Konstantinos Chalkias Dimitrios Hristu-Varsakelis George Stephanides Improved Anonymous Timed-Release Encryption. 311-326 2007 conf/esorics/2007 ESORICS http://dx.doi.org/10.1007/978-3-540-74835-9_21 db/conf/esorics/esorics2007.html#ChalkiasHS07