diff --git a/configure.ac b/configure.ac
index 4064bef..cd03067 100644
--- a/configure.ac
+++ b/configure.ac
@@ -33,6 +33,29 @@ AC_CHECK_HEADER(gcrypt.h, [], [AC_MSG_ERROR([unable to find the gcrypt.h header
 
 SAVE_LIBS=$LIBS
 
+# libgcrypt
+gcrypt=0
+NEED_LIBGCRYPT_API=1
+NEED_LIBGCRYPT_VERSION=1.7.0
+
+
+AM_PATH_LIBGCRYPT("$NEED_LIBGCRYPT_API:$NEED_LIBGCRYPT_VERSION", gcrypt=1)
+AC_CHECK_DECLS([gcry_mpi_set_opaque_copy], [], [], [[#include <gcrypt.h>]])
+
+if test $gcrypt = 0
+then
+  AC_MSG_ERROR([[
+***
+*** You need libgcrypt to build this program.
+**  This library is for example available at
+***   ftp://ftp.gnupg.org/gcrypt/libgcrypt/
+*** (at least version $NEED_LIBGCRYPT_VERSION (API $NEED_LIBGCRYPT_API)
+***  is required.)
+***]])
+fi
+AC_DEFINE_UNQUOTED([NEED_LIBGCRYPT_VERSION], "$NEED_LIBGCRYPT_VERSION", [required libgcrypt version])
+
+# libgnunetutil
 libgnunetutil=0
 AC_MSG_CHECKING([for libgnunetutil])
 AC_ARG_WITH(gnunet,
diff --git a/test_crypto.c b/test_crypto.c
index b3d86db..0aa4222 100644
--- a/test_crypto.c
+++ b/test_crypto.c
@@ -181,7 +181,7 @@ test_smc_zkp_0og ()
 }
 
 
-int
+static int
 test_setup_auction_data ()
 {
 	uint16_t i;
@@ -289,7 +289,7 @@ test_round2 ()
 }
 
 
-int
+static int
 test_round3 ()
 {
 	uint16_t      i, s;
@@ -319,7 +319,7 @@ test_round3 ()
 }
 
 
-int
+static int
 test_outcome ()
 {
 	int32_t ret = -1;
@@ -338,7 +338,7 @@ test_outcome ()
 }
 
 
-void
+static void
 cleanup_auction_data ()
 {
 	for (uint16_t i = 0; i < bidders; i++)