Lightweight stream cipher cryptosystems

摘要

There is disclosed an apparatus and method for generating a keystream with ideal two-level autocorrelation, which can be efficiently implemented in both software and hardware on mobile devices requiring high security protection and in resource limited smart devices such as RFID chips. In one embodiment, a 16-bit Welch-Gong (WG) transformation is used as the filtering function, which is applied to 16-bit input values generated from a linear feedback shift register. In another embodiment, an 8-bit WG transformation is used which is applied to 8-bit input values generated from a linear feedback shift register.

主权项

1. A method executable on a processing device having a processor and a memory for generating a linear cryptographic keystream on the processing device, comprising:
i) performing by the processor loading a secret key and an initial vector (IV) into a linear feedback shift register (LFSR); ii) performing by the processor running the LFSR for an initial clock cycle with a nonlinear feedback Welch-Gong n-bit (WG-n) transformation module as a filtering function, wherein a Welch-Gong (WG) transformation comprises a Welch-Gong (WG) permutation and trace function, and wherein n is equal to 2.sup.k, and wherein n and k are positive integers, such that a finite field (Galois-field) GF(2.sup.(2.sup.k)) can be decomposed into an equivalent tower field representation GF((((2.sup.2).sup.2) . . . ).sup.2); and iii) outputting a 1-bit keystream from the WG-n transformation module for each clock cycle after the initial clock cycle; thereby performing a memory-optimized implementation of a Welch-Gong (WG) transformation utilizing a stream cipher equivalent tower field representation.