4,110 research outputs found
Re-visiting the One-Time Pad
In 1949, Shannon proved the perfect secrecy of the Vernam cryptographic
system,also popularly known as the One-Time Pad (OTP). Since then, it has been
believed that the perfectly random and uncompressible OTP which is transmitted
needs to have a length equal to the message length for this result to be true.
In this paper, we prove that the length of the transmitted OTP which actually
contains useful information need not be compromised and could be less than the
message length without sacrificing perfect secrecy. We also provide a new
interpretation for the OTP encryption by treating the message bits as making
True/False statements about the pad, which we define as a private-object. We
introduce the paradigm of private-object cryptography where messages are
transmitted by verifying statements about a secret-object. We conclude by
suggesting the use of Formal Axiomatic Systems for investing N bits of secret.Comment: 13 pages, 3 figures, submitted for publication to IndoCrypt 2005
conferenc
The transmission of sonic boom signals into rooms through open windows. Part 1 - the steady state solution
Pressure field steady state calculations for sonic boom signal transmission into rooms through open window
Propagation of high amplitude higher order sounds in slightly soft rectangular ducts, carrying mean flow
The resonance expansion method, developed to study the propagation of sound in rigid rectangular ducts is applied to the case of slightly soft ducts. Expressions for the generation and decay of various harmonics are obtained. The effect of wall admittance is seen through a dissipation function in the system of nonlinear differential equations, governing the generation of harmonics. As the wall admittance increases, the resonance is reduced. For a given wall admittance this phenomenon is stronger at higher input intensities. Both the first and second order solutions are obtained and the results are extended to the case of ducts having mean flow
Astrophysical fluid simulations of thermally ideal gases with non-constant adiabatic index: numerical implementation
An Equation of State (\textit{EoS}) closes the set of fluid equations.
Although an ideal EoS with a constant \textit{adiabatic index} is the
preferred choice due to its simplistic implementation, many astrophysical fluid
simulations may benefit from a more sophisticated treatment that can account
for diverse chemical processes. Here, we first review the basic thermodynamic
principles of a gas mixture in terms of its thermal and caloric EoS by
including effects like ionization, dissociation as well as temperature
dependent degrees of freedom such as molecular vibrations and rotations. The
formulation is revisited in the context of plasmas that are either in
equilibrium conditions (local thermodynamic- or collisional excitation-
equilibria) or described by non-equilibrium chemistry coupled to optically thin
radiative cooling. We then present a numerical implementation of thermally
ideal gases obeying a more general caloric EoS with non-constant adiabatic
index in Godunov-type numerical schemes.We discuss the necessary modifications
to the Riemann solver and to the conversion between total energy and pressure
(or vice-versa) routinely invoked in Godunov-type schemes. We then present two
different approaches for computing the EoS.The first one employs root-finder
methods and it is best suited for EoS in analytical form. The second one leans
on lookup table and interpolation and results in a more computationally
efficient approach although care must be taken to ensure thermodynamic
consistency. A number of selected benchmarks demonstrate that the employment of
a non-ideal EoS can lead to important differences in the solution when the
temperature range is K where dissociation and ionization occur. The
implementation of selected EoS introduces additional computational costs
although using lookup table methods can significantly reduce the overhead by a
factor .Comment: 17 pages, 10 figures, Accepted for publication in A&
- …