pureikyubu/Docs/RE/Descrambler.c

// bootrom descrambler reversed by segher
// Copyright 2008 Segher Boessenkool <segher@kernel.crashing.org>
void Descrambler(u8* data, u32 size)
{
        u8 acc = 0;
        u8 nacc = 0;

        u16 t = 0x2953;
        u16 u = 0xd9c2;
        u16 v = 0x3ff1;

        u8 x = 1;

        for (u32 it = 0; it < size;)
        {
                int t0 = t & 1;
                int t1 = (t >> 1) & 1;
                int u0 = u & 1;
                int u1 = (u >> 1) & 1;
                int v0 = v & 1;

                x ^= t1 ^ v0;
                x ^= (u0 | u1);
                x ^= (t0 ^ u1 ^ v0) & (t0 ^ u0);

                if (t0 == u0)
                {
                        v >>= 1;
                        if (v0)
                                v ^= 0xb3d0;
                }

                if (t0 == 0)
                {
                        u >>= 1;
                        if (u0)
                                u ^= 0xfb10;
                }

                t >>= 1;
                if (t0)
                        t ^= 0xa740;

                nacc++;
                acc = 2*acc + x;
                if (nacc == 8)
                {
                        data[it++] ^= acc;
                        nacc = 0;
                }
        }
}