  Highly dynamic computing environments, like ubiquitous and pervasive
computing environments, require frequent adaptation of applications. Context is
a key to adapt suiting user needs. On the other hand, standard access control
trusts users once they have authenticated, despite the fact that they may reach
unauthorized contexts. We analyse how taking into account dynamic information
like context in the authorization subsystem can improve security, and how this
new access control applies to interaction patterns, like messaging or eventing.
We experiment and validate our approach using context as an authorization
factor for eventing in Web service for device (like UPnP or DPWS), in smart
home security.
