中文摘要：

采用双线性对原理,提出无需随机预言模型下可证明安全的基于身份门限的解密方案,解决了当前基于身份门限解密方案需要依赖随机预言模型,才能证明其安全性或其安全性归约松散性的问题.给出一个新的密钥提取算法,模拟者可成功应答敌手的私钥提取查询,使方案的选择密文安全性证明具有紧致的安全归约.与现有的基于身份的门限解密方案相比,该方案在不依赖随机预言模型下也能满足紧致安全性归约.

英文摘要：

Existing IBTD schemes either are only secure in the random oracles or have a loose security reduction. An identity-based threshold decryption （IBTD） scheme which made use of bilinear pairing to guarantee safety without random oracles was proposed. The novelty of lies in the extraction of keys, which enables the simulator to suc- cessfully answer private key extraction queries, thus the security proof for the chosen-ciphertext security has a tight security reduction. Compared with the existing IBTD schemes, this new scheme has the advantages of satisfying the tight security reduction without random oracles.