Abstract: Based on the assumption of ephemeral exponential leakage in eCK model,this paper analyzed the effect of this hidden trouble and built a new formal security model in which a much stronger adversary can be resisted and also a new security attribute can be satisfied．Futher more,a provable secure key agreement protocol-HCMQV was designed in this new model．The protocol modifies the generation function of e in a natural way and makes it in secrecy.The method reduces the times of HASH and also the reflect attack can be avoided．In order to prove the security of HCMQV,we did not prove the unforgeability for the signature scheme like HMQV,but a distinguisher was constructed to reduce the security of protocol to DDH assumption tightly．Actually,designing a secure key agreement protocol in which ephemeral exponential can be leaked is possible.

Key words: CMQV,eCK,Formal security model,Provable security