Hi Sukchan and list, I'm currently reading the MME code and I'm having some trouble understanding the handling of the uplink counter for NAS security. I only see mme_ue->ul_count.i32 ever being set to '0' when a new security context is used. But I don't see it ever being incremented? I only see ul_count.sqn incremented, but then the nas_mac_calculate() always gets ul_count.i32 passed as input. So I'm somehow not understanding how the MAC can ever verify on any uplink message beyond/after the first one which establishes a new security context. What am I missing? Thanks for your insight! -- - Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6)