From e070d5a694e9869375571dc349c8e1123b7c6f9f Mon Sep 17 00:00:00 2001
From: Hauke Petersen <hauke.petersen@fu-berlin.de>
Date: Fri, 8 Feb 2019 14:43:57 +0100
Subject: [PATCH 1/3] sys/random: fix indention in doxygen header

---
 sys/random/random.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/sys/random/random.c b/sys/random/random.c
index 8449507b3f9e..85f1bc3e041f 100644
--- a/sys/random/random.c
+++ b/sys/random/random.c
@@ -7,13 +7,13 @@
  */
 
  /**
- * @ingroup sys_random
+ * @ingroup     sys_random
  * @{
  * @file
  *
- * @brief PRNG seeding
+ * @brief       PRNG seeding
  *
- * @author Kaspar Schleiser <kaspar@schleiser.de>
+ * @author      Kaspar Schleiser <kaspar@schleiser.de>
  * @}
  */
 

From 8a135d3a433e527ceed4e94c8682af6277269747 Mon Sep 17 00:00:00 2001
From: Hauke Petersen <hauke.petersen@fu-berlin.de>
Date: Fri, 8 Feb 2019 14:43:09 +0100
Subject: [PATCH 2/3] sys/random: add guard for periph/cpuid include

---
 sys/random/random.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/sys/random/random.c b/sys/random/random.c
index 85f1bc3e041f..3d356c8dcab4 100644
--- a/sys/random/random.c
+++ b/sys/random/random.c
@@ -21,11 +21,13 @@
 
 #include "log.h"
 #include "luid.h"
-#include "periph/cpuid.h"
 #include "random.h"
 #ifdef MODULE_PUF_SRAM
 #include "puf_sram.h"
 #endif
+#ifdef MODULE_PERIPH_CPUID
+#include "periph/cpuid.h"
+#endif
 
 #define ENABLE_DEBUG (0)
 #include "debug.h"

From 64489e8b444efde859e9f048b17707e5da88a983 Mon Sep 17 00:00:00 2001
From: Hauke Petersen <hauke.petersen@fu-berlin.de>
Date: Fri, 8 Feb 2019 14:41:57 +0100
Subject: [PATCH 3/3] sys/random: add hwrng as seed source (if available)

---
 Makefile.dep        | 4 ++++
 sys/random/random.c | 7 +++++++
 2 files changed, 11 insertions(+)

diff --git a/Makefile.dep b/Makefile.dep
index fac58386961d..f89090bbb578 100644
--- a/Makefile.dep
+++ b/Makefile.dep
@@ -661,6 +661,10 @@ ifneq (,$(filter random,$(USEMODULE)))
     USEMODULE += hashes
   endif
 
+  ifeq (,$(filter puf_sram,$(USEMODULE)))
+    FEATURES_OPTIONAL += periph_hwrng
+  endif
+
   USEMODULE += luid
 endif
 
diff --git a/sys/random/random.c b/sys/random/random.c
index 3d356c8dcab4..ffd23fcfff93 100644
--- a/sys/random/random.c
+++ b/sys/random/random.c
@@ -1,5 +1,6 @@
 /**
  * Copyright (C) 2017 Kaspar Schleiser <kaspar@schleiser.de>
+ *               2019 Freie Universität Berlin
  *
  * This file is subject to the terms and conditions of the GNU Lesser
  * General Public License v2.1. See the file LICENSE in the top level
@@ -14,6 +15,7 @@
  * @brief       PRNG seeding
  *
  * @author      Kaspar Schleiser <kaspar@schleiser.de>
+ * @author      Hauke Petersen <hauke.petersen@fu-berlin.de>
  * @}
  */
 
@@ -25,6 +27,9 @@
 #ifdef MODULE_PUF_SRAM
 #include "puf_sram.h"
 #endif
+#ifdef MODULE_PERIPH_HWRNG
+#include "periph/hwrng.h"
+#endif
 #ifdef MODULE_PERIPH_CPUID
 #include "periph/cpuid.h"
 #endif
@@ -41,6 +46,8 @@ void auto_init_random(void)
         LOG_WARNING("random: PUF SEED not fresh\n");
     }
     seed = puf_sram_seed;
+#elif defined (MODULE_PERIPH_HWRNG)
+    hwrng_read(&seed, 4);
 #elif defined (MODULE_PERIPH_CPUID)
     luid_get(&seed, 4);
 #else