Ron Steinfeld Josef Pieprzyk Huaxiong Wang Lattice-Based Threshold Changeability for Standard Shamir Secret-Sharing Schemes. 2542-2559 2007 53 IEEE Transactions on Information Theory 7 http://dx.doi.org/10.1109/TIT.2007.899541 db/journals/tit/tit53.html#SteinfeldPW07