A NEW CATEGORY STREAM CIPHER USING NOVEL AND TESTEDPSEUDORANDOM CHARACTER SERIES WITH DYNAMIC SWAPPING

摘要

This symmetric key algorithm and its implementation convert manually entered password into mathematical expression, which is further used to generate an infinitely non-repetitive sequence of presumably random characters. These random series of characters are used to encrypt the data. This encrypted data stream is in turn swapped by dividing the data, block by block and the size of the blocks keep changing from the beginning of the data to the end of the data. The swapping commences from the beginning of the encryption and proceeds. The size of the block for swapping is narrow compared to the full length of the data and entirely depends on the one of the earlier characters which has already got swapped away from its initial position. All the characters will be mapped uniquely to mathematical expressions of a set of parameters in a pool of 256 expressions. These expressions corresponding to all characters in a password are added together to obtain a resultant expression. The above mentioned expressions corresponding to each character are further modified in advance (before summing up together) by including a 'position index'. This is inevitable to take care of the repetition of characters within a password and also in the case of a permutated password. In the case of permutated passwords, the random characters generated should be different in each case. In another words, each character and its position in the password have its own unique identity. Two pools of mathematical expressions are employed, coupled with different initiations to the parameters, to get a couple of pseudorandom character series, one's value being fed to the other. These are XORed together giving rise to a random series passing the popularly available randomness tests done by Nernst and Die hard. The initiating vector will be using, possibly the system time, and annexed with the original password to get the modified password. The system is similar to the conventional IV manipulation. The swapping will obviate substitution attack and the initiating vector method will prevent the possibility of reuse of key.