diff --git a/programs/x509/cert_write.c b/programs/x509/cert_write.c
index 94e88d4..0266cda 100644
--- a/programs/x509/cert_write.c
+++ b/programs/x509/cert_write.c
@@ -58,7 +58,9 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#if defined(_WIN32)
 #include <Windows.h>
+#endif
 
 #if defined(MBEDTLS_X509_CSR_PARSE_C)
 #define USAGE_CSR                                                           \
@@ -92,19 +94,6 @@
 #define DFL_CONSTRAINTS         1
 #define DFL_DIGEST              MBEDTLS_MD_SHA256
 
-typedef struct
-{
-    const char *    serial_port;
-    unsigned char   key_idx;
-}remote_serial_pk_context;
-
-int is_remote_key( const char * remote_info );
-int load_pubkey_from_remote( const char * remote_info, mbedtls_pk_context * ctx );
-int setup_opaque_privkey( const char * remote_info, mbedtls_pk_context * ctx );
-void mbedtls_pk_remote_free( mbedtls_pk_context * ctx );
-int serial_xfer( const char * serial_port, const unsigned char * tx_buf,
-                 size_t tx_buf_len, unsigned char * rx_buf, size_t rx_buf_len,
-                 size_t * rx_len );
 #define UNUSED(x) ((void)(x))
 
 #define USAGE \
@@ -196,6 +185,447 @@
     unsigned char ns_cert_type; /* NS cert type                         */
 } opt;
 
+#if defined(_WIN32)
+/** Below are the constants used for remote Opaque key implementation.
+ */
+
+/* Remote cryptoprocessor sync pattern. Sent to sync with the device before
+ * sending commands. */
+#define REMOTE_KEY_MAGIC_PATTERN    "rEmOtEkEy" 
+#define REMOTE_KEY_CMD_TAG          "//opaque_pk/ATCA"
+#define REMOTE_KEY_ID_MIN           0
+#define REMOTE_KEY_ID_MAX           7
+#define REMOTE_KEY_SERIAL_BAUD      CBR_9600
+
+#define REMOTE_KEY_FUNC_GET_PUBKEY  0xA
+#define REMOTE_KEY_FUNC_SIGN        0xB
+
+int is_remote_key( const char *remote_info )
+{
+    size_t tag_len = strlen( REMOTE_KEY_CMD_TAG );
+    if ( strlen( remote_info ) > tag_len &&
+            strncmp( remote_info, REMOTE_KEY_CMD_TAG, tag_len ) == 0 )
+        return( 1 );
+    return( 0 );
+}
+
+int parse_remote_info( const char *remote_info, int *key_idx, const char **serial_port )
+{
+    int offset = 0;
+    int remote_info_len = strlen( remote_info );
+
+    if( is_remote_key( remote_info ) == 0 )
+        return( -1 );
+
+    offset = strlen( REMOTE_KEY_CMD_TAG );
+    offset++; // Skip the delimiter. FUTURE: Add validation.
+    if( offset >= remote_info_len )
+        return( -1 );
+    *key_idx = (int) remote_info[offset++];
+    offset++; // Skip the delimiter
+    if( offset >= remote_info_len )
+        return( -1 );
+    *key_idx = *key_idx - 48; // ascii to decimal
+
+    if ( *key_idx < REMOTE_KEY_ID_MIN || *key_idx > REMOTE_KEY_ID_MAX )
+    {
+        mbedtls_printf( " failed\n  !  Invalid remote key index %d\n\n", *key_idx );
+        return( -1 );
+    }
+    *serial_port = remote_info + offset;
+    printf( "Got key id %d and com port %s\n", *key_idx, *serial_port );
+    return( 0 );
+}
+
+/**
+  * @brief  Send a command to remote cryptoprocessor and receive response.
+  *
+  * It
+  *     - first sends a sync pattern 'rEmOtEkEy' and waits for an echo to sync
+  * with the remote.
+  *     - Then it sends the tx buf supplied by the caller.
+  *     - It waits for a 4 byte length indicator. Value 0 means error.
+  *     - Finally it reads no. of bytes specified in received Length indicator
+  *       and fills received data in rx_buf and returns.
+  *     Note: success is considered when a length indicator > 0 is received and
+  *     data size == length indicator is successfully received.
+  * 
+  *
+  * @param serial_port  Serial port to send & recv data.
+  * @param tx_buf       Command Tx buffer
+  * @param tx_buf_len   Tx buffer length
+  * @param rx_buf       Out response Rx buffer
+  * @param rx_buf_len   Rx buffer length
+  * @param rx_len       Received data length
+  *
+  * @retval 0 if success, or -1.
+  */
+int serial_xfer( const char * serial_port, const unsigned char * tx_buf,
+                 size_t tx_buf_len, unsigned char * rx_buf, size_t rx_buf_len,
+                 size_t * rx_len )
+{
+    char c, comm_name[20]; /* \\\\.\\COMxy = 11 characters at least */
+    HANDLE h_comm;
+    DCB dcb_config;
+    COMMTIMEOUTS comm_timeout;
+    DWORD xfer_len;
+    unsigned char len_buf[sizeof(size_t)];
+    int ret = -1;
+    size_t len = 0, sync_pattern_idx = 0;
+
+    do
+    {
+        sprintf( comm_name, "\\\\.\\%s", serial_port );
+
+        h_comm = CreateFile( comm_name, GENERIC_READ | GENERIC_WRITE, 0, 0,
+                OPEN_EXISTING, 0, 0 );
+        if ( h_comm == INVALID_HANDLE_VALUE )
+        {
+            mbedtls_printf( " failed\n  ! failed to open port %s %lu\n\n", serial_port, GetLastError() );
+            break;
+        }
+
+        if( GetCommState( h_comm, &dcb_config ) )
+        {
+            dcb_config.BaudRate = REMOTE_KEY_SERIAL_BAUD;
+            dcb_config.Parity = NOPARITY;
+            dcb_config.ByteSize = 8;
+            dcb_config.StopBits = ONESTOPBIT;
+            dcb_config.fOutxCtsFlow = FALSE;         // No CTS output flow control
+            dcb_config.fOutxDsrFlow = FALSE;         // No DSR output flow control
+            dcb_config.fDtrControl = DTR_CONTROL_DISABLE; // DTR flow control type
+            dcb_config.fDsrSensitivity = FALSE;      // DSR sensitivity
+            dcb_config.fTXContinueOnXoff = TRUE;     // XOFF continues Tx
+            dcb_config.fOutX = FALSE;                // No XON/XOFF out flow control
+            dcb_config.fInX = FALSE;                 // No XON/XOFF in flow control
+            dcb_config.fErrorChar = FALSE;           // Disable error replacement
+            dcb_config.fNull = FALSE;                // Disable null stripping
+            dcb_config.fRtsControl = RTS_CONTROL_DISABLE; // RTS flow control
+            dcb_config.fAbortOnError = FALSE;        // Do not abort reads/writes on error
+        }
+        else
+        {
+            mbedtls_printf( " failed\n  ! GetCommState returned error %lu\n\n", GetLastError() );
+            break;
+        }
+
+        if( !SetCommState( h_comm, &dcb_config ) )
+        {
+            mbedtls_printf( " failed\n  ! SetCommState returned error %lu\n\n", GetLastError() );
+            break;
+        }
+
+        if( GetCommTimeouts( h_comm, &comm_timeout ) )
+        {
+            comm_timeout.ReadIntervalTimeout = 1000;
+            comm_timeout.ReadTotalTimeoutMultiplier = 10;
+            comm_timeout.ReadTotalTimeoutConstant = 1000;
+            comm_timeout.WriteTotalTimeoutConstant = 1000;
+            comm_timeout.WriteTotalTimeoutMultiplier = 10;
+        }
+        else
+        {
+            mbedtls_printf( " failed\n  ! GetCommTimeouts returned error %lu\n\n", GetLastError() );
+            break;
+        }
+
+        if( !SetCommTimeouts( h_comm, &comm_timeout ) )
+        {
+            mbedtls_printf( " failed\n  ! SetCommTimeouts returned error %lu\n\n", GetLastError() );
+            break;
+        }
+
+
+        /* Flush data on serial before sending sync pattern */
+        while( ReadFile( h_comm, &c, sizeof(c), &xfer_len, NULL ) && xfer_len != 0 );
+        /* Sync with peer */
+        if( !WriteFile( h_comm, REMOTE_KEY_MAGIC_PATTERN, strlen(REMOTE_KEY_MAGIC_PATTERN), 
+                    &xfer_len, NULL ) )
+        {
+            mbedtls_printf( " failed\n  ! WriteFile returned error %lu\n\n", GetLastError() );
+            break;
+        }
+
+        while( sync_pattern_idx != strlen(REMOTE_KEY_MAGIC_PATTERN) )
+        {
+            if( !ReadFile( h_comm, &c, sizeof(c), &xfer_len, NULL ) )
+            {
+                mbedtls_printf( " failed\n  ! ReadFile returned error %lu\n\n", GetLastError() );
+                break;
+            }
+            if ( c == REMOTE_KEY_MAGIC_PATTERN[sync_pattern_idx] )
+                sync_pattern_idx++;
+            else
+                sync_pattern_idx = 0;
+        }
+
+        /* Exit if there was a read error */
+        if ( sync_pattern_idx != strlen(REMOTE_KEY_MAGIC_PATTERN) )
+        {
+            mbedtls_printf("Failedi to sync!\n");
+            break;
+        }
+
+        {
+            size_t i;
+            printf("Tx: ");
+            for (i = 0; i < tx_buf_len; i++)
+                printf ("0x%02x ", (tx_buf)[i]);
+            printf("\n");
+        }
+        if( !WriteFile( h_comm, tx_buf, tx_buf_len, 
+                    &xfer_len, NULL ) )
+        {
+            mbedtls_printf( " failed\n  ! WriteFile returned error %lu\n\n", GetLastError() );
+            break;
+        }
+
+        /* Read LI (length indicator) */
+        if( !ReadFile( h_comm, len_buf, sizeof(len_buf), &xfer_len, NULL ) ) /* Serial error */
+        {
+            mbedtls_printf( " failed\n  ! ReadFile returned error %lu\n\n", GetLastError() );
+            break;
+        }
+
+        *rx_len = ( len_buf[0] << 24 ) | ( len_buf[1] << 16 ) | ( len_buf[2] << 8 ) | len_buf[3];
+        if ( *rx_len == 0 ) /* LI == 0 indicates remote error */
+        {
+            mbedtls_printf( " failed\n  ! Received length indicator == 0\n\n" );
+            break;
+        }
+        if ( *rx_len > rx_buf_len ) /* Buffer too small */
+        {
+            mbedtls_printf( " failed\n  ! Buffer too small to hold received data\n\n" );
+            break;
+        }
+        /* Read payload */
+        len = 0;
+        while( len < *rx_len )
+        {
+            if( !ReadFile( h_comm, rx_buf + len, *rx_len - len, &xfer_len, NULL ) )
+            {
+                mbedtls_printf( " failed\n  ! ReadFile returned error %lu\n\n", GetLastError() );
+                break;
+            }
+            len += xfer_len;
+        }
+        if( len < *rx_len ) /* Serial error */
+        {
+            mbedtls_printf( " failed\n  ! ReadFile returned error %lu\n\n", GetLastError() );
+            break;
+        }
+        printf("Received LI 0x%02x 0x%02x 0x%02x 0x%02x \n", len_buf[0], len_buf[1], len_buf[2], len_buf[3]);
+        {
+            size_t i;
+            printf("Rx: ");
+            for (i = 0; i < *rx_len; i++)
+                printf ("0x%02x ", (rx_buf)[i]);
+            printf("\n");
+        }
+
+        ret = 0;
+    } while( 0 );
+
+    if( h_comm != INVALID_HANDLE_VALUE )
+    {
+        CloseHandle( h_comm );
+        h_comm = INVALID_HANDLE_VALUE;
+    }
+
+    return( ret );
+}
+
+/** Load a transparent public key context with public key from remote device
+ *  over serial.
+ *  This function sends:
+ *      rEmOtEkEy<char encoded function code=GetPubKey><char encoded private key ID>
+ *  Receives:
+ *      <4 bytes length indicator in network order><concatenated public key>
+ */
+int load_pubkey_from_remote( const char * remote_info, mbedtls_pk_context * ctx )
+{
+    int key_idx = 0, offset = 0, ret = 0;
+    const char * serial_port = NULL;
+    unsigned char func_buffer[10];
+    unsigned char pub_key_buf[100];
+    size_t rx_len = 0;
+    static mbedtls_ecp_keypair ecp_key;
+
+    if( parse_remote_info( remote_info, &key_idx, &serial_port ) != 0 )
+        return( -1 );
+
+    /* Prepare command */
+    offset = 0;
+    func_buffer[offset++] = REMOTE_KEY_FUNC_GET_PUBKEY;
+    func_buffer[offset++] = key_idx;
+
+    if( serial_xfer( serial_port, func_buffer, offset, pub_key_buf, sizeof( pub_key_buf ), &rx_len ) != 0 )
+    {
+        mbedtls_printf( " failed\n  !  Serial error trying to get pulic key\n\n" );
+        return( -1 );
+    }
+
+    /* Import public key from received binary */
+    mbedtls_ecp_keypair_init(&ecp_key);
+    ret = mbedtls_ecp_group_load(&ecp_key.grp, MBEDTLS_ECP_DP_SECP256R1);
+    if( ret != 0 )
+    {
+        mbedtls_printf( " failed\n  !  Failed to load ecp group\n\n" );
+        return( ret );
+    }
+    ret = mbedtls_ecp_point_read_binary(&ecp_key.grp, &ecp_key.Q, pub_key_buf, rx_len );
+    if( ret != 0 )
+    {
+        mbedtls_printf( " failed\n  !  Failed to read ecp key from binary\n\n" );
+        return( ret );
+    }
+    ctx->pk_info = mbedtls_pk_info_from_type( MBEDTLS_PK_ECKEY );
+    ctx->pk_ctx = &ecp_key;
+    return( 0 );
+}
+
+/**
+ * @brief           Tell if the context can do the operation given by type
+ *
+ * @param ctx       PK Context
+ * @param type      Target type
+ *
+ * @return          0 if context can't do the operations,
+ *                  1 otherwise.
+ */
+static int remote_can_do_func(const void *ctx, mbedtls_pk_type_t type)
+{
+    UNUSED(ctx);
+    /* At the moment only ECDSA is supported */
+    return (MBEDTLS_PK_ECDSA == type);
+}
+
+typedef struct
+{
+    const char     *serial_port;
+    unsigned char   key_idx;
+} remote_serial_pk_context;
+
+/**
+  * @brief  Sign using remote cryptoprocessor accessed over serial.
+  *
+  * @param ctx       ECDSA context
+  * @param md_alg    Hash Algorithm that was used to hash the message.
+  *                  Only SHA256 is supported.
+  * @param hash      Message hash
+  * @param hash_len  Length of hash
+  * @param sig       Buffer that will hold the signature
+  * @param sig_len   Length of the signature written
+  * @param f_rng     RNG function
+  * @param p_rng     RNG parameter
+  *
+  * @retval 0 if successful, or 1.
+  */
+static int remote_sign_func(void *ctx, mbedtls_md_type_t md_alg,
+                            const unsigned char *hash, size_t hash_len,
+                            unsigned char *sig, size_t *sig_len,
+                            int (*f_rng)(void *, unsigned char *, size_t),
+                            void *p_rng)
+{
+    remote_serial_pk_context * remote_ctx = (remote_serial_pk_context *)ctx;
+    /* Required buffer = func 1 byte + key Id 1 byte + hash len 4 bytes + hash */
+    unsigned char func_buffer[MBEDTLS_MD_MAX_SIZE + 4 + 1 + 1];
+    size_t offset = 0; 
+
+    UNUSED( f_rng );
+    UNUSED( p_rng );
+
+    if( md_alg != MBEDTLS_MD_SHA256 )
+        return( MBEDTLS_ERR_PK_BAD_INPUT_DATA );
+
+    if( hash_len + 4 + 1 + 1 > sizeof( func_buffer ) )
+    {
+        return( MBEDTLS_ERR_PK_BUFFER_TOO_SMALL );
+    }
+
+    func_buffer[offset++] = REMOTE_KEY_FUNC_SIGN;
+    func_buffer[offset++] = remote_ctx->key_idx;
+    func_buffer[offset++] = hash_len >> 24;
+    func_buffer[offset++] = hash_len >> 16;
+    func_buffer[offset++] = hash_len >> 8;
+    func_buffer[offset++] = hash_len;
+
+    memcpy( func_buffer + offset, hash, hash_len );
+    offset += hash_len;
+
+    if( serial_xfer( remote_ctx->serial_port, func_buffer, offset, sig,
+                     100/* FIXME */, sig_len ) != 0 )
+    {
+        mbedtls_printf( " failed\n  !  Serial error in signing\n\n" );
+        return( -1 );
+    }
+
+    return( 0 );
+}
+
+void remote_free( void *ctx )
+{
+    /* Nothing to free since remote context is statically allocated.
+     * Within this app there is no need to scrub the memory.
+     */
+    UNUSED( ctx );
+}
+
+int mbedtls_pk_remote_setup( mbedtls_pk_context * ctx, const char * serial_port,
+                             unsigned char key_idx )
+{
+    /* allocate remote serial context */
+    static remote_serial_pk_context remote;
+    /* Opaque private key */
+    static const mbedtls_pk_info_t remote_pk_info =
+    {
+        /* MBEDTLS_PK_ECKEY, */
+        MBEDTLS_PK_OPAQUE,
+        "RemoteSerial",
+        NULL,
+        remote_can_do_func,
+        NULL,
+        NULL,
+        remote_sign_func,
+        NULL,
+        NULL,
+        NULL,
+        NULL,
+        remote_free,
+        NULL
+    };
+
+
+    if ( ctx == NULL )
+        return( MBEDTLS_ERR_PK_BAD_INPUT_DATA );
+
+    remote.serial_port = serial_port;
+    remote.key_idx = key_idx;
+    ctx->pk_ctx = (void *)&remote;
+    ctx->pk_info = &remote_pk_info;
+
+    return( 0 );
+}
+
+int setup_opaque_privkey( const char * remote_info, mbedtls_pk_context * ctx )
+{
+    int key_idx = 0, ret = 0;
+    const char * serial_port = NULL;
+
+    if( parse_remote_info( remote_info, &key_idx, &serial_port ) != 0 )
+        return( -1 );
+
+    ret = mbedtls_pk_remote_setup( ctx, serial_port, key_idx );
+    if( ret != 0 )
+    {
+        mbedtls_printf( " failed\n  ! remote pk setup failure \n\n" );
+        return( ret );
+    }
+
+    return( 0 );
+}
+#endif /* _WIN32 */
+
 int write_certificate( mbedtls_x509write_cert *crt, const char *output_file,
                        int (*f_rng)(void *, unsigned char *, size_t),
                        void *p_rng )
@@ -594,6 +1024,7 @@
         mbedtls_printf( "  . Loading the subject key ..." );
         fflush( stdout );
 
+#if defined(_WIN32)
         if ( is_remote_key( opt.subject_key ) )
         {
             ret = load_pubkey_from_remote( opt.subject_key, &loaded_subject_key );
@@ -601,6 +1032,7 @@
                 goto exit;
         }
         else
+#endif
         {
             ret = mbedtls_pk_parse_keyfile( &loaded_subject_key, opt.subject_key,
                     opt.subject_pwd );
@@ -619,6 +1051,7 @@
     mbedtls_printf( "  . Loading the issuer key ..." );
     fflush( stdout );
 
+#if defined(_WIN32)
     if ( is_remote_key( opt.issuer_key ) )
     {
         ret = setup_opaque_privkey( opt.issuer_key, &loaded_issuer_key );
@@ -626,6 +1059,7 @@
             goto exit;
     }
     else
+#endif
     {
         ret = mbedtls_pk_parse_keyfile( &loaded_issuer_key, opt.issuer_key,
                 opt.issuer_pwd );
@@ -827,10 +1261,7 @@
 exit:
     mbedtls_x509write_crt_free( &crt );
     mbedtls_pk_free( &loaded_subject_key );
-    if ( is_remote_key( opt.issuer_key ) )
-        mbedtls_pk_remote_free( &loaded_issuer_key );
-    else
-        mbedtls_pk_free( &loaded_issuer_key );
+    mbedtls_pk_free( &loaded_issuer_key );
     mbedtls_mpi_free( &serial );
     mbedtls_ctr_drbg_free( &ctr_drbg );
     mbedtls_entropy_free( &entropy );
@@ -843,351 +1274,6 @@
     return( ret );
 }
 
-/** Below magic pattern is used with ATCAECC508A demo application (or similar)
- *  running on target to differentiate between user input and cert_write.exe.
- */
-#define REMOTE_KEY_CMD_TAG          "remote"
-#define REMOTE_KEY_MAGIC_PATTERN    "rEmOtEkEy"
-#define REMOTE_KEY_ID_MIN           0
-#define REMOTE_KEY_ID_MAX           7
-#define REMOTE_KEY_SERIAL_BAUD      CBR_9600
-
-#define REMOTE_KEY_FUNC_GET_PUBKEY  0xA
-#define REMOTE_KEY_FUNC_SIGN        0xB
-
-extern mbedtls_pk_info_t mbedtls_eckey_info;
-
-int is_remote_key( const char * remote_info )
-{
-    size_t tag_len = strlen( REMOTE_KEY_CMD_TAG );
-    printf ("is_remote_key %s\n", remote_info);
-    if ( strlen( remote_info ) > tag_len &&
-            strncmp( remote_info, REMOTE_KEY_CMD_TAG, tag_len ) == 0 )
-        return 1;
-    return 0;
-}
-
-/** Load a transparent public key context with public key from remote device
- *  over serial.
- *  This function sends:
- *      rEmOtEkEy<char encoded function code=GetPubKey><char encoded private key ID>
- *  Receives:
- *      <4 bytes length indicator in network order><concatenated public key>
- */
-int load_pubkey_from_remote( const char * remote_info, mbedtls_pk_context * ctx )
-{
-    int key_idx = 0, offset = 0, ret = 0;
-    const char * serial_port = NULL;
-    unsigned char func_buffer[10];
-    unsigned char pub_key_buf[100];
-    size_t rx_len = 0;
-    static mbedtls_ecp_keypair ecp_key;
-
-    offset = strlen( REMOTE_KEY_CMD_TAG );
-    key_idx = (int)remote_info[offset++];
-    key_idx = key_idx - 48; // ascii to decimal
-
-    if ( key_idx < REMOTE_KEY_ID_MIN || key_idx > REMOTE_KEY_ID_MAX )
-    {
-        mbedtls_printf( " failed\n  !  Invalid remote key index %d\n\n", key_idx );
-        return( -1 );
-    }
-    serial_port = remote_info + offset;
-
-    /* Prepare command */
-    offset = 0;
-    func_buffer[offset++] = REMOTE_KEY_FUNC_GET_PUBKEY;
-    func_buffer[offset++] = key_idx;
-
-    if ( serial_xfer( serial_port, func_buffer, offset, pub_key_buf, sizeof( pub_key_buf ), &rx_len ) != 0 )
-    {
-        mbedtls_printf( " failed\n  !  Serial error trying to get pulic key\n\n" );
-        return( -1 );
-    }
-
-    /* Import public key from received binary */
-    mbedtls_ecp_keypair_init(&ecp_key);
-    ret = mbedtls_ecp_group_load(&ecp_key.grp, MBEDTLS_ECP_DP_SECP256R1);
-    if ( ret != 0 )
-        return( -1 );
-    ret = mbedtls_ecp_point_read_binary(&ecp_key.grp, &ecp_key.Q, pub_key_buf, rx_len );
-    if ( ret != 0 )
-    {
-        mbedtls_printf( " failed\n  !  Failed to read ecp key from binary\n\n" );
-        return( -1 );
-    }
-    ctx->pk_info = &mbedtls_eckey_info;
-    ctx->pk_ctx = &ecp_key;
-    return( 0 );
-}
-
-/**
- * @brief           Tell if can do the operation given by type
- *
- * @param type      Target type
- *
- * @return          0 if context can't do the operations,
- *                  1 otherwise.
- */
-static int remote_can_do_func(const void *ctx, mbedtls_pk_type_t type)
-{
-    UNUSED(ctx);
-    /* At the moment on ECDSA is supported */
-    return (MBEDTLS_PK_ECDSA == type);
-}
-
-/**
-  * @brief  Use STSAFE private key for signature.
-  *
-  * @param ctx       ECDSA context
-  * @param md_alg    Algorithm that was used to hash the message
-  * @param hash      Message hash
-  * @param hash_len  Length of hash
-  * @param sig       Buffer that will hold the signature
-  * @param sig_len   Length of the signature written
-  * @param f_rng     RNG function
-  * @param p_rng     RNG parameter
-  *
-  * @retval 0 if successful, or 1.
-  */
-static int remote_sign_func(void *ctx, mbedtls_md_type_t md_alg,
-                            const unsigned char *hash, size_t hash_len,
-                            unsigned char *sig, size_t *sig_len,
-                            int (*f_rng)(void *, unsigned char *, size_t),
-                            void *p_rng)
-{
-    remote_serial_pk_context * remote_ctx = (remote_serial_pk_context *)ctx;
-    unsigned char func_buffer[1024];
-    size_t offset = 0; 
-
-    UNUSED( f_rng );
-    UNUSED( p_rng );
-
-    if ( md_alg != MBEDTLS_MD_SHA256 )
-        return( MBEDTLS_ERR_PK_BAD_INPUT_DATA );
-
-    func_buffer[offset++] = REMOTE_KEY_FUNC_SIGN;
-    func_buffer[offset++] = remote_ctx->key_idx;
-    func_buffer[offset++] = hash_len >> 24;
-    func_buffer[offset++] = hash_len >> 16;
-    func_buffer[offset++] = hash_len >> 8;
-    func_buffer[offset++] = hash_len & 0xff;
-
-    memcpy( func_buffer + offset, hash, hash_len );
-    offset += hash_len;
-
-    if ( serial_xfer( remote_ctx->serial_port, func_buffer, offset, sig, 100/* FIXME */, sig_len ) != 0 )
-    {
-        mbedtls_printf( " failed\n  !  Serial error in signing\n\n" );
-        return( -1 );
-    }
-
-    return( 0 );
-}
-
-int mbedtls_pk_remote_setup( mbedtls_pk_context * ctx, const char * serial_port, unsigned char key_idx )
-{
-    // allocate remote serial context
-    static remote_serial_pk_context remote;
-    /* Opaque private key */
-    static const mbedtls_pk_info_t remote_pk_info =
-    {
-        /* MBEDTLS_PK_ECKEY, */
-        MBEDTLS_PK_OPAQUE,
-        "RemoteSerial",
-        NULL,
-        remote_can_do_func,
-        NULL,
-        NULL,
-        remote_sign_func,
-        NULL,
-        NULL,
-        NULL,
-        NULL,
-        NULL,
-        NULL
-    };
-
-
-    if ( ctx == NULL )
-        return( MBEDTLS_ERR_PK_BAD_INPUT_DATA );
-
-    remote.serial_port = serial_port;
-    remote.key_idx = key_idx;
-    ctx->pk_ctx = (void *)&remote;
-    ctx->pk_info = &remote_pk_info;
-
-    return( 0 );
-}
-
-void mbedtls_pk_remote_free( mbedtls_pk_context * ctx )
-{
-    /* Nothing to free since remote context is statically allocated.
-     * Within this app there is no need to scrub the memory.
-     */
-    UNUSED( ctx );
-}
-
-int setup_opaque_privkey( const char * remote_info, mbedtls_pk_context * ctx )
-{
-    int key_idx = 0, offset = 0, ret = 0;
-    const char * serial_port = NULL;
-
-    offset = strlen( REMOTE_KEY_CMD_TAG );
-    key_idx = (int)remote_info[offset++];
-    key_idx = key_idx - 48; // ascii to decimal
-
-    if ( key_idx < REMOTE_KEY_ID_MIN || key_idx > REMOTE_KEY_ID_MAX )
-    {
-        mbedtls_printf( " failed\n  !  Invalid remote key index %d\n\n", key_idx );
-        return( -1 );
-    }
-    serial_port = remote_info + offset;
-    ret = mbedtls_pk_remote_setup( ctx, serial_port, key_idx );
-    if ( ret != 0 )
-    {
-        mbedtls_printf( " failed\n  ! remote pk setup failure \n\n" );
-        return( -1 );
-    }
-
-    return( 0 );
-}
-
-int serial_xfer( const char * serial_port, const unsigned char * tx_buf,
-                 size_t tx_buf_len, unsigned char * rx_buf, size_t rx_buf_len,
-                 size_t * rx_len )
-{
-    char c, comm_name[20];
-    HANDLE hComm;
-    DCB dcbConfig;
-    COMMTIMEOUTS commTimeout;
-    DWORD xfer_len;
-    unsigned char len_buf[sizeof(size_t)];
-    int ret = -1;
-    size_t len = 0, sync_pattern_idx = 0;
-
-    do
-    {
-        sprintf( comm_name, "\\\\.\\%s", serial_port );
-
-        // Open port
-        hComm = CreateFile( comm_name, GENERIC_READ | GENERIC_WRITE, 0, 0,
-                OPEN_EXISTING, 0, 0 );
-        if ( hComm == INVALID_HANDLE_VALUE )
-        {
-            mbedtls_printf( " failed\n  ! failed to open port %s %lu\n\n", serial_port, GetLastError() );
-            break;
-        }
-
-        if( GetCommState( hComm, &dcbConfig ) )
-        {
-            dcbConfig.BaudRate = REMOTE_KEY_SERIAL_BAUD;
-            dcbConfig.Parity = NOPARITY;
-            dcbConfig.ByteSize = 8;
-            dcbConfig.StopBits = ONESTOPBIT;
-            dcbConfig.fOutxCtsFlow = FALSE;         // No CTS output flow control
-            dcbConfig.fOutxDsrFlow = FALSE;         // No DSR output flow control
-            dcbConfig.fDtrControl = DTR_CONTROL_DISABLE; // DTR flow control type
-            dcbConfig.fDsrSensitivity = FALSE;      // DSR sensitivity
-            dcbConfig.fTXContinueOnXoff = TRUE;     // XOFF continues Tx
-            dcbConfig.fOutX = FALSE;                // No XON/XOFF out flow control
-            dcbConfig.fInX = FALSE;                 // No XON/XOFF in flow control
-            dcbConfig.fErrorChar = FALSE;           // Disable error replacement
-            dcbConfig.fNull = FALSE;                // Disable null stripping
-            dcbConfig.fRtsControl = RTS_CONTROL_DISABLE; // RTS flow control
-            dcbConfig.fAbortOnError = FALSE;        // Do not abort reads/writes on error
-        }
-        else
-            break;
-
-        if( !SetCommState( hComm, &dcbConfig ) )
-            break;
-
-        if( GetCommTimeouts( hComm, &commTimeout ) )
-        {
-            commTimeout.ReadIntervalTimeout = 1000;
-            commTimeout.ReadTotalTimeoutMultiplier = 10;
-            commTimeout.ReadTotalTimeoutConstant = 1000;
-            commTimeout.WriteTotalTimeoutConstant = 1000;
-            commTimeout.WriteTotalTimeoutMultiplier = 10;
-        }
-        else
-            break;
-
-        if( !SetCommTimeouts( hComm, &commTimeout ) )
-            break;
-
-
-        /* Flush data on serial before sending sync pattern */
-        while( ReadFile( hComm, &c, sizeof(c), &xfer_len, NULL ) && xfer_len != 0 );
-        /* Sync with peer */
-        if( !WriteFile( hComm, REMOTE_KEY_MAGIC_PATTERN, strlen(REMOTE_KEY_MAGIC_PATTERN), 
-                    &xfer_len, NULL ) )
-            break;
-
-        while( sync_pattern_idx != strlen(REMOTE_KEY_MAGIC_PATTERN) )
-        {
-            if( !ReadFile( hComm, &c, sizeof(c), &xfer_len, NULL ) )
-                break;
-            if ( c == REMOTE_KEY_MAGIC_PATTERN[sync_pattern_idx] )
-                sync_pattern_idx++;
-            else
-                sync_pattern_idx = 0;
-        }
-
-        /* Exit if there was a read error */
-        if ( sync_pattern_idx != strlen(REMOTE_KEY_MAGIC_PATTERN) )
-        {
-            printf("Failedi to sync!");
-            break;
-        }
-
-        {
-            size_t i;
-            printf("Tx: ");
-            for (i = 0; i < tx_buf_len; i++)
-                printf ("0x%02x ", (tx_buf)[i]);
-            printf("\n");
-        }
-        if( !WriteFile( hComm, tx_buf, tx_buf_len, 
-                    &xfer_len, NULL ) )
-            break;
-
-        /* Read length indicator */
-        if( !ReadFile( hComm, len_buf, sizeof(len_buf), &xfer_len, NULL ) )
-            break;
-
-        *rx_len = ( len_buf[0] << 24 ) | ( len_buf[1] << 16 ) | ( len_buf[2] << 8 ) | len_buf[3];
-        if ( *rx_len > rx_buf_len )
-            return( -1 );
-        /* Read payload */
-        while( len < *rx_len )
-        {
-            if( !ReadFile( hComm, rx_buf + len, *rx_len - len, &xfer_len, NULL ) )
-                break;
-            len += xfer_len;
-        }
-        printf("Received LI 0x%02x 0x%02x 0x%02x 0x%02x \n", len_buf[0], len_buf[1], len_buf[2], len_buf[3]);
-        {
-            size_t i;
-            printf("Rx: ");
-            for (i = 0; i < *rx_len; i++)
-                printf ("0x%02x ", (rx_buf)[i]);
-            printf("\n");
-        }
-
-        ret = 0;
-    } while( 0 );
-
-    if( hComm != INVALID_HANDLE_VALUE )
-    {
-        CloseHandle( hComm );
-        hComm = INVALID_HANDLE_VALUE;
-    }
-
-    return( ret );
-}
-
 #endif /* MBEDTLS_X509_CRT_WRITE_C && MBEDTLS_X509_CRT_PARSE_C &&
           MBEDTLS_FS_IO && MBEDTLS_ENTROPY_C && MBEDTLS_CTR_DRBG_C &&
           MBEDTLS_ERROR_C && MBEDTLS_PEM_WRITE_C */