Comment on "Secure direct communication with a quantum one-time pad"
  In the paper [Phys. Rev. A \textbf{69}, 052319 (2004)], a quantum direct communication protocol is proposed which is claimed to be unconditionally secure even for the case of a noisy channel. We show that this is not the case by giving an undetectable attack scheme. 
H. Hoffmann, K. Bostroem, T. Felbinger