Examples set out herein provide a method comprising using first cryptographic key data specific to a computing device to verify a package of machine readable instructions to run on the computing device. The verified package may be executed to generate a random number using a true random number generator of the computing device, and to store the generated random number. Second cryptographic key data may be generated by a pseudorandom number generator of the computing device based on a seed comprising a combination of the random number as a first seed portion and a second seed portion. A portion of the second cryptographic key data may be sent to a certifying authority. The method may further comprising receiving a certification value based on the sent portion of the second cryptographic key data from the certifying authority and storing the certification value.