International Association
for Cryptologic Research

A cipher scheme related to ChaCha with the variation of using 64 bit operations instead of 32 bits, and the same 512 bit state size, is presented. We will provide strong argumentation to assert that the same security of ChaCha can be obtained with half number of instructions for the same number of 20 rounds. Also, an strategy to implement this cipher on SIMD extensions is presented, with a maximal throughput of about 3.37 bytes per cycle on a 256 bit SIMD extension with at least 11 vector registers.