2 * @file ed448goldilocks/decaf.c
6 * Copyright (c) 2015-2016 Cryptography Research, Inc. \n
7 * Released under the MIT License. See LICENSE.txt for license information.
9 * @brief Decaf high-level functions.
11 * @warning This file was automatically generated in Python.
12 * Please do not edit it.
14 #include <openssl/crypto.h>
18 #include "point_448.h"
20 #include "curve448_lcl.h"
23 #define SCALAR_BITS DECAF_448_SCALAR_BITS
24 #define SCALAR_SER_BYTES DECAF_448_SCALAR_BYTES
25 #define SCALAR_LIMBS DECAF_448_SCALAR_LIMBS
26 #define scalar_t curve448_scalar_t
27 #define point_t curve448_point_t
28 #define precomputed_s curve448_precomputed_s
31 /* Comb config: number of combs, n, t, s. */
35 #define DECAF_WINDOW_BITS 5
36 #define DECAF_WNAF_FIXED_TABLE_BITS 5
37 #define DECAF_WNAF_VAR_TABLE_BITS 3
39 static const int EDWARDS_D = -39081;
40 static const scalar_t precomputed_scalarmul_adjustment = {{{
41 SC_LIMB(0xc873d6d54a7bb0cf), SC_LIMB(0xe933d8d723a70aad), SC_LIMB(0xbb124b65129c96fd), SC_LIMB(0x00000008335dc163)
44 const uint8_t decaf_x448_base_point[DECAF_X448_PUBLIC_BYTES] = { 0x05 };
46 #define RISTRETTO_FACTOR DECAF_448_RISTRETTO_FACTOR
47 const gf RISTRETTO_FACTOR = {{{
48 0x42ef0f45572736, 0x7bf6aa20ce5296, 0xf4fd6eded26033, 0x968c14ba839a66, 0xb8d54b64a2d780, 0x6aa0a1f1a7b8a5, 0x683bf68d722fa2, 0x22d962fbeb24f7
52 #define TWISTED_D ((EDWARDS_D)-1)
54 #define EFF_D (-(TWISTED_D))
57 /* End of template stuff */
59 #define WBITS DECAF_WORD_BITS /* NB this may be different from ARCH_WORD_BITS */
61 /* Projective Niels coordinates */
62 typedef struct { gf a, b, c; } niels_s, niels_t[1];
63 typedef struct { niels_t n; gf z; } VECTOR_ALIGNED pniels_s, pniels_t[1];
65 /* Precomputed base */
66 struct precomputed_s { niels_t table [COMBS_N<<(COMBS_T-1)]; };
68 extern const gf curve448_precomputed_base_as_fe[];
69 const precomputed_s *curve448_precomputed_base =
70 (const precomputed_s *) &curve448_precomputed_base_as_fe;
74 gf_invert(gf y, const gf x, int assert_nonzero) {
77 mask_t ret = gf_isr(t2, t1); // +-1/sqrt(o^2) = +-1/o
79 if (assert_nonzero) assert(ret);
81 gf_mul(t2, t1, x); // not direct to y in case of alias.
85 /** identity = (0,1) */
86 const point_t curve448_point_identity = {{{{{0}}},{{{1}}},{{{1}}},{{{0}}}}};
88 static DECAF_NOINLINE void
89 point_double_internal (
97 gf_add_nr ( d, c, a ); /* 2+e */
98 gf_add_nr ( p->t, q->y, q->x ); /* 2+e */
100 gf_subx_nr ( b, b, d, 3 ); /* 4+e */
101 gf_sub_nr ( p->t, a, c ); /* 3+e */
102 gf_sqr ( p->x, q->z );
103 gf_add_nr ( p->z, p->x, p->x ); /* 2+e */
104 gf_subx_nr ( a, p->z, p->t, 4 ); /* 6+e */
105 if (GF_HEADROOM == 5) gf_weak_reduce(a); /* or 1+e */
106 gf_mul ( p->x, a, b );
107 gf_mul ( p->z, p->t, a );
108 gf_mul ( p->y, p->t, d );
109 if (!before_double) gf_mul ( p->t, b, d );
112 void curve448_point_double(point_t p, const point_t q) {
113 point_double_internal(p,q,0);
116 /* Operations on [p]niels */
117 static DECAF_INLINE void
122 gf_cond_swap(n->a, n->b, neg);
123 gf_cond_neg(n->c, neg);
126 static DECAF_NOINLINE void pt_to_pniels (
130 gf_sub ( b->n->a, a->y, a->x );
131 gf_add ( b->n->b, a->x, a->y );
132 gf_mulw ( b->n->c, a->t, 2*TWISTED_D );
133 gf_add ( b->z, a->z, a->z );
136 static DECAF_NOINLINE void pniels_to_pt (
141 gf_add ( eu, d->n->b, d->n->a );
142 gf_sub ( e->y, d->n->b, d->n->a );
143 gf_mul ( e->t, e->y, eu);
144 gf_mul ( e->x, d->z, e->y );
145 gf_mul ( e->y, d->z, eu );
146 gf_sqr ( e->z, d->z );
149 static DECAF_NOINLINE void
154 gf_add ( e->y, n->b, n->a );
155 gf_sub ( e->x, n->b, n->a );
156 gf_mul ( e->t, e->y, e->x );
157 gf_copy ( e->z, ONE );
160 static DECAF_NOINLINE void
167 gf_sub_nr ( b, d->y, d->x ); /* 3+e */
168 gf_mul ( a, e->a, b );
169 gf_add_nr ( b, d->x, d->y ); /* 2+e */
170 gf_mul ( d->y, e->b, b );
171 gf_mul ( d->x, e->c, d->t );
172 gf_add_nr ( c, a, d->y ); /* 2+e */
173 gf_sub_nr ( b, d->y, a ); /* 3+e */
174 gf_sub_nr ( d->y, d->z, d->x ); /* 3+e */
175 gf_add_nr ( a, d->x, d->z ); /* 2+e */
176 gf_mul ( d->z, a, d->y );
177 gf_mul ( d->x, d->y, b );
178 gf_mul ( d->y, a, c );
179 if (!before_double) gf_mul ( d->t, b, c );
182 static DECAF_NOINLINE void
189 gf_sub_nr ( b, d->y, d->x ); /* 3+e */
190 gf_mul ( a, e->b, b );
191 gf_add_nr ( b, d->x, d->y ); /* 2+e */
192 gf_mul ( d->y, e->a, b );
193 gf_mul ( d->x, e->c, d->t );
194 gf_add_nr ( c, a, d->y ); /* 2+e */
195 gf_sub_nr ( b, d->y, a ); /* 3+e */
196 gf_add_nr ( d->y, d->z, d->x ); /* 2+e */
197 gf_sub_nr ( a, d->z, d->x ); /* 3+e */
198 gf_mul ( d->z, a, d->y );
199 gf_mul ( d->x, d->y, b );
200 gf_mul ( d->y, a, c );
201 if (!before_double) gf_mul ( d->t, b, c );
211 gf_mul ( L0, p->z, pn->z );
212 gf_copy ( p->z, L0 );
213 add_niels_to_pt( p, pn->n, before_double );
223 gf_mul ( L0, p->z, pn->z );
224 gf_copy ( p->z, L0 );
225 sub_niels_from_pt( p, pn->n, before_double );
228 decaf_bool_t curve448_point_eq ( const point_t p, const point_t q ) {
229 /* equality mod 2-torsion compares x/y */
231 gf_mul ( a, p->y, q->x );
232 gf_mul ( b, q->y, p->x );
233 mask_t succ = gf_eq(a,b);
235 return mask_to_bool(succ);
238 decaf_bool_t curve448_point_valid (
244 mask_t out = gf_eq(a,b);
249 gf_mulw(c,b,TWISTED_D);
253 out &= ~gf_eq(p->z,ZERO);
254 return mask_to_bool(out);
257 static DECAF_INLINE void
258 constant_time_lookup_niels (
259 niels_s *__restrict__ ni,
260 const niels_t *table,
264 constant_time_lookup(ni, table, sizeof(niels_s), nelts, idx);
267 void curve448_precomputed_scalarmul (
269 const precomputed_s *table,
270 const scalar_t scalar
274 const unsigned int n = COMBS_N, t = COMBS_T, s = COMBS_S;
277 curve448_scalar_add(scalar1x, scalar, precomputed_scalarmul_adjustment);
278 curve448_scalar_halve(scalar1x,scalar1x);
282 for (i=s-1; i>=0; i--) {
283 if (i != (int)s-1) point_double_internal(out,out,0);
285 for (j=0; j<n; j++) {
288 for (k=0; k<t; k++) {
289 unsigned int bit = i + s*(k + j*t);
290 if (bit < SCALAR_BITS) {
291 tab |= (scalar1x->limb[bit/WBITS] >> (bit%WBITS) & 1) << k;
295 mask_t invert = (tab>>(t-1))-1;
297 tab &= (1<<(t-1)) - 1;
299 constant_time_lookup_niels(ni, &table->table[j<<(t-1)], 1<<(t-1), tab);
301 cond_neg_niels(ni, invert);
302 if ((i!=(int)s-1)||j) {
303 add_niels_to_pt(out, ni, j==n-1 && i);
305 niels_to_pt(out, ni);
310 OPENSSL_cleanse(ni,sizeof(ni));
311 OPENSSL_cleanse(scalar1x,sizeof(scalar1x));
314 void curve448_point_mul_by_ratio_and_encode_like_eddsa (
315 uint8_t enc[DECAF_EDDSA_448_PUBLIC_BYTES],
319 /* The point is now on the twisted curve. Move it to untwisted. */
322 curve448_point_copy(q,p);
325 /* 4-isogeny: 2xy/(y^+x^2), (y^2-x^2)/(2z^2-y^2+x^2) */
330 gf_add( z, q->y, q->x );
340 OPENSSL_cleanse(u,sizeof(u));
349 enc[DECAF_EDDSA_448_PRIVATE_BYTES-1] = 0;
350 gf_serialize(enc, x, 1);
351 enc[DECAF_EDDSA_448_PRIVATE_BYTES-1] |= 0x80 & gf_lobit(t);
353 OPENSSL_cleanse(x,sizeof(x));
354 OPENSSL_cleanse(y,sizeof(y));
355 OPENSSL_cleanse(z,sizeof(z));
356 OPENSSL_cleanse(t,sizeof(t));
357 curve448_point_destroy(q);
361 decaf_error_t curve448_point_decode_like_eddsa_and_mul_by_ratio (
363 const uint8_t enc[DECAF_EDDSA_448_PUBLIC_BYTES]
365 uint8_t enc2[DECAF_EDDSA_448_PUBLIC_BYTES];
366 memcpy(enc2,enc,sizeof(enc2));
368 mask_t low = ~word_is_zero(enc2[DECAF_EDDSA_448_PRIVATE_BYTES-1] & 0x80);
369 enc2[DECAF_EDDSA_448_PRIVATE_BYTES-1] &= ~0x80;
371 mask_t succ = gf_deserialize(p->y, enc2, 1, 0);
373 succ &= word_is_zero(enc2[DECAF_EDDSA_448_PRIVATE_BYTES-1]);
377 gf_sub(p->z,ONE,p->x); /* num = 1-y^2 */
378 gf_mulw(p->t,p->x,EDWARDS_D); /* dy^2 */
379 gf_sub(p->t,ONE,p->t); /* denom = 1-dy^2 or 1-d + dy^2 */
381 gf_mul(p->x,p->z,p->t);
382 succ &= gf_isr(p->t,p->x); /* 1/sqrt(num * denom) */
384 gf_mul(p->x,p->t,p->z); /* sqrt(num / denom) */
385 gf_cond_neg(p->x,gf_lobit(p->x)^low);
389 /* 4-isogeny 2xy/(y^2-ax^2), (y^2+ax^2)/(2-y^2-ax^2) */
394 gf_add ( p->t, p->y, p->x );
397 gf_sub ( p->t, a, c );
398 gf_sqr ( p->x, p->z );
399 gf_add ( p->z, p->x, p->x );
400 gf_sub ( a, p->z, d );
401 gf_mul ( p->x, a, b );
402 gf_mul ( p->z, p->t, a );
403 gf_mul ( p->y, p->t, d );
404 gf_mul ( p->t, b, d );
405 OPENSSL_cleanse(a,sizeof(a));
406 OPENSSL_cleanse(b,sizeof(b));
407 OPENSSL_cleanse(c,sizeof(c));
408 OPENSSL_cleanse(d,sizeof(d));
411 OPENSSL_cleanse(enc2,sizeof(enc2));
412 assert(curve448_point_valid(p) || ~succ);
414 return decaf_succeed_if(mask_to_bool(succ));
417 decaf_error_t decaf_x448 (
418 uint8_t out[X_PUBLIC_BYTES],
419 const uint8_t base[X_PUBLIC_BYTES],
420 const uint8_t scalar[X_PRIVATE_BYTES]
422 gf x1, x2, z2, x3, z3, t1, t2;
423 ignore_result(gf_deserialize(x1,base,1,0));
432 for (t = X_PRIVATE_BITS-1; t>=0; t--) {
433 uint8_t sb = scalar[t/8];
435 /* Scalar conditioning */
436 if (t/8==0) sb &= -(uint8_t)COFACTOR;
437 else if (t == X_PRIVATE_BITS-1) sb = -1;
439 mask_t k_t = (sb>>(t%8)) & 1;
440 k_t = -k_t; /* set to all 0s or all 1s */
443 gf_cond_swap(x2,x3,swap);
444 gf_cond_swap(z2,z3,swap);
447 gf_add_nr(t1,x2,z2); /* A = x2 + z2 */ /* 2+e */
448 gf_sub_nr(t2,x2,z2); /* B = x2 - z2 */ /* 3+e */
449 gf_sub_nr(z2,x3,z3); /* D = x3 - z3 */ /* 3+e */
450 gf_mul(x2,t1,z2); /* DA */
451 gf_add_nr(z2,z3,x3); /* C = x3 + z3 */ /* 2+e */
452 gf_mul(x3,t2,z2); /* CB */
453 gf_sub_nr(z3,x2,x3); /* DA-CB */ /* 3+e */
454 gf_sqr(z2,z3); /* (DA-CB)^2 */
455 gf_mul(z3,x1,z2); /* z3 = x1(DA-CB)^2 */
456 gf_add_nr(z2,x2,x3); /* (DA+CB) */ /* 2+e */
457 gf_sqr(x3,z2); /* x3 = (DA+CB)^2 */
459 gf_sqr(z2,t1); /* AA = A^2 */
460 gf_sqr(t1,t2); /* BB = B^2 */
461 gf_mul(x2,z2,t1); /* x2 = AA*BB */
462 gf_sub_nr(t2,z2,t1); /* E = AA-BB */ /* 3+e */
464 gf_mulw(t1,t2,-EDWARDS_D); /* E*-d = a24*E */
465 gf_add_nr(t1,t1,z2); /* AA + a24*E */ /* 2+e */
466 gf_mul(z2,t2,t1); /* z2 = E(AA+a24*E) */
470 gf_cond_swap(x2,x3,swap);
471 gf_cond_swap(z2,z3,swap);
474 gf_serialize(out,x1,1);
475 mask_t nz = ~gf_eq(x1,ZERO);
477 OPENSSL_cleanse(x1,sizeof(x1));
478 OPENSSL_cleanse(x2,sizeof(x2));
479 OPENSSL_cleanse(z2,sizeof(z2));
480 OPENSSL_cleanse(x3,sizeof(x3));
481 OPENSSL_cleanse(z3,sizeof(z3));
482 OPENSSL_cleanse(t1,sizeof(t1));
483 OPENSSL_cleanse(t2,sizeof(t2));
485 return decaf_succeed_if(mask_to_bool(nz));
488 /* Thanks Johan Pascal */
489 void decaf_ed448_convert_public_key_to_x448 (
490 uint8_t x[DECAF_X448_PUBLIC_BYTES],
491 const uint8_t ed[DECAF_EDDSA_448_PUBLIC_BYTES]
494 const uint8_t mask = (uint8_t)(0xFE<<(7));
495 ignore_result(gf_deserialize(y, ed, 1, mask));
500 /* u = y^2 * (1-dy^2) / (1-y^2) */
501 gf_sqr(n,y); /* y^2*/
502 gf_sub(d,ONE,n); /* 1-y^2*/
503 gf_invert(d,d,0); /* 1/(1-y^2)*/
504 gf_mul(y,n,d); /* y^2 / (1-y^2) */
505 gf_mulw(d,n,EDWARDS_D); /* dy^2*/
506 gf_sub(d, ONE, d); /* 1-dy^2*/
507 gf_mul(n, y, d); /* y^2 * (1-dy^2) / (1-y^2) */
510 OPENSSL_cleanse(y,sizeof(y));
511 OPENSSL_cleanse(n,sizeof(n));
512 OPENSSL_cleanse(d,sizeof(d));
516 void curve448_point_mul_by_ratio_and_encode_like_x448 (
517 uint8_t out[X_PUBLIC_BYTES],
521 curve448_point_copy(q,p);
522 gf_invert(q->t,q->x,0); /* 1/x */
523 gf_mul(q->z,q->t,q->y); /* y/x */
524 gf_sqr(q->y,q->z); /* (y/x)^2 */
525 gf_serialize(out,q->y,1);
526 curve448_point_destroy(q);
529 void decaf_x448_derive_public_key (
530 uint8_t out[X_PUBLIC_BYTES],
531 const uint8_t scalar[X_PRIVATE_BYTES]
533 /* Scalar conditioning */
534 uint8_t scalar2[X_PRIVATE_BYTES];
535 memcpy(scalar2,scalar,sizeof(scalar2));
536 scalar2[0] &= -(uint8_t)COFACTOR;
538 scalar2[X_PRIVATE_BYTES-1] &= ~(-1u<<((X_PRIVATE_BITS+7)%8));
539 scalar2[X_PRIVATE_BYTES-1] |= 1<<((X_PRIVATE_BITS+7)%8);
542 curve448_scalar_decode_long(the_scalar,scalar2,sizeof(scalar2));
544 /* Compensate for the encoding ratio */
545 for (unsigned i=1; i<DECAF_X448_ENCODE_RATIO; i<<=1) {
546 curve448_scalar_halve(the_scalar,the_scalar);
549 curve448_precomputed_scalarmul(p,curve448_precomputed_base,the_scalar);
550 curve448_point_mul_by_ratio_and_encode_like_x448(out,p);
551 curve448_point_destroy(p);
556 * Control for variable-time scalar multiply algorithms.
558 struct smvt_control {
562 static int recode_wnaf (
563 struct smvt_control *control, /* [nbits/(table_bits+1) + 3] */
564 const scalar_t scalar,
565 unsigned int table_bits
567 unsigned int table_size = SCALAR_BITS/(table_bits+1) + 3;
568 int position = table_size - 1; /* at the end */
570 /* place the end marker */
571 control[position].power = -1;
572 control[position].addend = 0;
575 /* PERF: Could negate scalar if it's large. But then would need more cases
576 * in the actual code that uses it, all for an expected reduction of like 1/5 op.
577 * Probably not worth it.
580 uint64_t current = scalar->limb[0] & 0xFFFF;
581 uint32_t mask = (1<<(table_bits+1))-1;
584 const unsigned int B_OVER_16 = sizeof(scalar->limb[0]) / 2;
585 for (w = 1; w<(SCALAR_BITS-1)/16+3; w++) {
586 if (w < (SCALAR_BITS-1)/16+1) {
587 /* Refill the 16 high bits of current */
588 current += (uint32_t)((scalar->limb[w/B_OVER_16]>>(16*(w%B_OVER_16)))<<16);
591 while (current & 0xFFFF) {
592 assert(position >= 0);
593 uint32_t pos = __builtin_ctz((uint32_t)current), odd = (uint32_t)current >> pos;
594 int32_t delta = odd & mask;
595 if (odd & 1<<(table_bits+1)) delta -= (1<<(table_bits+1));
596 current -= delta << pos;
597 control[position].power = pos + 16*(w-1);
598 control[position].addend = delta;
606 unsigned int n = table_size - position;
608 for (i=0; i<n; i++) {
609 control[i] = control[i+position];
617 const point_t working,
622 pt_to_pniels(output[0], working);
624 if (tbits == 0) return;
626 curve448_point_double(tmp,working);
628 pt_to_pniels(twop, tmp);
630 add_pniels_to_pt(tmp, output[0],0);
631 pt_to_pniels(output[1], tmp);
633 for (i=2; i < 1<<tbits; i++) {
634 add_pniels_to_pt(tmp, twop,0);
635 pt_to_pniels(output[i], tmp);
638 curve448_point_destroy(tmp);
639 OPENSSL_cleanse(twop,sizeof(twop));
642 extern const gf curve448_precomputed_wnaf_as_fe[];
643 static const niels_t *curve448_wnaf_base = (const niels_t *)curve448_precomputed_wnaf_as_fe;
645 void curve448_base_double_scalarmul_non_secret (
647 const scalar_t scalar1,
649 const scalar_t scalar2
651 const int table_bits_var = DECAF_WNAF_VAR_TABLE_BITS,
652 table_bits_pre = DECAF_WNAF_FIXED_TABLE_BITS;
653 struct smvt_control control_var[SCALAR_BITS/(table_bits_var+1)+3];
654 struct smvt_control control_pre[SCALAR_BITS/(table_bits_pre+1)+3];
656 int ncb_pre = recode_wnaf(control_pre, scalar1, table_bits_pre);
657 int ncb_var = recode_wnaf(control_var, scalar2, table_bits_var);
659 pniels_t precmp_var[1<<table_bits_var];
660 prepare_wnaf_table(precmp_var, base2, table_bits_var);
662 int contp=0, contv=0, i = control_var[0].power;
665 curve448_point_copy(combo, curve448_point_identity);
667 } else if (i > control_pre[0].power) {
668 pniels_to_pt(combo, precmp_var[control_var[0].addend >> 1]);
670 } else if (i == control_pre[0].power && i >=0 ) {
671 pniels_to_pt(combo, precmp_var[control_var[0].addend >> 1]);
672 add_niels_to_pt(combo, curve448_wnaf_base[control_pre[0].addend >> 1], i);
675 i = control_pre[0].power;
676 niels_to_pt(combo, curve448_wnaf_base[control_pre[0].addend >> 1]);
680 for (i--; i >= 0; i--) {
681 int cv = (i==control_var[contv].power), cp = (i==control_pre[contp].power);
682 point_double_internal(combo,combo,i && !(cv||cp));
685 assert(control_var[contv].addend);
687 if (control_var[contv].addend > 0) {
688 add_pniels_to_pt(combo, precmp_var[control_var[contv].addend >> 1], i&&!cp);
690 sub_pniels_from_pt(combo, precmp_var[(-control_var[contv].addend) >> 1], i&&!cp);
696 assert(control_pre[contp].addend);
698 if (control_pre[contp].addend > 0) {
699 add_niels_to_pt(combo, curve448_wnaf_base[control_pre[contp].addend >> 1], i);
701 sub_niels_from_pt(combo, curve448_wnaf_base[(-control_pre[contp].addend) >> 1], i);
707 /* This function is non-secret, but whatever this is cheap. */
708 OPENSSL_cleanse(control_var,sizeof(control_var));
709 OPENSSL_cleanse(control_pre,sizeof(control_pre));
710 OPENSSL_cleanse(precmp_var,sizeof(precmp_var));
712 assert(contv == ncb_var); (void)ncb_var;
713 assert(contp == ncb_pre); (void)ncb_pre;
716 void curve448_point_destroy (
719 OPENSSL_cleanse(point, sizeof(point_t));
722 int X448(uint8_t out_shared_key[56], const uint8_t private_key[56],
723 const uint8_t peer_public_value[56])
725 return decaf_x448(out_shared_key, peer_public_value, private_key)
729 void X448_public_from_private(uint8_t out_public_value[56],
730 const uint8_t private_key[56])
732 decaf_x448_derive_public_key(out_public_value, private_key);