Protecting against Partial Key Exposure in Key-Insulated Encryption

Key-insulated encryption (KIE) is one of the countermeasures against the exposure of secret keys in public-key cryptography. In KIE, a user can update secret keys with a helper key to ensure that even if many secret keys, where each of them corresponds to each time period, are leaked, the security for other time periods is not compromised. However, KIE does not have resilience against the partial exposure of secret keys. Although there is public key encryption resilient to such partial exposure, unlike KIE, it cannot ensure security against the exposure of a whole secret key. In this paper, we introduce leakage-resilient key-insulated encryption (LR-KIE) that satisfies resilience against both partial and whole exposure of secret keys. We show three LR-KIE schemes from any leakage-resilient identity-based encryption scheme and/or any leakage-resilient secret sharing scheme.