shithub: drawterm

ref: 19fc221351f4f1d159a7a5e2b6ea0d3bd2973bf3
dir: /libsec/chachablock.c/

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#include "os.h"

#define ROTATE(v,c) ((u32int)((v) << (c)) | ((v) >> (32 - (c))))

#define QUARTERROUND(ia,ib,ic,id) { \
	u32int a, b, c, d, t; \
	a = x[ia]; b = x[ib]; c = x[ic]; d = x[id]; \
	a += b; t = d^a; d = ROTATE(t,16); \
	c += d; t = b^c; b = ROTATE(t,12); \
	a += b; t = d^a; d = ROTATE(t, 8); \
	c += d; t = b^c; b = ROTATE(t, 7); \
	x[ia] = a; x[ib] = b; x[ic] = c; x[id] = d; \
}

void
_chachablock(u32int x[16], int rounds)
{
	for(; rounds > 0; rounds -= 2) {
		QUARTERROUND(0, 4, 8,12)
		QUARTERROUND(1, 5, 9,13)
		QUARTERROUND(2, 6,10,14)
		QUARTERROUND(3, 7,11,15)

		QUARTERROUND(0, 5,10,15)
		QUARTERROUND(1, 6,11,12)
		QUARTERROUND(2, 7, 8,13)
		QUARTERROUND(3, 4, 9,14)
	}
}