[C++知识库]To See the Basic Uses of libtomcrypt from an example of AES-CTR

The description of functions for following codes

The functions of the block could be categorized by

1. generate data
2. encrypt data
3. decrypt data

The codes in three different files

file_1 named Block.hpp

#ifndef BLOCK_HPP
#define BLOCK_HPP
#include "config.hpp"
// a block class
class Block{
    public:
        TYPE_INDEX index;
        TYPE_INDEX data_size;
        Block(TYPE_INDEX index, TYPE_INDEX block_size);
        ~Block();
        
        char* decrypt();
        char* encrypt();
        char* get_data();

    private:
        char *data;
        unsigned char *iv;
};


#endif

file_2 named Block.cpp

#include "Block.hpp"
#include "config.hpp"

#include <tomcrypt.h>
#include <cstring>
#include <cstdlib>
#include <ctime>
#include <iostream>
// constructor
Block::Block(TYPE_INDEX index, TYPE_INDEX data_size){
    this->index = index;
    this->data_size = data_size;
    this->data = new char[data_size];
    // initialize the data with some data some characters
    for(int i = 0; i < data_size; i++){
        data[i] = 'a' + i % 26;
    }
    this->iv = new unsigned char[IV_SIZE];

    // initialize the aes_desc 
    if (-1 == register_cipher(&aes_desc)) {
		std::cout << "[Block] Register cipher err" << std::endl;
		exit(-1);
	}
    // generate random IV
    srand((unsigned)time(NULL));
}
// destructor
Block::~Block(){
    delete[] data;
    delete[] iv;
}
// realize get_data()
char* Block::get_data(){
    return data;
}
char *Block::encrypt()
{
	/* Generate random IV */
	for (int i = 0; i < IV_SIZE; i += sizeof(int)) {
		int random_int = rand();
		memcpy(iv + i, &random_int, sizeof(int));
	}
	if (IV_SIZE / sizeof(int) != 0) {
		int random_int = rand();
		memcpy(iv + IV_SIZE - sizeof(int), &random_int, sizeof(int));
	}

	int err = 0;
	symmetric_CTR ctr;
	char cipher_data[this->data_size];
    
	/* encrypt */
	if ((err =  ctr_start(find_cipher("aes"), iv, ENCRYPT_KEY, sizeof(ENCRYPT_KEY), 0, CTR_COUNTER_LITTLE_ENDIAN, &ctr)) != CRYPT_OK) 
    {
        std::cout << "[Block] ctr_start err: " << error_to_string(err) << std::endl;
		exit(-1);
	}
	if ((err = ctr_encrypt((unsigned char *)data, (unsigned char *)cipher_data, this->data_size, &ctr)) != CRYPT_OK) {
        std::cout << "[Block] ctr_encrypt err: " << error_to_string(err) << std::endl;
        exit(-1);
	}
	if ((err = ctr_done(&ctr)) != CRYPT_OK) {
        std::cout << "[Block] ctr_done err: " << error_to_string(err) << std::endl;
		exit(-1);
	}

	memcpy(data, cipher_data, this->data_size);
    return data;
}

char *Block::decrypt()
{
	int err;
	symmetric_CTR ctr;
	char decipher_data[this->data_size];

	if ((err =  ctr_start(find_cipher("aes"), iv, ENCRYPT_KEY, sizeof(ENCRYPT_KEY), 0, CTR_COUNTER_LITTLE_ENDIAN, &ctr)) != CRYPT_OK) {
		std::cout << "[Block] ctr_start err: " << error_to_string(err) << std::endl;
		exit(-1);
	}
	if ((err = ctr_decrypt((unsigned char *)data, (unsigned char *)decipher_data, this->data_size, &ctr)) != CRYPT_OK) {
        std::cout << "[Block] ctr_encrypt err: " << error_to_string(err) << std::endl;
		exit(-1);
	}
	if ((err = ctr_done(&ctr)) != CRYPT_OK) {
        std::cout << "[Block] ctr_done err: " << error_to_string(err) << std::endl;
		exit(-1);
	}

	memcpy(data, decipher_data, this->data_size);
    return data;
}

file_3 main.cpp

#include <iostream>
#include "Block.hpp"
#include <cstring>
int main()
{
    Block block(1, 2);
    std::cout <<"The size of block " << sizeof(block) << std::endl;
    std::cout << block.index << std::endl;
    std::cout << block.data_size << std::endl;
    char *data = new char[2];
    data = block.get_data();
    char *encrypt_data = new char[2];
    encrypt_data = block.encrypt();
    char *decrypt_data = new char[2];
    decrypt_data = block.decrypt();
    // check out whether the data and decrypt_data are the same or not
    if (memcmp(data, decrypt_data, 2) == 0) {
        std::cout << "data and decrypt_data are the same" << std::endl;
    } else {
        std::cout << "data and decrypt_data are not the same" << std::endl;
    }

    return 0;
}

How to compile the above files simultaneously

g++ main.cpp Block.cpp -o direct_access -ltomcrypt

The corresponding results

The size of block 32
1
2
data and decrypt_data are the same

创作打卡挑战赛

赢取流量/现金/CSDN周边激励大奖