mdw@git.distorted.org.uk Git - catacomb/blob - utils/ecptdecompress.c

   1 #include <stdio.h>
   2 #include <string.h>
   3 #include <stdlib.h>
   4
   5 #include <mLib/alloc.h>
   6 #include <mLib/hex.h>
   7 #include <mLib/dstr.h>
   8 #include <mLib/macros.h>
   9
  10 #include "ec.h"
  11 #include "mp.h"
  12 #include "rand.h"
  13 #include "field-guts.h"
  14
  15 static void puthex(const char *name, mp *x, size_t n)
  16 {
  17   dstr d = DSTR_INIT;
  18   hex_ctx hc;
  19   char *p;
  20
  21   if (!n) n = mp_octets(x);
  22   p = xmalloc(n);
  23   hex_init(&hc);
  24   hc.indent = "";
  25   hc.maxline = 0;
  26   mp_storeb(x, p, n);
  27   hex_encode(&hc, p, n, &d);
  28   hex_encode(&hc, 0, 0, &d);
  29   printf("  %s 0x", name);
  30   dstr_write(&d, stdout);
  31   putchar('\n');
  32   dstr_destroy(&d);
  33   xfree(p);
  34 }
  35
  36 int main(int argc, char *argv[])
  37 {
  38   ec_curve *c;
  39   ec_info ei;
  40   ec pt = EC_INIT;
  41   qd_parse qd;
  42   hex_ctx hc;
  43   dstr d = DSTR_INIT;
  44   size_t n;
  45   octet *p;
  46   mp *x, *y = 0, *yy = 0;
  47   mp *t = MP_NEW;
  48   const char *err;
  49
  50   qd.p = argv[1];
  51   qd.e = 0;
  52   if ((c = ec_curveparse(&qd)) == 0 || !qd_eofp(&qd)) {
  53     fprintf(stderr, "bad curve: %s\n", qd.e);
  54     exit(1);
  55   }
  56   n = c->f->noctets;
  57
  58   ei.c = c;
  59   ei.r = mp_readstring(MP_NEW, argv[2], 0, 0);
  60   ei.h = mp_readstring(MP_NEW, argv[3], 0, 0);
  61
  62   EC_CREATE(&ei.g);
  63   hex_init(&hc);
  64   hex_decode(&hc, argv[4], strlen(argv[4]), &d);
  65   hex_decode(&hc, 0, 0, &d);
  66   p = (octet *)d.buf;
  67   if (p[0] == 0) {
  68     EC_SETINF(&ei.g);
  69   } else {
  70     if (d.len < n + 1) {
  71       fprintf(stderr, "missing x\n");
  72       exit(1);
  73     }
  74     x = mp_loadb(MP_NEW, p + 1, n);
  75     if (p[0] & 0x04) {
  76       if (d.len < 2 * n + 1) {
  77         fprintf(stderr, "missing y\n");
  78         exit(1);
  79       }
  80       y = mp_loadb(MP_NEW, p + n + 1, n);
  81     }
  82     if (p[0] & 0x02) {
  83       if (!ec_find(c, &pt, x)) {
  84         fprintf(stderr, "no matching y\n");
  85         exit(1);
  86       }
  87       yy = MP_COPY(pt.y);
  88       ec_destroy(&pt);
  89       switch (F_TYPE(c->f)) {
  90         case FTY_PRIME:
  91           if (!MP_ODDP(yy) != !(p[0] & 1))
  92             yy = mp_sub(yy, c->f->m, yy);
  93           break;
  94         case FTY_BINARY:
  95           if (MP_ZEROP(x))
  96             yy = F_SQRT(c->f, MP_NEW, c->b);
  97           else {
  98             mp *xin = F_IN(c->f, MP_NEW, x);
  99             mp *xx = F_SQR(c->f, MP_NEW, xin);
 100             mp *b = F_MUL(c->f, MP_NEW, xx, c->a);
 101             mp *xxx = F_MUL(c->f, MP_NEW, xx, xin);
 102             b = F_ADD(c->f, b, b, xxx);
 103             b = F_ADD(c->f, b, b, c->b);
 104             xx = F_INV(c->f, xx, xx);
 105             b = F_MUL(c->f, b, b, xx);
 106             mp_drop(xxx);
 107             yy = F_QUADSOLVE(c->f, MP_NEW, b);
 108             xx = F_OUT(c->f, xx, yy);
 109             if (!MP_ODDP(xx) != !(p[0] & 1))
 110               yy = gf_add(yy, yy, MP_ONE);
 111             yy = F_MUL(c->f, yy, yy, xin);
 112             yy = F_OUT(c->f, yy, yy);
 113             mp_drop(xin);
 114             mp_drop(xx);
 115           }
 116           break;
 117         default:
 118           abort();
 119       }
 120     }
 121     if (y && yy && !MP_EQ(y, yy)) {
 122       fprintf(stderr, "inconsistent answers\n");
 123       exit(1);
 124     }
 125     ei.g.x = x;
 126     ei.g.y = mp_copy(y ? y : yy);
 127     mp_drop(y); mp_drop(yy);
 128   }
 129
 130   if ((err = ec_checkinfo(&ei, &rand_global)) != 0)
 131     fprintf(stderr, "bad curve: %s\n", err);
 132   puthex("p", ei.c->f->m, 0);
 133   if (STRCMP(F_NAME(ei.c->f), ==, "binnorm")) {
 134     fctx_binnorm *fc = (fctx_binnorm *)ei.c->f;
 135     puthex("beta", fc->ntop.r[fc->ntop.n - 1], c->f->noctets);
 136   }
 137   t = F_OUT(ei.c->f, t, ei.c->a); puthex("a", t, c->f->noctets);
 138   t = F_OUT(ei.c->f, t, ei.c->b); puthex("b", t, c->f->noctets);
 139   puthex("r", ei.r, c->f->noctets);
 140   printf("  h "); mp_writefile(ei.h, stdout, 10); putchar('\n');
 141   puthex("gx", ei.g.x, c->f->noctets);
 142   puthex("gy", ei.g.y, c->f->noctets);
 143   ec_freeinfo(&ei);
 144   mp_drop(t);
 145   dstr_destroy(&d);
 146   return (0);
 147 }