Imports System.ComponentModel
Imports System.Security.Cryptography
Imports System.Text
Imports System.IO
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#Region " Rijndael Encryption Algorithm "
    Public Class RijndaelManagedEncryption
#Region " Global Variables "
        Private Shared encoding As New UTF8Encoding
        Private Shared RijndaelAlg As New RijndaelManaged
        Private Shared HashAlg As HashAlgorithm = New SHA256Managed
        Enum RijndaelCryptographicAction
            Encrypt = 0
            Decrypt = 1
        End Enum
#End Region
 
#Region " Encryption/Decryption Events "
        Public Overloads Shared Function EncryptDecrypt(ByVal text As String, ByVal key As String, _
                                                        ByVal action As RijndaelCryptographicAction) As String
            Dim textBytes As Byte() = encoding.GetBytes(text)
            Dim keyBytes As Byte() = CheckKey(key)
 
            Return EncryptDecrypt(textBytes, keyBytes, action)
        End Function
 
        Public Overloads Shared Function EncryptDecrypt(ByVal text As String, ByVal key As Byte(), _
                                                        ByVal action As RijndaelCryptographicAction) As String
            Dim textBytes As Byte() = encoding.GetBytes(text)
            Dim keyBytes As Byte() = CheckKey(key)
 
            Return EncryptDecrypt(textBytes, keyBytes, action)
        End Function
 
        Public Overloads Shared Function EncryptDecrypt(ByVal data As Byte(), ByVal key As String, _
                                                        ByVal action As RijndaelCryptographicAction) As String
            Dim keyBytes As Byte() = CheckKey(key)
 
            Return EncryptDecrypt(data, keyBytes, action)
        End Function
 
        Public Overloads Shared Function EncryptDecrypt(ByVal data As Byte(), ByVal key As Byte(), _
                                                        ByVal action As RijndaelCryptographicAction) As String
            RijndaelAlg.BlockSize = 256
 
            If Not key.Length = 32 Then
                key = CheckKey(key)
            End If
 
            Dim IV As Byte() = GenerateIV(key)
            Try
                Select Case action
                    Case CryptographicAction.Encrypt
                        Using memStream As New MemoryStream
                            Using cStream As New CryptoStream(memStream, _
                                                       RijndaelAlg.CreateEncryptor(key, IV), _
                                                       CryptoStreamMode.Write)
                                cStream.Write(data, 0, data.Length)
                            End Using
                            Return Convert.ToBase64String(memStream.ToArray)
                        End Using
 
                    Case CryptographicAction.Decrypt
                        Dim textBytes As Byte() = Convert.FromBase64String(encoding.GetString(data))
                        Using memStream As New MemoryStream(textBytes)
                            Dim decryptedData(textBytes.Length) As Byte
                            Using cStream As New CryptoStream(memStream, _
                                                       RijndaelAlg.CreateDecryptor(key, IV), _
                                                       CryptoStreamMode.Read)
                                cStream.Read(decryptedData, 0, decryptedData.Length)
                            End Using
                            Return encoding.GetString(decryptedData)
                        End Using
 
                    Case Else
                        Return Nothing
                End Select
 
            Catch ex As CryptographicException
                Return "Error - Invalid Password"
            End Try
        End Function
#End Region
 
        'Generate a byte array containing the generated hash from the given key.
#Region " Key Check "
        Private Overloads Shared Function CheckKey(ByVal key As String) As Byte()
            Dim byteKey As Byte() = encoding.GetBytes(key)
 
            Return CheckKey(byteKey)
        End Function
 
        Private Overloads Shared Function CheckKey(ByVal key As Byte()) As Byte()
            Return HashAlg.ComputeHash(key)
        End Function
#End Region
 
        'Generate a byte array containing the generated IV from the given key.
#Region " Generate IV "
        Private Overloads Shared Function GenerateIV(ByVal key As String) As Byte()
            Dim keyBytes As Byte() = encoding.GetBytes(key)
 
            Return GenerateIV(keyBytes)
        End Function
 
        Private Overloads Shared Function GenerateIV(ByVal key As Byte()) As Byte()
            Dim keyReverse As String = encoding.GetString(key).ToCharArray.Reverse.ToString
            Dim NewKey As Byte() = encoding.GetBytes(keyReverse)
 
            Return HashAlg.ComputeHash(NewKey)
        End Function
#End Region
    End Class
#End Region