Figure 1
From: A new distinguishing attack on reduced round ChaCha permutation

Diagram of quarter round function (QRF) applied on \((S_a^r,S_b^r,S_c^r,S_d^r)\).
From: A new distinguishing attack on reduced round ChaCha permutation

Diagram of quarter round function (QRF) applied on \((S_a^r,S_b^r,S_c^r,S_d^r)\).