The Tor Browser: security/nss/lib/freebl/ecl/ecp

security/nss/lib/freebl/ecl/ecp_jm.c@b8a032363ba2 (annotated)

security/nss/lib/freebl/ecl/ecp_jm.c

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 #include "ecp.h"
 #include "ecl-priv.h"
 #include "mplogic.h"
 #include <stdlib.h>
 #define MAX_SCRATCH 6
 /* Computes R = 2P.  Elliptic curve points P and R can be identical.  Uses
  * Modified Jacobian coordinates.
  *
  * Assumes input is already field-encoded using field_enc, and returns
  * output that is still field-encoded.
  *
  */
 mp_err
 ec_GFp_pt_dbl_jm(const mp_int *px, const mp_int *py, const mp_int *pz,
 				 const mp_int *paz4, mp_int *rx, mp_int *ry, mp_int *rz,
 				 mp_int *raz4, mp_int scratch[], const ECGroup *group)
 {
 	mp_err res = MP_OKAY;
 	mp_int *t0, *t1, *M, *S;
 	t0 = &scratch[0];
 	t1 = &scratch[1];
 	M = &scratch[2];
 	S = &scratch[3];
 #if MAX_SCRATCH < 4
 #error "Scratch array defined too small "
 #endif
 	/* Check for point at infinity */
 	if (ec_GFp_pt_is_inf_jac(px, py, pz) == MP_YES) {
 		/* Set r = pt at infinity by setting rz = 0 */
 		MP_CHECKOK(ec_GFp_pt_set_inf_jac(rx, ry, rz));
 		goto CLEANUP;
 	}
 	/* M = 3 (px^2) + a*(pz^4) */
 	MP_CHECKOK(group->meth->field_sqr(px, t0, group->meth));
 	MP_CHECKOK(group->meth->field_add(t0, t0, M, group->meth));
 	MP_CHECKOK(group->meth->field_add(t0, M, t0, group->meth));
 	MP_CHECKOK(group->meth->field_add(t0, paz4, M, group->meth));
 	/* rz = 2 * py * pz */
 	MP_CHECKOK(group->meth->field_mul(py, pz, S, group->meth));
 	MP_CHECKOK(group->meth->field_add(S, S, rz, group->meth));
 	/* t0 = 2y^2 , t1 = 8y^4 */
 	MP_CHECKOK(group->meth->field_sqr(py, t0, group->meth));
 	MP_CHECKOK(group->meth->field_add(t0, t0, t0, group->meth));
 	MP_CHECKOK(group->meth->field_sqr(t0, t1, group->meth));
 	MP_CHECKOK(group->meth->field_add(t1, t1, t1, group->meth));
 	/* S = 4 * px * py^2 = 2 * px * t0 */
 	MP_CHECKOK(group->meth->field_mul(px, t0, S, group->meth));
 	MP_CHECKOK(group->meth->field_add(S, S, S, group->meth));
 	/* rx = M^2 - 2S */
 	MP_CHECKOK(group->meth->field_sqr(M, rx, group->meth));
 	MP_CHECKOK(group->meth->field_sub(rx, S, rx, group->meth));
 	MP_CHECKOK(group->meth->field_sub(rx, S, rx, group->meth));
 	/* ry = M * (S - rx) - t1 */
 	MP_CHECKOK(group->meth->field_sub(S, rx, S, group->meth));
 	MP_CHECKOK(group->meth->field_mul(S, M, ry, group->meth));
 	MP_CHECKOK(group->meth->field_sub(ry, t1, ry, group->meth));
 	/* ra*z^4 = 2*t1*(apz4) */
 	MP_CHECKOK(group->meth->field_mul(paz4, t1, raz4, group->meth));
 	MP_CHECKOK(group->meth->field_add(raz4, raz4, raz4, group->meth));
   CLEANUP:
 	return res;
 }
 /* Computes R = P + Q where R is (rx, ry, rz), P is (px, py, pz) and Q is
  * (qx, qy, 1).  Elliptic curve points P, Q, and R can all be identical.
  * Uses mixed Modified_Jacobian-affine coordinates. Assumes input is
  * already field-encoded using field_enc, and returns output that is still
  * field-encoded. */
 mp_err
 ec_GFp_pt_add_jm_aff(const mp_int *px, const mp_int *py, const mp_int *pz,
 					 const mp_int *paz4, const mp_int *qx,
 					 const mp_int *qy, mp_int *rx, mp_int *ry, mp_int *rz,
 					 mp_int *raz4, mp_int scratch[], const ECGroup *group)
 {
 	mp_err res = MP_OKAY;
 	mp_int *A, *B, *C, *D, *C2, *C3;
 	A = &scratch[0];
 	B = &scratch[1];
 	C = &scratch[2];
 	D = &scratch[3];
 	C2 = &scratch[4];
 	C3 = &scratch[5];
 #if MAX_SCRATCH < 6
 #error "Scratch array defined too small "
 #endif
 	/* If either P or Q is the point at infinity, then return the other
 	 * point */
 	if (ec_GFp_pt_is_inf_jac(px, py, pz) == MP_YES) {
 		MP_CHECKOK(ec_GFp_pt_aff2jac(qx, qy, rx, ry, rz, group));
 		MP_CHECKOK(group->meth->field_sqr(rz, raz4, group->meth));
 		MP_CHECKOK(group->meth->field_sqr(raz4, raz4, group->meth));
 		MP_CHECKOK(group->meth->
 				   field_mul(raz4, &group->curvea, raz4, group->meth));
 		goto CLEANUP;
 	}
 	if (ec_GFp_pt_is_inf_aff(qx, qy) == MP_YES) {
 		MP_CHECKOK(mp_copy(px, rx));
 		MP_CHECKOK(mp_copy(py, ry));
 		MP_CHECKOK(mp_copy(pz, rz));
 		MP_CHECKOK(mp_copy(paz4, raz4));
 		goto CLEANUP;
 	}
 	/* A = qx * pz^2, B = qy * pz^3 */
 	MP_CHECKOK(group->meth->field_sqr(pz, A, group->meth));
 	MP_CHECKOK(group->meth->field_mul(A, pz, B, group->meth));
 	MP_CHECKOK(group->meth->field_mul(A, qx, A, group->meth));
 	MP_CHECKOK(group->meth->field_mul(B, qy, B, group->meth));
 	/* C = A - px, D = B - py */
 	MP_CHECKOK(group->meth->field_sub(A, px, C, group->meth));
 	MP_CHECKOK(group->meth->field_sub(B, py, D, group->meth));
 	/* C2 = C^2, C3 = C^3 */
 	MP_CHECKOK(group->meth->field_sqr(C, C2, group->meth));
 	MP_CHECKOK(group->meth->field_mul(C, C2, C3, group->meth));
 	/* rz = pz * C */
 	MP_CHECKOK(group->meth->field_mul(pz, C, rz, group->meth));
 	/* C = px * C^2 */
 	MP_CHECKOK(group->meth->field_mul(px, C2, C, group->meth));
 	/* A = D^2 */
 	MP_CHECKOK(group->meth->field_sqr(D, A, group->meth));
 	/* rx = D^2 - (C^3 + 2 * (px * C^2)) */
 	MP_CHECKOK(group->meth->field_add(C, C, rx, group->meth));
 	MP_CHECKOK(group->meth->field_add(C3, rx, rx, group->meth));
 	MP_CHECKOK(group->meth->field_sub(A, rx, rx, group->meth));
 	/* C3 = py * C^3 */
 	MP_CHECKOK(group->meth->field_mul(py, C3, C3, group->meth));
 	/* ry = D * (px * C^2 - rx) - py * C^3 */
 	MP_CHECKOK(group->meth->field_sub(C, rx, ry, group->meth));
 	MP_CHECKOK(group->meth->field_mul(D, ry, ry, group->meth));
 	MP_CHECKOK(group->meth->field_sub(ry, C3, ry, group->meth));
 	/* raz4 = a * rz^4 */
 	MP_CHECKOK(group->meth->field_sqr(rz, raz4, group->meth));
 	MP_CHECKOK(group->meth->field_sqr(raz4, raz4, group->meth));
 	MP_CHECKOK(group->meth->
 			   field_mul(raz4, &group->curvea, raz4, group->meth));
 CLEANUP:
 	return res;
 }
 /* Computes R = nP where R is (rx, ry) and P is the base point. Elliptic
  * curve points P and R can be identical. Uses mixed Modified-Jacobian
  * co-ordinates for doubling and Chudnovsky Jacobian coordinates for
  * additions. Assumes input is already field-encoded using field_enc, and
  * returns output that is still field-encoded. Uses 5-bit window NAF
  * method (algorithm 11) for scalar-point multiplication from Brown,
  * Hankerson, Lopez, Menezes. Software Implementation of the NIST Elliptic
  * Curves Over Prime Fields. */
 mp_err
 ec_GFp_pt_mul_jm_wNAF(const mp_int *n, const mp_int *px, const mp_int *py,
 					  mp_int *rx, mp_int *ry, const ECGroup *group)
 {
 	mp_err res = MP_OKAY;
 	mp_int precomp[16][2], rz, tpx, tpy;
 	mp_int raz4;
 	mp_int scratch[MAX_SCRATCH];
 	signed char *naf = NULL;
 	int i, orderBitSize;
 	MP_DIGITS(&rz) = 0;
 	MP_DIGITS(&raz4) = 0;
 	MP_DIGITS(&tpx) = 0;
 	MP_DIGITS(&tpy) = 0;
 	for (i = 0; i < 16; i++) {
 		MP_DIGITS(&precomp[i][0]) = 0;
 		MP_DIGITS(&precomp[i][1]) = 0;
 	}
 	for (i = 0; i < MAX_SCRATCH; i++) {
 		MP_DIGITS(&scratch[i]) = 0;
 	}
 	ARGCHK(group != NULL, MP_BADARG);
 	ARGCHK((n != NULL) && (px != NULL) && (py != NULL), MP_BADARG);
 	/* initialize precomputation table */
 	MP_CHECKOK(mp_init(&tpx));
 	MP_CHECKOK(mp_init(&tpy));;
 	MP_CHECKOK(mp_init(&rz));
 	MP_CHECKOK(mp_init(&raz4));
 	for (i = 0; i < 16; i++) {
 		MP_CHECKOK(mp_init(&precomp[i][0]));
 		MP_CHECKOK(mp_init(&precomp[i][1]));
 	}
 	for (i = 0; i < MAX_SCRATCH; i++) {
 		MP_CHECKOK(mp_init(&scratch[i]));
 	}
 	/* Set out[8] = P */
 	MP_CHECKOK(mp_copy(px, &precomp[8][0]));
 	MP_CHECKOK(mp_copy(py, &precomp[8][1]));
 	/* Set (tpx, tpy) = 2P */
 	MP_CHECKOK(group->
 			   point_dbl(&precomp[8][0], &precomp[8][1], &tpx, &tpy,
 						 group));
 	/* Set 3P, 5P, ..., 15P */
 	for (i = 8; i < 15; i++) {
 		MP_CHECKOK(group->
 				   point_add(&precomp[i][0], &precomp[i][1], &tpx, &tpy,
 							 &precomp[i + 1][0], &precomp[i + 1][1],
 							 group));
 	}
 	/* Set -15P, -13P, ..., -P */
 	for (i = 0; i < 8; i++) {
 		MP_CHECKOK(mp_copy(&precomp[15 - i][0], &precomp[i][0]));
 		MP_CHECKOK(group->meth->
 				   field_neg(&precomp[15 - i][1], &precomp[i][1],
 							 group->meth));
 	}
 	/* R = inf */
 	MP_CHECKOK(ec_GFp_pt_set_inf_jac(rx, ry, &rz));
 	orderBitSize = mpl_significant_bits(&group->order);
 	/* Allocate memory for NAF */
 	naf = (signed char *) malloc(sizeof(signed char) * (orderBitSize + 1));
 	if (naf == NULL) {
 		res = MP_MEM;
 		goto CLEANUP;
 	}
 	/* Compute 5NAF */
 	ec_compute_wNAF(naf, orderBitSize, n, 5);
 	/* wNAF method */
 	for (i = orderBitSize; i >= 0; i--) {
 		/* R = 2R */
 		ec_GFp_pt_dbl_jm(rx, ry, &rz, &raz4, rx, ry, &rz,
 					     &raz4, scratch, group);
 		if (naf[i] != 0) {
 			ec_GFp_pt_add_jm_aff(rx, ry, &rz, &raz4,
 								 &precomp[(naf[i] + 15) / 2][0],
 								 &precomp[(naf[i] + 15) / 2][1], rx, ry,
 								 &rz, &raz4, scratch, group);
 		}
 	}
 	/* convert result S to affine coordinates */
 	MP_CHECKOK(ec_GFp_pt_jac2aff(rx, ry, &rz, rx, ry, group));
   CLEANUP:
 	for (i = 0; i < MAX_SCRATCH; i++) {
 		mp_clear(&scratch[i]);
 	}
 	for (i = 0; i < 16; i++) {
 		mp_clear(&precomp[i][0]);
 		mp_clear(&precomp[i][1]);
 	}
 	mp_clear(&tpx);
 	mp_clear(&tpy);
 	mp_clear(&rz);
 	mp_clear(&raz4);
 	free(naf);
 	return res;
 }

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security/nss/lib/freebl/ecl/ecp_jm.c@b8a032363ba2 (annotated)

security/nss/lib/freebl/ecl/ecp_jm.c