Abstract: Security of context-aware ubiquitous systems is
paramount, and authentication plays an important aspect in cloud
computing and ubiquitous computing. Trust management has been
identified as vital component for establishing and maintaining
successful relational exchanges between trading partners in cloud
and ubiquitous systems. Establishing trust is the way to build good
relationship with both client and provider which positive activates will
increase trust level, otherwise destroy trust immediately. We propose
a new context-aware authentication system using a trust management
system between client and server, and between servers, a trust which
induces partnership, thus to a close cooperation between these servers.
We defined the rules (algorithms), as well as the formulas to manage
and calculate the trusting degrees depending on context, in order to
uniquely authenticate a user, thus a single sign-on, and to provide
him better services.