Paper 2006/373

Self-Generated-Certificate Public Key Cryptography and Certificateless Signature / Encryption Scheme in the Standard Model

Joseph K. Liu, Man Ho Au, and Willy Susilo

Abstract

Certificateless Public Key Cryptography (CL-PKC) enjoys a number of features of Identity-Based Cryptography (IBC) while without having the problem of key escrow. However, it \textit{does} suffer to an attack where the adversary, Carol, replaces Alice's public key by someone's public key so that Bob, who wants to send an encrypted message to Alice, uses Alice's identity and other's public key as the inputs to the encryption function. As a result, Alice cannot decrypt the message while Bob is unaware of this. We call it \textit{Denial-of-Decryption (DoD) Attack} as its nature is similar to the well known Denial-of-Service (DoS) Attack. Based on CL-PKC, we propose a new paradigm called \textit{Self-Generated-Certificate Public Key Cryptography (SGC-PKC)} that captures the DoD Attack. We also provide a generic construction of a self-generated-certificate public key encryption scheme in the standard model. Our generic construction uses certificateless signature and certificateless encryption as the building block. In addition, we further propose a certificateless signature and a certificateless encryption scheme with concrete implementation that are all provably secure in the standard model, which are the first in the literature regardless of the generic constructions by Yum and Lee which may contain security weaknesses as pointed out by others. We believe these concrete implementations are of independent interest.