Parallel key-insulated public key encryption

Security is constantly been infringed by inadvertent loss of secret keys, and as a solution, Dodis, Katz, Xu, and Yung [11], in Eurocrypt 2002, proposed a new paradigm called key-insulated security which provides tolerance against key exposures. Their scheme introduces a "helper key" which is used to periodically update the decryption key. The most attractive part of this scheme is that even if a decryption key of a time period is exposed, the security of the rest of the periods are unaffected. But how does this helper key managed? Can it be done efficiently? As, to alleviate the damage caused by key exposures, decryption key has to be updated at very short intervals, although frequent updating will, in contrary, increase the risk of helper key exposure. In this paper, we propose parallel key-insulated public key encryption in which two distinct helper keys alternately update a decryption key. The helper key of one system is independent from the other. Not only does it decrease the chance of helper key exposures, it also allows frequent updating of the decryption key, and over all, increases the security of the system.