Physical Security

A cryptographic primitive can be considered from two points of view: on the one hand, it can be viewed as an abstract mathematical object or black box (i.e. a trans-formation, possibly parameterized by a key, turning some input into some output); on the other hand, this primitive will in fine have to be implemented in a program that will run on a given processor, in a given environment, and will therefore present specific characteristics. The first point of view is that of classical cryptanalysis; the second one is that of physical security. Physical attacks on cryptographic devices take advantage of implementation specific characteristics to recover the secret parameters involved in the computation. They are therefore much less general, since specific to a given implementation, but often much more powerful than classical cryptanalysis, and are considered very seriously by cryptographic devices implementors. Physical attacks can be classified in many ways. The literature usually sorts them along two orthogonal axes. Invasive vs. non-invasive: invasive attacks require depackaging the chip to get direct access to its inside components; a typical example of this is the connection o