Wireless embedded devices are predominant in the Internet of Things: Objects tagged with Radio Frequency IDentification and Near Field Communication technology, smartphones, and other embedded tokens interact from device to device and thereby often process information that is security or privacy relevant for humans. For protecting sensitive data and preventing attacks, many embedded devices employ cryptographic algorithms and authentication schemes. In the past years, various vulnerabilities have been found in commercial products that enable to bypass the security mechanisms. Since a large number of the devices in the field are in the hands of potential adversaries, implementation attacks (such as side-channel analysis and reverse engineering) can play a critical role for the overall security of a system. At hand of several examples of assailable commercial products we demonstrate the potential impact of the found security weaknesses and illustrate “how to not do it”.