diff --git a/library/psa_its_file.c b/library/psa_its_file.c
new file mode 100644
index 0000000..3a854b5
--- /dev/null
+++ b/library/psa_its_file.c
@@ -0,0 +1,233 @@
+/*
+ *  PSA ITS simulator over stdio files.
+ */
+/*  Copyright (C) 2018, ARM Limited, All Rights Reserved
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"); you may
+ *  not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ *  This file is part of mbed TLS (https://tls.mbed.org)
+ */
+
+#if defined(MBEDTLS_CONFIG_FILE)
+#include MBEDTLS_CONFIG_FILE
+#else
+#include "mbedtls/config.h"
+#endif
+
+#if defined(MBEDTLS_PSA_ITS_FILE_C)
+
+#if defined(MBEDTLS_PLATFORM_C)
+#include "mbedtls/platform.h"
+#else
+#define mbedtls_snprintf   snprintf
+#endif
+
+#include "psa_crypto_its.h"
+
+#include <limits.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+#define PSA_ITS_STORAGE_PREFIX ""
+
+#define PSA_ITS_STORAGE_FILENAME_PATTERN "%08lx%08lx"
+#define PSA_ITS_STORAGE_SUFFIX ".psa_its"
+#define PSA_ITS_STORAGE_FILENAME_LENGTH         \
+    ( sizeof( PSA_ITS_STORAGE_PREFIX ) - 1 + /*prefix without terminating 0*/ \
+      16 + /*UID (64-bit number in hex)*/                               \
+      sizeof( PSA_ITS_STORAGE_SUFFIX ) - 1 + /*suffix without terminating 0*/ \
+      1 /*terminating null byte*/ )
+#define PSA_ITS_STORAGE_TEMP \
+    PSA_ITS_STORAGE_PREFIX "tempfile" PSA_ITS_STORAGE_SUFFIX
+
+/* The maximum value of psa_storage_info_t.size */
+#define PSA_ITS_MAX_SIZE 0xffffffff
+
+#define PSA_ITS_MAGIC_STRING "PSA\0ITS\0"
+#define PSA_ITS_MAGIC_LENGTH 8
+
+typedef struct
+{
+    uint8_t magic[PSA_ITS_MAGIC_LENGTH];
+    uint8_t size[sizeof( uint32_t )];
+    uint8_t flags[sizeof( psa_storage_create_flags_t )];
+} psa_its_file_header_t;
+
+static void psa_its_fill_filename( psa_storage_uid_t uid, char *filename )
+{
+    /* Break up the UID into two 32-bit pieces so as not to rely on
+     * long long support in snprintf. */
+    mbedtls_snprintf( filename, PSA_ITS_STORAGE_FILENAME_LENGTH,
+                      "%s" PSA_ITS_STORAGE_FILENAME_PATTERN "%s",
+                      PSA_ITS_STORAGE_PREFIX,
+                      (unsigned long) ( uid >> 32 ),
+                      (unsigned long) ( uid & 0xffffffff ),
+                      PSA_ITS_STORAGE_SUFFIX );
+}
+
+static psa_status_t psa_its_read_file( psa_storage_uid_t uid,
+                                       struct psa_storage_info_t *p_info,
+                                       FILE **p_stream )
+{
+    char filename[PSA_ITS_STORAGE_FILENAME_LENGTH];
+    psa_its_file_header_t header;
+    size_t n;
+
+    *p_stream = NULL;
+    psa_its_fill_filename( uid, filename );
+    *p_stream = fopen( filename, "rb" );
+    if( *p_stream == NULL )
+        return( PSA_ERROR_DOES_NOT_EXIST );
+
+    n = fread( &header, 1, sizeof( header ), *p_stream );
+    if( n != sizeof( header ) )
+        return( PSA_ERROR_DATA_CORRUPT );
+    if( memcmp( header.magic, PSA_ITS_MAGIC_STRING,
+                PSA_ITS_MAGIC_LENGTH ) != 0 )
+        return( PSA_ERROR_DATA_CORRUPT );
+
+    p_info->size = ( header.size[0] |
+                     header.size[1] << 8 |
+                     header.size[2] << 16 |
+                     header.size[3] << 24 );
+    p_info->flags = ( header.flags[0] |
+                      header.flags[1] << 8 |
+                      header.flags[2] << 16 |
+                      header.flags[3] << 24 );
+    return( PSA_SUCCESS );
+}
+
+psa_status_t psa_its_get_info( psa_storage_uid_t uid,
+                               struct psa_storage_info_t *p_info )
+{
+    psa_status_t status;
+    FILE *stream = NULL;
+    status = psa_its_read_file( uid, p_info, &stream );
+    if( stream != NULL )
+        fclose( stream );
+    return( status );
+}
+
+psa_status_t psa_its_get( psa_storage_uid_t uid,
+                          uint32_t data_offset,
+                          uint32_t data_length,
+                          void *p_data )
+{
+    psa_status_t status;
+    FILE *stream = NULL;
+    size_t n;
+    struct psa_storage_info_t info;
+
+    status = psa_its_read_file( uid, &info, &stream );
+    if( status != PSA_SUCCESS )
+        goto exit;
+    status = PSA_ERROR_DATA_CORRUPT;
+    if( data_offset + data_length < data_offset )
+        goto exit;
+#if SIZE_MAX < 0xffffffff
+    if( data_offset + data_length > SIZE_MAX )
+        goto exit;
+#endif
+    if( data_offset + data_length > info.size )
+        goto exit;
+
+    status = PSA_ERROR_DATA_CORRUPT;
+#if LONG_MAX < 0xffffffff
+    while( data_offset > LONG_MAX )
+    {
+        if( fseek( stream, LONG_MAX, SEEK_CUR ) != 0 )
+            goto exit;
+        data_offset -= LONG_MAX;
+    }
+#endif
+    if( fseek( stream, data_offset, SEEK_CUR ) != 0 )
+        goto exit;
+    n = fread( p_data, 1, data_length, stream );
+    if( n != data_length )
+        goto exit;
+    status = PSA_SUCCESS;
+
+exit:
+    if( stream != NULL )
+        fclose( stream );
+    return( status );
+}
+
+psa_status_t psa_its_set( psa_storage_uid_t uid,
+                          uint32_t data_length,
+                          const void *p_data,
+                          psa_storage_create_flags_t create_flags )
+{
+    psa_status_t status = PSA_ERROR_STORAGE_FAILURE;
+    char filename[PSA_ITS_STORAGE_FILENAME_LENGTH];
+    FILE *stream = NULL;
+    psa_its_file_header_t header;
+    size_t n;
+
+    memcpy( header.magic, PSA_ITS_MAGIC_STRING, PSA_ITS_MAGIC_LENGTH );
+    header.size[0] = data_length & 0xff;
+    header.size[1] = ( data_length >> 8 ) & 0xff;
+    header.size[2] = ( data_length >> 16 ) & 0xff;
+    header.size[3] = ( data_length >> 24 ) & 0xff;
+    header.flags[0] = create_flags & 0xff;
+    header.flags[1] = ( create_flags >> 8 ) & 0xff;
+    header.flags[2] = ( create_flags >> 16 ) & 0xff;
+    header.flags[3] = ( create_flags >> 24 ) & 0xff;
+
+    psa_its_fill_filename( uid, filename );
+    stream = fopen( PSA_ITS_STORAGE_TEMP, "wb" );
+    if( stream == NULL )
+        goto exit;
+
+    status = PSA_ERROR_INSUFFICIENT_STORAGE;
+    n = fwrite( &header, 1, sizeof( header ), stream );
+    if( n != sizeof( header ) )
+        goto exit;
+    n = fwrite( p_data, 1, data_length, stream );
+    if( n != data_length )
+        goto exit;
+    status = PSA_SUCCESS;
+
+exit:
+    if( stream != NULL )
+    {
+        int ret = fclose( stream );
+        if( status == PSA_SUCCESS && ret != 0 )
+            status = PSA_ERROR_INSUFFICIENT_STORAGE;
+    }
+    if( status == PSA_SUCCESS )
+    {
+        if( rename( PSA_ITS_STORAGE_TEMP, filename ) != 0 )
+            status = PSA_ERROR_STORAGE_FAILURE;
+    }
+    remove( PSA_ITS_STORAGE_TEMP );
+    return( status );
+}
+
+psa_status_t psa_its_remove( psa_storage_uid_t uid )
+{
+    char filename[PSA_ITS_STORAGE_FILENAME_LENGTH];
+    FILE *stream;
+    psa_its_fill_filename( uid, filename );
+    stream = fopen( filename, "rb" );
+    if( stream == NULL )
+        return( PSA_ERROR_DOES_NOT_EXIST );
+    fclose( stream );
+    if( remove( filename ) != 0 )
+        return( PSA_ERROR_STORAGE_FAILURE );
+    return( PSA_SUCCESS );
+}
+
+#endif /* MBEDTLS_PSA_ITS_FILE_C */