create crypto_pow, in preparation for #3795

3 files changed, 60 insertions, 24 deletions

diff --git a/src/util/Makefile.am b/src/util/Makefile.am
index 67e131810..0f6251f96 100644
--- a/src/util/Makefile.am
+++ b/src/util/Makefile.am
@@ -64,6 +64,7 @@ libgnunetutil_la_SOURCES = \
   crypto_kdf.c \
   crypto_mpi.c \
   crypto_paillier.c \
+  crypto_pow.c \
   crypto_random.c \
   crypto_rsa.c \
   disk.c \
diff --git a/src/util/crypto_pow.c b/src/util/crypto_pow.c
new file mode 100644
index 000000000..b4dfbf53a
--- /dev/null
+++ b/src/util/crypto_pow.c
@@ -0,0 +1,58 @@
+/*
+     This file is part of GNUnet.
+     Copyright (C) 2012, 2013, 2019 GNUnet e.V.
+
+     GNUnet is free software: you can redistribute it and/or modify it
+     under the terms of the GNU Affero General Public License as published
+     by the Free Software Foundation, either version 3 of the License,
+     or (at your option) any later version.
+
+     GNUnet 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
+     Affero General Public License for more details.
+
+     You should have received a copy of the GNU Affero General Public License
+     along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+     SPDX-License-Identifier: AGPL3.0-or-later
+ */
+/**
+ * @file util/crypto_pow.c
+ * @brief proof-of-work hashing
+ * @author Christian Grothoff
+ * @author Bart Polot
+ */
+
+#include "platform.h"
+#include "gnunet_crypto_lib.h"
+#include <gcrypt.h>
+
+
+/**
+ * Calculate the 'proof-of-work' hash (an expensive hash).
+ * We're using a non-standard formula to avoid issues with
+ * ASICs appearing (see #3795).
+ *
+ * @param buf data to hash
+ * @param buf_len number of bytes in @a buf
+ * @param result where to write the resulting hash
+ */
+void
+GNUNET_CRYPTO_pow_hash (const void *buf, size_t buf_len, struct
+                        GNUNET_HashCode *result)
+{
+  GNUNET_break (
+    0 == gcry_kdf_derive (buf,
+                          buf_len,
+                          GCRY_KDF_SCRYPT,
+                          1 /* subalgo */,
+                          "gnunet-proof-of-work",
+                          strlen ("gnunet-proof-of-work"),
+                          2 /* iterations; keep cost of individual op small */,
+                          sizeof(struct GNUNET_HashCode),
+                          result));
+}
+
+
+/* end of crypto_pow.c */
diff --git a/src/util/gnunet-scrypt.c b/src/util/gnunet-scrypt.c
index 8d8451950..d84f486a7 100644
--- a/src/util/gnunet-scrypt.c
+++ b/src/util/gnunet-scrypt.c
@@ -68,29 +68,6 @@ shutdown_task (void *cls)
 
 
 /**
- * Calculate the 'proof-of-work' hash (an expensive hash).
- *
- * @param buf data to hash
- * @param buf_len number of bytes in @a buf
- * @param result where to write the resulting hash
- */
-static void
-pow_hash (const void *buf, size_t buf_len, struct GNUNET_HashCode *result)
-{
-  GNUNET_break (
-    0 == gcry_kdf_derive (buf,
-                          buf_len,
-                          GCRY_KDF_SCRYPT,
-                          1 /* subalgo */,
-                          "gnunet-proof-of-work",
-                          strlen ("gnunet-proof-of-work"),
-                          2 /* iterations; keep cost of individual op small */,
-                          sizeof(struct GNUNET_HashCode),
-                          result));
-}
-
-
-/**
  * Count the leading zeroes in hash.
  *
  * @param hash to count leading zeros in
@@ -140,7 +117,7 @@ find_proof (void *cls)
   while ((counter != UINT64_MAX) && (i < ROUND_SIZE))
   {
     GNUNET_memcpy (buf, &counter, sizeof(uint64_t));
-    pow_hash (buf, sizeof(buf), &result);
+    GNUNET_CRYPTO_pow_hash (buf, sizeof(buf), &result);
     if (nse_work_required <= count_leading_zeroes (&result))
     {
       proof = counter;