1 files changed, 58 insertions, 0 deletions

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 */