Private Sub Main()
    Dim Key As New RijndaelManaged
    Dim Buffer() As Byte
    Dim PlainText As String
    
    ' Encrypt a string to a byte array.
    Buffer = Encrypt("This is some plaintext!", Key)
    
    Debug.Print "Encrypted data"
    PrintBytes Buffer
    Debug.Print
    
    ' Decrypt the byte array back to a string.
    PlainText = Decrypt(Buffer, Key)

    ' Display the plaintext value to the console.
    Debug.Print "Original data"
    Debug.Print PlainText
End Sub

Private Sub PrintBytes(ByRef Bytes() As Byte)
    Dim i As Long
    
    For i = LBound(Bytes) To UBound(Bytes)
        Debug.Print Object.ToString(Bytes(i), "X2"); " ";
    Next
    
    Debug.Print
End Sub

' Encrypt the string.
Private Function Encrypt(ByVal PlainText As String, ByVal Key As SymmetricAlgorithm) As Byte()
    Dim Encryptor As ICryptoTransform
    Dim Buffer() As Byte
    
    Buffer = Encoding.UTF8.GetBytes(PlainText)
    Set Encryptor = Key.CreateEncryptor
    Encrypt = Encryptor.TransformFinalBlock(Buffer, 0, CorArray.Length(Buffer))
End Function

' Decrypt the byte array.
Public Function Decrypt(ByRef CypherText() As Byte, ByVal Key As SymmetricAlgorithm) As String
    Dim Decryptor As ICryptoTransform
    Dim Buffer() As Byte
    
    Set Decryptor = Key.CreateDecryptor
    Buffer = Decryptor.TransformFinalBlock(CypherText, 0, CorArray.Length(CypherText))
    Decrypt = Encoding.UTF8.GetString(Buffer)
End Function

' This example produces the following output.
'
'    Encrypted Data (may be different because key is generated)
'    FA 5B 69 FB 30 48 B6 08 C3 68 4C 63 45 BE F9 FA 17 DC 4D B9 EC FC E7 84 3A 35 CB 41 1C 5E 1D E5
'
'    Original Data
'    This is some plaintext!