/* $OpenBSD: ge25519.c,v 1.3 2013/12/09 11:03:45 markus Exp $ */
/*
* Public Domain, Authors: Daniel J. Bernstein, Niels Duif, Tanja Lange,
* Peter Schwabe, Bo-Yin Yang.
* Copied from supercop-20130419/crypto_sign/ed25519/ref/ge25519.c
*/
#include "includes.h"
#include "fe25519.h"
#include "sc25519.h"
#include "ge25519.h"
/*
* Arithmetic on the twisted Edwards curve -x^2 + y^2 = 1 + dx^2y^2
* with d = -(121665/121666) = 37095705934669439343138083508754565189542113879843219016388785533085940283555
* Base point: (15112221349535400772501151409588531511454012693041857206046113283949847762202,46316835694926478169428394003475163141307993866256225615783033603165251855960);
*/
/* d */
static const fe25519 ge25519_ecd = {{0xA3, 0x78, 0x59, 0x13, 0xCA, 0x4D, 0xEB, 0x75, 0xAB, 0xD8, 0x41, 0x41, 0x4D, 0x0A, 0x70, 0x00,
0x98, 0xE8, 0x79, 0x77, 0x79, 0x40, 0xC7, 0x8C, 0x73, 0xFE, 0x6F, 0x2B, 0xEE, 0x6C, 0x03, 0x52}};
/* 2*d */
static const fe25519 ge25519_ec2d = {{0x59, 0xF1, 0xB2, 0x26, 0x94, 0x9B, 0xD6, 0xEB, 0x56, 0xB1, 0x83, 0x82, 0x9A, 0x14, 0xE0, 0x00,
0x30, 0xD1, 0xF3, 0xEE, 0xF2, 0x80, 0x8E, 0x19, 0xE7, 0xFC, 0xDF, 0x56, 0xDC, 0xD9, 0x06, 0x24}};
/* sqrt(-1) */
static const fe25519 ge25519_sqrtm1 = {{0xB0, 0xA0, 0x0E, 0x4A, 0x27, 0x1B, 0xEE, 0xC4, 0x78, 0xE4, 0x2F, 0xAD, 0x06, 0x18, 0x43, 0x2F,
0xA7, 0xD7, 0xFB, 0x3D, 0x99, 0x00, 0x4D, 0x2B, 0x0B, 0xDF, 0xC1, 0x4F, 0x80, 0x24, 0x83, 0x2B}};
#define ge25519_p3 ge25519
typedef struct
{
fe25519 x;
fe25519 z;
fe25519 y;
fe25519 t;
} ge25519_p1p1;
typedef struct
{
fe25519 x;
fe25519 y;
fe25519 z;
} ge25519_p2;
typedef struct
{
fe25519 x;
fe25519 y;
} ge25519_aff;
/* Packed coordinates of the base point */
const ge25519 ge25519_base = {{{0x1A, 0xD5, 0x25, 0x8F, 0x60, 0x2D, 0x56, 0xC9, 0xB2, 0xA7, 0x25, 0x95, 0x60, 0xC7, 0x2C, 0x69,
0x5C, 0xDC, 0xD6, 0xFD, 0x31, 0xE2, 0xA4, 0xC0, 0xFE, 0x53, 0x6E, 0xCD, 0xD3, 0x36, 0x69, 0x21}},
{{0x58, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66,
0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66}},
{{0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}},
{{0xA3, 0xDD, 0xB7, 0xA5, 0xB3, 0x8A, 0xDE, 0x6D, 0xF5, 0x52, 0x51, 0x77, 0x80, 0x9F, 0xF0, 0x20,
0x7D, 0xE3, 0xAB, 0x64, 0x8E, 0x4E, 0xEA, 0x66, 0x65, 0x76, 0x8B, 0xD7, 0x0F, 0x5F, 0x87, 0x67}}};
/* Multiples of the base point in affine representation */
static const ge25519_aff ge25519_base_multiples_affine[425] = {
#include "ge25519_base.data"
};
static void p1p1_to_p2(ge25519_p2 *r, const ge25519_p1p1 *p)
{
fe25519_mul(&r->x, &p->x, &p->t);
fe25519_mul(&r->y, &p->y, &p->z);
fe25519_mul(&r->z, &p->z, &p->t);
}
static void p1p1_to_p3(ge25519_p3 *r, const ge25519_p1p1 *p)
{
p1p1_to_p2((ge25519_p2 *)r, p);
fe25519_mul(&r->t, &p->x, &p->y);
}
static void ge25519_mixadd2(ge25519_p3 *r, const ge25519_aff *q)
{
fe25519 a,b,t1,t2,c,d,e,f,g,h,qt;
fe25519_mul(&qt, &q->x, &q->y);
fe25519_sub(&a, &r->y, &r->x); /* A = (Y1-X1)*(Y2-X2) */
fe25519_add(&b, &r->y, &r->x); /* B = (Y1+X1)*(Y2+X2) */
fe25519_sub(&t1, &q->y, &q->x);
fe25519_add(&t2, &q->y, &q->x);
fe25519_mul(&a, &a, &t1);
fe25519_mul(&b, &b, &t2);
fe25519_sub(&e, &b, &a); /* E = B-A */
fe25519_add(&h, &b, &a); /* H = B+A */
fe25519_mul(&c, &r->t, &qt); /* C = T1*k*T2 */
fe25519_mul(&c, &c, &ge25519_ec2d);
fe25519_add(&d, &r->z, &r->z); /* D = Z1*2 */
fe25519_sub(&f, &d, &c); /* F = D-C */
fe25519_add(&g, &d, &c); /* G = D+C */
fe25519_mul(&r->x, &e, &f);
fe25519_mul(&r->y, &h, &g);
fe25519_mul(&r->z, &g, &f);
fe25519_mul(&r->t, &e, &h);
}
static void add_p1p1(ge25519_p1p1 *r, const ge25519_p3 *p, const ge25519_p3 *q)
{
fe25519 a, b, c, d, t;
fe25519_sub(&a, &p->y, &p->x); /* A = (Y1-X1)*(Y2-X2) */
fe25519_sub(&t, &q->y, &q->x);
fe25519_mul(&a, &a, &t);
fe25519_add(&b, &p->x, &p->y); /* B = (Y1+X1)*(Y2+X2) */
fe25519_add(&t, &q->x, &q->y);
fe25519_mul(&b, &b, &t);
fe25519_mul(&c, &p->t, &q->t); /* C = T1*k*T2 */
fe25519_mul(&c, &c, &ge25519_ec2d);
fe25519_mul(&d, &p->z, &q->z); /* D = Z1*2*Z2 */
fe25519_add(&d, &d, &d);
fe25519_sub(&r->x, &b, &a); /* E = B-A */
fe25519_sub(&r->t, &d, &c); /* F = D-C */
fe25519_add(&r->z, &d, &c); /* G = D+C */
fe25519_add(&r->y, &b, &a); /* H = B+A */
}
/* See http://www.hyperelliptic.org/EFD/g1p/auto-twisted-extended-1.html#doubling-dbl-2008-hwcd */
static void dbl_p1p1(ge25519_p1p1 *r, const ge25519_p2 *p)
{
fe25519 a,b,c,d;
fe25519_square(&a