Universal Leaky Random Oracle

Yoneyama et al. introduces the Leaky Random Oracle Model at ProvSec2008 to capture the leakages from the hash list of a hash function used by a cryptography construction due to various attacks caused by sloppy usages or implementations in the real world. However, an important fact is that such attacks would leak not only the hash list, but also other secret states (e.g. the secret key) outside the hash list. Therefore, the Leaky Random Oracle Model is very limited in the sense that it considers the leakages from the hash list alone, instead of taking into consideration other possible leakages from secret states simultaneously. In this paper, we present an augmented model of the Leaky Random Oracle Model. In our new model, both the secret key and the hash list can be leaked. Furthermore, the secret key can be leaked continually during the whole lifecycle of the cryptography construction. Hence, our new model is more universal and stronger than the Leaky Random Oracle Model and some other leakage models (e.g. only computation leaks model and memory leakage model). As an application example, we also present a public key encryption scheme which is provably IND-CCA secure in our new model.