On The Security of The ElGamal Encryption Scheme and Damgards Variant
In this paper, we discuss the security of the ElGamal encryption scheme and its variant by Damgard. For the ElGamal encryption, we show that (1) under the generalized knowledge-of-exponent assumption and the one-more discrete log assumption, ElGamal encryption is one-way under nonadaptive chosen cipher attacks; (2) one-wayness of ElGamal encryption under non-adaptive chosen cipher attacks is equivalent to the hardness of one-more computational Diffie-Hellman problem. For a variant of ElGamal encryption proposed by Damgard (DEG), we give a new proof that DEG is semantically secure against non-adaptive chosen ciphertext attacks under the one-more decisional Diffie-Hellman assumption (although the same result for DEG security has been presented in the literature before, our proof is simpler). We also give a new security proof for DEG based on the decisional Diffie- Hellman assumption (DDHA) and a weaker version of the knowledge-of-exponent assumption (KEA), and note that KEA is stronger than necessary in the security proof of DEG, for which KEA was originally proposed.
How To Ensure Forward and Backward Untraceability of RFID Identification Schemes By Using A Robust PRBG
In this paper, we analyze an RFID identification scheme which is designed to provide forward untraceability and backward untraceability. We show that if a standard cryptographic pseudorandom bit generator (PRBG) is used in the scheme, then the scheme may fail to provide forward untraceability and backward untraceability. To achieve the desired untraceability features, the scheme can use a robust PRBG which provides forward security and backward security. We also note that the backward security is stronger than necessary for the backward untraceability of the scheme.
Authorship Proof for Textual Document
In this paper, we investigate the problem of how to prove the authorship of textual documents. First we define the basic functionalities of an authorship proof scheme (APS) based on natural language watermarking, and identify two essential security requirements for an APS to be secure against various attacks. We review existing natural language watermarking schemes, and we propose two new schemes with improved security.
A Zero-Knowledge Identification and Key Agreement Protocol
In this paper, we propose a zero-knowledge authenticated key agreement protocol with key confirmation (AKC) in asymmetric setting. The protocol has several desirable security attributes like some classical AKCs such as STS and MQV. One highlight of our protocol is its zero-knowledge property, which enables succinct proofs of the claimed security attributes, while the overhead in communication and computation resulting from the special design to achieve zero-knowledge is insignificant.
An Efficient and Secure Two-flow Zero-Knowledge Identification Protocol
In this paper, we propose a new zero-knowledge identification protocol. While the protocol consists of only two message flows, it does not rely on any underlying signature or encryption scheme. Its zero-knowledge property is preserved under concurrent composition and reset settings. It is secure under the strongest attack model which incorporates concurrent attacks, active-intruder attacks and reset attacks. Meanwhile its performance in computation and communication is close to that of the most efficient identification protocols not based on signature or encryption systems, most of which are insecure in this strong attack model.
Comments on ``Distributed Symmetric Key Management for Mobile Ad hoc Networks" from INFOCOM 2004
In IEEE INFOCOM 2004, Chan proposed a distributed key management scheme for mobile ad hoc networks, and deduced the condition under which the key sets distributed to the network nodes can form a cover-free family (CFF), which is the precondition that the scheme can work. In this paper, we indicate that the condition is falsely deduced. Furthermore, we discuss whether CFF is capable for key distributions in ad hoc networks.