  We propose a simple timed broadcasting process calculus for modelling
wireless network protocols. The operational semantics of our calculus is given
in terms of a labelled transition semantics which is used to derive a standard
(weak) bi-simulation theory. Based on our simulation theory, we reformulate
Gorrieri and Martinelli's timed Generalized Non-Deducibility on Compositions
(tGNDC) scheme, a well-known general framework for the definition of timed
properties of security protocols. We use tGNDC to perform a semantic analysis
of three well-known key management protocols for wireless sensor networks: \mu
TESLA, LEAP+ and LiSP. As a main result, we provide a number of attacks to
these protocols which, to our knowledge, have not yet appeared in the
literature.
