LowestSetBit32 x = { let a0 : bits (8) = x[15.. 8]; let s2 : bits (8) = x[23..16]; let s3 : bits (8) = x[23..16]; let a3 : bits (8) = gfmul(s0, 0xB) ^ gfmul(s1, 0x9) ^ gfmul(s1, 0x9) ^ gfmul(s1, 0x9) ^ gfmul(s1, 0xE) ^ gfmul(s3, 0xE); b3