symmetricKey.CreateDecryptor(keyBytes, initVectorBytes)

        Dim memoryStream As MemoryStream
        memoryStream = New MemoryStream(cipherTextBytes)

        Dim cryptoStream As CryptoStream
        cryptoStream = New CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read)

        Dim plainTextBytes As Byte()
        ReDim plainTextBytes(cipherTextBytes.Length)

        Dim decryptedByteCount As Integer
        decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length)

        memoryStream.Close()
        cryptoStream.Close()

        Dim plainText As String
        plainText = Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount)

        Decrypt = plainText
    End Function
End Class