In modern cryptography, the random oracle model is widely used as an imaginary framework in which the security of a cryptographic scheme is discussed. Since the random oracle is an imaginary object, even if the security of a cryptographic scheme is proved in the random oracle model, the random oracle has to be instantiated using a concrete cryptographic hash function such as the SHA hash functi...

A study of the random oracle model seems to be concentrated to showing the gap between the schemes in the random oracle model and the schemes whose random oracles are replaced with functions chosen at random from some function ensembles. We consider a different direction on the study of the schemes in the random oracle model. We focus on the size of the tables necessary to describe all of the e...

A generative model may generate utter nonsense when it is fit to maximize the likelihood of observed data. This happens due to “model error,” i.e., when the true data generating distribution does not fit within the class of generative models being learned. To address this, we propose a model of active distribution learning using a binary invalidity oracle that identifies some examples as clearl...

We discuss a reduction notion relating the random oracles in two cryptographic schemes A and B. Basically, the random oracle of scheme B reduces to the one of scheme A if any hash function instantiation of the random oracle (possibly still oracle based) which makes A secure also makes B secure. In a sense, instantiating the random oracle in scheme B is thus not more demanding than the one for s...

The random oracle model is a very convenient setting for designing cryptographic protocols. In this idealized model all parties have access to a common, public random function, called a random oracle. Protocols in this model are often very simple and efficient; also the analysis is often clearer. However, we do not have a general mechanism for transforming protocols that are secure in the rando...

In this paper, we discuss how to construct secure cryptosystems and secure hash functions in weakened random oracle models. The weakened random oracle model (WROM), which was introduced by Numayama et al. at PKC 2008, is a random oracle with several weaknesses. Though the security of cryptosystems in the random oracle model, ROM, has been discussed sufficiently, the same is not true for WROM. A...

We give the first proof of security for an identity-based encryption scheme in the quantum random oracle model. This is the first proof of security for any scheme in this model that requires no additional assumptions. Our techniques are quite general and we use them to obtain security proofs for two random oracle hierarchical identity-based encryption schemes and a random oracle signature schem...

The Random Oracle Model and the Ideal Cipher Model are two well known idealised models of computation for proving the security of cryptosystems. At Crypto 2005, Coron et al. showed that security in the random oracle model implies security in the ideal cipher model; namely they showed that a random oracle can be replaced by a block cipher-based construction, and the resulting scheme remains secu...