Identity-Based Encryption from the Weil Pairing
SIAM Journal on Computing
Key-Insulated Public Key Cryptosystems
EUROCRYPT '02 Proceedings of the International Conference on the Theory and Applications of Cryptographic Techniques: Advances in Cryptology
A forward-secure public-key encryption scheme
EUROCRYPT'03 Proceedings of the 22nd international conference on Theory and applications of cryptographic techniques
Intrusion-resilient public-key encryption
CT-RSA'03 Proceedings of the 2003 RSA conference on The cryptographers' track
Reducing the spread of damage of key exposures in key-insulated encryption
VIETCRYPT'06 Proceedings of the First international conference on Cryptology in Vietnam
Identity-Based hierarchical strongly key-insulated encryption and its application
ASIACRYPT'05 Proceedings of the 11th international conference on Theory and Application of Cryptology and Information Security
Parallel key-insulated public key encryption
PKC'06 Proceedings of the 9th international conference on Theory and Practice of Public-Key Cryptography
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To deal with the problem of secret key exposure, Dodis, Katz, Xu and Yung [6] proposed a key-insulated public key encryption (KIE), which uses the secure helper key to update the secret key more often and helps to minimize the damage overall. We take this idea further in improving the helper key security by introducing an auxiliary helper key besides of the main helper key. The auxiliary helper key is used less than the main helper key and can help the system to reduce the damage even in case of helper key exposure. This paper give two different schemes of KIE with auxiliary helper key. There are trade-offs between public key length and ciphertext size, as well as between encryption algorithms and decryption algorithms in these two schemes. With these trade-offs, it is flexible to choose an efficient one to implement in reality. We also show concrete constructions with chosen-ciphertext security. The formal security proofs for all schemes are given in this paper, based on the CBDH assumption [2] in the random oracle model.