certificateless public key cryptography (cl-pkc) is a useful method in order to solve the problems of traditional public key infrastructure (i. e. large amount of computation, storage and communication cost for managing certificates) and id-based public key cryptography (i. e. key escrow problem), simultaneously. a signcryption scheme is an important primitive in cryptographic protocols which p...

We show the following generic result: When a quantum query algorithm in random-oracle model outputs classical value t that is promised to be some tight relation with H(x) for x, then x can efficiently extracted almost certainty. The extraction by means of suitable simulation random oracle and works online, meaning it straightline, i.e., without rewinding, on-the-fly, during protocol execution (...

K. Yoneyama et al. introduces the Leaky Random Oracle Model at ProvSec2008, which only considers the leakage of the hash list of a hash function used by a cryptosystem due to various attacks caused by implementation or sloppy usages. However, an important fact is that such attacks not only leak the hash list of a hash function, but also leak other secret states outside the hash list of a crypto...

As we discussed in the previous lecture, a cryptographic scheme defined in the random oracle model is allowed to use a random function H : {0, 1} → {0, 1} which is known to all the parties. In an implementation, usually a cryptographic hash function replaces the random oracle. In general, the fact that a scheme is proved secure in the random oracle model does not imply that it is secure when th...

In this paper we investigate the problem of secure instantiation of the random oracle, based on the concepts and methods of algorithmic randomness. We show that, for any secure signature scheme in the random oracle model, there exists a specific computable function which can instantiate the random oracle while keeping the security originally proved in the random oracle model. Our results use th...

The interest in post-quantum cryptography — classical systems that remain secure in the presence of a quantum adversary — has generated elegant proposals for new cryptosystems. Some of these systems are set in the random oracle model and are proven secure relative to adversaries that have classical access to the random oracle. We argue that to prove post-quantum security one needs to prove secu...

We introduce a variant of the random oracle model where oracledependent auxiliary input is allowed. In this setting, the adversary gets an auxiliary input that can contain information about the random oracle. Using simple examples we show that this model should be preferred over the classical variant where the auxiliary input is independent of the random oracle. In the presence of oracle-depend...