diff --git a/include/polarssl/bignum.h b/include/polarssl/bignum.h
index 1308557..12435f7 100644
--- a/include/polarssl/bignum.h
+++ b/include/polarssl/bignum.h
@@ -539,7 +539,9 @@
  * \return         0 if successful,
  *                 1 if memory allocation failed
  */
-int mpi_fill_random( mpi *X, size_t size, int (*f_rng)(void *), void *p_rng );
+int mpi_fill_random( mpi *X, size_t size,
+                     int (*f_rng)(void *, unsigned char *, size_t),
+                     void *p_rng );
 
 /**
  * \brief          Greatest common divisor: G = gcd(A, B)
@@ -578,7 +580,9 @@
  *                 1 if memory allocation failed,
  *                 POLARSSL_ERR_MPI_NOT_ACCEPTABLE if X is not prime
  */
-int mpi_is_prime( mpi *X, int (*f_rng)(void *), void *p_rng );
+int mpi_is_prime( mpi *X,
+                  int (*f_rng)(void *, unsigned char *, size_t),
+                  void *p_rng );
 
 /**
  * \brief          Prime number generation
@@ -594,7 +598,8 @@
  *                 POLARSSL_ERR_MPI_BAD_INPUT_DATA if nbits is < 3
  */
 int mpi_gen_prime( mpi *X, size_t nbits, int dh_flag,
-                   int (*f_rng)(void *), void *p_rng );
+                   int (*f_rng)(void *, unsigned char *, size_t),
+                   void *p_rng );
 
 /**
  * \brief          Checkup routine
diff --git a/include/polarssl/dhm.h b/include/polarssl/dhm.h
index 1cbfc6c..52b0bf9 100644
--- a/include/polarssl/dhm.h
+++ b/include/polarssl/dhm.h
@@ -90,7 +90,8 @@
  */
 int dhm_make_params( dhm_context *ctx, int x_size,
                      unsigned char *output, size_t *olen,
-                     int (*f_rng)(void *), void *p_rng );
+                     int (*f_rng)(void *, unsigned char *, size_t),
+                     void *p_rng );
 
 /**
  * \brief          Import the peer's public value G^Y
@@ -118,7 +119,8 @@
  */
 int dhm_make_public( dhm_context *ctx, int x_size,
                      unsigned char *output, size_t olen,
-                     int (*f_rng)(void *), void *p_rng );
+                     int (*f_rng)(void *, unsigned char *, size_t),
+                     void *p_rng );
 
 /**
  * \brief          Derive and export the shared secret (G^Y)^X mod P
diff --git a/include/polarssl/havege.h b/include/polarssl/havege.h
index 4be0e59..48d0f16 100644
--- a/include/polarssl/havege.h
+++ b/include/polarssl/havege.h
@@ -27,6 +27,8 @@
 #ifndef POLARSSL_HAVEGE_H
 #define POLARSSL_HAVEGE_H
 
+#include <string.h>
+
 #define COLLECT_SIZE 1024
 
 /**
@@ -55,10 +57,12 @@
  * \brief          HAVEGE rand function
  *
  * \param p_rng    A HAVEGE state
+ * \param output   Buffer to fill
+ * \param len      Length of buffer
  *
  * \return         A random int
  */
-int havege_rand( void *p_rng );
+int havege_random( void *p_rng, unsigned char *output, size_t len );
 
 #ifdef __cplusplus
 }
diff --git a/include/polarssl/rsa.h b/include/polarssl/rsa.h
index c9ecbcd..629aa0f 100644
--- a/include/polarssl/rsa.h
+++ b/include/polarssl/rsa.h
@@ -186,7 +186,7 @@
  * \return         0 if successful, or an POLARSSL_ERR_RSA_XXX error code
  */
 int rsa_gen_key( rsa_context *ctx,
-                 int (*f_rng)(void *),
+                 int (*f_rng)(void *, unsigned char *, size_t),
                  void *p_rng,
                  unsigned int nbits, int exponent );
 
@@ -261,7 +261,7 @@
  *                 of ctx->N (eg. 128 bytes if RSA-1024 is used).
  */
 int rsa_pkcs1_encrypt( rsa_context *ctx,
-                       int (*f_rng)(void *),
+                       int (*f_rng)(void *, unsigned char *, size_t),
                        void *p_rng,
                        int mode, size_t ilen,
                        const unsigned char *input,
@@ -314,7 +314,7 @@
  *                 keep both hashes the same.
  */
 int rsa_pkcs1_sign( rsa_context *ctx,
-                    int (*f_rng)(void *),
+                    int (*f_rng)(void *, unsigned char *, size_t),
                     void *p_rng,
                     int mode,
                     int hash_id,
diff --git a/include/polarssl/ssl.h b/include/polarssl/ssl.h
index 5e2cae3..02d75c7 100644
--- a/include/polarssl/ssl.h
+++ b/include/polarssl/ssl.h
@@ -232,7 +232,7 @@
     /*
      * Callbacks (RNG, debug, I/O, verification)
      */
-    int  (*f_rng)(void *);
+    int  (*f_rng)(void *, unsigned char *, size_t);
     void (*f_dbg)(void *, int, const char *);
     int (*f_recv)(void *, unsigned char *, size_t);
     int (*f_send)(void *, const unsigned char *, size_t);
@@ -438,7 +438,7 @@
  * \param p_rng    RNG parameter
  */
 void ssl_set_rng( ssl_context *ssl,
-                  int (*f_rng)(void *),
+                  int (*f_rng)(void *, unsigned char *, size_t),
                   void *p_rng );
 
 /**