Hardware Framework for the Rabbit Stream Cipher

Rabbit is a software-oriented synchronous stream cipher with very strong security properties and support for 128-bit keys. Rabbit is part of the European Union’s eSTREAM portfolio of stream ciphers addressing the need for strong and computationally efficient (i.e., fast) ciphers. Extensive cryptanalysis confirms Rabbit’s strength against modern attacks; attacks with complexity lower than an exhaustive key search have not been found. Previous software implementations have demonstrated Rabbit’s high throughput, however, the performance in hardware has only been estimated. Three reconfigurable hardware designs of the Rabbit stream cipher – direct, interleaved and generalized folded structure (GFS) – are presented. On the Xilinx Virtex-5 LXT FPGA, a direct, resource-efficient (568 slices) implementation delivers throughputs of up to 9.16 Gbits/s, a 4-slow interleaved design reaches 25.62 Gbits/s using 1163 slices, and a 3-slow 8-GFS implementations delivers throughputs of up to 3.46 Gbits/s using only 233 slices.