authcrypt.h

00001 /*
00002  *  Hello world example of using the authenticated encryption with Mbed TLS
00003  *
00004  *  Copyright (C) 2017, Arm Limited, All Rights Reserved
00005  *  SPDX-License-Identifier: Apache-2.0
00006  *
00007  *  Licensed under the Apache License, Version 2.0 (the "License"); you may
00008  *  not use this file except in compliance with the License.
00009  *  You may obtain a copy of the License at
00010  *
00011  *  http://www.apache.org/licenses/LICENSE-2.0
00012  *
00013  *  Unless required by applicable law or agreed to in writing, software
00014  *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
00015  *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00016  *  See the License for the specific language governing permissions and
00017  *  limitations under the License.
00018  */
00019 
00020 #ifndef _AUTHCRYPT_H_
00021 #define _AUTHCRYPT_H_
00022 
00023 #include "mbedtls/cipher.h"
00024 #include "mbedtls/entropy.h"
00025 #include "mbedtls/ctr_drbg.h"
00026 #include "mbedtls/platform.h"
00027 
00028 /**
00029  * This class implements the logic to demonstrate authenticated encryption using
00030  * mbed TLS.
00031  */
00032 class Authcrypt
00033 {
00034 public:
00035     /**
00036      * Construct an Authcrypt instance
00037      */
00038     Authcrypt();
00039 
00040     /**
00041      * Free any allocated resources
00042      */
00043     ~Authcrypt();
00044 
00045     /**
00046      * Run the authenticated encryption example
00047      *
00048      * \return  0 if successful
00049      */
00050     int run();
00051 
00052 private:
00053     /**
00054      * Print a buffer's contents in hexadecimal
00055      *
00056      * \param[in]   title
00057      *              The string to print before the hex string
00058      * \param[in]   buf
00059      *              The buffer to print in hex
00060      * \param[in]   len
00061      *              The length of the buffer
00062      */
00063     void print_hex(const char *title, const unsigned char buf[], size_t len);
00064 
00065     /**
00066      * The pre-shared key
00067      *
00068      * \note This should be generated randomly and be unique to the
00069      *       device/channel/etc. Just used a fixed on here for simplicity.
00070      */
00071     static const unsigned char secret_key[16];
00072 
00073     /**
00074      * Message that should be protected
00075      */
00076     static const char message[];
00077 
00078     /**
00079      * Metadata transmitted in the clear but authenticated
00080      */
00081     static const char metadata[];
00082 
00083     /**
00084      * Ciphertext buffer large enough to hold message + nonce + tag
00085      */
00086     unsigned char ciphertext[128];
00087 
00088     /**
00089      * Plaintext buffer large enough to hold the decrypted message
00090      */
00091     unsigned char decrypted[128];
00092 
00093     /**
00094      * Entropy pool for seeding PRNG
00095      */
00096     mbedtls_entropy_context entropy;
00097 
00098     /**
00099      * Pseudo-random generator
00100      */
00101     mbedtls_ctr_drbg_context drbg;
00102 
00103     /**
00104      * The block cipher configuration
00105      */
00106     mbedtls_cipher_context_t cipher;
00107 };
00108 
00109 #endif /* _AUTHCRYPT_H_ */