A Strong Identity Based Key-Insulated Cryptosystem

Key-insulated cryptosystem was proposed in order to minimize the damage of secret key exposure. In this paper, we propose a strong identity based (ID-based) key-insulated cryptosystem security model, including ID-based key-insulated encryption (IB-KIE) security model and ID-based key-insulated signature (IB-KIS) security model. Based on the security models, provably secure strong IB-KIE and IBKIS schemes are constructed in order to decrease the damage of user’s secret key exposure. These schemes are secure in the remaining time periods against an adversary who compromises the insecure device and obtains secret keys for the periods of its choice. Furthermore, the schemes remain secure (for all time periods) against an adversary who compromises only the physically-secure device. All the key-insulated encryption and signature schemes in this paper are provably secure in the random oracle model and support random-access key-updates.