Arabic cursive optical character recognition (OCR) based on the dynamic time warping (DTW) algorithm provides simultaneously very interesting segmentation and recognition rates. However, the computing complexity of the DTW algorithm restricts its widespread utilization and its consideration at a commercial scale. Accelerating the DTW execution time has attracted many researchers and several solutions have already been proposed. These solutions are commonly based on very specialized processors and hardware architectures and as such they remain very expensive and not amenable to a large scale utilization. In a previous work, we found that loosely coupled architectures can indeed provide viable infrastructures to implement a distributed Arabic OCR. Our objective here is to allow the recognition of huge quantities of Arabic documents such as those of certain national libraries. Undoubtedly, enough processing power and storage capabilities are needed. In this paper, we proposed and used a peer-to-peer (P2P) architecture using the scientific research Tunisian grid (SRTG). Conducted experiments testify that our proposed architecture provides very adequate speedups of the DTWbased

Intensive experiences show and confirm that grid environments can be considered as the most promising way to solve several kinds of problems relating either to cooperative work especially where involved collaborators are dispersed geographically or to some very greedy applications which require enough power of computing or/and storage. Such environments can be classified into two categories; first, dedicated grids where the federated computers are solely devoted to a specific work through its end. Second, Volunteer grids where federated computers are not completely devoted to a specific work but instead they can be randomly and intermittently used, at the same time, for any other purpose or they can be connected or disconnected at will by their owners without any prior notification. Each category of grids includes surely several advantages and disadvantages; nevertheless, we think that volunteer grids are very promising and more convenient especially to build a general multipurpose distributed scalable environment. Unfortunately, the big challenge of such environments is, however, security and trust. Indeed, owing to the fact that every federated computer in such an environment can randomly be used at the same time by several users or can be disconnected suddenly, several security problems will automatically arise. In this paper, we propose a novel solution based on identity federation, agent technology and the dynamic enforcement of access control policies that lead to the design and implementation of trusted volunteer grid environments. KEYWORDS Volunteer grid environments; security and trust of Volunteer grid environments; Identity federation; Agent technology; dynamic enforcement of access control policies. 1.