X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=src%2Futil%2Fcrypto_ecc_dlog.c;h=f6eb58a9ac4ddcdd729c101820f2fc01260732a9;hb=225ea594e86e56160b0f89b5cace24291cc6184b;hp=29cba3336faf8d64df23c7e1beebcc0f30b47ac9;hpb=f1a73a358739cd2bebf7b83ef1c097a04dc50cd4;p=oweals%2Fgnunet.git

diff --git a/src/util/crypto_ecc_dlog.c b/src/util/crypto_ecc_dlog.c
index 29cba3336..f6eb58a9a 100644
--- 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
@@ -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.
  *