Proposed a Variable Length Block Cipher Algorithm
Keywords:Block Cipher Design, Fixed Length Block Cipher, Variable Length Block Cipher, Elastic Block Cipher, NPCBC mode, S-boxes, key schedule.
This paper will introduce a propose algorithm to improve an elastic block cipher algorithm by benefiting from an efficient properties of a secure cryptographic mode New Plaintext-Ciphertext Block Chaining mode (NPCBC) and by creating a good key schedule and two new S-Boxes. This paper will describe the concept of a proposed elastic block cipher that refer to stretch the supported block size into any length up to twice of the original block size. Also it defines a method for converting any existing block cipher into a new elastic block cipher. The results show that the security is increased by using the multiplication-addition operations in NPCBC mode which it provides the confusion and diffusion properties that cause difficulty of attacks on a new algorithm. And Also by using a good key schedule and two new S-Boxes which they increase the complexity with keep on speed of a new algorithm when compare it with a traditional algorithm which it has a weakness point when encrypt multiple blocks with using a fixed secret key.