Online/Offline Blind Signature

AbstractThe processing ablity and response speed of the wireless communication terminals are limited, common signatures become the bottleneck to the development of the wireless networks. For that problem, based on the characteristics of the blind signature, the online/offline blind signature is given in this paper which incorporates with the optimal online/offline signature. Most computations are finished before the blind message is given, after that, only a few operations are needed. The performance analysis is also given in this paper, the new signature scheme can be applied to the security of wireless network, it protect the users’ privacy efficiently

Identity-Based Online/Offline Key Encapsulation and Encryption

An identity-based online/offline encryption (IBOOE) scheme splits the encryption process into two phases. The first phase performs most of the heavy computations, such as modular exponentiation or pairing over points on elliptic curve. The knowledge of the plaintext or the receiver\u27s identity is not required until the second phase, where the ciphertext is produced by only light computations, such as integer addition/multiplication or hashing. This division of computations makes encryption affordable by devices with limited computation power since the preparation works can be executed ``offline\u27\u27 or possibly by some powerful devices. Since efficiency is the main concern, smaller ciphertext size and less burden in the computation requirements of all phases (i.e., both phases of encryption and the decryption phase) are desirable. In this paper, we proposed new schemes with improved efficiency over previous schemes by assuming random oracles. Our first construction is a very efficient scheme which is secure against chosen-plaintext attack (CPA), This scheme is slightly modified from an existing scheme. In particular, the setup and the user private key remain the same. We then proceed to propose the notion of ID-based Online/Offline KEM (IBOOKEM) that allows the key encapsulation process to be split into offline and online stages, in the same way as IBOOE does. We also present a generic transformation to get security against chosen-ciphertext attack (CCA) for IBOOE from any IBOOKEM scheme with one-wayness only. Our schemes (both CPA and CCA) are the most efficient one in the state-of-the-art, in terms of online computation and ciphertext size, which are the two main focuses of online/offline schemes. Our schemes are very suitable to be deployed on embedded devices such as smartcard or wireless sensor which have very limited computation powers and the communication bandwidth is very expensive

On-Line/Off-Line DCR-based Homomorphic Encryption and Applications

On-line/off-line encryption schemes enable the fast encryption of a message from a pre-computed coupon. The paradigm was put forward in the case of digital signatures. This work introduces a compact public-key additively homomorphic encryption scheme. The scheme is semantically secure under the decisional composite residuosity (DCR) assumption. Compared to Paillier cryptosystem, it merely requires one or two integer additions in the on-line phase and no increase in the ciphertext size. This work also introduces a compact on-line/off-line trapdoor commitment scheme featuring the same fast on-line phase. Finally, applications to chameleon signatures are presented