diff --git a/makefiles/c25519.mk b/makefiles/c25519.mk
index ae3c7ec..57bcd05 100644
--- a/makefiles/c25519.mk
+++ b/makefiles/c25519.mk
@@ -1,7 +1,6 @@
 C25519_DIR ?= ../c25519
 CFLAGS+=-DCRYPTO_C25519 -I../c25519/src
 CRYPTOSRC=$(SRC_DIR)/crypt/c25519.c
-CRYPTOSRC+=$(SRC_DIR)/crypt/helpers.c
 CFLAGS_CRYPTO += -I$(C25519_DIR)/src
 CRYPTOOBJS+=$(C25519_DIR)/src/edsign.o
 CRYPTOOBJS+=$(C25519_DIR)/src/ed25519.o
diff --git a/makefiles/hacl.mk b/makefiles/hacl.mk
index b4e01e8..10ca9f1 100644
--- a/makefiles/hacl.mk
+++ b/makefiles/hacl.mk
@@ -2,6 +2,5 @@ HACL_DIR ?= ../hacl-c
 CFLAGS+=-DCRYPTO_HACL
 HACLLIB=hacl
 CRYPTOSRC += $(SRC_DIR)/crypt/hacl.c
-CRYPTOSRC += $(SRC_DIR)/crypt/helpers.c
 CFLAGS_CRYPTO += -I$(HACL_DIR)
 LDFLAGS_CRYPTO += -Wl,$(HACL_DIR)/libhacl.so
diff --git a/makefiles/monocypher.mk b/makefiles/monocypher.mk
index 135f48a..f9ea19a 100644
--- a/makefiles/monocypher.mk
+++ b/makefiles/monocypher.mk
@@ -1,7 +1,6 @@
 MONOCYPHERLIB=monocypher
 
 CFLAGS +=-DCRYPTO_MONOCYPHER -DED25519_SHA512
-CRYPTOSRC +=$(SRC_DIR)/crypt/helpers.c
 CRYPTOSRC +=$(SRC_DIR)/crypt/monocypher.c
 
 MONOCYPHER_DIR ?= $(PWD)/../Monocypher
diff --git a/src/crypt/c25519.c b/src/crypt/c25519.c
index a6293a7..8dc9a90 100644
--- a/src/crypt/c25519.c
+++ b/src/crypt/c25519.c
@@ -18,7 +18,9 @@
 #include "cose/crypto/c25519.h"
 #include "cose/crypto/selectors.h"
 
-extern void randombytes(uint8_t *target, uint64_t n);
+
+extern cose_crypt_rng cose_crypt_get_random;
+extern void *cose_crypt_rng_arg;
 
 #ifdef CRYPTO_C25519_INCLUDE_ED25519
 int cose_crypto_sign_ed25519(const cose_key_t *key, uint8_t *sign, size_t *signlen, uint8_t *msg, unsigned long long int msglen)
@@ -38,7 +40,7 @@ int cose_crypto_verify_ed25519(const cose_key_t *key, const uint8_t *sign, size_
 
 void cose_crypto_keypair_ed25519(cose_key_t *key)
 {
-    randombytes(key->d, EDSIGN_SECRET_KEY_SIZE);
+    cose_crypt_get_random(cose_crypt_rng_arg, key->d, EDSIGN_SECRET_KEY_SIZE);
     edsign_sec_to_pub(key->x, key->d);
 }
 #endif /* CRYPTO_C25519_INCLUDE_ED25519 */
diff --git a/src/crypt/hacl.c b/src/crypt/hacl.c
index 0d320cf..7908d54 100644
--- a/src/crypt/hacl.c
+++ b/src/crypt/hacl.c
@@ -22,7 +22,8 @@
 
 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);
+extern cose_crypt_rng cose_crypt_get_random;
+extern void *cose_crypt_rng_arg;
 
 #ifdef CRYPTO_HACL_INCLUDE_CHACHAPOLY
 int cose_crypto_aead_encrypt_chachapoly(uint8_t *c,
diff --git a/src/crypt/helpers.c b/src/crypt/helpers.c
deleted file mode 100644
index b79c764..0000000
--- a/src/crypt/helpers.c
+++ /dev/null
@@ -1,18 +0,0 @@
-/*
- * Copyright (C) 2018 Freie Universitat Berlin
- * Copyright (C) 2018 Inria
- *
- * 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
- * directory for more details.
- */
-
-#include <stdint.h>
-#include <stdlib.h>
-
-void randombytes(uint8_t *target, uint64_t n)
-{
-    for(uint64_t i = 0; i < n; i++) {
-        target[i] = rand() % 256;
-    }
-}
diff --git a/src/crypt/monocypher.c b/src/crypt/monocypher.c
index 57cd5ed..154c97e 100644
--- a/src/crypt/monocypher.c
+++ b/src/crypt/monocypher.c
@@ -19,7 +19,9 @@
 #include "cose/crypto.h"
 #include "cose/crypto/selectors.h"
 
-extern void randombytes(uint8_t *target, uint64_t n);
+
+extern cose_crypt_rng cose_crypt_get_random;
+extern void *cose_crypt_rng_arg;
 static const uint8_t zero[32] = { 0 };
 
 #ifdef CRYPTO_MONOCYPHER_INCLUDE_CHACHAPOLY
@@ -128,7 +130,7 @@ static void _ed25519_clamp(uint8_t *key)
 
 void cose_crypto_keypair_ed25519(cose_key_t *key)
 {
-    randombytes(key->d, COSE_CRYPTO_SIGN_ED25519_SECRETKEYBYTES);
+    cose_crypt_get_random(cose_crypt_rng_arg, key->d, COSE_CRYPTO_SIGN_ED25519_SECRETKEYBYTES);
     _ed25519_clamp(key->d);
     crypto_ed25519_public_key(key->x, key->d);
 }