diff --git a/programs/ssl/ssl_client2.c b/programs/ssl/ssl_client2.c
index 515a42d..8f7586c 100644
--- a/programs/ssl/ssl_client2.c
+++ b/programs/ssl/ssl_client2.c
@@ -131,6 +131,7 @@
 #define DFL_ETM                 -1
 #define DFL_CA_CALLBACK         0
 #define DFL_EAP_TLS             0
+#define DFL_REPRODUCIBLE        0
 
 #define GET_REQUEST "GET %s HTTP/1.0\r\nExtra-header: "
 #define GET_REQUEST_END "\r\n\r\n"
@@ -313,6 +314,9 @@
 #define USAGE_ETM ""
 #endif
 
+#define USAGE_REPRODUCIBLE \
+    "    reproducible=0/1     default: 0 (disabled)\n"
+
 #if defined(MBEDTLS_SSL_RENEGOTIATION)
 #define USAGE_RENEGO \
     "    renegotiation=%%d    default: 0 (disabled)\n"      \
@@ -384,6 +388,7 @@
     USAGE_FALLBACK                                          \
     USAGE_EMS                                               \
     USAGE_ETM                                               \
+    USAGE_REPRODUCIBLE                                      \
     USAGE_CURVES                                            \
     USAGE_RECSPLIT                                          \
     USAGE_DHMLEN                                            \
@@ -484,6 +489,7 @@
     const char *cid_val;        /* the CID to use for incoming messages     */
     const char *cid_val_renego; /* the CID to use for incoming messages
                                  * after renegotiation                      */
+    int reproducible;           /* make communication reproducible          */
 } opt;
 
 int query_config( const char *config );
@@ -540,6 +546,28 @@
     fflush(  (FILE *) ctx  );
 }
 
+
+mbedtls_time_t dummy_constant_time( mbedtls_time_t* time )
+{
+    (void) time;
+    return 0x5af2a056;
+}
+
+int dummy_entropy( void *data, unsigned char *output, size_t len )
+{
+    size_t i;
+    int ret;
+    (void) data;
+
+    ret = mbedtls_entropy_func( data, output, len );
+    for ( i = 0; i < len; i++ )
+    {
+        //replace result with pseudo random
+        output[i] = (unsigned char) rand();
+    }
+    return( ret );
+}
+
 #if defined(MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK)
 int ca_callback( void *data, mbedtls_x509_crt const *child,
                  mbedtls_x509_crt **candidates )
@@ -1027,6 +1055,7 @@
     opt.etm                 = DFL_ETM;
     opt.dgram_packing       = DFL_DGRAM_PACKING;
     opt.eap_tls             = DFL_EAP_TLS;
+    opt.reproducible        = DFL_REPRODUCIBLE;
 
     for( i = 1; i < argc; i++ )
     {
@@ -1413,6 +1442,10 @@
             if( opt.eap_tls < 0 || opt.eap_tls > 1 )
                 goto usage;
         }
+        else if( strcmp( p, "reproducible" ) == 0 )
+        {
+            opt.reproducible = 1;
+        }
         else
             goto usage;
     }
@@ -1665,13 +1698,28 @@
     fflush( stdout );
 
     mbedtls_entropy_init( &entropy );
-    if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func,
-                                       &entropy, (const unsigned char *) pers,
-                                       strlen( pers ) ) ) != 0 )
+    if (opt.reproducible)
     {
-        mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned -0x%x\n",
-                        -ret );
-        goto exit;
+        srand( 1 );
+        if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, dummy_entropy,
+                                           &entropy, (const unsigned char *) pers,
+                                           strlen( pers ) ) ) != 0 )
+        {
+            mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned -0x%x\n",
+                            -ret );
+            goto exit;
+        }
+    }
+    else
+    {
+        if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func,
+                                           &entropy, (const unsigned char *) pers,
+                                           strlen( pers ) ) ) != 0 )
+        {
+            mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned -0x%x\n",
+                            -ret );
+            goto exit;
+        }
     }
 
     mbedtls_printf( " ok\n" );
@@ -1964,6 +2012,16 @@
         }
 #endif
 
+    if (opt.reproducible)
+    {
+#if defined(MBEDTLS_HAVE_TIME)
+#if defined(MBEDTLS_PLATFORM_TIME_ALT)
+        mbedtls_platform_set_time( dummy_constant_time );
+#else
+        fprintf( stderr, "Warning: reproducible option used without constant time\n" );
+#endif
+#endif
+    }
     mbedtls_ssl_conf_rng( &conf, mbedtls_ctr_drbg_random, &ctr_drbg );
     mbedtls_ssl_conf_dbg( &conf, my_debug, stdout );
 
diff --git a/programs/ssl/ssl_server2.c b/programs/ssl/ssl_server2.c
index 3c75c65..c671fde 100644
--- a/programs/ssl/ssl_server2.c
+++ b/programs/ssl/ssl_server2.c
@@ -173,6 +173,7 @@
 #define DFL_ETM                 -1
 #define DFL_CA_CALLBACK         0
 #define DFL_EAP_TLS             0
+#define DFL_REPRODUCIBLE        0
 
 #define LONG_RESPONSE "<p>01-blah-blah-blah-blah-blah-blah-blah-blah-blah\r\n" \
     "02-blah-blah-blah-blah-blah-blah-blah-blah-blah-blah-blah-blah-blah\r\n"  \
@@ -403,6 +404,9 @@
 #define USAGE_ETM ""
 #endif
 
+#define USAGE_REPRODUCIBLE \
+    "    reproducible=0/1     default: 0 (disabled)\n"
+
 #if defined(MBEDTLS_SSL_RENEGOTIATION)
 #define USAGE_RENEGO \
     "    renegotiation=%%d    default: 0 (disabled)\n"      \
@@ -471,6 +475,7 @@
     "\n"                                                    \
     USAGE_TICKETS                                           \
     USAGE_EAP_TLS                                           \
+    USAGE_REPRODUCIBLE                                      \
     USAGE_CACHE                                             \
     USAGE_MAX_FRAG_LEN                                      \
     USAGE_TRUNC_HMAC                                        \
@@ -599,6 +604,7 @@
     const char *cid_val;        /* the CID to use for incoming messages     */
     const char *cid_val_renego; /* the CID to use for incoming messages
                                  * after renegotiation                      */
+    int reproducible;           /* make communication reproducible          */
 } opt;
 
 int query_config( const char *config );
@@ -654,6 +660,26 @@
     fflush(  (FILE *) ctx  );
 }
 
+mbedtls_time_t dummy_constant_time( mbedtls_time_t* time )
+{
+    (void) time;
+    return 0x5af2a056;
+}
+
+int dummy_entropy( void *data, unsigned char *output, size_t len )
+{
+    size_t i;
+    int ret;
+    (void) data;
+
+    ret = mbedtls_entropy_func( data, output, len );
+    for (i = 0; i < len; i++ ) {
+        //replace result with pseudo random
+        output[i] = (unsigned char) rand();
+    }
+    return( ret );
+}
+
 #if defined(MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK)
 int ca_callback( void *data, mbedtls_x509_crt const *child,
                  mbedtls_x509_crt **candidates)
@@ -1730,6 +1756,7 @@
     opt.extended_ms         = DFL_EXTENDED_MS;
     opt.etm                 = DFL_ETM;
     opt.eap_tls             = DFL_EAP_TLS;
+    opt.reproducible        = DFL_REPRODUCIBLE;
 
     for( i = 1; i < argc; i++ )
     {
@@ -2148,6 +2175,10 @@
             if( opt.eap_tls < 0 || opt.eap_tls > 1 )
                 goto usage;
         }
+        else if( strcmp( p, "reproducible" ) == 0 )
+        {
+            opt.reproducible = 1;
+        }
         else
             goto usage;
     }
@@ -2448,13 +2479,28 @@
     fflush( stdout );
 
     mbedtls_entropy_init( &entropy );
-    if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func,
-                                       &entropy, (const unsigned char *) pers,
-                                       strlen( pers ) ) ) != 0 )
+    if (opt.reproducible)
     {
-        mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned -0x%x\n",
-                        -ret );
-        goto exit;
+        srand( 1 );
+        if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, dummy_entropy,
+                                           &entropy, (const unsigned char *) pers,
+                                           strlen( pers ) ) ) != 0 )
+        {
+            mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned -0x%x\n",
+                            -ret );
+            goto exit;
+        }
+    }
+    else
+    {
+        if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func,
+                                           &entropy, (const unsigned char *) pers,
+                                           strlen( pers ) ) ) != 0 )
+        {
+            mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned -0x%x\n",
+                            -ret );
+            goto exit;
+        }
     }
 
     mbedtls_printf( " ok\n" );
@@ -2786,6 +2832,16 @@
         }
 #endif
 
+    if (opt.reproducible)
+    {
+#if defined(MBEDTLS_HAVE_TIME)
+#if defined(MBEDTLS_PLATFORM_TIME_ALT)
+        mbedtls_platform_set_time( dummy_constant_time );
+#else
+        fprintf( stderr, "Warning: reproducible option used without constant time\n" );
+#endif
+#endif
+    }
     mbedtls_ssl_conf_rng( &conf, mbedtls_ctr_drbg_random, &ctr_drbg );
     mbedtls_ssl_conf_dbg( &conf, my_debug, stdout );