Catálogo de publicaciones - libros

Secret handshake, introduced recently by Balfanz et al, is a very useful cryptographic mechanism which allows two members of the same group to authenticate each other secretly. In a secret handshake protocol, an honest member in the group will never reveal his group affiliation unless the other party is a valid member of the same group. In other words, only the members who have certificates from the Group Administrator can be successful in handshaking. If a handshake between two parties fails, the identity of either party will not be disclosed. Several secret handshake schemes have been found in the literature, which are based on pairing, CA-Oblivious Encryption and RSA. Furthermore, several Oblivious Signature-Based Envelopes (OSBE) schemes based on the ElGamal signature family were introduced recently by Nasserian and Tsudik, and they proposed a generic construction of secret handshake from OSBE based on ElGamal signature family as well. It is shown in the generic construction that any ElGamal signature family based OSBE scheme can be converted to secret handshake within three communication rounds, except the ElGamal and DSA signature. In this paper, to complement the previous result, we show a three-round secret handshake scheme based on ElGamal signature. We prove that the scheme is existentially unforgeable in the Random Oracle Model (ROM). Finally we extend our scheme to a DSA-based secret handshake which also requires only three rounds.

Flexible features of C can be misused and result in potential vulnerabilities which are hard to detect by performing only static checking. Existing tools either give up run-time type checking or employ a type system whose granularity is too coarse (it does not differentiate between pointer types) so that many errors may go undetected. This paper presents a dynamic checking approach to conquer them. A type system that is based on the physical layout of data types and has the proper granularity has been employed. Rules for propagating dynamic types and checking for compatibility of types during execution of the target program are also set up. Then a model of dynamic type checking on this type system to capture run-time type errors is built. Experimental results show that it can catch most errors, including those may become system vulnerabilities and the overhead is moderate.

In this paper we propose a robust software watermarking based on chaos against several limitations of existing software watermarking. The algorithm combines the anti-reverse engineering technique, chaotic system and the idea of Easter Egg software watermarks. The global protection for the program is provided by dispersing watermark over the whole code of the program with chaotic dispersion coding; the resistance against reverse engineering is improved by using the anti-reverse engineering technique. In the paper, we implement the scheme in the Intel i386 architecture and the Windows operating system, and analyze the robustness and the performance degradation of watermarked program. Analysis indicates that the algorithm resists various types of semantics-preserving transformation attacks and is good tolerance for reverse engineering attacks.

We propose a general efficient transformation from Private Information Retrieval (PIR) to Symmetrically Private Information Retrieval (SPIR). Unlike existing schemes using inefficient zero-knowledge proofs, our transformation exploits an efficient construction of Oblivious Transfer (OT) to reduce the communication complexity which is a main goal of PIR and SPIR. The proposed SPIR enjoys almost the same communication complexity as the underlying PIR. As an independent interest, we propose a novel homomorphic public-key cryptosytem derived from Okamoto-Uchiyama cryptosystem and prove its security. The new homomorphic cryptosystem has an additional useful advantage to enable one to encrypt messages in changeable size with fixed extension bits. Based on the proposed cryptosystem, the implementation of PIR/SPIR makes PIR and SPIR applicable to large databases.

For reliability and confidentiality of information security systems, the security engineering methodologies are accepted in many organizations. A security institution in Korea faced the effectiveness of security engineering. To solve the problems of security engineering, the institution creates a security methodology called ISEM, and a tool called SENT. This paper presents ISEM methodology considering both product assurance and production processes take advantages in terms of quality and cost. ISEM methodology can make up for the current security engineering methodology. For support ISEM methodology, SENT tool, which is operated in Internet, support the production processes and the product assurances which ISEM demands automatically.