Decim − 128 ∗

Decim is a hardware oriented stream cipher submitted to the ECRYPT stream cipher project. The design of Decim is based on both a non linearly filtered LFSR and an irregular decimation mechanism called the ABSG. While the initial call for contributions required hardware-oriented stream ciphers to manage 80-bit secret keys and 64-bit public initialization, designers have been invited to demonstrate flexibility of their cipher design by proposing variants that take 128-bit keys as well. In this note, we propose a 128-bit security version of Decim, called Decim−128, and we detail the steps required to adapt Decim to different security levels.