Merge branch 'master' of git+ssh://metalzone.distorted.org.uk/~mdw/public-git/catacomb/

[u/mdw/catacomb] / utils / ecptdecompress.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include <mLib/alloc.h>
#include <mLib/hex.h>
#include <mLib/dstr.h>

#include "ec.h"
#include "mp.h"
#include "rand.h"
#include "field-guts.h"

static void puthex(const char *name, mp *x, size_t n)
{
  dstr d = DSTR_INIT;
  hex_ctx hc;
  char *p;

  if (!n) n = mp_octets(x);
  p = xmalloc(n);
  hex_init(&hc);
  hc.indent = "";
  hc.maxline = 0;
  mp_storeb(x, p, n);
  hex_encode(&hc, p, n, &d);
  hex_encode(&hc, 0, 0, &d);
  printf("  %s 0x", name);
  dstr_write(&d, stdout);
  putchar('\n');
  dstr_destroy(&d);
  xfree(p);
}

int main(int argc, char *argv[])
{
  ec_curve *c;
  ec_info ei;
  ec pt = EC_INIT;
  qd_parse qd;
  hex_ctx hc;
  dstr d = DSTR_INIT;
  size_t n;
  octet *p;
  mp *x, *y = 0, *yy = 0;
  mp *t = MP_NEW;
  const char *err;

  qd.p = argv[1];
  qd.e = 0;
  if ((c = ec_curveparse(&qd)) == 0 || !qd_eofp(&qd)) {
    fprintf(stderr, "bad curve: %s\n", qd.e);
    exit(1);
  }
  n = c->f->noctets;

  ei.c = c;
  ei.r = mp_readstring(MP_NEW, argv[2], 0, 0);
  ei.h = mp_readstring(MP_NEW, argv[3], 0, 0);

  EC_CREATE(&ei.g);
  hex_init(&hc);
  hex_decode(&hc, argv[4], strlen(argv[4]), &d);
  hex_decode(&hc, 0, 0, &d);
  p = (octet *)d.buf;
  if (p[0] == 0) {
    EC_SETINF(&ei.g);
  } else {
    if (d.len < n + 1) {
      fprintf(stderr, "missing x\n");
      exit(1);
    }
    x = mp_loadb(MP_NEW, p + 1, n);
    if (p[0] & 0x04) {
      if (d.len < 2 * n + 1) {
	fprintf(stderr, "missing y\n");
	exit(1);
      }
      y = mp_loadb(MP_NEW, p + n + 1, n);
    }
    if (p[0] & 0x02) {
      if (!ec_find(c, &pt, x)) {
	fprintf(stderr, "no matching y\n");
	exit(1);
      }
      yy = MP_COPY(pt.y);
      ec_destroy(&pt);
      switch (F_TYPE(c->f)) {
	case FTY_PRIME:
	  if (!MP_ODDP(yy) != !(p[0] & 1))
	    yy = mp_sub(yy, c->f->m, yy);
	  break;
	case FTY_BINARY:
	  if (MP_ZEROP(x))
	    yy = F_SQRT(c->f, MP_NEW, c->b);
	  else {
	    mp *xin = F_IN(c->f, MP_NEW, x);
	    mp *xx = F_SQR(c->f, MP_NEW, xin);
	    mp *b = F_MUL(c->f, MP_NEW, xx, c->a);
	    mp *xxx = F_MUL(c->f, MP_NEW, xx, xin);
	    b = F_ADD(c->f, b, b, xxx);
	    b = F_ADD(c->f, b, b, c->b);
	    xx = F_INV(c->f, xx, xx);
	    b = F_MUL(c->f, b, b, xx);
	    mp_drop(xxx);
	    yy = F_QUADSOLVE(c->f, MP_NEW, b);
	    xx = F_OUT(c->f, xx, yy);
	    if (!MP_ODDP(xx) != !(p[0] & 1))
	      yy = gf_add(yy, yy, MP_ONE);
	    yy = F_MUL(c->f, yy, yy, xin);
	    yy = F_OUT(c->f, yy, yy);
	    mp_drop(xin);
	    mp_drop(xx);
	  }
	  break;
	default:
	  abort();
      }
    }
    if (y && yy && !MP_EQ(y, yy)) {
      fprintf(stderr, "inconsistent answers\n");
      exit(1);
    }
    ei.g.x = x;
    ei.g.y = mp_copy(y ? y : yy);
    mp_drop(y); mp_drop(yy);
  }

  if ((err = ec_checkinfo(&ei, &rand_global)) != 0)
    fprintf(stderr, "bad curve: %s\n", err);
  puthex("p", ei.c->f->m, 0);
  if (strcmp(F_NAME(ei.c->f), "binnorm") == 0) {
    fctx_binnorm *fc = (fctx_binnorm *)ei.c->f;
    puthex("beta", fc->ntop.r[fc->ntop.n - 1], c->f->noctets);
  }
  t = F_OUT(ei.c->f, t, ei.c->a); puthex("a", t, c->f->noctets);
  t = F_OUT(ei.c->f, t, ei.c->b); puthex("b", t, c->f->noctets);
  puthex("r", ei.r, c->f->noctets);
  printf("  h "); mp_writefile(ei.h, stdout, 10); putchar('\n');
  puthex("gx", ei.g.x, c->f->noctets);
  puthex("gy", ei.g.y, c->f->noctets);
  ec_freeinfo(&ei);
  mp_drop(t);
  dstr_destroy(&d);
  return (0);
}