diff --git a/include/mbedtls/bignum.h b/include/mbedtls/bignum.h
index 8367cd34e6..1e1c06330f 100644
--- a/include/mbedtls/bignum.h
+++ b/include/mbedtls/bignum.h
@@ -12,6 +12,7 @@
 #include "mbedtls/private_access.h"
 
 #include "mbedtls/build_info.h"
+#include "mbedtls/platform_util.h"
 
 #include <stddef.h>
 #include <stdint.h>
@@ -928,7 +929,7 @@ int mbedtls_mpi_exp_mod(mbedtls_mpi *X, const mbedtls_mpi *A,
  *                 be relevant in applications like deterministic ECDSA.
  */
 int mbedtls_mpi_fill_random(mbedtls_mpi *X, size_t size,
-                            int (*f_rng)(void *, unsigned char *, size_t),
+                            mbedtls_f_rng_t *f_rng,
                             void *p_rng);
 
 /** Generate a random number uniformly in a range.
@@ -966,7 +967,7 @@ int mbedtls_mpi_fill_random(mbedtls_mpi *X, size_t size,
 int mbedtls_mpi_random(mbedtls_mpi *X,
                        mbedtls_mpi_sint min,
                        const mbedtls_mpi *N,
-                       int (*f_rng)(void *, unsigned char *, size_t),
+                       mbedtls_f_rng_t *f_rng,
                        void *p_rng);
 
 /**
@@ -1030,7 +1031,7 @@ int mbedtls_mpi_inv_mod(mbedtls_mpi *X, const mbedtls_mpi *A,
  * \return         Another negative error code on other kinds of failure.
  */
 int mbedtls_mpi_is_prime_ext(const mbedtls_mpi *X, int rounds,
-                             int (*f_rng)(void *, unsigned char *, size_t),
+                             mbedtls_f_rng_t *f_rng,
                              void *p_rng);
 /**
  * \brief Flags for mbedtls_mpi_gen_prime()
@@ -1063,7 +1064,7 @@ typedef enum {
  *                 \c 3 and #MBEDTLS_MPI_MAX_BITS.
  */
 int mbedtls_mpi_gen_prime(mbedtls_mpi *X, size_t nbits, int flags,
-                          int (*f_rng)(void *, unsigned char *, size_t),
+                          mbedtls_f_rng_t *f_rng,
                           void *p_rng);
 
 #if defined(MBEDTLS_SELF_TEST)
diff --git a/include/mbedtls/dhm.h b/include/mbedtls/dhm.h
index fcba3d2af0..bbfe6ea8d5 100644
--- a/include/mbedtls/dhm.h
+++ b/include/mbedtls/dhm.h
@@ -183,7 +183,7 @@ int mbedtls_dhm_read_params(mbedtls_dhm_context *ctx,
  */
 int mbedtls_dhm_make_params(mbedtls_dhm_context *ctx, int x_size,
                             unsigned char *output, size_t *olen,
-                            int (*f_rng)(void *, unsigned char *, size_t),
+                            mbedtls_f_rng_t *f_rng,
                             void *p_rng);
 
 /**
@@ -250,7 +250,7 @@ int mbedtls_dhm_read_public(mbedtls_dhm_context *ctx,
  */
 int mbedtls_dhm_make_public(mbedtls_dhm_context *ctx, int x_size,
                             unsigned char *output, size_t olen,
-                            int (*f_rng)(void *, unsigned char *, size_t),
+                            mbedtls_f_rng_t *f_rng,
                             void *p_rng);
 
 /**
@@ -281,7 +281,7 @@ int mbedtls_dhm_make_public(mbedtls_dhm_context *ctx, int x_size,
  */
 int mbedtls_dhm_calc_secret(mbedtls_dhm_context *ctx,
                             unsigned char *output, size_t output_size, size_t *olen,
-                            int (*f_rng)(void *, unsigned char *, size_t),
+                            mbedtls_f_rng_t *f_rng,
                             void *p_rng);
 
 /**
diff --git a/include/mbedtls/ecdh.h b/include/mbedtls/ecdh.h
index a6a5069337..a919ad27e6 100644
--- a/include/mbedtls/ecdh.h
+++ b/include/mbedtls/ecdh.h
@@ -189,7 +189,7 @@ int mbedtls_ecdh_can_do(mbedtls_ecp_group_id gid);
  *                  \c MBEDTLS_MPI_XXX error code on failure.
  */
 int mbedtls_ecdh_gen_public(mbedtls_ecp_group *grp, mbedtls_mpi *d, mbedtls_ecp_point *Q,
-                            int (*f_rng)(void *, unsigned char *, size_t),
+                            mbedtls_f_rng_t *f_rng,
                             void *p_rng);
 
 /**
@@ -225,7 +225,7 @@ int mbedtls_ecdh_gen_public(mbedtls_ecp_group *grp, mbedtls_mpi *d, mbedtls_ecp_
  */
 int mbedtls_ecdh_compute_shared(mbedtls_ecp_group *grp, mbedtls_mpi *z,
                                 const mbedtls_ecp_point *Q, const mbedtls_mpi *d,
-                                int (*f_rng)(void *, unsigned char *, size_t),
+                                mbedtls_f_rng_t *f_rng,
                                 void *p_rng);
 
 /**
@@ -290,7 +290,7 @@ void mbedtls_ecdh_free(mbedtls_ecdh_context *ctx);
  */
 int mbedtls_ecdh_make_params(mbedtls_ecdh_context *ctx, size_t *olen,
                              unsigned char *buf, size_t blen,
-                             int (*f_rng)(void *, unsigned char *, size_t),
+                             mbedtls_f_rng_t *f_rng,
                              void *p_rng);
 
 /**
@@ -372,7 +372,7 @@ int mbedtls_ecdh_get_params(mbedtls_ecdh_context *ctx,
  */
 int mbedtls_ecdh_make_public(mbedtls_ecdh_context *ctx, size_t *olen,
                              unsigned char *buf, size_t blen,
-                             int (*f_rng)(void *, unsigned char *, size_t),
+                             mbedtls_f_rng_t *f_rng,
                              void *p_rng);
 
 /**
@@ -428,7 +428,7 @@ int mbedtls_ecdh_read_public(mbedtls_ecdh_context *ctx,
  */
 int mbedtls_ecdh_calc_secret(mbedtls_ecdh_context *ctx, size_t *olen,
                              unsigned char *buf, size_t blen,
-                             int (*f_rng)(void *, unsigned char *, size_t),
+                             mbedtls_f_rng_t *f_rng,
                              void *p_rng);
 
 #if defined(MBEDTLS_ECP_RESTARTABLE)
diff --git a/include/mbedtls/ecdsa.h b/include/mbedtls/ecdsa.h
index 2ecf349115..119ee26463 100644
--- a/include/mbedtls/ecdsa.h
+++ b/include/mbedtls/ecdsa.h
@@ -160,7 +160,7 @@ int mbedtls_ecdsa_can_do(mbedtls_ecp_group_id gid);
  */
 int mbedtls_ecdsa_sign(mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s,
                        const mbedtls_mpi *d, const unsigned char *buf, size_t blen,
-                       int (*f_rng)(void *, unsigned char *, size_t), void *p_rng);
+                       mbedtls_f_rng_t *f_rng, void *p_rng);
 
 #if defined(MBEDTLS_ECDSA_DETERMINISTIC)
 /**
@@ -271,7 +271,7 @@ int mbedtls_ecdsa_sign_restartable(
     mbedtls_mpi *r, mbedtls_mpi *s,
     const mbedtls_mpi *d,
     const unsigned char *buf, size_t blen,
-    int (*f_rng)(void *, unsigned char *, size_t),
+    mbedtls_f_rng_t *f_rng,
     void *p_rng,
     int (*f_rng_blind)(void *, unsigned char *, size_t),
     void *p_rng_blind,
@@ -473,7 +473,7 @@ int mbedtls_ecdsa_write_signature(mbedtls_ecdsa_context *ctx,
                                   mbedtls_md_type_t md_alg,
                                   const unsigned char *hash, size_t hlen,
                                   unsigned char *sig, size_t sig_size, size_t *slen,
-                                  int (*f_rng)(void *, unsigned char *, size_t),
+                                  mbedtls_f_rng_t *f_rng,
                                   void *p_rng);
 
 /**
@@ -520,7 +520,7 @@ int mbedtls_ecdsa_write_signature_restartable(mbedtls_ecdsa_context *ctx,
                                               mbedtls_md_type_t md_alg,
                                               const unsigned char *hash, size_t hlen,
                                               unsigned char *sig, size_t sig_size, size_t *slen,
-                                              int (*f_rng)(void *, unsigned char *, size_t),
+                                              mbedtls_f_rng_t *f_rng,
                                               void *p_rng,
                                               mbedtls_ecdsa_restart_ctx *rs_ctx);
 
@@ -608,7 +608,7 @@ int mbedtls_ecdsa_read_signature_restartable(mbedtls_ecdsa_context *ctx,
  * \return         An \c MBEDTLS_ERR_ECP_XXX code on failure.
  */
 int mbedtls_ecdsa_genkey(mbedtls_ecdsa_context *ctx, mbedtls_ecp_group_id gid,
-                         int (*f_rng)(void *, unsigned char *, size_t), void *p_rng);
+                         mbedtls_f_rng_t *f_rng, void *p_rng);
 
 /**
  * \brief           This function sets up an ECDSA context from an EC key pair.
diff --git a/include/mbedtls/ecjpake.h b/include/mbedtls/ecjpake.h
index c2148a2bd1..7da8cb4e5b 100644
--- a/include/mbedtls/ecjpake.h
+++ b/include/mbedtls/ecjpake.h
@@ -162,7 +162,7 @@ int mbedtls_ecjpake_check(const mbedtls_ecjpake_context *ctx);
  */
 int mbedtls_ecjpake_write_round_one(mbedtls_ecjpake_context *ctx,
                                     unsigned char *buf, size_t len, size_t *olen,
-                                    int (*f_rng)(void *, unsigned char *, size_t),
+                                    mbedtls_f_rng_t *f_rng,
                                     void *p_rng);
 
 /**
@@ -203,7 +203,7 @@ int mbedtls_ecjpake_read_round_one(mbedtls_ecjpake_context *ctx,
  */
 int mbedtls_ecjpake_write_round_two(mbedtls_ecjpake_context *ctx,
                                     unsigned char *buf, size_t len, size_t *olen,
-                                    int (*f_rng)(void *, unsigned char *, size_t),
+                                    mbedtls_f_rng_t *f_rng,
                                     void *p_rng);
 
 /**
@@ -243,7 +243,7 @@ int mbedtls_ecjpake_read_round_two(mbedtls_ecjpake_context *ctx,
  */
 int mbedtls_ecjpake_derive_secret(mbedtls_ecjpake_context *ctx,
                                   unsigned char *buf, size_t len, size_t *olen,
-                                  int (*f_rng)(void *, unsigned char *, size_t),
+                                  mbedtls_f_rng_t *f_rng,
                                   void *p_rng);
 
 /**
@@ -266,7 +266,7 @@ int mbedtls_ecjpake_derive_secret(mbedtls_ecjpake_context *ctx,
  */
 int mbedtls_ecjpake_write_shared_key(mbedtls_ecjpake_context *ctx,
                                      unsigned char *buf, size_t len, size_t *olen,
-                                     int (*f_rng)(void *, unsigned char *, size_t),
+                                     mbedtls_f_rng_t *f_rng,
                                      void *p_rng);
 
 /**
diff --git a/include/mbedtls/ecp.h b/include/mbedtls/ecp.h
index 623910bcbd..5cc0271432 100644
--- a/include/mbedtls/ecp.h
+++ b/include/mbedtls/ecp.h
@@ -966,7 +966,7 @@ int mbedtls_ecp_tls_write_group(const mbedtls_ecp_group *grp,
  */
 int mbedtls_ecp_mul(mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
                     const mbedtls_mpi *m, const mbedtls_ecp_point *P,
-                    int (*f_rng)(void *, unsigned char *, size_t), void *p_rng);
+                    mbedtls_f_rng_t *f_rng, void *p_rng);
 
 /**
  * \brief           This function performs multiplication of a point by
@@ -1000,7 +1000,7 @@ int mbedtls_ecp_mul(mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
  */
 int mbedtls_ecp_mul_restartable(mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
                                 const mbedtls_mpi *m, const mbedtls_ecp_point *P,
-                                int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,
+                                mbedtls_f_rng_t *f_rng, void *p_rng,
                                 mbedtls_ecp_restart_ctx *rs_ctx);
 
 #if defined(MBEDTLS_ECP_SHORT_WEIERSTRASS_ENABLED)
@@ -1179,7 +1179,7 @@ int mbedtls_ecp_check_privkey(const mbedtls_ecp_group *grp,
  */
 int mbedtls_ecp_gen_privkey(const mbedtls_ecp_group *grp,
                             mbedtls_mpi *d,
-                            int (*f_rng)(void *, unsigned char *, size_t),
+                            mbedtls_f_rng_t *f_rng,
                             void *p_rng);
 
 /**
@@ -1212,7 +1212,7 @@ int mbedtls_ecp_gen_privkey(const mbedtls_ecp_group *grp,
 int mbedtls_ecp_gen_keypair_base(mbedtls_ecp_group *grp,
                                  const mbedtls_ecp_point *G,
                                  mbedtls_mpi *d, mbedtls_ecp_point *Q,
-                                 int (*f_rng)(void *, unsigned char *, size_t),
+                                 mbedtls_f_rng_t *f_rng,
                                  void *p_rng);
 
 /**
@@ -1240,7 +1240,7 @@ int mbedtls_ecp_gen_keypair_base(mbedtls_ecp_group *grp,
  */
 int mbedtls_ecp_gen_keypair(mbedtls_ecp_group *grp, mbedtls_mpi *d,
                             mbedtls_ecp_point *Q,
-                            int (*f_rng)(void *, unsigned char *, size_t),
+                            mbedtls_f_rng_t *f_rng,
                             void *p_rng);
 
 /**
@@ -1257,7 +1257,7 @@ int mbedtls_ecp_gen_keypair(mbedtls_ecp_group *grp, mbedtls_mpi *d,
  *                  on failure.
  */
 int mbedtls_ecp_gen_key(mbedtls_ecp_group_id grp_id, mbedtls_ecp_keypair *key,
-                        int (*f_rng)(void *, unsigned char *, size_t),
+                        mbedtls_f_rng_t *f_rng,
                         void *p_rng);
 
 /** \brief          Set the public key in a key pair object.
@@ -1451,7 +1451,7 @@ int mbedtls_ecp_write_public_key(const mbedtls_ecp_keypair *key,
  */
 int mbedtls_ecp_check_pub_priv(
     const mbedtls_ecp_keypair *pub, const mbedtls_ecp_keypair *prv,
-    int (*f_rng)(void *, unsigned char *, size_t), void *p_rng);
+    mbedtls_f_rng_t *f_rng, void *p_rng);
 
 /** \brief          Calculate the public key from a private key in a key pair.
  *
@@ -1468,7 +1468,7 @@ int mbedtls_ecp_check_pub_priv(
  */
 int mbedtls_ecp_keypair_calc_public(
     mbedtls_ecp_keypair *key,
-    int (*f_rng)(void *, unsigned char *, size_t), void *p_rng);
+    mbedtls_f_rng_t *f_rng, void *p_rng);
 
 /** \brief          Query the group that a key pair belongs to.
  *
diff --git a/include/mbedtls/lms.h b/include/mbedtls/lms.h
index 95fce21337..2f297914be 100644
--- a/include/mbedtls/lms.h
+++ b/include/mbedtls/lms.h
@@ -364,7 +364,7 @@ void mbedtls_lms_private_free(mbedtls_lms_private_t *ctx);
 int mbedtls_lms_generate_private_key(mbedtls_lms_private_t *ctx,
                                      mbedtls_lms_algorithm_type_t type,
                                      mbedtls_lmots_algorithm_type_t otstype,
-                                     int (*f_rng)(void *, unsigned char *, size_t),
+                                     mbedtls_f_rng_t *f_rng,
                                      void *p_rng, const unsigned char *seed,
                                      size_t seed_size);
 
@@ -427,7 +427,7 @@ int mbedtls_lms_calculate_public_key(mbedtls_lms_public_t *ctx,
  * \return         A non-zero error code on failure.
  */
 int mbedtls_lms_sign(mbedtls_lms_private_t *ctx,
-                     int (*f_rng)(void *, unsigned char *, size_t),
+                     mbedtls_f_rng_t *f_rng,
                      void *p_rng, const unsigned char *msg,
                      unsigned int msg_size, unsigned char *sig, size_t sig_size,
                      size_t *sig_len);
diff --git a/include/mbedtls/pk.h b/include/mbedtls/pk.h
index 52f4cc6c9e..2b7f34bc0b 100644
--- a/include/mbedtls/pk.h
+++ b/include/mbedtls/pk.h
@@ -285,7 +285,7 @@ typedef int (*mbedtls_pk_rsa_alt_decrypt_func)(void *ctx, size_t *olen,
                                                const unsigned char *input, unsigned char *output,
                                                size_t output_max_len);
 typedef int (*mbedtls_pk_rsa_alt_sign_func)(void *ctx,
-                                            int (*f_rng)(void *, unsigned char *, size_t),
+                                            mbedtls_f_rng_t *f_rng,
                                             void *p_rng,
                                             mbedtls_md_type_t md_alg, unsigned int hashlen,
                                             const unsigned char *hash, unsigned char *sig);
@@ -849,7 +849,7 @@ int mbedtls_pk_verify_ext(mbedtls_pk_type_t type, const void *options,
 int mbedtls_pk_sign(mbedtls_pk_context *ctx, mbedtls_md_type_t md_alg,
                     const unsigned char *hash, size_t hash_len,
                     unsigned char *sig, size_t sig_size, size_t *sig_len,
-                    int (*f_rng)(void *, unsigned char *, size_t), void *p_rng);
+                    mbedtls_f_rng_t *f_rng, void *p_rng);
 
 /**
  * \brief           Make signature given a signature type.
@@ -885,7 +885,7 @@ int mbedtls_pk_sign_ext(mbedtls_pk_type_t pk_type,
                         mbedtls_md_type_t md_alg,
                         const unsigned char *hash, size_t hash_len,
                         unsigned char *sig, size_t sig_size, size_t *sig_len,
-                        int (*f_rng)(void *, unsigned char *, size_t),
+                        mbedtls_f_rng_t *f_rng,
                         void *p_rng);
 
 /**
@@ -921,7 +921,7 @@ int mbedtls_pk_sign_restartable(mbedtls_pk_context *ctx,
                                 mbedtls_md_type_t md_alg,
                                 const unsigned char *hash, size_t hash_len,
                                 unsigned char *sig, size_t sig_size, size_t *sig_len,
-                                int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,
+                                mbedtls_f_rng_t *f_rng, void *p_rng,
                                 mbedtls_pk_restart_ctx *rs_ctx);
 
 /**
@@ -947,7 +947,7 @@ int mbedtls_pk_sign_restartable(mbedtls_pk_context *ctx,
 int mbedtls_pk_decrypt(mbedtls_pk_context *ctx,
                        const unsigned char *input, size_t ilen,
                        unsigned char *output, size_t *olen, size_t osize,
-                       int (*f_rng)(void *, unsigned char *, size_t), void *p_rng);
+                       mbedtls_f_rng_t *f_rng, void *p_rng);
 
 /**
  * \brief           Encrypt message (including padding if relevant).
@@ -973,7 +973,7 @@ int mbedtls_pk_decrypt(mbedtls_pk_context *ctx,
 int mbedtls_pk_encrypt(mbedtls_pk_context *ctx,
                        const unsigned char *input, size_t ilen,
                        unsigned char *output, size_t *olen, size_t osize,
-                       int (*f_rng)(void *, unsigned char *, size_t), void *p_rng);
+                       mbedtls_f_rng_t *f_rng, void *p_rng);
 
 /**
  * \brief           Check if a public-private pair of keys matches.
@@ -991,7 +991,7 @@ int mbedtls_pk_encrypt(mbedtls_pk_context *ctx,
  */
 int mbedtls_pk_check_pair(const mbedtls_pk_context *pub,
                           const mbedtls_pk_context *prv,
-                          int (*f_rng)(void *, unsigned char *, size_t),
+                          mbedtls_f_rng_t *f_rng,
                           void *p_rng);
 
 /**
@@ -1109,7 +1109,7 @@ static inline mbedtls_ecp_keypair *mbedtls_pk_ec(const mbedtls_pk_context pk)
 int mbedtls_pk_parse_key(mbedtls_pk_context *ctx,
                          const unsigned char *key, size_t keylen,
                          const unsigned char *pwd, size_t pwdlen,
-                         int (*f_rng)(void *, unsigned char *, size_t), void *p_rng);
+                         mbedtls_f_rng_t *f_rng, void *p_rng);
 
 /** \ingroup pk_module */
 /**
@@ -1173,7 +1173,7 @@ int mbedtls_pk_parse_public_key(mbedtls_pk_context *ctx,
  */
 int mbedtls_pk_parse_keyfile(mbedtls_pk_context *ctx,
                              const char *path, const char *password,
-                             int (*f_rng)(void *, unsigned char *, size_t), void *p_rng);
+                             mbedtls_f_rng_t *f_rng, void *p_rng);
 
 /** \ingroup pk_module */
 /**
diff --git a/include/mbedtls/rsa.h b/include/mbedtls/rsa.h
index c1e76b3927..3f0881a434 100644
--- a/include/mbedtls/rsa.h
+++ b/include/mbedtls/rsa.h
@@ -465,7 +465,7 @@ size_t mbedtls_rsa_get_len(const mbedtls_rsa_context *ctx);
  * \return         An \c MBEDTLS_ERR_RSA_XXX error code on failure.
  */
 int mbedtls_rsa_gen_key(mbedtls_rsa_context *ctx,
-                        int (*f_rng)(void *, unsigned char *, size_t),
+                        mbedtls_f_rng_t *f_rng,
                         void *p_rng,
                         unsigned int nbits, int exponent);
 
@@ -590,7 +590,7 @@ int mbedtls_rsa_public(mbedtls_rsa_context *ctx,
  *
  */
 int mbedtls_rsa_private(mbedtls_rsa_context *ctx,
-                        int (*f_rng)(void *, unsigned char *, size_t),
+                        mbedtls_f_rng_t *f_rng,
                         void *p_rng,
                         const unsigned char *input,
                         unsigned char *output);
@@ -619,7 +619,7 @@ int mbedtls_rsa_private(mbedtls_rsa_context *ctx,
  * \return         An \c MBEDTLS_ERR_RSA_XXX error code on failure.
  */
 int mbedtls_rsa_pkcs1_encrypt(mbedtls_rsa_context *ctx,
-                              int (*f_rng)(void *, unsigned char *, size_t),
+                              mbedtls_f_rng_t *f_rng,
                               void *p_rng,
                               size_t ilen,
                               const unsigned char *input,
@@ -646,7 +646,7 @@ int mbedtls_rsa_pkcs1_encrypt(mbedtls_rsa_context *ctx,
  * \return         An \c MBEDTLS_ERR_RSA_XXX error code on failure.
  */
 int mbedtls_rsa_rsaes_pkcs1_v15_encrypt(mbedtls_rsa_context *ctx,
-                                        int (*f_rng)(void *, unsigned char *, size_t),
+                                        mbedtls_f_rng_t *f_rng,
                                         void *p_rng,
                                         size_t ilen,
                                         const unsigned char *input,
@@ -680,7 +680,7 @@ int mbedtls_rsa_rsaes_pkcs1_v15_encrypt(mbedtls_rsa_context *ctx,
  * \return           An \c MBEDTLS_ERR_RSA_XXX error code on failure.
  */
 int mbedtls_rsa_rsaes_oaep_encrypt(mbedtls_rsa_context *ctx,
-                                   int (*f_rng)(void *, unsigned char *, size_t),
+                                   mbedtls_f_rng_t *f_rng,
                                    void *p_rng,
                                    const unsigned char *label, size_t label_len,
                                    size_t ilen,
@@ -723,7 +723,7 @@ int mbedtls_rsa_rsaes_oaep_encrypt(mbedtls_rsa_context *ctx,
  * \return         An \c MBEDTLS_ERR_RSA_XXX error code on failure.
  */
 int mbedtls_rsa_pkcs1_decrypt(mbedtls_rsa_context *ctx,
-                              int (*f_rng)(void *, unsigned char *, size_t),
+                              mbedtls_f_rng_t *f_rng,
                               void *p_rng,
                               size_t *olen,
                               const unsigned char *input,
@@ -765,7 +765,7 @@ int mbedtls_rsa_pkcs1_decrypt(mbedtls_rsa_context *ctx,
  *
  */
 int mbedtls_rsa_rsaes_pkcs1_v15_decrypt(mbedtls_rsa_context *ctx,
-                                        int (*f_rng)(void *, unsigned char *, size_t),
+                                        mbedtls_f_rng_t *f_rng,
                                         void *p_rng,
                                         size_t *olen,
                                         const unsigned char *input,
@@ -806,7 +806,7 @@ int mbedtls_rsa_rsaes_pkcs1_v15_decrypt(mbedtls_rsa_context *ctx,
  * \return         An \c MBEDTLS_ERR_RSA_XXX error code on failure.
  */
 int mbedtls_rsa_rsaes_oaep_decrypt(mbedtls_rsa_context *ctx,
-                                   int (*f_rng)(void *, unsigned char *, size_t),
+                                   mbedtls_f_rng_t *f_rng,
                                    void *p_rng,
                                    const unsigned char *label, size_t label_len,
                                    size_t *olen,
@@ -849,7 +849,7 @@ int mbedtls_rsa_rsaes_oaep_decrypt(mbedtls_rsa_context *ctx,
  * \return         An \c MBEDTLS_ERR_RSA_XXX error code on failure.
  */
 int mbedtls_rsa_pkcs1_sign(mbedtls_rsa_context *ctx,
-                           int (*f_rng)(void *, unsigned char *, size_t),
+                           mbedtls_f_rng_t *f_rng,
                            void *p_rng,
                            mbedtls_md_type_t md_alg,
                            unsigned int hashlen,
@@ -881,7 +881,7 @@ int mbedtls_rsa_pkcs1_sign(mbedtls_rsa_context *ctx,
  * \return         An \c MBEDTLS_ERR_RSA_XXX error code on failure.
  */
 int mbedtls_rsa_rsassa_pkcs1_v15_sign(mbedtls_rsa_context *ctx,
-                                      int (*f_rng)(void *, unsigned char *, size_t),
+                                      mbedtls_f_rng_t *f_rng,
                                       void *p_rng,
                                       mbedtls_md_type_t md_alg,
                                       unsigned int hashlen,
@@ -933,7 +933,7 @@ int mbedtls_rsa_rsassa_pkcs1_v15_sign(mbedtls_rsa_context *ctx,
  * \return         An \c MBEDTLS_ERR_RSA_XXX error code on failure.
  */
 int mbedtls_rsa_rsassa_pss_sign_ext(mbedtls_rsa_context *ctx,
-                                    int (*f_rng)(void *, unsigned char *, size_t),
+                                    mbedtls_f_rng_t *f_rng,
                                     void *p_rng,
                                     mbedtls_md_type_t md_alg,
                                     unsigned int hashlen,
@@ -983,7 +983,7 @@ int mbedtls_rsa_rsassa_pss_sign_ext(mbedtls_rsa_context *ctx,
  * \return         An \c MBEDTLS_ERR_RSA_XXX error code on failure.
  */
 int mbedtls_rsa_rsassa_pss_sign(mbedtls_rsa_context *ctx,
-                                int (*f_rng)(void *, unsigned char *, size_t),
+                                mbedtls_f_rng_t *f_rng,
                                 void *p_rng,
                                 mbedtls_md_type_t md_alg,
                                 unsigned int hashlen,
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index cc9da3417d..960200f4b3 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -2260,7 +2260,7 @@ void mbedtls_ssl_conf_verify(mbedtls_ssl_config *conf,
  * \param p_rng    RNG parameter
  */
 void mbedtls_ssl_conf_rng(mbedtls_ssl_config *conf,
-                          int (*f_rng)(void *, unsigned char *, size_t),
+                          mbedtls_f_rng_t *f_rng,
                           void *p_rng);
 
 /**
diff --git a/include/mbedtls/ssl_cookie.h b/include/mbedtls/ssl_cookie.h
index 71c258ea48..0f211e632a 100644
--- a/include/mbedtls/ssl_cookie.h
+++ b/include/mbedtls/ssl_cookie.h
@@ -70,7 +70,7 @@ void mbedtls_ssl_cookie_init(mbedtls_ssl_cookie_ctx *ctx);
  * \brief          Setup cookie context (generate keys)
  */
 int mbedtls_ssl_cookie_setup(mbedtls_ssl_cookie_ctx *ctx,
-                             int (*f_rng)(void *, unsigned char *, size_t),
+                             mbedtls_f_rng_t *f_rng,
                              void *p_rng);
 
 /**
diff --git a/include/mbedtls/ssl_ticket.h b/include/mbedtls/ssl_ticket.h
index 2ee1400210..bf3bc7648d 100644
--- a/include/mbedtls/ssl_ticket.h
+++ b/include/mbedtls/ssl_ticket.h
@@ -122,7 +122,7 @@ void mbedtls_ssl_ticket_init(mbedtls_ssl_ticket_context *ctx);
  *                  or a specific MBEDTLS_ERR_XXX error code
  */
 int mbedtls_ssl_ticket_setup(mbedtls_ssl_ticket_context *ctx,
-                             int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,
+                             mbedtls_f_rng_t *f_rng, void *p_rng,
                              mbedtls_cipher_type_t cipher,
                              uint32_t lifetime);
 
diff --git a/include/mbedtls/x509_crt.h b/include/mbedtls/x509_crt.h
index 1ce0d23619..6b96039597 100644
--- a/include/mbedtls/x509_crt.h
+++ b/include/mbedtls/x509_crt.h
@@ -1176,7 +1176,7 @@ void mbedtls_x509write_crt_free(mbedtls_x509write_cert *ctx);
  * \note            \p f_rng is used for the signature operation.
  */
 int mbedtls_x509write_crt_der(mbedtls_x509write_cert *ctx, unsigned char *buf, size_t size,
-                              int (*f_rng)(void *, unsigned char *, size_t),
+                              mbedtls_f_rng_t *f_rng,
                               void *p_rng);
 
 #if defined(MBEDTLS_PEM_WRITE_C)
@@ -1194,7 +1194,7 @@ int mbedtls_x509write_crt_der(mbedtls_x509write_cert *ctx, unsigned char *buf, s
  * \note            \p f_rng is used for the signature operation.
  */
 int mbedtls_x509write_crt_pem(mbedtls_x509write_cert *ctx, unsigned char *buf, size_t size,
-                              int (*f_rng)(void *, unsigned char *, size_t),
+                              mbedtls_f_rng_t *f_rng,
                               void *p_rng);
 #endif /* MBEDTLS_PEM_WRITE_C */
 #endif /* MBEDTLS_X509_CRT_WRITE_C */
diff --git a/include/mbedtls/x509_csr.h b/include/mbedtls/x509_csr.h
index 8c31c09af4..c4bd7f1220 100644
--- a/include/mbedtls/x509_csr.h
+++ b/include/mbedtls/x509_csr.h
@@ -349,7 +349,7 @@ void mbedtls_x509write_csr_free(mbedtls_x509write_csr *ctx);
  * \note            \p f_rng is used for the signature operation.
  */
 int mbedtls_x509write_csr_der(mbedtls_x509write_csr *ctx, unsigned char *buf, size_t size,
-                              int (*f_rng)(void *, unsigned char *, size_t),
+                              mbedtls_f_rng_t *f_rng,
                               void *p_rng);
 
 #if defined(MBEDTLS_PEM_WRITE_C)
@@ -368,7 +368,7 @@ int mbedtls_x509write_csr_der(mbedtls_x509write_csr *ctx, unsigned char *buf, si
  * \note            \p f_rng is used for the signature operation.
  */
 int mbedtls_x509write_csr_pem(mbedtls_x509write_csr *ctx, unsigned char *buf, size_t size,
-                              int (*f_rng)(void *, unsigned char *, size_t),
+                              mbedtls_f_rng_t *f_rng,
                               void *p_rng);
 #endif /* MBEDTLS_PEM_WRITE_C */
 #endif /* MBEDTLS_X509_CSR_WRITE_C */