diff --git a/util.c b/util.c
index 2b44710..1eff0d4 100644
--- a/util.c
+++ b/util.c
@@ -16,9 +16,10 @@
 
 /**
  * @file util.c
- * @brief \todo
+ * @brief Implementation of common utility functions.
  * @author Markus Teich
  */
+#include <errno.h>
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -27,30 +28,44 @@
 #include "util.h"
 
 
+static FILE *logstream = NULL;
+
+
+/**
+ * setlog sets another output for logging.
+ *
+ * @param[in] stream The new logging target.
+ */
+void
+setlog (FILE *stream)
+{
+	logstream = stream;
+}
+
+
 /**
  * xvprintf prints a formatstring with prefix "libbrandt: ". If the format
  * string ends with a ':', the strerror() from errno.h output will be appended.
  * The output is always terminated with a newline.
  *
- * @param fmt The format string
- * @param ap The inputs to the format string
+ * @param[in] fmt The format string
+ * @param[in] ap The inputs to the format string
  */
-void
+static void
 xvprintf (const char *fmt, va_list ap)
 {
-	/**\todo: provide other logging target than stderr */
-	fputs ("libbrandt: ", stderr);
+	fputs ("libbrandt: ", logstream ? logstream : stderr);
 
-	vfprintf (stderr, fmt, ap);
+	vfprintf (logstream ? logstream : stderr, fmt, ap);
 
 	if (fmt[0] && fmt[strlen (fmt) - 1] == ':')
 	{
-		fputc (' ', stderr);
-		perror (NULL);
+		fputc (' ', logstream ? logstream : stderr);
+		fputs (strerror (errno), logstream ? logstream : stderr);
 	}
 	else
 	{
-		fputc ('\n', stderr);
+		fputc ('\n', logstream ? logstream : stderr);
 	}
 }
 
@@ -59,8 +74,8 @@ xvprintf (const char *fmt, va_list ap)
  * eprintf prints an error message and then calls abort() to terminate the
  * process.
  *
- * @param fmt The format string
- * @param ... The inputs to the format string
+ * @param[in] fmt The format string
+ * @param[in] ... The inputs to the format string
  */
 void
 eprintf (const char *fmt, ...)
@@ -78,8 +93,8 @@ eprintf (const char *fmt, ...)
 /**
  * weprintf prints a warning message
  *
- * @param fmt The format string
- * @param ... The inputs to the format string
+ * @param[in] fmt The format string
+ * @param[in] ... The inputs to the format string
  */
 void
 weprintf (const char *fmt, ...)
diff --git a/util.h b/util.h
index d21cc89..1e67197 100644
--- a/util.h
+++ b/util.h
@@ -16,37 +16,51 @@
 
 /**
  * @file util.h
- * @brief \todo
+ * @brief Interface for the common utility functions.
  * @author Markus Teich
  */
 
 #ifndef _BRANDT_UTIL_H
 #define _BRANDT_UTIL_H
 
-void eprintf(const char *fmt, ...);
-void weprintf(const char *fmt, ...);
+void setlog (FILE *stream);
+void eprintf (const char *fmt, ...);
+void weprintf (const char *fmt, ...);
 
-# undef brandt_assert
-# undef brandt_assert_perror
-# undef brandt_assert_gpgerr
+#undef brandt_assert
+#undef brandt_assert_perror
+#undef brandt_assert_gpgerr
 
 #ifdef NDEBUG
 
-# 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))))
+#define brandt_assert(expr)          ((expr)    ? (void)(0) : \
+eprintf("Assertion failed in file %s line %d function %s: %s", \
+        __FILE__, \
+        __LINE__, \
+        __PRETTY_FUNCTION__, \
+		(#expr)))
 
-# define DP(point) ((void)(gcry_log_debugpnt (#point, point, ec_ctx)))
-# define DM(mpi) ((void)(gcry_log_debugmpi (#mpi, mpi, ec_ctx)))
+#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))))
+
+#define DP(point) ((void)(gcry_log_debugpnt (#point, point, ec_ctx)))
+#define DM(mpi) ((void)(gcry_log_debugmpi (#mpi, mpi, ec_ctx)))
 
 #else
 
-# define brandt_assert(expr)          ((void)(expr))
-# define brandt_assert_perror(errnum) ((void)(errnum))
-# define brandt_assert_gpgerr(errnum) ((void)(errnum))
+#define brandt_assert(expr)          ((void)(expr))
+#define brandt_assert_perror(errnum) ((void)(errnum))
+#define brandt_assert_gpgerr(errnum) ((void)(errnum))
 
 #endif