Hardware Implementation of the Stone Metamorphic Cipher

ABSTRACT: The Stone Cipher is a metamorphic cipher that uses a variable word size and variable-size user’s key. The cipher employs two basic functions; the encryption function and a Pseudo Random Number Generator (PRG) that is based on a specially-developed one-way hash function. Four bit-balanced operations are pseudo-randomly selected to generate the sequence of operations constituting the cipher. These operations are: XOR, INV, ROR, NOP for bitwise xor, invert, rotate right and no operation respectively. The user key is encrypted using the cipher encryption function with agreed-upon initial values then it is used to generate the bit stream required to select these operations. In this work, we provide a Field Programmable Gate Array (FPGA) hardware implementation of this cipher