diff --git a/programs/x509/cert_write.c b/programs/x509/cert_write.c
index 5c7dd86..c671888 100644
--- a/programs/x509/cert_write.c
+++ b/programs/x509/cert_write.c
@@ -26,6 +26,15 @@
 #include POLARSSL_CONFIG_FILE
 #endif
 
+#if defined(POLARSSL_PLATFORM_C)
+#include "polarssl/platform.h"
+#else
+#define polarssl_printf     printf
+#define polarssl_fprintf    fprintf
+#define polarssl_malloc     malloc
+#define polarssl_free       free
+#endif
+
 #include <string.h>
 #include <stdlib.h>
 #include <stdio.h>
@@ -39,7 +48,7 @@
     ((void) argc);
     ((void) argv);
 
-    printf( "POLARSSL_X509_CRT_WRITE_C and/or POLARSSL_X509_CRT_PARSE_C and/or "
+    polarssl_printf( "POLARSSL_X509_CRT_WRITE_C and/or POLARSSL_X509_CRT_PARSE_C and/or "
             "POLARSSL_FS_IO and/or "
             "POLARSSL_ENTROPY_C and/or POLARSSL_CTR_DRBG_C and/or "
             "POLARSSL_ERROR_C not defined.\n");
@@ -216,7 +225,7 @@
     if( argc == 0 )
     {
     usage:
-        printf( USAGE );
+        polarssl_printf( USAGE );
         ret = 1;
         goto exit;
     }
@@ -358,12 +367,12 @@
             goto usage;
     }
 
-    printf("\n");
+    polarssl_printf("\n");
 
     /*
      * 0. Seed the PRNG
      */
-    printf( "  . Seeding the random number generator..." );
+    polarssl_printf( "  . Seeding the random number generator..." );
     fflush( stdout );
 
     entropy_init( &entropy );
@@ -372,25 +381,25 @@
                                strlen( pers ) ) ) != 0 )
     {
         polarssl_strerror( ret, buf, 1024 );
-        printf( " failed\n  !  ctr_drbg_init returned %d - %s\n", ret, buf );
+        polarssl_printf( " failed\n  !  ctr_drbg_init returned %d - %s\n", ret, buf );
         goto exit;
     }
 
-    printf( " ok\n" );
+    polarssl_printf( " ok\n" );
 
     // Parse serial to MPI
     //
-    printf( "  . Reading serial number..." );
+    polarssl_printf( "  . Reading serial number..." );
     fflush( stdout );
 
     if( ( ret = mpi_read_string( &serial, 10, opt.serial ) ) != 0 )
     {
         polarssl_strerror( ret, buf, 1024 );
-        printf( " failed\n  !  mpi_read_string returned -0x%02x - %s\n\n", -ret, buf );
+        polarssl_printf( " failed\n  !  mpi_read_string returned -0x%02x - %s\n\n", -ret, buf );
         goto exit;
     }
 
-    printf( " ok\n" );
+    polarssl_printf( " ok\n" );
 
     // Parse issuer certificate if present
     //
@@ -399,13 +408,13 @@
         /*
          * 1.0.a. Load the certificates
          */
-        printf( "  . Loading the issuer certificate ..." );
+        polarssl_printf( "  . Loading the issuer certificate ..." );
         fflush( stdout );
 
         if( ( ret = x509_crt_parse_file( &issuer_crt, opt.issuer_crt ) ) != 0 )
         {
             polarssl_strerror( ret, buf, 1024 );
-            printf( " failed\n  !  x509_crt_parse_file returned -0x%02x - %s\n\n", -ret, buf );
+            polarssl_printf( " failed\n  !  x509_crt_parse_file returned -0x%02x - %s\n\n", -ret, buf );
             goto exit;
         }
 
@@ -414,13 +423,13 @@
         if( ret < 0 )
         {
             polarssl_strerror( ret, buf, 1024 );
-            printf( " failed\n  !  x509_dn_gets returned -0x%02x - %s\n\n", -ret, buf );
+            polarssl_printf( " failed\n  !  x509_dn_gets returned -0x%02x - %s\n\n", -ret, buf );
             goto exit;
         }
 
         opt.issuer_name = issuer_name;
 
-        printf( " ok\n" );
+        polarssl_printf( " ok\n" );
     }
 
 #if defined(POLARSSL_X509_CSR_PARSE_C)
@@ -431,13 +440,13 @@
         /*
          * 1.0.b. Load the CSR
          */
-        printf( "  . Loading the certificate request ..." );
+        polarssl_printf( "  . Loading the certificate request ..." );
         fflush( stdout );
 
         if( ( ret = x509_csr_parse_file( &csr, opt.request_file ) ) != 0 )
         {
             polarssl_strerror( ret, buf, 1024 );
-            printf( " failed\n  !  x509_csr_parse_file returned -0x%02x - %s\n\n", -ret, buf );
+            polarssl_printf( " failed\n  !  x509_csr_parse_file returned -0x%02x - %s\n\n", -ret, buf );
             goto exit;
         }
 
@@ -446,14 +455,14 @@
         if( ret < 0 )
         {
             polarssl_strerror( ret, buf, 1024 );
-            printf( " failed\n  !  x509_dn_gets returned -0x%02x - %s\n\n", -ret, buf );
+            polarssl_printf( " failed\n  !  x509_dn_gets returned -0x%02x - %s\n\n", -ret, buf );
             goto exit;
         }
 
         opt.subject_name = subject_name;
         subject_key = &csr.pk;
 
-        printf( " ok\n" );
+        polarssl_printf( " ok\n" );
     }
 #endif /* POLARSSL_X509_CSR_PARSE_C */
 
@@ -462,7 +471,7 @@
      */
     if( !opt.selfsign && !strlen( opt.request_file ) )
     {
-        printf( "  . Loading the subject key ..." );
+        polarssl_printf( "  . Loading the subject key ..." );
         fflush( stdout );
 
         ret = pk_parse_keyfile( &loaded_subject_key, opt.subject_key,
@@ -470,14 +479,14 @@
         if( ret != 0 )
         {
             polarssl_strerror( ret, buf, 1024 );
-            printf( " failed\n  !  pk_parse_keyfile returned -0x%02x - %s\n\n", -ret, buf );
+            polarssl_printf( " failed\n  !  pk_parse_keyfile returned -0x%02x - %s\n\n", -ret, buf );
             goto exit;
         }
 
-        printf( " ok\n" );
+        polarssl_printf( " ok\n" );
     }
 
-    printf( "  . Loading the issuer key ..." );
+    polarssl_printf( "  . Loading the issuer key ..." );
     fflush( stdout );
 
     ret = pk_parse_keyfile( &loaded_issuer_key, opt.issuer_key,
@@ -485,7 +494,7 @@
     if( ret != 0 )
     {
         polarssl_strerror( ret, buf, 1024 );
-        printf( " failed\n  !  pk_parse_keyfile returned -x%02x - %s\n\n", -ret, buf );
+        polarssl_printf( " failed\n  !  pk_parse_keyfile returned -x%02x - %s\n\n", -ret, buf );
         goto exit;
     }
 
@@ -499,13 +508,13 @@
             mpi_cmp_mpi( &pk_rsa( issuer_crt.pk )->E,
                          &pk_rsa( *issuer_key )->E ) != 0 )
         {
-            printf( " failed\n  !  issuer_key does not match issuer certificate\n\n" );
+            polarssl_printf( " failed\n  !  issuer_key does not match issuer certificate\n\n" );
             ret = -1;
             goto exit;
         }
     }
 
-    printf( " ok\n" );
+    polarssl_printf( " ok\n" );
 
     if( opt.selfsign )
     {
@@ -522,25 +531,25 @@
     if( ( ret = x509write_crt_set_subject_name( &crt, opt.subject_name ) ) != 0 )
     {
         polarssl_strerror( ret, buf, 1024 );
-        printf( " failed\n  !  x509write_crt_set_subject_name returned -0x%02x - %s\n\n", -ret, buf );
+        polarssl_printf( " failed\n  !  x509write_crt_set_subject_name returned -0x%02x - %s\n\n", -ret, buf );
         goto exit;
     }
 
     if( ( ret = x509write_crt_set_issuer_name( &crt, opt.issuer_name ) ) != 0 )
     {
         polarssl_strerror( ret, buf, 1024 );
-        printf( " failed\n  !  x509write_crt_set_issuer_name returned -0x%02x - %s\n\n", -ret, buf );
+        polarssl_printf( " failed\n  !  x509write_crt_set_issuer_name returned -0x%02x - %s\n\n", -ret, buf );
         goto exit;
     }
 
-    printf( "  . Setting certificate values ..." );
+    polarssl_printf( "  . Setting certificate values ..." );
     fflush( stdout );
 
     ret = x509write_crt_set_serial( &crt, &serial );
     if( ret != 0 )
     {
         polarssl_strerror( ret, buf, 1024 );
-        printf( " failed\n  !  x509write_crt_set_serial returned -0x%02x - %s\n\n", -ret, buf );
+        polarssl_printf( " failed\n  !  x509write_crt_set_serial returned -0x%02x - %s\n\n", -ret, buf );
         goto exit;
     }
 
@@ -548,13 +557,13 @@
     if( ret != 0 )
     {
         polarssl_strerror( ret, buf, 1024 );
-        printf( " failed\n  !  x509write_crt_set_validity returned -0x%02x - %s\n\n", -ret, buf );
+        polarssl_printf( " failed\n  !  x509write_crt_set_validity returned -0x%02x - %s\n\n", -ret, buf );
         goto exit;
     }
 
-    printf( " ok\n" );
+    polarssl_printf( " ok\n" );
 
-    printf( "  . Adding the Basic Constraints extension ..." );
+    polarssl_printf( "  . Adding the Basic Constraints extension ..." );
     fflush( stdout );
 
     ret = x509write_crt_set_basic_constraints( &crt, opt.is_ca,
@@ -562,87 +571,87 @@
     if( ret != 0 )
     {
         polarssl_strerror( ret, buf, 1024 );
-        printf( " failed\n  !  x509write_crt_set_basic_contraints returned -0x%02x - %s\n\n", -ret, buf );
+        polarssl_printf( " failed\n  !  x509write_crt_set_basic_contraints returned -0x%02x - %s\n\n", -ret, buf );
         goto exit;
     }
 
-    printf( " ok\n" );
+    polarssl_printf( " ok\n" );
 
 #if defined(POLARSSL_SHA1_C)
-    printf( "  . Adding the Subject Key Identifier ..." );
+    polarssl_printf( "  . Adding the Subject Key Identifier ..." );
     fflush( stdout );
 
     ret = x509write_crt_set_subject_key_identifier( &crt );
     if( ret != 0 )
     {
         polarssl_strerror( ret, buf, 1024 );
-        printf( " failed\n  !  x509write_crt_set_subject_key_identifier returned -0x%02x - %s\n\n", -ret, buf );
+        polarssl_printf( " failed\n  !  x509write_crt_set_subject_key_identifier returned -0x%02x - %s\n\n", -ret, buf );
         goto exit;
     }
 
-    printf( " ok\n" );
+    polarssl_printf( " ok\n" );
 
-    printf( "  . Adding the Authority Key Identifier ..." );
+    polarssl_printf( "  . Adding the Authority Key Identifier ..." );
     fflush( stdout );
 
     ret = x509write_crt_set_authority_key_identifier( &crt );
     if( ret != 0 )
     {
         polarssl_strerror( ret, buf, 1024 );
-        printf( " failed\n  !  x509write_crt_set_authority_key_identifier returned -0x%02x - %s\n\n", -ret, buf );
+        polarssl_printf( " failed\n  !  x509write_crt_set_authority_key_identifier returned -0x%02x - %s\n\n", -ret, buf );
         goto exit;
     }
 
-    printf( " ok\n" );
+    polarssl_printf( " ok\n" );
 #endif /* POLARSSL_SHA1_C */
 
     if( opt.key_usage )
     {
-        printf( "  . Adding the Key Usage extension ..." );
+        polarssl_printf( "  . Adding the Key Usage extension ..." );
         fflush( stdout );
 
         ret = x509write_crt_set_key_usage( &crt, opt.key_usage );
         if( ret != 0 )
         {
             polarssl_strerror( ret, buf, 1024 );
-            printf( " failed\n  !  x509write_crt_set_key_usage returned -0x%02x - %s\n\n", -ret, buf );
+            polarssl_printf( " failed\n  !  x509write_crt_set_key_usage returned -0x%02x - %s\n\n", -ret, buf );
             goto exit;
         }
 
-        printf( " ok\n" );
+        polarssl_printf( " ok\n" );
     }
 
     if( opt.ns_cert_type )
     {
-        printf( "  . Adding the NS Cert Type extension ..." );
+        polarssl_printf( "  . Adding the NS Cert Type extension ..." );
         fflush( stdout );
 
         ret = x509write_crt_set_ns_cert_type( &crt, opt.ns_cert_type );
         if( ret != 0 )
         {
             polarssl_strerror( ret, buf, 1024 );
-            printf( " failed\n  !  x509write_crt_set_ns_cert_type returned -0x%02x - %s\n\n", -ret, buf );
+            polarssl_printf( " failed\n  !  x509write_crt_set_ns_cert_type returned -0x%02x - %s\n\n", -ret, buf );
             goto exit;
         }
 
-        printf( " ok\n" );
+        polarssl_printf( " ok\n" );
     }
 
     /*
      * 1.2. Writing the request
      */
-    printf( "  . Writing the certificate..." );
+    polarssl_printf( "  . Writing the certificate..." );
     fflush( stdout );
 
     if( ( ret = write_certificate( &crt, opt.output_file,
                                    ctr_drbg_random, &ctr_drbg ) ) != 0 )
     {
         polarssl_strerror( ret, buf, 1024 );
-        printf( " failed\n  !  write_certifcate -0x%02x - %s\n\n", -ret, buf );
+        polarssl_printf( " failed\n  !  write_certifcate -0x%02x - %s\n\n", -ret, buf );
         goto exit;
     }
 
-    printf( " ok\n" );
+    polarssl_printf( " ok\n" );
 
 exit:
     x509write_crt_free( &crt );
@@ -653,7 +662,7 @@
     entropy_free( &entropy );
 
 #if defined(_WIN32)
-    printf( "  + Press Enter to exit this program.\n" );
+    polarssl_printf( "  + Press Enter to exit this program.\n" );
     fflush( stdout ); getchar();
 #endif