When we talk about security context then it has 3 types and 2 states.
TYPE in security context
1> PARTIAL
2> FULL
3> MAPPED( UMTS )
STATES in security context
1> current
2> Non-current
At first we see the contents of EPS security context. They are :
1> KSI
2> UE capability( security related )
3> KASME
4> UL/DL COUNT
The content of partial security context is exactly same as of EPS native security context.
So the question comes why it is called partial : It is said partial because SECURITY MODE COMMAND or you can say key derivation is not at all done on that KASME. Partial security context will always in non-current state.
And onces on that partial security context ( KASME) SECURITY MODE COMMAND is done or Key derivation is done then it becomes FULL NATIVE EPS SECURITY CONTEXT. FULL NATIVE EPS SECURITY CONTEXT can be current or non-current state depends upon the situation to which network(LTE OR UMTS/GSM) UE is connected with.
NOTE: only partial can transform into full . Any other transformation in types is not possible. for eg. full never become partial.
I hope i tried to clarify your doubts. But for further and in-depth clarification refer spec : 24.301 ( security context ) & 33.401 ( security spec) .
