nist P-192 optimized recude for ecdsa

[avr-crypto-lib.git] / ecdsa / nist_p192.c

diff --git a/ecdsa/nist_p192.c b/ecdsa/nist_p192.c
new file mode 100644 (file)
index 0000000..ed3db58
--- /dev/null
+++ b/ecdsa/nist_p192.c
@@ -0,0 +1,152 @@
+/* p192.c */
+/*
+    This file is part of the AVR-Crypto-Lib.
+    Copyright (C) 2006-2012 Daniel Otte (daniel.otte@rub.de)
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <inttypes.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "bigint.h"
+
+/*
+ * p = 6277101735386680763835789423207666416083908700390324961279
+ *   = 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFFFFFFFFFFFF
+ */
+
+static
+uint8_t nist_curve_p192_p_w[] = {
+        0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+        0xfe, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+        0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff
+};
+
+bigint_t nist_curve_p192_p = {
+        .length_W = 192 / BIGINT_WORD_SIZE,
+        .wordv = nist_curve_p192_p_w,
+        .info = 7
+};
+
+/*
+ * A = ( A5 || A4 || A3 || A2 || A1 || A0 ) ; An if 64-bit
+ * A mod p = B = T + S1 + S2 + S3 mod p
+ *
+ * T  = ( A2 || A1 || A0 )
+ * S1 = ( A3 || A3 )
+ * S2 = ( A4 || A4 || 0 )
+ * S3 = ( A5 || A5 || A5 )
+ *
+ */
+
+int bigint_reduce_p192(bigint_t *a){
+
+    bigint_word_t s_w[3 * 64 / BIGINT_WORD_SIZE];
+    bigint_t s;
+    uint16_t o_length;
+
+    o_length = a->length_W;
+
+    if(o_length < 192 / BIGINT_WORD_SIZE){
+        return 0;
+    }
+
+    if(o_length > 192 * 2 / BIGINT_WORD_SIZE){
+        bigint_reduce(a, &nist_curve_p192_p);
+    }
+
+    if(o_length > 192 / BIGINT_WORD_SIZE){
+        s.wordv = s_w;
+        s.length_W = 2 * 64 / BIGINT_WORD_SIZE;
+
+        /*
+         * copy A3 twice in s
+         */
+        if(o_length >= 4 * 64 / BIGINT_WORD_SIZE){
+            memcpy(s.wordv, a->wordv + 3 * 64 / BIGINT_WORD_SIZE, 64 / 8);
+        }else{
+            memset(s.wordv, 0, 8);
+            memcpy(s.wordv, a->wordv + 3 * 64 / BIGINT_WORD_SIZE,
+                    o_length * BIGINT_WORD_SIZE / 8 - 3 * 64 / 8);
+        }
+
+        memcpy(s.wordv + 64 / BIGINT_WORD_SIZE, s.wordv, 64 / 8);
+        bigint_adjust(&s);
+
+        /*
+         * Set A3 to zero so we can use a as T
+         */
+        memset(a->wordv + 3 * 64 / BIGINT_WORD_SIZE, 0, BIGINT_WORD_SIZE / 8);
+        a->length_W = 3 * 64 / BIGINT_WORD_SIZE;
+        bigint_adjust(a);
+
+        /*
+         * Add s (alias S1) to a (alias T)
+         */
+        bigint_add_u(a, a, &s);
+
+
+        if(o_length > 4 * 64 / BIGINT_WORD_SIZE){
+            /*
+             * copy A4 twice in s
+             */
+            if(o_length >= 5 * 64 / BIGINT_WORD_SIZE){
+                memcpy(s.wordv, a->wordv + 4 * 64 / BIGINT_WORD_SIZE, 64 / 8);
+            }else{
+                memset(s.wordv, 0, 8);
+                memcpy(s.wordv, a->wordv + 4 * 64 / BIGINT_WORD_SIZE,
+                        o_length * BIGINT_WORD_SIZE / 8 - 4 * 64 / 8);
+            }
+            memcpy(s.wordv + 64 / BIGINT_WORD_SIZE, s.wordv, 64 / 8);
+            bigint_adjust(&s);
+
+            /*
+             * Add s (alias S2) to a (alias T + S1)
+             */
+            bigint_add_scale_u(a, &s, 8);
+
+
+            if(o_length > 5 * 64 / BIGINT_WORD_SIZE){
+                /*
+                 * copy A5 three times in s
+                 */
+                if(o_length == 6 * 64 / BIGINT_WORD_SIZE){
+                    memcpy(s.wordv, a->wordv + 5 * 64 / BIGINT_WORD_SIZE, 64 / 8);
+                } else {
+                    memset(s.wordv, 0, 8);
+                    memcpy(s.wordv, a->wordv + 5 * 64 / BIGINT_WORD_SIZE,
+                            o_length * BIGINT_WORD_SIZE / 8 - 5 * 64 / 8);
+                }
+                memcpy(s.wordv + 64 / BIGINT_WORD_SIZE, s.wordv, 64 / 8);
+                memcpy(s.wordv + 2 * 64 / BIGINT_WORD_SIZE, s.wordv, 64 / 8);
+                s.length_W = 3 * 64 / BIGINT_WORD_SIZE;
+                bigint_adjust(&s);
+
+                /*
+                 * Add s (alias S2) to a (alias T + S1)
+                 */
+                bigint_add_u(a, a, &s);
+            }
+        }
+
+    }
+    while(bigint_cmp_u(a, &nist_curve_p192_p) >= 0){
+        bigint_sub_u(a, a, &nist_curve_p192_p);
+    }
+
+    return 0;
+}
+