This article presents the state-of-the-art of the physical security of smart devices. Electronic devices are getting ubiquitous and autonomous: their security is thus becoming a predominant feature. Attacks targeting the physical layer are all the more serious as hardware is not naturally protected against them. The attacks typically consist in either tampering with the device so as to make it malfunction or in spying at some information it leaks. Those attacks, either active or passive, belong to the side-channel attack class. Active attacks operate by writing on an ad hoc side-channel: a degree a freedom normally not available to the end-user is modified by force. Passive attacks consist in listening to a side-channel: the attacker is thus able to gain more information about the device operation than it is supposed to. Countermeasures against both types of attacks have been proposed and we show that only some of them are relevant. Active attacks are forfeited by an appropriate detection mechanism and passive attacks by the removal of all sorts of information leakage. As a consequence, securing hardware consists in watching side-channels or removing them if possible. The increase of security is mainly driven by two trends: integration of the system (on a SoC) for improved discretion and development of a dedicated symptom-free electronic CAD. SoC security is thus foreseen to become a discipline in itself.