diff --git a/pkg/libcose/patches/0001-RIOT-Use-RIOT-random_bytes-function-instead-of-rando.patch b/pkg/libcose/patches/0001-RIOT-Use-RIOT-random_bytes-function-instead-of-rando.patch
new file mode 100644
index 0000000000..204e307923
--- /dev/null
+++ b/pkg/libcose/patches/0001-RIOT-Use-RIOT-random_bytes-function-instead-of-rando.patch
@@ -0,0 +1,46 @@
+From 2d37e015c9fbf3711a7f931564983b20f2267da4 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Joakim=20Nohlg=C3=A5rd?= <joakim.nohlgard@eistec.se>
+Date: Tue, 15 May 2018 13:24:16 +0200
+Subject: [PATCH] RIOT: Use RIOT random_bytes function instead of randombytes
+
+---
+ src/crypt/hacl.c | 6 +++---
+ 1 file changed, 3 insertions(+), 3 deletions(-)
+
+diff --git a/src/crypt/hacl.c b/src/crypt/hacl.c
+index a16dbd7e30..cb4808d684 100644
+--- a/src/crypt/hacl.c
++++ b/src/crypt/hacl.c
+@@ -18,10 +18,10 @@
+ #include <stdint.h>
+ #include <stdlib.h>
+ #include <string.h>
++#include "random.h"
+ 
+ extern void Hacl_Ed25519_sign(uint8_t *signature, uint8_t *secret, uint8_t *msg, uint32_t len1);
+ extern bool Hacl_Ed25519_verify(uint8_t *public, uint8_t *msg, uint32_t len1, uint8_t *signature);
+-extern void randombytes(uint8_t *target, uint64_t n);
+ 
+ int cose_crypto_aead_encrypt_chachapoly(uint8_t *c,
+                                         size_t *clen,
+@@ -65,7 +65,7 @@ ssize_t cose_crypto_keygen_chachapoly(uint8_t *sk, size_t len)
+     if (len < COSE_CRYPTO_AEAD_CHACHA20POLY1305_KEYBYTES) {
+         return COSE_ERR_NOMEM;
+     }
+-    randombytes(sk, COSE_CRYPTO_AEAD_CHACHA20POLY1305_KEYBYTES);
++    random_bytes(sk, COSE_CRYPTO_AEAD_CHACHA20POLY1305_KEYBYTES);
+     return COSE_CRYPTO_AEAD_CHACHA20POLY1305_KEYBYTES;
+ }
+ 
+@@ -74,7 +74,7 @@ size_t cose_crypto_aead_nonce_chachapoly(uint8_t *nonce, size_t len)
+     if (len < COSE_CRYPTO_AEAD_CHACHA20POLY1305_NONCEBYTES) {
+         return 0;
+     }
+-    randombytes(nonce, COSE_CRYPTO_AEAD_CHACHA20POLY1305_NONCEBYTES);
++    random_bytes(nonce, COSE_CRYPTO_AEAD_CHACHA20POLY1305_NONCEBYTES);
+     return COSE_CRYPTO_AEAD_CHACHA20POLY1305_NONCEBYTES;
+ }
+ 
+-- 
+2.17.0
+