We show that any OT extension protocol based on one-way functions (or more generally any symmetric-key primitive) either requires an additional round compared to the base OTs or must make a non-blackbox use of one-way functions. This result also holds in the semi-honest setting or in the case of certain setup models such as the common random string model. This implies that OT extension in any s...

A broadcast encryption system generally involves three kinds of entities: the group manager that deals with the membership, the encryptor that encrypts the data to the registered users according to a specific policy (the target set), and the users that decrypt the data if they are authorized by the policy. Public-key broadcast encryption can be seen as removing this special role of encryptor, b...

Algebraic attacks on block ciphers and stream ciphers have gained more and more attention in cryptography. The idea is to express a cipher by a system of equations whose solution reveals the secret key. The complexity of an algebraic attack is closely related to the degree of the equations. Hence, low-degree equations are crucial for algebraic attacks. So far, the existence of low-degree equati...

A nonlinear substitution operation of bytes is the main strength factor of the Advanced Encryption Standard (AES) and other modern cipher systems. In this paper we have presented a new simple algorithm to generate key-dependent S-boxes and inverse S-boxes for block cipher systems. The quality of this algorithm was tested by using NIST tests, and changing only one bit of the secret key to genera...

A private-key cryptosystem may be viewed as a means by which a trusted dealer privately conveys a large, shared pseudo-random object to a pair of players, using little communication. Alternatively, the messages distributed by the dealer may be viewed as a secure compression of a pair of large identical random pads (or random functions) into a shorter shared “key” or “seed”. We pose the question...

Symmetric encryption has been a standout amongst the most reliable option by which security is accomplished. In modern block symmetric ciphers, the substitution-boxes have been playing a critical role of nonlinear components that drives the actual security of ciphers. In this paper, the travelling salesman problem and piece-wise linear chaotic map are explored to synthesize an efficient configu...

T box riboswitches are cis-acting RNA elements that bind to tRNA and sense its aminoacylation state to influence gene expression. Here, we present the 3.2 Å resolution X-ray crystal structures of the T box Stem I-tRNA complex and tRNA, in isolation. T box Stem I forms an arched conformation with extensive intermolecular contacts to two key points of tRNA, the anticodon and D/T-loops. Free and c...

introduction: learning and memory deficits in some diseases are new subjects of research. bupropion, as dopamine and noradrenaline reuptake inhibitor and an antidepressant agent, has been previously shown to affect learning and memory processes. this study was designed to test the effect of intra-hippocompal bupropion injection on active avoidance learning task in rats. methods: adult male wist...

Title of dissertation: A STUDY OF SEPARATIONS IN CRYPTOGRAPHY: NEW RESULTS AND NEW MODELS Arkady Yerukhimovich, Doctor of Philosophy, 2011 Dissertation directed by: Professor Jonathan Katz Department of Computer Science For more than 20 years, black-box impossibility results have been used to argue the infeasibility of constructing certain cryptographic primitives (e.g., key agreement) from oth...

In this paper, the design and evaluation of security enhancement for data transmission in 4G networks is presented. An enhanced encryption method with AES algorithm is used here. Enhancement is done by applying dynamic S-box to Round structured AES. The static S-box is made dynamic using cipher key. The inverse S-box is also modified accordingly. Complexity is increased using Round structure to...