--- /dev/null
+/* -*-c-*-
+ *
+ * DSA signature verification
+ *
+ * (c) 1999 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------*
+ *
+ * This file is part of Catacomb.
+ *
+ * Catacomb is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * Catacomb 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 Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with Catacomb; if not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+/*----- Header files ------------------------------------------------------*/
+
+#include "dsa.h"
+#include "mp.h"
+#include "mpmont.h"
+
+/*----- Main code ---------------------------------------------------------*/
+
+/* --- @dsa_vrfy@ --- *
+ *
+ * Arguments: @const dsa_param *dp@ = pointer to DSA parameters
+ * @mp *y@ = public verification key
+ * @mp *m@ = message which was signed
+ * @mp *r, *s@ = the signature
+ *
+ * Returns: Zero if the signature is a forgery, nonzero if it's valid.
+ *
+ * Use: Verifies a DSA digital signature.
+ */
+
+int dsa_vrfy(const dsa_param *dp, mp *y, mp *m, mp *r, mp *s)
+{
+ mpmont pm, qm;
+ mp *w;
+ mp_expfactor f[2];
+ int ok;
+
+ /* --- Ensure that all of the signature bits are in range --- */
+
+ if ((r->f | s->f) & MP_NEG)
+ return (0);
+ if (MP_CMP(r, >=, dp->q) || MP_CMP(s, >=, dp->q))
+ return (0);
+
+ /* --- Set up Montgomery contexts --- */
+
+ mpmont_create(&pm, dp->p);
+ mpmont_create(&qm, dp->q);
+
+ /* --- Compute %$w = s^{-1} \bmod q$% --- */
+
+ {
+ mp *z = mp_modinv(MP_NEW, s, dp->q);
+ w = mpmont_mul(&qm, MP_NEW, z, qm.r2);
+ mp_drop(z);
+ }
+
+ /* --- Compute %$wr$% and %$wm$% --- */
+
+ f[0].exp = mpmont_mul(&qm, MP_NEW, w, m);
+ f[1].exp = mpmont_mul(&qm, MP_NEW, w, r);
+ mp_drop(w);
+ mpmont_destroy(&qm);
+
+ /* --- Do the exponentiation and take residue mod @q@ --- */
+
+ f[0].base = dp->g;
+ f[1].base = y;
+ w = mpmont_mexp(&pm, MP_NEW, f, 2);
+ mp_div(0, &w, w, dp->q);
+ ok = MP_EQ(w, r);
+
+ /* --- Tidy up --- */
+
+ mp_drop(w);
+ mp_drop(f[0].exp);
+ mp_drop(f[1].exp);
+ mpmont_destroy(&pm);
+ return (ok);
+}
+
+/* --- @dsa_verify@ --- *
+ *
+ * Arguments: @const dsa_param *dp@ = pointer to DSA parameters
+ * @mp *y@ = public verification key
+ * @const void *m@ = pointer to message block
+ * @size_t msz@ = size of message block
+ * @const void *r@ = pointer to @r@ signature half
+ * @size_t rsz@ = size of @r@
+ * @const void *s@ = pointer to @s@ signature half
+ * @size_t ssz@ = size of @s@
+ *
+ * Returns: Zero if the signature is a forgery, nonzero if it's valid.
+ *
+ * Use: Verifies a DSA digital signature.
+ */
+
+int dsa_verify(const dsa_param *dp, mp *y,
+ const void *m, size_t msz,
+ const void *r, size_t rsz,
+ const void *s, size_t ssz)
+{
+ mp *mm = dsa_h2n(MP_NEW, dp->q, m, msz);
+ mp *rm = mp_loadb(MP_NEW, r, rsz);
+ mp *sm = mp_loadb(MP_NEW, s, ssz);
+ int ok = dsa_vrfy(dp, y, mm, rm, sm);
+ mp_drop(mm);
+ mp_drop(rm);
+ mp_drop(sm);
+ return (ok);
+}
+
+/*----- Test rig ----------------------------------------------------------*/
+
+#ifdef TEST_RIG
+
+#include <mLib/testrig.h>
+
+#include "sha.h"
+
+static int verify(int good, dstr *v)
+{
+ dsa_param dp;
+ mp *y;
+ sha_ctx c;
+ octet hash[SHA_HASHSZ];
+ int ok = 1;
+ int rc;
+
+ dp.q = *(mp **)v[0].buf;
+ dp.p = *(mp **)v[1].buf;
+ dp.g = *(mp **)v[2].buf;
+ y = *(mp **)v[3].buf;
+
+ sha_init(&c);
+ sha_hash(&c, v[4].buf, v[4].len);
+ sha_done(&c, hash);
+
+ rc = dsa_verify(&dp, y, hash, sizeof(hash),
+ v[5].buf, v[5].len, v[6].buf, v[6].len);
+
+ if (!rc != !good) {
+ if (good)
+ fputs("\n*** verification failed", stderr);
+ else
+ fputs("\n*** verification succeeded", stderr);
+ fputs("\nq = ", stderr); mp_writefile(dp.q, stderr, 16);
+ fputs("\np = ", stderr); mp_writefile(dp.p, stderr, 16);
+ fputs("\ng = ", stderr); mp_writefile(dp.g, stderr, 16);
+ fputs("\ny = ", stderr); mp_writefile(y, stderr, 16);
+ fprintf(stderr, "\nmessage = `%s'", v[4].buf);
+ fputs("\nr = ", stderr); type_hex.dump(&v[5], stderr);
+ fputs("\ns = ", stderr); type_hex.dump(&v[6], stderr);
+ fputc('\n', stderr);
+ ok = 0;
+ }
+
+ mp_drop(dp.p);
+ mp_drop(dp.q);
+ mp_drop(dp.g);
+ mp_drop(y);
+ assert(mparena_count(MPARENA_GLOBAL) == 0);
+ return (ok);
+}
+
+static int vgood(dstr *v) { return verify(1, v); }
+static int vbad(dstr *v) { return verify(0, v); }
+
+static test_chunk tests[] = {
+ { "verify-good", vgood,
+ { &type_mp, &type_mp, &type_mp, &type_mp,
+ &type_string, &type_hex, &type_hex, 0 } },
+ { "verify-bad", vbad,
+ { &type_mp, &type_mp, &type_mp, &type_mp,
+ &type_string, &type_hex, &type_hex, 0 } },
+ { 0, 0, { 0 } }
+};
+
+int main(int argc, char *argv[])
+{
+ sub_init();
+ test_run(argc, argv, tests, SRCDIR "/t/dsa");
+ return (0);
+}
+
+#endif
+
+/*----- That's all, folks -------------------------------------------------*/
projects / u / mdw / catacomb / blobdiff