— Smart cards are widely known for their tamper resistance, but only contain a small amount of memory. Though very small, this memory often contains highly valuable information (identification data, cryptographic key, etc). This is why it is often subject to many attacks, as the other parts of the smart card, and thus requires appropriately chosen protections. The use of memories in smart cards induces security problems, but also other more particular ones. The main constraint is naturally the limited physical expansion and integration, but fault level, aging and power consumption are not to be discarded. Indeed, Kuhn [3] has proved that it is possible to read the content of a ROM by simply using a microscope. This is of course completely unacceptable because ROM contains sensitive information. The operating system and some particular applications, for example, are written in ROM. Skorobogatov [15], in his turn, has explained how the interaction between light and silicon can be used...