The t-Class of SOBER Stream Ciphers

This paper proposes the t-class of SOBER stream ciphers: t8, t16 and t32. t8, t16 and t32 offer 64-, 128and 256-bit key strength respectively. The t-class ciphers are based on the same principles as the original SOBER family: SOBER [17], SOBER-II [18], S16 and S32 [19], utilising the structure SOBER-II and S16 are based. The t-class ciphers are software stream ciphers designed for software implementation. Changes between the t-class and the original SOBER family are centred around constructing a stronger non-linear filter and more secure key loading. Also, t32 is now based on the same structure as t8 and t16 (S32 had a different structure). Much of the analysis of SOBER-II and S16 applies to the t-class; this paper discusses the applications of such analyses to the t-class and introduces further analyses. The output streams from these ciphers have proven to perform well in all statistical tests.