Souvik Ray - Academia.edu (original) (raw)
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Hong Kong University of Science and Technology
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Papers by Souvik Ray
Cryptography and Communications, 2018
The internal state of RC4 stream cipher is a permutation over ZN and its state transition is effe... more The internal state of RC4 stream cipher is a permutation over ZN and its state transition is effectively a transposition or swapping of two elements. How the randomness of RC4 state evolves due to its state transitions has been studied for many years. As the number of swaps increases, the state comes closer to a uniform random permutation. We call the burn-in period of RC4 state transition as the number of swaps required to make the state very close to uniform random permutation under some suitably defined distance measure. Earlier, Mantin in his Master's thesis (2001) has performed an approximate analysis of the burn-in period. In this paper, we perform a rigorous analysis of the burn-in period and in the process derive the exact distribution of the RC4 state elements at any stage.
Designs, Codes and Cryptography, 2017
We revisit the different approaches used in the literature to estimate the data complexity of dis... more We revisit the different approaches used in the literature to estimate the data complexity of distinguishing attacks on stream ciphers and analyze their interrelationships. In the process, we formally argue which approach is applicable (or not applicable) in what scenario. To our knowledge, this is the first kind of such an exposition. We also perform a rigorous statistical analysis of the message recovery attack that exploits a distinguisher and show that in practice there is a significant gap between the data complexities of a message recovery attack and the underlying distinguishing attack. This gap is not necessarily determined by a constant factor as a function of the false positive and negative rate, as one would expect. Rather this gap is also a function of the number of samples of the distinguishing attack. We perform a case study on RC4 stream cipher to demonstrate that the typical complexities for message recovery attack inferred in the literature are but underestimates and the actual estimates are quite larger.
The density power divergence (DPD) and related measures have produced many useful statistical pro... more The density power divergence (DPD) and related measures have produced many useful statistical procedures which provide a good balance between model efficiency on one hand, and outlier stability or robustness on the other. The large number of citations received by the original DPD paper (Basu et al. 1998) and its many demonstrated applications indicate the popularity of these divergences and the related methods of inference. The estimators that are derived from this family of divergences are all M-estimators where the defining ψ function is based explicitly on the form of the model density. The success of the minimum divergence estimators based on the density power divergence makes it imperative and meaningful to look for other, similar divergences in the same spirit. The logarithmic density power divergence (Jones et al., 2001), a logarithmic transform of the density power divergence, has also been very successful in producing inference procedures with a high degree of efficiency si...
Cryptography and Communications, 2018
The internal state of RC4 stream cipher is a permutation over ZN and its state transition is effe... more The internal state of RC4 stream cipher is a permutation over ZN and its state transition is effectively a transposition or swapping of two elements. How the randomness of RC4 state evolves due to its state transitions has been studied for many years. As the number of swaps increases, the state comes closer to a uniform random permutation. We call the burn-in period of RC4 state transition as the number of swaps required to make the state very close to uniform random permutation under some suitably defined distance measure. Earlier, Mantin in his Master's thesis (2001) has performed an approximate analysis of the burn-in period. In this paper, we perform a rigorous analysis of the burn-in period and in the process derive the exact distribution of the RC4 state elements at any stage.
Designs, Codes and Cryptography, 2017
We revisit the different approaches used in the literature to estimate the data complexity of dis... more We revisit the different approaches used in the literature to estimate the data complexity of distinguishing attacks on stream ciphers and analyze their interrelationships. In the process, we formally argue which approach is applicable (or not applicable) in what scenario. To our knowledge, this is the first kind of such an exposition. We also perform a rigorous statistical analysis of the message recovery attack that exploits a distinguisher and show that in practice there is a significant gap between the data complexities of a message recovery attack and the underlying distinguishing attack. This gap is not necessarily determined by a constant factor as a function of the false positive and negative rate, as one would expect. Rather this gap is also a function of the number of samples of the distinguishing attack. We perform a case study on RC4 stream cipher to demonstrate that the typical complexities for message recovery attack inferred in the literature are but underestimates and the actual estimates are quite larger.
The density power divergence (DPD) and related measures have produced many useful statistical pro... more The density power divergence (DPD) and related measures have produced many useful statistical procedures which provide a good balance between model efficiency on one hand, and outlier stability or robustness on the other. The large number of citations received by the original DPD paper (Basu et al. 1998) and its many demonstrated applications indicate the popularity of these divergences and the related methods of inference. The estimators that are derived from this family of divergences are all M-estimators where the defining ψ function is based explicitly on the form of the model density. The success of the minimum divergence estimators based on the density power divergence makes it imperative and meaningful to look for other, similar divergences in the same spirit. The logarithmic density power divergence (Jones et al., 2001), a logarithmic transform of the density power divergence, has also been very successful in producing inference procedures with a high degree of efficiency si...