code: drawterm

ref: 19fc221351f4f1d159a7a5e2b6ea0d3bd2973bf3
dir: /libsec/curve25519_dh.c/

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#include "os.h"
#include <mp.h>
#include <libsec.h>

static uchar nine[32] = {9};

void
curve25519_dh_new(uchar x[32], uchar y[32])
{
	uchar b;

	/* new public/private key pair */
	genrandom(x, 32);
	b = x[31];
	x[0] &= ~7;			/* clear bit 0,1,2 */
	x[31] = 0x40 | (b & 0x7f);	/* set bit 254, clear bit 255 */
	curve25519(y, x, nine);

	/* bit 255 is always 0, so make it random */
	y[31] |= b & 0x80;
}

void
curve25519_dh_finish(uchar x[32], uchar y[32], uchar z[32])
{
	/* remove the random bit */
	y[31] &= 0x7f;

	/* calculate dhx key */
	curve25519(z, x, y);

	memset(x, 0, 32);
	memset(y, 0, 32);
}