An uninstantiable random-oracle-model scheme for a hybrid-encryption problem

摘要: We present a simple, natural random-oracle (RO) model scheme, for practical goal, that is uninstantiable, meaning proven in the RO to meet its goal yet admits no standard-model instantiation meets this goal. The question IND-CCA-preserving asymmetric encryption which formally captures security of most common usage encryption, namely transport symmetric key such way under latter remains secure. scheme an ElGamal variant, called Hash ElGamal, resembles numerous existing RO-model schemes, and on surface shows evidence anomalous properties. These results extend our understanding gap between standard models, bring concerns raised by previous work closer practice indicating problem schemes admitting secure can arise domains where are commonly designed.