diff --git a/util.c b/util.c
new file mode 100644
index 0000000..99d4c9b
--- /dev/null
+++ b/util.c
@@ -0,0 +1,47 @@
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "util.h"
+
+static void xvprintf(const char *, va_list);
+
+void
+eprintf(const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	xvprintf(fmt, ap);
+	va_end(ap);
+
+	abort();
+}
+
+void
+weprintf(const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	xvprintf(fmt, ap);
+	va_end(ap);
+}
+
+void
+xvprintf(const char *fmt, va_list ap)
+{
+	/**TODO: provide other logging target than stderr */
+	fputs("libbrandt: ", stderr);
+
+	vfprintf(stderr, fmt, ap);
+
+	if (fmt[0] && fmt[strlen(fmt)-1] == ':') {
+		fputc(' ', stderr);
+		perror(NULL);
+	} else {
+		fputc('\n', stderr);
+	}
+}
diff --git a/util.h b/util.h
index f40dd36..7e4df86 100644
--- a/util.h
+++ b/util.h
@@ -1,25 +1,28 @@
-/* This file is part of libgotr.
- * (C) 2014-2015 Markus Teich, Jannik Theiß
- *
- * libgotr is free software; you can redistribute it and/or modify
- * it under the terms of the GNU Lesser General Public License as published
- * by the Free Software Foundation; either version 3, or (at your
- * option) any later version.
- *
- * libgotr 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
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public License
- * along with libgotr; see the file LICENSE.  If not, write to the
- * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
- * Boston, MA 02111-1307, USA.
- */
-
 #ifndef _BRANDT_UTIL_H
 #define _BRANDT_UTIL_H
 
-void brandt_eprintf(const char *format, ...);
+void eprintf(const char *fmt, ...);
+void weprintf(const char *fmt, ...);
+
+# undef brandt_assert
+# undef brandt_assert_perror
+# undef brandt_assert_gpgerr
+
+#ifdef NDEBUG
+
+# define brandt_assert(expr)          ((void)(0))
+# define brandt_assert_perror(errnum) ((void)(0))
+# define brandt_assert_gpgerr(errnum) ((void)(0))
+
+#else
+
+# define brandt_assert(expr)          ((expr)    ? (void)(0) : \
+eprintf("Assertion failed in file %s line %d function %s: %s", __FILE__, __LINE__, __PRETTY_FUNCTION__, (#expr)))
+# define brandt_assert_perror(errnum) (!(errnum) ? (void)(0) : \
+eprintf("Assertion failed in file %s line %d function %s:", __FILE__, __LINE__, __PRETTY_FUNCTION__))
+# define brandt_assert_gpgerr(errnum) (!(errnum) ? (void)(0) : \
+eprintf("Assertion failed in file %s line %d function %s: %s", __FILE__, __LINE__, __PRETTY_FUNCTION__, gcry_strerror((errnum))))
+
+#endif
 
 #endif