International Association
for Cryptologic Research

Security is a key component for information technologies and

communication. Among the security threats, a very important one is

certainly due to vulnerabilities of the integrated circuits that implement

cryptographic algorithms. These electronic devices (such as smartcards)

could fall into the hands of malicious people and then could be sub-

ject to \\physical attacks\". These attacks are generally classied into two

categories : fault and side-channel attacks. One of the main challenges

to secure circuits against such attacks is to propose methods and tools

to estimate as soundly as possible, the eciency of protections. Numer-

ous works attend to provide tools based on sound statistical techniques

but, to our knowledge, only address side-channel attacks. In this article,

a formal link between fault and side-channel attacks is presented. The

common factor between them is what we called the \'physical\' function

which is an extension of the concept of \'leakage function\' widely used

in side-channel community. We think that our work could make possible

the re-use (certainly modulo some adjustments) for fault attacks of the

strong theoretical background developed for side-channel attacks. This

work could also make easier the combination of side-channel and fault

attacks and thus, certainly could facilitate the discovery of new attack

paths. But more importantly, the notion of physical functions opens from

now new challenges about estimating the protection of circuits.