Research On Certificateless Public Key Encryption

Certificateless public key cryptography(CL-PKC) is a new type of public key cryptography, which is developed on the foundation of identity-based cryptography (ID-PKC). CL-PKC eliminates the key escrow problem and the need for public key certificate, which combines the virtues of ID-PKC and certificate-based public key systems, so it has been a very active research in the field of cryptography. In recent years, the researchers put forward many of certificateless encryption (CLE) schemes from bilinear pairings, which construction mainly combine Identity-Based Encryption (IBE) and traditional public key Encryption (PKE) by double encryption technology. However, this method poses many questions, for example, the ciphertext of these schemes are longer than the used IBE or PKE’s. So they are not very efficient both on computation and communication. This paper conducts the thorough research on the certificateless encryption schemes from bilinear pairings and gets some research results. The main researches in the paper are as follows:1. Based on some existing pairing-based IBE schemes, we propose a general construction of CLE scheme, and directly apply it to CLE scheme. Our method is based on Boneh-Franklin IBE, Sakai-Kasahara IBE and Boneh-Boyen IBE, we divide their master key of public key and private key into two value, one acts as master key and another acts as secret value of CLE. In this way, the public key and private key of IBE are in contrast with CLE’s. The encryption algorithm and decryption algorithm of CLE are still use IBE’s. Obviously our new construction of CLE can be viewed as IBE scheme when the master key and the secret value of CLE are regarded as one value. It is really worth mentioning here is most of pairing-based IBE schemes are derived from above three schemes, which means the common pairing-based IBE schemes can convert to CLE. Hence, the proposed scheme is creative on theory.2. We provide the security of our scheme, give two different formworks of security proof for CLE and give efficiency analysis. On the security, because the private key of CLE is no longer two components, two different types of CL-PKE adversaries can be based on the same computational problems which simplify the security proof. In addition, the security proof is seldom discussed, we conclude two different formworks and give out specific examples. On the efficiency, the computation complexity of our scheme compares favorably with previous known schemes. Our scheme is no longer use double encryption, but directly from IBE scheme, so its ciphertext is identical to IBE’s. This shows our scheme effective solve the problem of IBE’s, the work has theory and practical value.3. We apply our scheme to key management of Ad Hoc Network and present a certificateless key management. It effectively eliminates the key escrow problem and provides protection for the final private key. It also overcomes the disadvantage of the dishonest D-KGCs conspire to get private key. This work means our scheme has practical significance.