Giovanni Di Crescenzo Rafail Ostrovsky Sivaramakrishnan Rajagopalan Conditional Oblivious Transfer and Timed-Release Encryption. 74-89 1999 conf/eurocrypt/99 EUROCRYPT http://dx.doi.org/10.1007/3-540-48910-X_6 db/conf/eurocrypt/eurocrypt99.html#CrescenzoOR99