  In several critical military missions, more than one decision level are
involved. These decision levels are often independent and distributed, and
sensitive pieces of information making up the military mission must be kept
hidden from one level to another even if all of the decision levels cooperate
to accomplish the same task. Usually, a mission is negotiated through insecure
networks such as the Internet using cryptographic protocols. In such protocols,
few security properties have to be ensured. However, designing a secure
cryptographic protocol that ensures several properties at once is a very
challenging task. In this paper, we propose a new secure protocol for multipart
military missions that involve two independent and distributed decision levels
having different security levels. We show that it ensures the secrecy,
authentication, and non-repudiation properties. In addition, we show that it
resists against man-in-the-middle attacks.
