Australian Computer Society
To minimize the damage caused by key-exposure in ID-based signatures, in ISPEC'06 the researchers proposed an ID-Based Key-Insulated Signature (IBKIS) scheme. However, their scheme is not strong key-insulated, i.e. if a user's helper is compromised, the adversary can derive all of this user's secret keys for any time period. Moreover, in practice, to alleviate the damage in case of key-exposure, secret keys in IBKIS schemes have to be updated at very short intervals, which will increase the risk of helper key-exposure.