Research On Identity Based Cryptography And Its Application

Since 2001,when the first identity based encryption scheme was created andproved,it has surely become the interest of many cryptography researchers,just be—cause it beautifully soIved the inconvenience and high cost of the maintainance ofpublic key infrastructure in the certificate based public key cryptosystems．This article will give an introduction to and analysis of identity based cryptogra—phy,especially identity based encryption,from multiple perspectives．In 2009,Watersproposed dual encryption system．a noval way to compose an identity based encryp—tion and its coresponding proof．His method is realy new and flesh in the field ofidentity based encryption．However,it will always make private key larger,which wiIIlead to inefficient transmit,particularly in a forward secure circustance,where privatekeys need to be updated regularly．Take the hierarchical identity based encryption byA．Lewko and B．Waters as an example,here gives a way to soIve this problem,reduc—ing the private key which used to be linear in hierarchy,to be sublinear．All branches in cryptography are not relatively independent．they are closely con—nected and interwined in a complex way．Generally speaking．an identity based en—cryption can be transformed into a signature,furthermore,if the identity based encryp—tion is proved under a bilinear form hard problem,the resuIt signature schemes can beproved secure under the non—bilinear form of the same problem．The example we givehere,is an identity based encryption under CBDH assumption,and the signature isunforgeability secure under CDH assumption．...