基于Waters的ID加密的高效选择密文安全公钥密码体制

Efficient Chosen Ciphertext Secure Public Key Cryptosystem from the ID-Based Encryption of Waters

2004年的欧密会上,Canetti,Halevi和Katz提出了将Selectivre-ID安全的基于身份加密方案转化为选择密文安全(即,CCA安全)的公钥加密方案的方法。但由于该方法需要用到一次性签名,给所基于的方案增加了明显的通信和计算负载。该文由Waters提出的Adaptive-ID安全的基于身份加密(IDE)方案构造了一个新的CCA安全公钥加密方案。这里的“身份”由前两部分密文的hash值得到,密文合法性由双线性映射来验证。其效率比直接利用CHK 的一般转化得到方案有明显提高。新方案的安全性在标准的决定性双线性Diffie-Hellman假设下被证明。

In Eurocrypt 2004, Canetti, Halevi and Katz proposed a method for constructing Chosen Ciphertext secure （ ie., CCA secure） public key encryption from any Selective-ID secure ID-Based Encryption （IBE）. However, this method needs one time signature and thus adds noticeable overhead to the underling scheme. In this paper, a new CCA secure public key cryptosystem is constructed from the Adaptive-ID secure IBE scheme proposed by Waters. Here, the ＂identity＂ is the hash of the first two parts of the ciphertext, and the bilinear map is used to test the ciphertext validity. The proposal is much more efficient than those obtained from the general CHK method. The security of the new scheme is proved under the standard Decisional Bilinear Diffie-Hellman （DBDH） assumption.