1 An Efficient Stream Cipher Using Variable Sizes of Key-Streams

This paper proposes a stream cipher with the advantages of efficiency and non-linearity of a key stream to against eavesdroppers invading communication protocols. Three transformations, KeyStream, DataHiding and SecureNonce, based on segmenting, XORing, and shifting operations are used to generate a sequence of variable key-stream numbers and ciphertext, respectively. Five different types of plaintext files are simulated by C language codes, where their encrypting time, the sizes of key streams, and the sizes of ciphertexts are listed. We also illustrate the distribution of a chosen plaintext and its ciphertext with the conditions of the secret key and the nonce slightly modified. The experimental results show that the generated sequence of key-stream numbers with high non-linearity won’t be reused associated with each encryption. The mechanism won’t use plenty of RAM to store a look-up table and temporary data