Stephan Mueller works in the field of IT security for more than 20 years with atsec. The tasks mainly revolve around supporting vendors and developers to successfully perform various types of validations including FIPS 140-2. In addition, assessments of cryptographic implementations in general and random number generators with their entropy sources in particular are handled as well. This includes the writing of the public Linux /dev/random analysis sponsored by BSI for several years. Based on the experience the challenges in the existing /dev/random implementation became apparent leading to the start of the new implementation of /dev/random. Also, various cryptographic algorithm implementations found in current Linux kernels are provided developed as private exercises.