A secure and efficient e-will system based on PKI

Recently, Chien et al. suggested an e-will system based on ID-based cryptosystem. They argued that their scheme was secure enough to be used in practice. However, we found several problems of Chien et al.'s scheme. First, the Trust Authority can easily compute the user's private key. Therefore, it does not provide the non-repudiation property and it does not conform to the R.O.C. Civil Law and Electronic Signatures Act. Second, their scheme does not provide any long-term validation method of digital signatures. Therefore, we may fail to check the validity of the testator's will after death. To overcome these drawbacks, we propose two kinds of e-will schemes that can be used in practice.