Encryption recommendations

I have a tdes class that looks like this:

Imports Microsoft.VisualBasic
Imports System
Imports System.Collections.Generic
Imports System.Text
Imports System.Security.Cryptography
Imports System.IO

Namespace security
    Public Class tdes
        Private des As New TripleDESCryptoServiceProvider()
        Private utf8 As New UTF8Encoding()

    Private keyValue As Byte()
    Private iVValue As Byte()

    Public Property Key() As Byte()
        Get
            Return keyValue
        End Get
        Set(ByVal value As Byte())
            keyValue = value
        End Set
    End Property

    Public Property iV() As Byte()
        Get
            Return iVValue
        End Get
        Set(ByVal value As Byte())
            iVValue = value
        End Set
    End Property

    Public Sub New(ByVal key As Byte(), ByVal iV As Byte())
        Me.keyValue = key
        Me.iVValue = iV
    End Sub

    Public Function ByteDecrypt(ByVal bytes As Byte()) As String
        Dim output As Byte()
        output = Transform(bytes, des.CreateDecryptor(Me.keyValue, Me.iVValue))
        'Return Convert.ToBase64String(output)
        Return utf8.GetString(output)
    End Function

    Public Function ByteEncrypt(ByVal bytes As Byte()) As Byte()
        Return Transform(bytes, des.CreateEncryptor(Me.keyValue, Me.iVValue))
    End Function

    Public Function StringDecrypt(ByVal text As String) As String
        Dim input As Byte() = Convert.FromBase64String(text)
        Dim output As Byte() = Transform(input, des.CreateDecryptor(Me.keyValue, Me.iVValue))
        Return utf8.GetString(output)
    End Function

    Public Function StringEncrypt(ByVal text As String) As String
        Dim input As Byte() = utf8.GetBytes(text)
        Dim output As Byte() = Transform(input, des.CreateEncryptor(Me.keyValue, Me.iVValue))
        Return Convert.ToBase64String(output)
    End Function

    Public Function StringEncryptByte(ByVal text As String) As Byte()
        Dim input As Byte() = utf8.GetBytes(text)
        Dim output As Byte() = Transform(input, des.CreateEncryptor(Me.keyValue, Me.iVValue))
        'Return Convert.ToBase64String(output)
        Return output
    End Function

    Private Function Transform(ByVal input As Byte(), ByVal cryptoTransform As ICryptoTransform) As Byte()
        ' Create the necessary streams
        Dim memory As New MemoryStream()
        Dim stream As New CryptoStream(memory, cryptoTransform, CryptoStreamMode.Write)

        ' Transform the bytes as requesed
        stream.Write(input, 0, input.Length)
        stream.FlushFinalBlock()

        ' Read the memory stream and convert it back into byte array
        memory.Position = 0
        Dim result As Byte() = New Byte(memory.Length - 1) {}
        memory.Read(result, 0, result.Length)

        ' Clean up
        memory.Close()
        stream.Close()

        ' Return result
        Return result
    End Function

    End Class
End Namespace

      

        
        
        
      

    

And it works well in encryption and decryption. I want to encrypt some existing passwords in the database table, so I ran a little script on them that encrypt them the same way (missing for brevity):

Dim key As Byte() = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24}
Dim iv As Byte() = {8, 7, 6, 5, 4, 3, 2, 1}
Dim enc As New security.tdes(key, iv)
Dim i As Integer = 0

Using oConn As New SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings("pitstopConnectionString").ConnectionString)
    Using cmd As New SqlCommand("doUpdatePasswords", oConn)
        cmd.CommandType = CommandType.StoredProcedure
        cmd.Parameters.AddWithValue("@userid", userid)
        cmd.Parameters.AddWithValue("@newpassword", enc.StringEncryptByte(currentPassword))
        oConn.Open()
        Try
            i = cmd.ExecuteNonQuery()
        Catch ex As Exception
            Exit Sub
        End Try
    End Using
End Using

      

        
        
        
      

    

This successfully encrypted all my passwords for all entries in the table. Now when I allow someone to login, I want to compare two values ​​(what was entered versus what the password is stored) and I assumed the best way would be to decrypt the stored ones and compare with strings? For instance:

If (enc.ByteDecrypt(pwdenc).ToString() = pitstop.doMakeSafeForSQL(txtPassword.Text.ToString.ToLower)) Then

      

        
        
        
      

    

However, I am getting all sorts of bizarre errors; Cannot cast object of type "System.String" to type "System.Byte []". one, invalid character in Base-64 string. this is a different one based on how I am calling the password in the existing SQLDataReader:

 Using oConn As New SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings("pitstopConnectionString").ConnectionString)
     Using cmd As New SqlCommand("doGetEncryptedForLogin", oConn)
         cmd.CommandType = CommandType.StoredProcedure
         cmd.Parameters.AddWithValue("@email", pitstop.doMakeSafeForSQL(txtEmail.Text.ToString.ToLower))
         oConn.Open()
         Using dr As SqlDataReader = cmd.ExecuteReader()
             If dr.HasRows() = True Then
                 While dr.Read()
                     pwdenc = dr("password_b")
                 End While
             Else
                 pitstop.doLogIt("Denied login for [" & txtEmail.Text & "]")
                 litError.Text = "The details you have provided are incorrect. Please try again."
                 pnlDenied.Visible = True
                 Exit Sub
             End If
             dr.Close()
         End Using
     End Using
 End Using

      

        
        
        
      

    

Help or advice is appreciated as I'm stumped here ...