A smart card contains an embedded microchip with metallic contacts on the front. The smart card does not usually have its own power supply, yet it operates as a very small computer. The embedded operating system (OS) controls application execution, access condition, cryptographic routines, and communication protocols with the outside world(usually a terminal). Some smart cards have several applications embedded at a time; these are called "multi-application" smart cards. Invasive attacks refer to attacks of physical systems where the physical properties of the chip are irreversibly modified. Different kinds of attacks are possible using "standard" reverse engineering techniques with optical or scanning electron microscopes (SEM). The aim is to capture information stored in memory areas, or data flowing through the data bus, registers, etc. Such techniques are also used to disconnect circuits, to override sensors, or to defeat blown fuse links (using probe stations or Focused Ion Beam [FIB])