@article{backes06real,
  author       = {Backes, Michael},
  title        = {Real-or-Random Key Secrecy of the Otway-Rees Protocol via a Symbolic Security Proof},
  journal      = {Electronic Notes in Theoretical Computer Science (ENTCS)},
  volume       = {155},
  year         = {2006},
  pages        = {111-145}
}