Embedded systems present significant security challenges due to their limited resources and power constraints. We propose a novel security architecture for embedded systems (SANES) that leverages the capabilities of reconfigurable hardware to provide efficient and flexible architectural support to both security standards and a range of attacks. This paper shows the efficiency of reconfigurable architecture to implement security primitives within embedded systems. We also propose the use of hardware monitors to detect and defend against attacks. The SANES architecture is based on three main ideas: 1) reconfigurable security primitives, 2) reconfigurable hardware monitors and 3) a hierarchy of security controllers at the primitive, system and executive level. Results are presented for a reconfigurable AES security primitive within the IPSec standard and highlight the interest of such a solution.