From 50f587c36f4cb673c7fb79adf453b7af0c6e8ab0 Mon Sep 17 00:00:00 2001
From: Giovanni Bajo <rasky@develer.com>
Date: Tue, 20 Sep 2011 11:02:53 +0200
Subject: [PATCH 1/4] Bugfix: clear the exceeding destination digits.

Currently, the fp_sqr_comba_* functions do not fully clear the destination
number, but only overwrites the digits they care about. Eg: if
you call a comba4, it will overwrite the first 8 digits and leave
the others unchanged.

On the other hand, fp_mul_comba_* functions do *not* check incoming
unused digits (relying on the guarantee that they must be zero),
so they will happily compute the wrong result if those digits
are not empty. Testcase for a 32-bit system:

   char buf[64];
   fp_int num, num2, d;

   memset(buf, 0xFF, sizeof(buf);
   fp_read_unsigned_bin(&num, buf);
   fp_set(&d, 1);

   fp_sqr_comba_3(&d, &num);
   // now num is { 0x1, 0x0, 0x0, 0x0, 0x0, 0x0,
   //              0xFFFFFFFF, 0xFFFFFFFF ... }
   // only first 6 digits have been written, but even
   // if num.used is correctly set to 6, this can trigger
   // bugs.

   // Create a number larger than 6 digits
   fp_2expt(&num2, 8*32+4);

   fp_mul_comba_8(&num, &num2, &num2);
   // wrong result has been computed, because the first 8
   // digits of num have been read and multiplied
   // even if num->used == 6, relying on the fact that
   // they should be zero.
---
 src/generators/comba_sqr_gen.c      | 3 ++-
 src/generators/comba_sqr_smallgen.c | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/generators/comba_sqr_gen.c b/src/generators/comba_sqr_gen.c
index 57e0737..a949294 100644
--- a/src/generators/comba_sqr_gen.c
+++ b/src/generators/comba_sqr_gen.c
@@ -90,8 +90,9 @@ printf(
 "   B->used = %d;\n"
 "   B->sign = FP_ZPOS;\n"
 "   memcpy(B->dp, b, %d * sizeof(fp_digit));\n"
+"   memset(B->dp + %d, 0, (FP_SIZE - %d) * sizeof(fp_digit));\n"
 "   fp_clamp(B);\n"
-"}\n#endif\n\n\n", N+N, N+N);
+"}\n#endif\n\n\n", N+N, N+N, N+N, N+N);
 
   return 0;
 }
diff --git a/src/generators/comba_sqr_smallgen.c b/src/generators/comba_sqr_smallgen.c
index c6e58c9..d8d62fe 100644
--- a/src/generators/comba_sqr_smallgen.c
+++ b/src/generators/comba_sqr_smallgen.c
@@ -95,8 +95,9 @@ printf(
 "      B->used = %d;\n"
 "      B->sign = FP_ZPOS;\n"
 "      memcpy(B->dp, b, %d * sizeof(fp_digit));\n"
+"      memset(B->dp + %d, 0, (FP_SIZE - %d) * sizeof(fp_digit));\n"
 "      fp_clamp(B);\n"
-"      break;\n\n", N+N, N+N);
+"      break;\n\n", N+N, N+N, N+N, N+N);
 }
 
 printf("}\n\n}\n");

From 8f059cd52fcd6da945c45d7377dec068ffa9b675 Mon Sep 17 00:00:00 2001
From: Giovanni Bajo <rasky@develer.com>
Date: Tue, 20 Sep 2011 11:35:51 +0200
Subject: [PATCH 2/4] Add makefile for sqr generators

---
 src/generators/.gitignore |  2 ++
 src/generators/makefile   | 17 +++++++++++++++++
 2 files changed, 19 insertions(+)
 create mode 100644 src/generators/.gitignore
 create mode 100644 src/generators/makefile

diff --git a/src/generators/.gitignore b/src/generators/.gitignore
new file mode 100644
index 0000000..7da1b6a
--- /dev/null
+++ b/src/generators/.gitignore
@@ -0,0 +1,2 @@
+comba_sqr_gen
+comba_sqr_smallgen
diff --git a/src/generators/makefile b/src/generators/makefile
new file mode 100644
index 0000000..6af8ea0
--- /dev/null
+++ b/src/generators/makefile
@@ -0,0 +1,17 @@
+all: comba_sqr_gen comba_sqr_smallgen
+
+clean:
+	rm -f comba_sqr_gen
+	rm -f comba_sqr_smallgen
+
+comba_sqr_gen: comba_sqr_gen.c
+	gcc -o comba_sqr_gen comba_sqr_gen.c
+comba_sqr_smallgen: comba_sqr_smallgen.c
+	gcc -o comba_sqr_smallgen comba_sqr_smallgen.c
+
+regen: comba_sqr_gen comba_sqr_smallgen
+	for i in 3 4 6 7 8 9 12 17 20 24 28 32 48 64; do \
+		./comba_sqr_gen $$i > ../sqr/fp_sqr_comba_$$i.c; \
+	done
+	./comba_sqr_smallgen > ../sqr/fp_sqr_comba_small_set.c
+

From 782c6e52debe1c4c69476d3b101327e4083107b4 Mon Sep 17 00:00:00 2001
From: Giovanni Bajo <rasky@develer.com>
Date: Tue, 20 Sep 2011 11:36:41 +0200
Subject: [PATCH 3/4] Realign generators with existing files in repo.

---
 src/generators/comba_sqr_gen.c      | 6 ++++++
 src/generators/comba_sqr_smallgen.c | 9 ++++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/generators/comba_sqr_gen.c b/src/generators/comba_sqr_gen.c
index a949294..a5a8ed1 100644
--- a/src/generators/comba_sqr_gen.c
+++ b/src/generators/comba_sqr_gen.c
@@ -16,10 +16,16 @@ int main(int argc, char **argv)
    N = atoi(argv[1]);
 
 printf(
+"#define TFM_DEFINES\n"
+"#include \"fp_sqr_comba.c\"\n"
+"\n"
 "#ifdef TFM_SQR%d\n"
 "void fp_sqr_comba%d(fp_int *A, fp_int *B)\n"
 "{\n"
 "   fp_digit *a, b[%d], c0, c1, c2, sc0, sc1, sc2;\n"
+"#ifdef TFM_ISO\n"
+"   fp_word tt;\n"
+"#endif\n"
 "\n"
 "   a = A->dp;\n"
 "   COMBA_START; \n"
diff --git a/src/generators/comba_sqr_smallgen.c b/src/generators/comba_sqr_smallgen.c
index d8d62fe..f4718f0 100644
--- a/src/generators/comba_sqr_smallgen.c
+++ b/src/generators/comba_sqr_smallgen.c
@@ -16,9 +16,16 @@ int main(int argc, char **argv)
    int x, y, z, N, f;
 
 printf(
+"#define TFM_DEFINES\n"
+"#include \"fp_sqr_comba.c\"\n"
+"\n"
+"#if defined(TFM_SMALL_SET)\n"
 "void fp_sqr_comba_small(fp_int *A, fp_int *B)\n"
 "{\n"
 "   fp_digit *a, b[32], c0, c1, c2, sc0, sc1, sc2;\n"
+"#ifdef TFM_ISO\n"
+"   fp_word tt;\n"
+"#endif\n"
 );
 
 printf("   switch (A->used) { \n");
@@ -100,7 +107,7 @@ printf(
 "      break;\n\n", N+N, N+N, N+N, N+N);
 }
 
-printf("}\n\n}\n");
+printf("}\n}\n\n#endif /* TFM_SMALL_SET */\n");
 
   return 0;
 }

From ab4374299c46150f6850fb56b524d044134f97c8 Mon Sep 17 00:00:00 2001
From: Giovanni Bajo <rasky@develer.com>
Date: Tue, 20 Sep 2011 11:37:23 +0200
Subject: [PATCH 4/4] Regenerate sqr comba files with bugfix

---
 src/sqr/fp_sqr_comba_12.c        |  4 +---
 src/sqr/fp_sqr_comba_17.c        |  4 +---
 src/sqr/fp_sqr_comba_20.c        |  4 +---
 src/sqr/fp_sqr_comba_24.c        |  4 +---
 src/sqr/fp_sqr_comba_28.c        |  4 +---
 src/sqr/fp_sqr_comba_3.c         |  4 +---
 src/sqr/fp_sqr_comba_32.c        |  4 +---
 src/sqr/fp_sqr_comba_4.c         |  4 +---
 src/sqr/fp_sqr_comba_48.c        |  4 +---
 src/sqr/fp_sqr_comba_6.c         |  4 +---
 src/sqr/fp_sqr_comba_64.c        |  4 +---
 src/sqr/fp_sqr_comba_7.c         |  4 +---
 src/sqr/fp_sqr_comba_8.c         |  4 +---
 src/sqr/fp_sqr_comba_9.c         |  4 +---
 src/sqr/fp_sqr_comba_small_set.c | 25 +++++++++++++++++++------
 15 files changed, 33 insertions(+), 48 deletions(-)

diff --git a/src/sqr/fp_sqr_comba_12.c b/src/sqr/fp_sqr_comba_12.c
index a1ed092..4a2e2d8 100644
--- a/src/sqr/fp_sqr_comba_12.c
+++ b/src/sqr/fp_sqr_comba_12.c
@@ -134,11 +134,9 @@ void fp_sqr_comba12(fp_int *A, fp_int *B)
    B->used = 24;
    B->sign = FP_ZPOS;
    memcpy(B->dp, b, 24 * sizeof(fp_digit));
+   memset(B->dp + 24, 0, (FP_SIZE - 24) * sizeof(fp_digit));
    fp_clamp(B);
 }
 #endif
 
 
-/* $Source$ */
-/* $Revision$ */
-/* $Date$ */
diff --git a/src/sqr/fp_sqr_comba_17.c b/src/sqr/fp_sqr_comba_17.c
index 798c190..015298a 100644
--- a/src/sqr/fp_sqr_comba_17.c
+++ b/src/sqr/fp_sqr_comba_17.c
@@ -184,11 +184,9 @@ void fp_sqr_comba17(fp_int *A, fp_int *B)
    B->used = 34;
    B->sign = FP_ZPOS;
    memcpy(B->dp, b, 34 * sizeof(fp_digit));
+   memset(B->dp + 34, 0, (FP_SIZE - 34) * sizeof(fp_digit));
    fp_clamp(B);
 }
 #endif
 
 
-/* $Source$ */
-/* $Revision$ */
-/* $Date$ */
diff --git a/src/sqr/fp_sqr_comba_20.c b/src/sqr/fp_sqr_comba_20.c
index 35b80e5..d7cb2b9 100644
--- a/src/sqr/fp_sqr_comba_20.c
+++ b/src/sqr/fp_sqr_comba_20.c
@@ -214,11 +214,9 @@ void fp_sqr_comba20(fp_int *A, fp_int *B)
    B->used = 40;
    B->sign = FP_ZPOS;
    memcpy(B->dp, b, 40 * sizeof(fp_digit));
+   memset(B->dp + 40, 0, (FP_SIZE - 40) * sizeof(fp_digit));
    fp_clamp(B);
 }
 #endif
 
 
-/* $Source$ */
-/* $Revision$ */
-/* $Date$ */
diff --git a/src/sqr/fp_sqr_comba_24.c b/src/sqr/fp_sqr_comba_24.c
index 7628c32..81e146c 100644
--- a/src/sqr/fp_sqr_comba_24.c
+++ b/src/sqr/fp_sqr_comba_24.c
@@ -254,11 +254,9 @@ void fp_sqr_comba24(fp_int *A, fp_int *B)
    B->used = 48;
    B->sign = FP_ZPOS;
    memcpy(B->dp, b, 48 * sizeof(fp_digit));
+   memset(B->dp + 48, 0, (FP_SIZE - 48) * sizeof(fp_digit));
    fp_clamp(B);
 }
 #endif
 
 
-/* $Source$ */
-/* $Revision$ */
-/* $Date$ */
diff --git a/src/sqr/fp_sqr_comba_28.c b/src/sqr/fp_sqr_comba_28.c
index 043574d..89fd3d6 100644
--- a/src/sqr/fp_sqr_comba_28.c
+++ b/src/sqr/fp_sqr_comba_28.c
@@ -294,11 +294,9 @@ void fp_sqr_comba28(fp_int *A, fp_int *B)
    B->used = 56;
    B->sign = FP_ZPOS;
    memcpy(B->dp, b, 56 * sizeof(fp_digit));
+   memset(B->dp + 56, 0, (FP_SIZE - 56) * sizeof(fp_digit));
    fp_clamp(B);
 }
 #endif
 
 
-/* $Source$ */
-/* $Revision$ */
-/* $Date$ */
diff --git a/src/sqr/fp_sqr_comba_3.c b/src/sqr/fp_sqr_comba_3.c
index 7aefa4f..a702fed 100644
--- a/src/sqr/fp_sqr_comba_3.c
+++ b/src/sqr/fp_sqr_comba_3.c
@@ -44,11 +44,9 @@ void fp_sqr_comba3(fp_int *A, fp_int *B)
    B->used = 6;
    B->sign = FP_ZPOS;
    memcpy(B->dp, b, 6 * sizeof(fp_digit));
+   memset(B->dp + 6, 0, (FP_SIZE - 6) * sizeof(fp_digit));
    fp_clamp(B);
 }
 #endif
 
 
-/* $Source$ */
-/* $Revision$ */
-/* $Date$ */
diff --git a/src/sqr/fp_sqr_comba_32.c b/src/sqr/fp_sqr_comba_32.c
index 2e8ca55..e2446d8 100644
--- a/src/sqr/fp_sqr_comba_32.c
+++ b/src/sqr/fp_sqr_comba_32.c
@@ -334,11 +334,9 @@ void fp_sqr_comba32(fp_int *A, fp_int *B)
    B->used = 64;
    B->sign = FP_ZPOS;
    memcpy(B->dp, b, 64 * sizeof(fp_digit));
+   memset(B->dp + 64, 0, (FP_SIZE - 64) * sizeof(fp_digit));
    fp_clamp(B);
 }
 #endif
 
 
-/* $Source$ */
-/* $Revision$ */
-/* $Date$ */
diff --git a/src/sqr/fp_sqr_comba_4.c b/src/sqr/fp_sqr_comba_4.c
index cd8de7e..568f71e 100644
--- a/src/sqr/fp_sqr_comba_4.c
+++ b/src/sqr/fp_sqr_comba_4.c
@@ -54,11 +54,9 @@ void fp_sqr_comba4(fp_int *A, fp_int *B)
    B->used = 8;
    B->sign = FP_ZPOS;
    memcpy(B->dp, b, 8 * sizeof(fp_digit));
+   memset(B->dp + 8, 0, (FP_SIZE - 8) * sizeof(fp_digit));
    fp_clamp(B);
 }
 #endif
 
 
-/* $Source$ */
-/* $Revision$ */
-/* $Date$ */
diff --git a/src/sqr/fp_sqr_comba_48.c b/src/sqr/fp_sqr_comba_48.c
index 256f7b9..c2dc85d 100644
--- a/src/sqr/fp_sqr_comba_48.c
+++ b/src/sqr/fp_sqr_comba_48.c
@@ -494,11 +494,9 @@ void fp_sqr_comba48(fp_int *A, fp_int *B)
    B->used = 96;
    B->sign = FP_ZPOS;
    memcpy(B->dp, b, 96 * sizeof(fp_digit));
+   memset(B->dp + 96, 0, (FP_SIZE - 96) * sizeof(fp_digit));
    fp_clamp(B);
 }
 #endif
 
 
-/* $Source$ */
-/* $Revision$ */
-/* $Date$ */
diff --git a/src/sqr/fp_sqr_comba_6.c b/src/sqr/fp_sqr_comba_6.c
index 2537621..951d1e6 100644
--- a/src/sqr/fp_sqr_comba_6.c
+++ b/src/sqr/fp_sqr_comba_6.c
@@ -74,11 +74,9 @@ void fp_sqr_comba6(fp_int *A, fp_int *B)
    B->used = 12;
    B->sign = FP_ZPOS;
    memcpy(B->dp, b, 12 * sizeof(fp_digit));
+   memset(B->dp + 12, 0, (FP_SIZE - 12) * sizeof(fp_digit));
    fp_clamp(B);
 }
 #endif
 
 
-/* $Source$ */
-/* $Revision$ */
-/* $Date$ */
diff --git a/src/sqr/fp_sqr_comba_64.c b/src/sqr/fp_sqr_comba_64.c
index 88871ac..49a75c4 100644
--- a/src/sqr/fp_sqr_comba_64.c
+++ b/src/sqr/fp_sqr_comba_64.c
@@ -654,11 +654,9 @@ void fp_sqr_comba64(fp_int *A, fp_int *B)
    B->used = 128;
    B->sign = FP_ZPOS;
    memcpy(B->dp, b, 128 * sizeof(fp_digit));
+   memset(B->dp + 128, 0, (FP_SIZE - 128) * sizeof(fp_digit));
    fp_clamp(B);
 }
 #endif
 
 
-/* $Source$ */
-/* $Revision$ */
-/* $Date$ */
diff --git a/src/sqr/fp_sqr_comba_7.c b/src/sqr/fp_sqr_comba_7.c
index 08c520f..48ab6f3 100644
--- a/src/sqr/fp_sqr_comba_7.c
+++ b/src/sqr/fp_sqr_comba_7.c
@@ -84,11 +84,9 @@ void fp_sqr_comba7(fp_int *A, fp_int *B)
    B->used = 14;
    B->sign = FP_ZPOS;
    memcpy(B->dp, b, 14 * sizeof(fp_digit));
+   memset(B->dp + 14, 0, (FP_SIZE - 14) * sizeof(fp_digit));
    fp_clamp(B);
 }
 #endif
 
 
-/* $Source$ */
-/* $Revision$ */
-/* $Date$ */
diff --git a/src/sqr/fp_sqr_comba_8.c b/src/sqr/fp_sqr_comba_8.c
index 9300b17..b648d31 100644
--- a/src/sqr/fp_sqr_comba_8.c
+++ b/src/sqr/fp_sqr_comba_8.c
@@ -94,11 +94,9 @@ void fp_sqr_comba8(fp_int *A, fp_int *B)
    B->used = 16;
    B->sign = FP_ZPOS;
    memcpy(B->dp, b, 16 * sizeof(fp_digit));
+   memset(B->dp + 16, 0, (FP_SIZE - 16) * sizeof(fp_digit));
    fp_clamp(B);
 }
 #endif
 
 
-/* $Source$ */
-/* $Revision$ */
-/* $Date$ */
diff --git a/src/sqr/fp_sqr_comba_9.c b/src/sqr/fp_sqr_comba_9.c
index 880e29e..97be21d 100644
--- a/src/sqr/fp_sqr_comba_9.c
+++ b/src/sqr/fp_sqr_comba_9.c
@@ -104,11 +104,9 @@ void fp_sqr_comba9(fp_int *A, fp_int *B)
    B->used = 18;
    B->sign = FP_ZPOS;
    memcpy(B->dp, b, 18 * sizeof(fp_digit));
+   memset(B->dp + 18, 0, (FP_SIZE - 18) * sizeof(fp_digit));
    fp_clamp(B);
 }
 #endif
 
 
-/* $Source$ */
-/* $Revision$ */
-/* $Date$ */
diff --git a/src/sqr/fp_sqr_comba_small_set.c b/src/sqr/fp_sqr_comba_small_set.c
index 1d505ea..3f21b8a 100644
--- a/src/sqr/fp_sqr_comba_small_set.c
+++ b/src/sqr/fp_sqr_comba_small_set.c
@@ -6,8 +6,8 @@ void fp_sqr_comba_small(fp_int *A, fp_int *B)
 {
    fp_digit *a, b[32], c0, c1, c2, sc0, sc1, sc2;
 #ifdef TFM_ISO
-   fp_word   tt;   
-#endif   
+   fp_word tt;
+#endif
    switch (A->used) { 
    case 1:
       a = A->dp;
@@ -25,6 +25,7 @@ void fp_sqr_comba_small(fp_int *A, fp_int *B)
       B->used = 2;
       B->sign = FP_ZPOS;
       memcpy(B->dp, b, 2 * sizeof(fp_digit));
+      memset(B->dp + 2, 0, (FP_SIZE - 2) * sizeof(fp_digit));
       fp_clamp(B);
       break;
 
@@ -54,6 +55,7 @@ void fp_sqr_comba_small(fp_int *A, fp_int *B)
       B->used = 4;
       B->sign = FP_ZPOS;
       memcpy(B->dp, b, 4 * sizeof(fp_digit));
+      memset(B->dp + 4, 0, (FP_SIZE - 4) * sizeof(fp_digit));
       fp_clamp(B);
       break;
 
@@ -93,6 +95,7 @@ void fp_sqr_comba_small(fp_int *A, fp_int *B)
       B->used = 6;
       B->sign = FP_ZPOS;
       memcpy(B->dp, b, 6 * sizeof(fp_digit));
+      memset(B->dp + 6, 0, (FP_SIZE - 6) * sizeof(fp_digit));
       fp_clamp(B);
       break;
 
@@ -142,6 +145,7 @@ void fp_sqr_comba_small(fp_int *A, fp_int *B)
       B->used = 8;
       B->sign = FP_ZPOS;
       memcpy(B->dp, b, 8 * sizeof(fp_digit));
+      memset(B->dp + 8, 0, (FP_SIZE - 8) * sizeof(fp_digit));
       fp_clamp(B);
       break;
 
@@ -201,6 +205,7 @@ void fp_sqr_comba_small(fp_int *A, fp_int *B)
       B->used = 10;
       B->sign = FP_ZPOS;
       memcpy(B->dp, b, 10 * sizeof(fp_digit));
+      memset(B->dp + 10, 0, (FP_SIZE - 10) * sizeof(fp_digit));
       fp_clamp(B);
       break;
 
@@ -270,6 +275,7 @@ void fp_sqr_comba_small(fp_int *A, fp_int *B)
       B->used = 12;
       B->sign = FP_ZPOS;
       memcpy(B->dp, b, 12 * sizeof(fp_digit));
+      memset(B->dp + 12, 0, (FP_SIZE - 12) * sizeof(fp_digit));
       fp_clamp(B);
       break;
 
@@ -349,6 +355,7 @@ void fp_sqr_comba_small(fp_int *A, fp_int *B)
       B->used = 14;
       B->sign = FP_ZPOS;
       memcpy(B->dp, b, 14 * sizeof(fp_digit));
+      memset(B->dp + 14, 0, (FP_SIZE - 14) * sizeof(fp_digit));
       fp_clamp(B);
       break;
 
@@ -438,6 +445,7 @@ void fp_sqr_comba_small(fp_int *A, fp_int *B)
       B->used = 16;
       B->sign = FP_ZPOS;
       memcpy(B->dp, b, 16 * sizeof(fp_digit));
+      memset(B->dp + 16, 0, (FP_SIZE - 16) * sizeof(fp_digit));
       fp_clamp(B);
       break;
 
@@ -537,6 +545,7 @@ void fp_sqr_comba_small(fp_int *A, fp_int *B)
       B->used = 18;
       B->sign = FP_ZPOS;
       memcpy(B->dp, b, 18 * sizeof(fp_digit));
+      memset(B->dp + 18, 0, (FP_SIZE - 18) * sizeof(fp_digit));
       fp_clamp(B);
       break;
 
@@ -646,6 +655,7 @@ void fp_sqr_comba_small(fp_int *A, fp_int *B)
       B->used = 20;
       B->sign = FP_ZPOS;
       memcpy(B->dp, b, 20 * sizeof(fp_digit));
+      memset(B->dp + 20, 0, (FP_SIZE - 20) * sizeof(fp_digit));
       fp_clamp(B);
       break;
 
@@ -765,6 +775,7 @@ void fp_sqr_comba_small(fp_int *A, fp_int *B)
       B->used = 22;
       B->sign = FP_ZPOS;
       memcpy(B->dp, b, 22 * sizeof(fp_digit));
+      memset(B->dp + 22, 0, (FP_SIZE - 22) * sizeof(fp_digit));
       fp_clamp(B);
       break;
 
@@ -894,6 +905,7 @@ void fp_sqr_comba_small(fp_int *A, fp_int *B)
       B->used = 24;
       B->sign = FP_ZPOS;
       memcpy(B->dp, b, 24 * sizeof(fp_digit));
+      memset(B->dp + 24, 0, (FP_SIZE - 24) * sizeof(fp_digit));
       fp_clamp(B);
       break;
 
@@ -1033,6 +1045,7 @@ void fp_sqr_comba_small(fp_int *A, fp_int *B)
       B->used = 26;
       B->sign = FP_ZPOS;
       memcpy(B->dp, b, 26 * sizeof(fp_digit));
+      memset(B->dp + 26, 0, (FP_SIZE - 26) * sizeof(fp_digit));
       fp_clamp(B);
       break;
 
@@ -1182,6 +1195,7 @@ void fp_sqr_comba_small(fp_int *A, fp_int *B)
       B->used = 28;
       B->sign = FP_ZPOS;
       memcpy(B->dp, b, 28 * sizeof(fp_digit));
+      memset(B->dp + 28, 0, (FP_SIZE - 28) * sizeof(fp_digit));
       fp_clamp(B);
       break;
 
@@ -1341,6 +1355,7 @@ void fp_sqr_comba_small(fp_int *A, fp_int *B)
       B->used = 30;
       B->sign = FP_ZPOS;
       memcpy(B->dp, b, 30 * sizeof(fp_digit));
+      memset(B->dp + 30, 0, (FP_SIZE - 30) * sizeof(fp_digit));
       fp_clamp(B);
       break;
 
@@ -1510,13 +1525,11 @@ void fp_sqr_comba_small(fp_int *A, fp_int *B)
       B->used = 32;
       B->sign = FP_ZPOS;
       memcpy(B->dp, b, 32 * sizeof(fp_digit));
+      memset(B->dp + 32, 0, (FP_SIZE - 32) * sizeof(fp_digit));
       fp_clamp(B);
       break;
+
 }
 }
 
 #endif /* TFM_SMALL_SET */
-
-/* $Source$ */
-/* $Revision$ */
-/* $Date$ */