The HTML5 Local Storage APIs have proven their ability
to improve the web application performances and the quality
of experience while giving up the imperative need to focus
on the data security and availability. In this paper, we address
these two characteristics, and we focus mainly on the security
of data stored locally. In fact, we integrated the user into
the local storage strategy and the local data encryption. The
data synchronization is introduced to make the proposal in
its context and to emphasize the need of encrypting the data
before their externalization.