pub const ROW_SOURCE: [[(usize, usize); 64]; 20];Expand description
Where byte p of commitment block j comes from: (source, byte).
Message byte m = 64j + p: m < 16 is pk_nonce[m]; then chain
c = (m − 16) / 18, byte (m − 16) mod 18, held in end bank
5·(c mod 3) + (c/3 mod 5); past 1,240 bytes, zero.