Huawei Technologies Co.,Ltd This document mainly analyzes the key revocation issue with host identities (HIs) in the Host Identity Protocol (HIP). Generally, key revocation is an important functionality of key management systems; it is concerned with the issues of removing antique cryptographic keys from operational usages when they are not secure or not secure enough any more. This functionality is particularly important for the security systems expected to execute for long periods. This document also attempts to investigate several key issues that a designer of HI revocation mechanisms need to carefully consider.