Anyone know how to Encrypt a String via 128+-bit Encryption?

[The High Roller]

Hey guys. Me one more time, except I am not sure if there is such thing in VB.NET via 128-bit Encryption or more. I only know of 64-bit, can someone please teach me? Here is my code for 64-bit:

Encryption:

Public Function EncryptXString(ByVal sData As String) As String
        Dim mSHA As New SHA1Managed
        Dim dString() As Byte = ASCIIEncoding.ASCII.GetBytes(sData)
        Dim cString As String = Convert.ToBase64String(dString)
        Convert.ToBase64String(mSHA.ComputeHash(Encoding.ASCII.GetBytes(sData)))
        EncryptXString = cString
    End Function

And Decryption:

    Public Function FindXString(ByVal sData As String) As String
        Dim dData() As Byte = Convert.FromBase64String(sData)
        Dim dString As String = ASCIIEncoding.ASCII.GetString(dData)
        FindXString = dString
    End Function

Teach me... I want to know the truth, please.