Sergey Korotkov enhanced entropy subsystem security and reliability across the nrfconnect/sdk-nrf and nrfconnect/sdk-zephyr repositories by enforcing hardware RNG usage and enabling PSA RNG as the default entropy provider for nrf9280pdk targets. He reverted the fake entropy PRNG driver, ensuring that only hardware-based random number generation is used, and updated manifest revisions to maintain cross-repository consistency. Working primarily in C and YAML, Sergey focused on embedded systems and firmware development, addressing both feature implementation and bug resolution. His work demonstrated careful cross-repo coordination and a deep understanding of hardware integration, resulting in reduced entropy-related risks for downstream teams.