Link libgnunetblockgroup to libgnunetblock

[oweals/gnunet.git] / src / util / crypto_ecc_dlog.c

diff --git a/src/util/crypto_ecc_dlog.c b/src/util/crypto_ecc_dlog.c
index 29cba3336faf8d64df23c7e1beebcc0f30b47ac9..38e2088cc07780e5c436647fae7400e046f5d304 100644 (file)
--- a/src/util/crypto_ecc_dlog.c
+++ b/src/util/crypto_ecc_dlog.c
@@ -1,6 +1,6 @@
 /*
      This file is part of GNUnet.
-     Copyright (C) 2012, 2013, 2015 Christian Grothoff (and other contributing authors)
+     Copyright (C) 2012, 2013, 2015 GNUnet e.V.
 
      GNUnet is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published
@@ -151,7 +151,7 @@ GNUNET_CRYPTO_ecc_bin_to_point (struct GNUNET_CRYPTO_EccDlogContext *edc,
  *
  * @param max maximum value the factor can be
  * @param mem memory to use (should be smaller than @a max), must not be zero.
- * @return @a max if dlog failed, otherwise the factor
+ * @return NULL on error
  */
 struct GNUNET_CRYPTO_EccDlogContext *
 GNUNET_CRYPTO_ecc_dlog_prepare (unsigned int max,
@@ -219,7 +219,7 @@ GNUNET_CRYPTO_ecc_dlog_prepare (unsigned int max,
  *
  * @param edc precalculated values, determine range of factors
  * @param input point on the curve to factor
- * @return `edc->max` if dlog failed, otherwise the factor
+ * @return INT_MAX if dlog failed, otherwise the factor
  */
 int
 GNUNET_CRYPTO_ecc_dlog (struct GNUNET_CRYPTO_EccDlogContext *edc,
@@ -237,7 +237,7 @@ GNUNET_CRYPTO_ecc_dlog (struct GNUNET_CRYPTO_EccDlogContext *edc,
   GNUNET_assert (NULL != g);
   q = gcry_mpi_point_new (0);
 
-  res = edc->max;
+  res = INT_MAX;
   for (i=0;i<=edc->max/edc->mem;i++)
   {
     if (0 == i)
@@ -466,6 +466,29 @@ GNUNET_CRYPTO_ecc_rnd (struct GNUNET_CRYPTO_EccDlogContext *edc,
 }
 
 
+/**
+ * Obtain a random scalar for point multiplication on the curve and
+ * its multiplicative inverse.
+ *
+ * @param edc calculation context for ECC operations
+ * @param[out] r set to a random scalar on the curve
+ * @param[out] r_inv set to the multiplicative inverse of @a r
+ */
+void
+GNUNET_CRYPTO_ecc_rnd_mpi (struct GNUNET_CRYPTO_EccDlogContext *edc,
+                           gcry_mpi_t *r,
+                           gcry_mpi_t *r_inv)
+{
+  gcry_mpi_t n;
+
+  *r = GNUNET_CRYPTO_ecc_random_mod_n (edc);
+  /* r_inv = n - r = - r */
+  *r_inv = gcry_mpi_new (0);
+  n = gcry_mpi_ec_get_mpi ("n", edc->ctx, 1);
+  gcry_mpi_sub (*r_inv, n, *r);
+}
+
+
 /**
  * Free a point value returned by the API.
  *