Hello world example of using the hashing functions of mbed TLS. The canonical source for this example lives at https://github.com/ARMmbed/mbed-os-example-tls

SHA-256 Hash example on mbed OS

This application performs hashing of a buffer with SHA-256 using various APIs. It serves as a tutorial for the basic hashing APIs of mbed TLS.

Getting started

Building with mbed CLI

If you'd like to use mbed CLI to build this, then you should set up your environment if you have not done so already. For instructions, refer to the main readme. The instructions on this page relate to using the developer.mbed.org Online Compiler

Import the program in to the Online Compiler, select your board from the drop down in the top right hand corner and then compile the application. Once it has built, you can drag and drop the binary onto your device.

Monitoring the application

The output in the terminal window should be similar to this:

terminal output

Method 1: 315f5bdb76d078c43b8ac0064e4a0164612b1fce77c869345bfc94c75894edd3
Method 2: 315f5bdb76d078c43b8ac0064e4a0164612b1fce77c869345bfc94c75894edd3
Method 3: 315f5bdb76d078c43b8ac0064e4a0164612b1fce77c869345bfc94c75894edd3
Method 4: 315f5bdb76d078c43b8ac0064e4a0164612b1fce77c869345bfc94c75894edd3

DONE
Revision:
0:faef56ba465f
Child:
45:9152ca3b575e
diff -r 000000000000 -r faef56ba465f main.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Wed Jul 27 14:30:35 2016 +0100
@@ -0,0 +1,159 @@
+/*
+ *  Hello world example of using the hashing functions of mbed TLS
+ *
+ *  Copyright (C) 2016, 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 program illustrates various ways of hashing a buffer.
+ * You normally need only one of these two includes.
+ */
+#include "mbed.h"
+#include "mbedtls/sha256.h" /* SHA-256 only */
+#include "mbedtls/md.h"     /* generic interface */
+
+#if DEBUG_LEVEL > 0
+#include "mbedtls/debug.h"
+#endif
+
+#include "mbedtls/platform.h"
+
+#include <string.h>
+
+static void print_hex(const char *title, const unsigned char buf[], size_t len)
+{
+    mbedtls_printf("%s: ", title);
+
+    for (size_t i = 0; i < len; i++)
+        mbedtls_printf("%02x", buf[i]);
+
+    mbedtls_printf("\r\n");
+}
+
+static const char hello_str[] = "Hello, world!";
+static const unsigned char *hello_buffer = (const unsigned char *) hello_str;
+static const size_t hello_len = strlen(hello_str);
+
+static int example(void)
+{
+    mbedtls_printf("\r\n\r\n");
+
+    /*
+     * Method 1: use all-in-one function of a specific SHA-xxx module
+     */
+    unsigned char output1[32]; /* SHA-256 outputs 32 bytes */
+
+    /* 0 here means use the full SHA-256, not the SHA-224 variant */
+    mbedtls_sha256(hello_buffer, hello_len, output1, 0);
+
+    print_hex("Method 1", output1, sizeof output1);
+
+
+    /*
+     * Method 2: use the streaming interface of a specific SHA-xxx module
+     * This is useful if we get our input piecewise.
+     */
+    unsigned char output2[32];
+    mbedtls_sha256_context ctx2;
+
+    mbedtls_sha256_init(&ctx2);
+    mbedtls_sha256_starts(&ctx2, 0); /* SHA-256, not 224 */
+
+    /* Simulating multiple fragments */
+    mbedtls_sha256_update(&ctx2, hello_buffer, 1);
+    mbedtls_sha256_update(&ctx2, hello_buffer + 1, 1);
+    mbedtls_sha256_update(&ctx2, hello_buffer + 2, hello_len - 2);
+
+    mbedtls_sha256_finish(&ctx2, output2);
+    print_hex("Method 2", output2, sizeof output2);
+
+    /* Or you could re-use the context by doing mbedtls_sha256_starts() again */
+    mbedtls_sha256_free(&ctx2);
+
+    /*
+     * Method 3: use all-in-one function of the generice interface
+     */
+    unsigned char output3[MBEDTLS_MD_MAX_SIZE]; /* Enough for any hash */
+
+    /* Can easily pick any hash you want, by identifier */
+    const mbedtls_md_info_t *md_info3 = mbedtls_md_info_from_type(MBEDTLS_MD_SHA256);
+
+    if (md_info3 == NULL)
+    {
+        mbedtls_printf("SHA256 not available\r\n");
+        return 1;
+    }
+
+    int ret3 = mbedtls_md(md_info3, hello_buffer, hello_len, output3);
+
+    if (ret3 != 0)
+    {
+        mbedtls_printf("md() returned -0x%04X\r\n", -ret3);
+        return 1;
+    }
+
+    print_hex("Method 3", output3, mbedtls_md_get_size(md_info3));
+
+
+    /*
+     * Method 4: streaming & generic interface
+     */
+    unsigned char output4[MBEDTLS_MD_MAX_SIZE]; /* Enough for any hash */
+
+    const mbedtls_md_info_t *md_info4 = mbedtls_md_info_from_type(MBEDTLS_MD_SHA256);
+
+    if (md_info4 == NULL)
+    {
+        mbedtls_printf("SHA256 not available\r\n");
+        return 1;
+    }
+
+    mbedtls_md_context_t ctx4;
+
+    mbedtls_md_init(&ctx4);
+
+    int ret4 = mbedtls_md_init_ctx(&ctx4, md_info4);
+    if (ret4 != 0)
+    {
+        mbedtls_printf("md_init_ctx() returned -0x%04X\r\n", -ret4);
+        return 1;
+    }
+
+    mbedtls_md_starts(&ctx4);
+
+    /* Simulating multiple fragments */
+    mbedtls_md_update(&ctx4, hello_buffer, 1);
+    mbedtls_md_update(&ctx4, hello_buffer + 1, 1);
+    mbedtls_md_update(&ctx4, hello_buffer + 2, hello_len - 2);
+
+    mbedtls_md_finish(&ctx4, output4);
+    print_hex("Method 4", output4, mbedtls_md_get_size(md_info4));
+
+    /* Or you could re-use the context by doing mbedtls_md_starts() again */
+    mbedtls_md_free(&ctx4);
+
+
+    mbedtls_printf("\r\nDONE\r\n");
+
+    return 0;
+}
+
+int main() {
+    int ret = example();
+    if (ret != 0) {
+        mbedtls_printf("Example failed with error %d\r\n", ret);
+    }
+}