added inversion templates

inversion-c/inversion_template.c

@@ -0,0 +1,55 @@
+#define MAKE_FN_NAME1(x,y) x ## y
+#define MAKE_FN_NAME(x,y) MAKE_FN_NAME1(x,y)
+
+#define PRECOMP MAKE_FN_NAME(CURVE_DESCRIPTION,_divstep_precomp)
+#define MSAT MAKE_FN_NAME(CURVE_DESCRIPTION,_msat)
+#define MONE MAKE_FN_NAME(CURVE_DESCRIPTION,_set_one)
+#define DIVSTEP MAKE_FN_NAME(CURVE_DESCRIPTION,_divstep)
+#define OPP MAKE_FN_NAME(CURVE_DESCRIPTION,_opp)
+#define MUL MAKE_FN_NAME(CURVE_DESCRIPTION,_mul)
+
+#if LEN_PRIME < 46
+#define ITERATIONS (((49 * LEN_PRIME) + 80) / 17)
+#else
+#define ITERATIONS (((49 * LEN_PRIME) + 57) / 17)
+#endif
+
+#define SAT_LIMBS LIMBS + 1 /* we might need 2 more bits to represent m in twos complement */
+#define BYTES 8 * (((LEN_PRIME - 1) / 64) + 1)
+
+void inverse(WORD out[LIMBS], WORD g[SAT_LIMBS]) {
+
+  WORD precomp[LIMBS];
+  PRECOMP(precomp);
+
+  WORD d = 1;
+  WORD f[SAT_LIMBS];
+  WORD v[LIMBS];
+  WORD r[LIMBS];
+  WORD out1;
+  WORD out2[SAT_LIMBS], out3[SAT_LIMBS], out4[LIMBS], out5[LIMBS];
+
+  MSAT(f);
+  MONE(r);
+  for (int j = 0; j < LIMBS; j++) v[j] = 0;
+
+  for (int i = 0; i < ITERATIONS - (ITERATIONS % 2); i+=2) {
+    DIVSTEP(&out1,out2,out3,out4,out5,d,f,g,v,r);
+    DIVSTEP(&d,f,g,v,r,out1,out2,out3,out4,out5);
+  }
+  if (ITERATIONS % 2) {
+    DIVSTEP(&out1,out2,out3,out4,out5,d,f,g,v,r);
+    for (int k = 0; k < LIMBS; k++) v[k] = out4[k];
+    for (int k = 0; k < SAT_LIMBS; k++) f[k] = out2[k];
+  }
+
+  WORD h[LIMBS];
+  if (f[SAT_LIMBS - 1] >> (WORDSIZE - 1)) {
+    OPP(h, v);
+    for (int k = 0; k < LIMBS; k++) v[k] = h[k];
+  }
+
+  MUL(out, v, precomp);
+
+  return;
+}

inversion-c/inversion_test_template.c

@@ -0,0 +1,54 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+
+#define MAKE_FN_NAME1(x,y) x ## y
+#define MAKE_FN_NAME(x,y) MAKE_FN_NAME1(x,y)
+
+#define FROM_BYTES MAKE_FN_NAME(CURVE_DESCRIPTION,_from_bytes)
+#define TO_BYTES MAKE_FN_NAME(CURVE_DESCRIPTION,_to_bytes)
+#define FROM_MONTGOMERY MAKE_FN_NAME(CURVE_DESCRIPTION,_from_montgomery)
+
+int main() {
+  WORD res[LIMBS], out[LIMBS], g[SAT_LIMBS], g1[LIMBS], g2[LIMBS], g3[LIMBS];
+  uint8_t a[BYTES];
+
+  int seed = time(0);
+  srand(seed);
+  printf("%i\n", seed);
+
+  for (int j = 0; j < 1000; j++) {
+    int i;
+    for (i = 0; i < BYTES; i++) {
+      a[i] = rand() % 256;
+      if (i > BYTES - 8) a[i] = 0;
+    }
+
+    FROM_BYTES(g1,a);
+    FROM_BYTES(g2,a);
+    FROM_MONTGOMERY(g3,g2);
+
+    for (int i = 0; i < LIMBS; i++) g[i] = g3[i];
+    g[SAT_LIMBS - 1] = 0;
+
+    inverse(out,g);
+
+    MUL(res,out,g1);
+    FROM_MONTGOMERY(out,res);
+    TO_BYTES(a,out);
+
+    if (a[0] != 1) {
+      printf("FAIL\n");
+      return 2;
+    }
+    for (i = 1; i < BYTES; i++) {
+      if (a[i] != 0) {
+        printf("FAIL\n");
+        return 1;
+      }
+    }
+  }
+  printf("PASS\n");
+  return 0;
+}