| || Some New Mathematical Tools in Cryptology
Author : Kumar, I.J.;Kumari, Meena
Source : Defence Science Journal ; Vol:40(1) ; 1990 ; pp 39-54
Subject : 51 Mathematics;681.3 Computer Science
Keywords : Cipher system;Encryption;Cryptanalysis;Artificial intelligence;Stream cipher
Abstract : In this paper some new mathematical technique used in the design and analysis of cipher systems have been reviewed. Firstly, some modern cryptosystems like stream ciphers, permutation-based systems and public key encryption systems are described and the mathematical tools used in their design have been outlined. Special emphasis has been laid on the problems related to application of computational complexity to cryptosystems. Recent work on the design of the systems based on a combined encryption and coding for error correction has also been reviewed. Some recent system-oriented techniques of cryptanalysis have been discussed. It has been brought out that with the increase in the complexity of the cryptosystems it is necessary to apply some statistical and classification techniques for the purpose of identifying a cryptosystem as also for classification of the total key set into smaller classes. Finally, some very recent work on the application of artificial intelligence technique in cryptography and cryptanalysis has been mentioned.
| || Heat Flow in a Cylinder in Contact with Well Stirred Fluid
Author : Kumar, I.J.
Source : Defence Science Journal ; Vol:14(2) ; 1964 ; pp 99-108
Subject : 536 Thermodynamics
Keywords : Cylinder;Well stirred fluid
Abstract : The transient temperature distribution in a finite hollow cylinder in contact with a well stirred fluid at its outr surface has been obtained. At the inner cylindrical surface cylinder has ben assumed to absorb flux which is sinusoidal along the length of the cylinder and the plane ends of the cylinder have been assumed to be impervious to heat. Some numerical results have been exhibited graphically
| || Heat flow in built up gun barrels
Author : Kumar, I.J.
Source : Defence Science Journal ; Vol:13(1) ; 1963 ; pp 23-32
Subject : 623.45 Ammunition;623.4 Armaments and Ballistics
Keywords : Gun barrels
Abstract : A uniformly heated hollow circular cylinder is instantaneously brought in contact with another hollow circular cylinder at zero temperature whose outer radius is just equal to that of internal radius of the first cylinder so that the second one closely fits into the first. The resulting temperature distribution in the solid has been obtained with the assumption boundary condition at both the inner and outer surface of the solid. The problem has been solved by the use of Laplace transform and numerical results for some values of wall ratio have been exhibited graphically.
| || Melting of Thin Cylindrical Tubes
Author : Ahuja, K.L.;Kumar, I.J.
Source : Defence Science Journal ; Vol:16(4) ; 1966 ; pp 203-216
Subject : 531 Mechanics
Keywords : Temperature distribution;Heat balance integral;Constant heat flux
Abstract : It has been shown that the use of a polynomial profile for the temperature distribution in the case of thin cylindrical tubes is justified in the Goodman's technique of heat balance integral. The above technique has been used to obtain an approximate solution to the problem of melting (solidification) in a tube which is subjected to a constant heat flux at the inner surface while its outer surface is kept insulated. The temperature history and the melting rate are studied for the time during which the melting proceeds. Lighthill's technique for rendering approximate solution uniformly valid has been used and the first three terms of the series solution have been expressed in terms of an intrinsically small parameter.