Biblio

The signcryption technique was first proposed by Y. Zheng, where two cryptographic operations digital signature and message encryption are made combinedly. We cryptanalyze the technique and observe that the signature and encryption become vulnerable if the forged public keys are used. This paper proposes an improvement using modified DSS (Digital Signature Standard) version of ElGamal signature and DHP (Diffie-Hellman key exchange protocol), and shows that the vulnerabilities in both the signature and encryption methods used in Zheng's signcryption are circumvented. DHP is used for session symmetric key establishment and it is combined with the signature in such a way that the vulnerabilities of DHP can be avoided. The security and performance analysis of our signcryption technique are provided and found that our scheme is secure and designed using minimum possible operations with comparable computation cost of Zheng's scheme.

Pseudorandom bit generators (PRBG) can be designed to take the advantage of some hard number theoretic problems such as the discrete logarithm problem (DLP). Such type of generators will have good randomness and unpredictability properties as it is so difficult to find an easy solution to the regarding mathematical dilemma. Hash functions in turn play a remarkable role in many cryptographic tasks to achieve various security strengths. In this paper, a pseudorandom bit generator mechanism that is based mainly on the elliptic curve discrete logarithm problem (ECDLP) and hash derivation function is proposed. The cryptographic hash functions are used in consuming applications that require various security strengths. In a good hash function, finding whatever the input that can be mapped to any pre-specified output is considered computationally infeasible. The obtained pseudorandom bits are tested with NIST statistical tests and it also could fulfill the up-to-date standards. Moreover, a 256 × 256 grayscale images are encrypted with the obtained pseudorandom bits following by necessary analysis of the cipher images for security prove.

Cryptographic hash functions play a crucial role in information security. Cryptographic hash functions are used in various cryptographic applications to verify the message authenticity and integrity. In this paper we propose a Cellular Automata Based Hashing Algorithm (CABHA) for generating strong cryptographic hash function. The proposed CABHA algorithm uses the cellular automata rules and a custom transformation function to create a strong hash from an input message and a key.

Considering application to communication among wireless sensors, Ma and Tsudik introduced the notion of forward-secure sequential aggregate (FssAgg) authentication in 2007. They also proposed an FssAgg MAC scheme composed of a MAC function and cryptographic hash functions at the same time. The security of their proposed scheme has not been analyzed yet and remains open. It is shown in this paper that a slight variant of the Ma-Tsudik FssAgg MAC scheme is secure under reasonable and standard assumptions on security of the underlying primitives. An efficient instantiation of the underlying MAC function using a cryptographic hash function is also discussed.

The Java platform and its third-party libraries provide useful features to facilitate secure coding. However, misusing them can cost developers time and effort, as well as introduce security vulnerabilities in software. We conducted an empirical study on StackOverflow posts, aiming to understand developers' concerns on Java secure coding, their programming obstacles, and insecure coding practices. We observed a wide adoption of the authentication and authorization features provided by Spring Security - a third-party framework designed to secure enterprise applications. We found that programming challenges are usually related to APIs or libraries, including the complicated cross-language data handling of cryptography APIs, and the complex Java-based or XML-based approaches to configure Spring Security. In addition, we reported multiple security vulnerabilities in the suggested code of accepted answers on the StackOverflow forum. The vulnerabilities included disabling the default protection against Cross-Site Request Forgery (CSRF) attacks, breaking SSL/TLS security through bypassing certificate validation, and using insecure cryptographic hash functions. Our findings reveal the insufficiency of secure coding assistance and documentation, as well as the huge gap between security theory and coding practices.