From: Niels Möller <nisse@lysator.liu.se>
Date: Sun, 8 Nov 2020 10:53:56 +0000 (+0100)
Subject: Reduce scratch need for ecc_add_jjj some more
X-Git-Tag: nettle_3.7rc1~52^2~3
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=92f657b3d6038be6d23c2dfab05e40bbcda79ebb;p=thirdparty%2Fnettle.git

Reduce scratch need for ecc_add_jjj some more
---

diff --git a/ChangeLog b/ChangeLog
index 1479cec5..a7acd45d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,10 +1,8 @@
 2020-11-08  Niels Möller  <nisse@lysator.liu.se>
 
 	* ecc-add-jja.c (ecc_add_jja): Reduce scratch need.
-	* ecc-internal.h (ECC_ADD_JJA_ITCH): Now 5*size.
-
 	* ecc-add-jjj.c (ecc_add_jjj): Reduce scratch need.
-	* ecc-internal.h (ECC_ADD_JJJ_ITCH): Now 6*size.
+	* ecc-internal.h (ECC_ADD_JJA_ITCH, ECC_ADD_JJJ_ITCH): Now 5*size.
 
 2020-11-06  Niels Möller  <nisse@lysator.liu.se>
 
diff --git a/ecc-add-jjj.c b/ecc-add-jjj.c
index a5a7e7a0..4a5d727c 100644
--- a/ecc-add-jjj.c
+++ b/ecc-add-jjj.c
@@ -77,36 +77,38 @@ ecc_add_jjj (const struct ecc_curve *ecc,
 
 #define h scratch
 #define z1z1 (scratch + ecc->p.size)
-#define z2z2 (scratch + 2*ecc->p.size)
-#define z1z2 (scratch + 3*ecc->p.size)
+#define z2z2 z1z1
+#define z1z2 (scratch + 2*ecc->p.size)
 
 #define w (scratch + ecc->p.size)
 #define i (scratch + 2*ecc->p.size)
 #define j h
 #define v i
 
-#define tp  (scratch + 4*ecc->p.size)
+#define tp  (scratch + 3*ecc->p.size)
 
-  ecc_mod_sqr (&ecc->p, z1z1, z1, tp);		/* z1z1 */
-  ecc_mod_sqr (&ecc->p, z2z2, z2, tp);		/* z1z1, z2z2 */
+  ecc_mod_sqr (&ecc->p, z2z2, z2, tp);		/* z2z2 */
   /* Store u1 at x3 */
-  ecc_mod_mul (&ecc->p, x3, x1, z2z2, tp);	/* z1z1, z2z2 */
-  ecc_mod_mul (&ecc->p, h, x2, z1z1, tp);	/* z1z1, z2z2, h */
-  ecc_mod_sub (&ecc->p, h, h, x3);
+  ecc_mod_mul (&ecc->p, x3, x1, z2z2, tp);	/* z2z2 */
 
-  ecc_mod_add (&ecc->p, z1z2, z1, z2);		/* z1z1, z2z2, z1z2, h */
+  ecc_mod_add (&ecc->p, z1z2, z1, z2);		/* z2z2, z1z2 */
   ecc_mod_sqr (&ecc->p, z1z2, z1z2, tp);
+  ecc_mod_sub (&ecc->p, z1z2, z1z2, z2z2);	/* z2z2, z1z2 */
+
+  /* Do s1 early, store at y3 */
+  ecc_mod_mul (&ecc->p, z2z2, z2z2, z2, tp);	/* z2z2, z1z2 */
+  ecc_mod_mul (&ecc->p, y3, z2z2, y1, tp);	/* z1z2 */
+
+  ecc_mod_sqr (&ecc->p, z1z1, z1, tp);		/* z1z1, z1z2 */
   ecc_mod_sub (&ecc->p, z1z2, z1z2, z1z1);
-  ecc_mod_sub (&ecc->p, z1z2, z1z2, z2z2);
+  ecc_mod_mul (&ecc->p, h, x2, z1z1, tp);	/* z1z1, z1z2, h */
+  ecc_mod_sub (&ecc->p, h, h, x3);
 
-  /* z1^3, z2^3 */
+  /* z1^3 */
   ecc_mod_mul (&ecc->p, z1z1, z1z1, z1, tp);
-  ecc_mod_mul (&ecc->p, z2z2, z2z2, z2, tp);
 
   /* z3 <-- h z1 z2 delayed until now, since that may clobber z1. */
-  ecc_mod_mul (&ecc->p, z3, z1z2, h, tp);	/* z1z1, z2z2, h */
-  /* Store s1 at y3 */
-  ecc_mod_mul (&ecc->p, y3, z2z2, y1, tp);	/* z1z1, h */
+  ecc_mod_mul (&ecc->p, z3, z1z2, h, tp);	/* z1z1, h */
   /* w = 2 (s2 - s1) */
   ecc_mod_mul (&ecc->p, w, z1z1, y2, tp);	/* h, w */
   ecc_mod_sub (&ecc->p, w, w, y3);
diff --git a/ecc-internal.h b/ecc-internal.h
index ed725d9c..81c1c39a 100644
--- a/ecc-internal.h
+++ b/ecc-internal.h
@@ -448,7 +448,7 @@ curve448_eh_to_x (mp_limb_t *xp, const mp_limb_t *p,
 #define ECC_DUP_EH_ITCH(size) (3*(size))
 #define ECC_DUP_TH_ITCH(size) (3*(size))
 #define ECC_ADD_JJA_ITCH(size) (5*(size))
-#define ECC_ADD_JJJ_ITCH(size) (6*(size))
+#define ECC_ADD_JJJ_ITCH(size) (5*(size))
 #define ECC_ADD_EH_ITCH(size) (4*(size))
 #define ECC_ADD_EHH_ITCH(size) (4*(size))
 #define ECC_ADD_TH_ITCH(size) (4*(size))