With the expansion and the convergence of computing and communication, the dynamic provisioning of customized pro- cessing and networking infrastructures as well as resource virtualization are appealing concepts and technologies. There- fore, new models and tools are needed to allow users to create, trust and exploit such on-demand virtual infrastruc- tures within wide area distributed environments. This pa- per proposes to combine network and system virtualization with cryptographic identification and SPKI/HIP principles to help the user communities to build and share their own re- source reservoirs. These ideas are implemented in the HIPer- Net framework enabling the creation and the management of customized confined execution environments in a large scale context. Based on the example of biomedical applications, the paper focuses on the security model of the HIPerNet system and develops the key aspects of our distributed se- curity approach. Then the paper discusses and illustrates how HIPerNet solutions fulfill the security requirements of applications through different scenarios.