diff --git a/core/net/llsec/anti-replay.c b/core/net/llsec/anti-replay.c
new file mode 100644
index 000000000..0500f7a87
--- /dev/null
+++ b/core/net/llsec/anti-replay.c
@@ -0,0 +1,110 @@
+/**
+ * \addtogroup llsec802154
+ * @{
+ */
+
+/*
+ * Copyright (c) 2014, Hasso-Plattner-Institut.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the Institute nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * This file is part of the Contiki operating system.
+ *
+ */
+
+/**
+ * \file
+ *         Protects against replay attacks by comparing with the last
+ *         unicast or broadcast frame counter of the sender.
+ * \author
+ *         Konrad Krentz <konrad.krentz@gmail.com>
+ */
+
+#include "net/llsec/anti-replay.h"
+#include "net/packetbuf.h"
+
+/* This node's current frame counter value */
+static uint32_t counter;
+
+/*---------------------------------------------------------------------------*/
+void
+anti_replay_set_counter(void)
+{
+  frame802154_frame_counter_t reordered_counter;
+  
+  reordered_counter.u32 = LLSEC802154_HTONL(++counter);
+  
+  packetbuf_set_attr(PACKETBUF_ATTR_FRAME_COUNTER_BYTES_0_1, reordered_counter.u16[0]);
+  packetbuf_set_attr(PACKETBUF_ATTR_FRAME_COUNTER_BYTES_2_3, reordered_counter.u16[1]);
+}
+/*---------------------------------------------------------------------------*/
+uint32_t
+anti_replay_get_counter(void)
+{
+  frame802154_frame_counter_t disordered_counter;
+  
+  disordered_counter.u16[0] = packetbuf_attr(PACKETBUF_ATTR_FRAME_COUNTER_BYTES_0_1);
+  disordered_counter.u16[1] = packetbuf_attr(PACKETBUF_ATTR_FRAME_COUNTER_BYTES_2_3);
+  
+  return LLSEC802154_HTONL(disordered_counter.u32); 
+}
+/*---------------------------------------------------------------------------*/
+void
+anti_replay_init_info(struct anti_replay_info *info)
+{
+  info->last_broadcast_counter
+      = info->last_unicast_counter
+      = anti_replay_get_counter();
+}
+/*---------------------------------------------------------------------------*/
+int
+anti_replay_was_replayed(struct anti_replay_info *info)
+{
+  uint32_t received_counter;
+  
+  received_counter = anti_replay_get_counter();
+  
+  if(linkaddr_cmp(packetbuf_addr(PACKETBUF_ADDR_RECEIVER), &linkaddr_null)) {
+    /* broadcast */
+    if(received_counter <= info->last_broadcast_counter) {
+      return 1;
+    } else {
+      info->last_broadcast_counter = received_counter;
+      return 0;
+    }
+  } else {
+    /* unicast */
+    if(received_counter <= info->last_unicast_counter) {
+      return 1;
+    } else {
+      info->last_unicast_counter = received_counter;
+      return 0;
+    }
+  }
+}
+/*---------------------------------------------------------------------------*/
+
+/** @} */
diff --git a/core/net/llsec/anti-replay.h b/core/net/llsec/anti-replay.h
new file mode 100644
index 000000000..637243660
--- /dev/null
+++ b/core/net/llsec/anti-replay.h
@@ -0,0 +1,79 @@
+/**
+ * \addtogroup llsec802154
+ * @{
+ */
+
+/*
+ * Copyright (c) 2014, Hasso-Plattner-Institut.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the Institute nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * This file is part of the Contiki operating system.
+ *
+ */
+
+/**
+ * \file
+ *         Interface to anti-replay mechanisms.
+ * \author
+ *         Konrad Krentz <konrad.krentz@gmail.com>
+ */
+
+#ifndef ANTI_REPLAY_H
+#define ANTI_REPLAY_H
+
+#include "contiki.h"
+
+struct anti_replay_info {
+  uint32_t last_broadcast_counter;
+  uint32_t last_unicast_counter;
+};
+
+/**
+ * \brief Sets the frame counter packetbuf attributes.
+ */
+void anti_replay_set_counter(void);
+
+/**
+ * \brief Gets the frame counter from packetbuf.
+ */
+uint32_t anti_replay_get_counter(void);
+
+/**
+ * \brief Initializes the anti-replay information about the sender
+ */
+void anti_replay_init_info(struct anti_replay_info *info);
+
+/**
+ * \brief               Checks if received frame was replayed
+ * \param last_counters Anti-replay information about the sender
+ * \retval 0            <-> received frame was not replayed
+ */
+int anti_replay_was_replayed(struct anti_replay_info *info);
+
+#endif /* ANTI_REPLAY_H */
+
+/** @} */