C++ uses openssl to encrypt and decrypt data

Obtaining OpenSSL library files and headers You can obtain openSSL library files and headers in either of the following ways:

1) Download the OpenSSL source code and compile it for use

2) Download the compiled installation package, and you can directly obtain openSSL library files and header files after installation

Using the first method to obtain openSSL library files, the process is very tedious, and the compilation process may produce a variety of problems, so the second method is used to obtain openSSL library files and header files.

Download the installation package (slproweb.com/products/Wi…

2. Encrypt and decrypt data using OpenSSL 1) Create a project to import openSSL header files and library files

2) The sample code is as follows, including:

A. Digest (hash) algorithm MD5 and SHA256;

B. Symmetric encryption algorithm DES;

C. Rsa is an asymmetric encryption algorithm.

#include <iostream>
#include <cassert>
#include <string>
#include <vector>
#include "openssl/md5.h"
#include "openssl/sha.h"
#include "openssl/des.h"
#include "openssl/rsa.h"
#include "openssl/pem.h"
 
#pragma comment(lib,"libcrypto.lib")
 
// ---- md5摘要哈希 ---- //
void md5(const std::string &srcStr, std::string &encodedStr, std::string &encodedHexStr)
{
	unsigned char mdStr[33] = { 0 };
	MD5((const unsigned char *)srcStr.c_str(), srcStr.length(), mdStr);// 调用md5哈希
	encodedStr = std::string((const char *)mdStr);// 哈希后的字符串
	
	char buf[65] = { 0 };
	char tmp[3] = { 0 };
	for (int i = 0; i < 32; i++)// 哈希后的十六进制串 32字节  
	{
		sprintf(tmp, "%02x", mdStr[i]);
		strcat(buf, tmp);
	}
	buf[32] = '\0'; // 后面都是0，从32字节截断  
	encodedHexStr = std::string(buf);
}
 
// ---- sha256摘要哈希 ---- //  
void sha256(const std::string &srcStr, std::string &encodedStr, std::string &encodedHexStr)
{
	
	unsigned char mdStr[33] = { 0 };
	SHA256((const unsigned char *)srcStr.c_str(), srcStr.length(), mdStr);// 调用sha256哈希
	encodedStr = std::string((const char *)mdStr);// 哈希后的字符串
	
	char buf[65] = { 0 };
	char tmp[3] = { 0 };
	for (int i = 0; i < 32; i++)// 哈希后的十六进制串 32字节  
	{
		sprintf(tmp, "%02x", mdStr[i]);
		strcat(buf, tmp);
	}
	buf[32] = '\0'; // 后面都是0，从32字节截断  
	encodedHexStr = std::string(buf);
}
 
// ---- des对称加解密 ---- //  
// 加密 ecb模式  
std::string des_encrypt(const std::string &clearText, const std::string &key)
{
	std::string cipherText; // 密文
 
	DES_cblock keyEncrypt;
	memset(keyEncrypt, 0, 8);
 
	// 构造补齐后的密钥  
	if (key.length() <= 8)
		memcpy(keyEncrypt, key.c_str(), key.length());
	else
		memcpy(keyEncrypt, key.c_str(), 8);
 
	// 密钥置换  
	DES_key_schedule keySchedule;
	DES_set_key_unchecked(&keyEncrypt, &keySchedule);
 
	// 循环加密，每8字节一次  
	const_DES_cblock inputText;
	DES_cblock outputText;
	std::vector<unsigned char> vecCiphertext;
	unsigned char tmp[8];
 
	for (int i = 0; i < clearText.length() / 8; i++)
	{
		memcpy(inputText, clearText.c_str() + i * 8, 8);
		DES_ecb_encrypt(&inputText, &outputText, &keySchedule, DES_ENCRYPT);
		memcpy(tmp, outputText, 8);
 
		for (int j = 0; j < 8; j++)
			vecCiphertext.push_back(tmp[j]);
	}
 
	if (clearText.length() % 8 != 0)
	{
		int tmp1 = clearText.length() / 8 * 8;
		int tmp2 = clearText.length() - tmp1;
		memset(inputText, 0, 8);
		memcpy(inputText, clearText.c_str() + tmp1, tmp2);
		DES_ecb_encrypt(&inputText, &outputText, &keySchedule, DES_ENCRYPT);// 加密函数
		memcpy(tmp, outputText, 8);
 
		for (int j = 0; j < 8; j++)
			vecCiphertext.push_back(tmp[j]);
	}
 
	cipherText.clear();
	cipherText.assign(vecCiphertext.begin(), vecCiphertext.end());
	return cipherText;
}
 
// 解密 ecb模式  
std::string des_decrypt(const std::string &cipherText, const std::string &key)
{
	std::string clearText; // 明文  
 
	DES_cblock keyEncrypt;
	memset(keyEncrypt, 0, 8);
 
	if (key.length() <= 8)
		memcpy(keyEncrypt, key.c_str(), key.length());
	else
		memcpy(keyEncrypt, key.c_str(), 8);
 
	DES_key_schedule keySchedule;
	DES_set_key_unchecked(&keyEncrypt, &keySchedule);
 
	const_DES_cblock inputText;
	DES_cblock outputText;
	std::vector<unsigned char> vecCleartext;
	unsigned char tmp[8];
 
	for (int i = 0; i < cipherText.length() / 8; i++)
	{
		memcpy(inputText, cipherText.c_str() + i * 8, 8);
		DES_ecb_encrypt(&inputText, &outputText, &keySchedule, DES_DECRYPT);
		memcpy(tmp, outputText, 8);
 
		for (int j = 0; j < 8; j++)
			vecCleartext.push_back(tmp[j]);
	}
 
	if (cipherText.length() % 8 != 0)
	{
		int tmp1 = cipherText.length() / 8 * 8;
		int tmp2 = cipherText.length() - tmp1;
		memset(inputText, 0, 8);
		memcpy(inputText, cipherText.c_str() + tmp1, tmp2);
		DES_ecb_encrypt(&inputText, &outputText, &keySchedule, DES_DECRYPT);// 解密函数
		memcpy(tmp, outputText, 8);
 
		for (int j = 0; j < 8; j++)
			vecCleartext.push_back(tmp[j]);
	}
 
	clearText.clear();
	clearText.assign(vecCleartext.begin(), vecCleartext.end());
 
	return clearText;
}
 
 
// ---- rsa非对称加解密 ---- //  
#define KEY_LENGTH  2048               // 密钥长度
#define PUB_KEY_FILE "pubkey.pem"    // 公钥路径
#define PRI_KEY_FILE "prikey.pem"    // 私钥路径
 
// 函数方法生成密钥对 
void generateRSAKey(std::string strKey[2])
{
	// 公私密钥对  
	size_t pri_len;
	size_t pub_len;
	char *pri_key = NULL;
	char *pub_key = NULL;
 
	// 生成密钥对  
	RSA *keypair = RSA_generate_key(KEY_LENGTH, RSA_3, NULL, NULL);
 
	BIO *pri = BIO_new(BIO_s_mem());
	BIO *pub = BIO_new(BIO_s_mem());
 
	PEM_write_bio_RSAPrivateKey(pri, keypair, NULL, NULL, 0, NULL, NULL);
	PEM_write_bio_RSAPublicKey(pub, keypair);
 
	// 获取长度  
	pri_len = BIO_pending(pri);
	pub_len = BIO_pending(pub);
 
	// 密钥对读取到字符串  
	pri_key = (char *)malloc(pri_len + 1);
	pub_key = (char *)malloc(pub_len + 1);
 
	BIO_read(pri, pri_key, pri_len);
	BIO_read(pub, pub_key, pub_len);
 
	pri_key[pri_len] = '\0';
	pub_key[pub_len] = '\0';
 
	// 存储密钥对  
	strKey[0] = pub_key;
	strKey[1] = pri_key;
 
	// 存储到磁盘（这种方式存储的是begin rsa public key/ begin rsa private key开头的）
	FILE *pubFile = fopen(PUB_KEY_FILE, "w");
	if (pubFile == NULL)
	{
		assert(false);
		return;
	}
	fputs(pub_key, pubFile);
	fclose(pubFile);
 
	FILE *priFile = fopen(PRI_KEY_FILE, "w");
	if (priFile == NULL)
	{
		assert(false);
		return;
	}
	fputs(pri_key, priFile);
	fclose(priFile);
 
	// 内存释放
	RSA_free(keypair);
	BIO_free_all(pub);
	BIO_free_all(pri);
 
	free(pri_key);
	free(pub_key);
}
 
// 命令行方法生成公私钥对（begin public key/ begin private key）
// 找到openssl命令行工具，运行以下
// openssl genrsa -out prikey.pem 1024 
// openssl rsa - in privkey.pem - pubout - out pubkey.pem
 
// 公钥加密  
std::string rsa_pub_encrypt(const std::string &clearText, const std::string &pubKey)
{
	std::string strRet;
	RSA *rsa = NULL;
	BIO *keybio = BIO_new_mem_buf((unsigned char *)pubKey.c_str(), -1);
	// 此处有三种方法
	// 1, 读取内存里生成的密钥对，再从内存生成rsa
	// 2, 读取磁盘里生成的密钥对文本文件，在从内存生成rsa
	// 3，直接从读取文件指针生成rsa
	RSA* pRSAPublicKey = RSA_new();
	rsa = PEM_read_bio_RSAPublicKey(keybio, &rsa, NULL, NULL);
 
	int len = RSA_size(rsa);
	char *encryptedText = (char *)malloc(len + 1);
	memset(encryptedText, 0, len + 1);
 
	// 加密函数
	int ret = RSA_public_encrypt(clearText.length(), (const unsigned char*)clearText.c_str(), (unsigned char*)encryptedText, rsa, RSA_PKCS1_PADDING);
	if (ret >= 0)
		strRet = std::string(encryptedText, ret);
 
	// 释放内存
	free(encryptedText);
	BIO_free_all(keybio);
	RSA_free(rsa);
 
	return strRet;
}
 
// 私钥解密  
std::string rsa_pri_decrypt(const std::string &cipherText, const std::string &priKey)
{
	std::string strRet;
	RSA *rsa = RSA_new();
	BIO *keybio;
	keybio = BIO_new_mem_buf((unsigned char *)priKey.c_str(), -1);
 
	// 此处有三种方法
	// 1, 读取内存里生成的密钥对，再从内存生成rsa
	// 2, 读取磁盘里生成的密钥对文本文件，在从内存生成rsa
	// 3，直接从读取文件指针生成rsa
	rsa = PEM_read_bio_RSAPrivateKey(keybio, &rsa, NULL, NULL);
 
	int len = RSA_size(rsa);
	char *decryptedText = (char *)malloc(len + 1);
	memset(decryptedText, 0, len + 1);
 
	// 解密函数
	int ret = RSA_private_decrypt(cipherText.length(), (const unsigned char*)cipherText.c_str(), (unsigned char*)decryptedText, rsa, RSA_PKCS1_PADDING);
	if (ret >= 0)
		strRet = std::string(decryptedText, ret);
 
	// 释放内存
	free(decryptedText);
	BIO_free_all(keybio);
	RSA_free(rsa);
 
	return strRet;
}
 
int main(int argc, char **argv)
{
	// 原始明文  
	std::string srcText = "this is an example";
 
	std::string encryptText;
	std::string encryptHexText;
	std::string decryptText;
 
	std::cout << "=== 原始明文 ===" << std::endl;
	std::cout << srcText << std::endl;
 
	// md5  
	std::cout << "=== md5哈希 ===" << std::endl;
	md5(srcText, encryptText, encryptHexText);
	std::cout << "摘要字符： " << encryptText << std::endl;
	std::cout << "摘要串： " << encryptHexText << std::endl;
 
	// sha256  
	std::cout << "=== sha256哈希 ===" << std::endl;
	sha256(srcText, encryptText, encryptHexText);
	std::cout << "摘要字符： " << encryptText << std::endl;
	std::cout << "摘要串： " << encryptHexText << std::endl;
 
	// des  
	std::cout << "=== des加解密 ===" << std::endl;
	std::string desKey = "12345";
	encryptText = des_encrypt(srcText, desKey);
	std::cout << "加密字符： " << std::endl;
	std::cout << encryptText << std::endl;
	decryptText = des_decrypt(encryptText, desKey);
	std::cout << "解密字符： " << std::endl;
	std::cout << decryptText << std::endl;
 
	// rsa  
	std::cout << "=== rsa加解密 ===" << std::endl;
	std::string key[2];
	generateRSAKey(key);
	std::cout << "公钥: " << std::endl;
	std::cout << key[0] << std::endl;
	std::cout << "私钥： " << std::endl;
	std::cout << key[1] << std::endl;
	encryptText = rsa_pub_encrypt(srcText, key[0]);
	std::cout << "加密字符： " << std::endl;
	std::cout << encryptText << std::endl;
	decryptText = rsa_pri_decrypt(encryptText, key[1]);
	std::cout << "解密字符： " << std::endl;
	std::cout << decryptText << std::endl;
 
	system("pause");
	return 0;
}
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