What is correct/recommended config.h contents to enable just one EC cipher suite for DTLS server so that RAM usage (max. some tens on kB) and flash usage (preferably under 100 kB) is as low as possible and DTLS handshake performance is fast enough (under 1 s, preferably under 0.5 s). Both client and server must identify (and verify) itself by certificate.
Target server platform STM32F407@168 MHz. Client runs on PC, so no limitations there.