Linux系統中C++如何加密

在Linux系統中，C++可以通過多種方式實現加密。以下是一些常用的加密庫和方法：

1. OpenSSL

OpenSSL是一個強大的開源加密庫，提供了廣泛的加密算法和工具。

安裝OpenSSL

sudo apt-get update
sudo apt-get install libssl-dev

使用OpenSSL進行加密和解密

#include <openssl/aes.h>
#include <openssl/rand.h>
#include <iostream>
#include <vector>

void encrypt(const std::string& plaintext, std::vector<unsigned char>& ciphertext) {
    AES_KEY enc_key;
    unsigned char key[AES_KEYLEN_256];
    unsigned char iv[AES_BLOCK_SIZE];

    // Generate a random key and IV
    if (!RAND_bytes(key, sizeof(key)) || !RAND_bytes(iv, sizeof(iv))) {
        throw std::runtime_error("Failed to generate key or IV");
    }

    // Set up the encryption key
    AES_set_encrypt_key(key, sizeof(key) * 8, &enc_key);

    // Allocate space for the ciphertext
    ciphertext.resize(plaintext.size() + AES_BLOCK_SIZE);

    // Perform the encryption
    AES_cbc_encrypt(reinterpret_cast<const unsigned char*>(plaintext.c_str()), 
                    ciphertext.data(), 
                    plaintext.size(), 
                    &enc_key, 
                    iv, 
                    AES_ENCRYPT);
}

void decrypt(const std::vector<unsigned char>& ciphertext, std::string& plaintext) {
    AES_KEY dec_key;
    unsigned char key[AES_KEYLEN_256];
    unsigned char iv[AES_BLOCK_SIZE];

    // Use the same key and IV used for encryption
    // In a real application, you should store the key and IV securely
    if (!RAND_bytes(key, sizeof(key)) || !RAND_bytes(iv, sizeof(iv))) {
        throw std::runtime_error("Failed to generate key or IV");
    }

    // Set up the decryption key
    AES_set_decrypt_key(key, sizeof(key) * 8, &dec_key);

    // Allocate space for the decrypted text
    plaintext.resize(ciphertext.size());

    // Perform the decryption
    AES_cbc_encrypt(ciphertext.data(), 
                    reinterpret_cast<unsigned char*>(&plaintext), 
                    ciphertext.size(), 
                    &dec_key, 
                    iv, 
                    AES_DECRYPT);
}

int main() {
    std::string plaintext = "Hello, World!";
    std::vector<unsigned char> ciphertext;

    try {
        encrypt(plaintext, ciphertext);

        std::cout << "Ciphertext: ";
        for (auto byte : ciphertext) {
            std::cout << std::hex << byte;
        }
        std::cout << std::endl;

        std::string decrypted_text;
        decrypt(ciphertext, decrypted_text);

        std::cout << "Decrypted text: " << decrypted_text << std::endl;
    } catch (const std::exception& e) {
        std::cerr << "Error: " << e.what() << std::endl;
    }

    return 0;
}

2. Crypto++

Crypto++是一個純C++編寫的加密庫，提供了豐富的加密算法和工具。

安裝Crypto++

sudo apt-get update
sudo apt-get install libcrypto++-dev

使用Crypto++進行加密和解密

#include <cryptopp/aes.h>
#include <cryptopp/modes.h>
#include <cryptopp/filters.h>
#include <iostream>
#include <vector>

void encrypt(const std::string& plaintext, std::vector<unsigned char>& ciphertext) {
    CryptoPP::AES::Encryption aesEncryption((const byte*)key, CryptoPP::AES::DEFAULT_KEYLENGTH);
    CryptoPP::CBC_Mode_ExternalCipher::Encryption cbcEncryption(aesEncryption, (const byte*)iv);

    CryptoPP::StreamTransformationFilter stfEncryptor(cbcEncryption, new CryptoPP::StringSink(ciphertext));
    stfEncryptor.Put(reinterpret_cast<const byte*>(plaintext.c_str()), plaintext.size());
    stfEncryptor.MessageEnd();
}

void decrypt(const std::vector<unsigned char>& ciphertext, std::string& plaintext) {
    CryptoPP::AES::Decryption aesDecryption((const byte*)key, CryptoPP::AES::DEFAULT_KEYLENGTH);
    CryptoPP::CBC_Mode_ExternalCipher::Decryption cbcDecryption(aesDecryption, (const byte*)iv);

    CryptoPP::StreamTransformationFilter stfDecryptor(cbcDecryption, new CryptoPP::StringSink(plaintext));
    stfDecryptor.Put(ciphertext.data(), ciphertext.size());
    stfDecryptor.MessageEnd();
}

int main() {
    std::string key = "0123456789abcdef"; // 128-bit key
    std::string iv = "abcdef0123456789";   // 128-bit IV
    std::string plaintext = "Hello, World!";
    std::vector<unsigned char> ciphertext;

    try {
        encrypt(plaintext, ciphertext);

        std::cout << "Ciphertext: ";
        for (auto byte : ciphertext) {
            std::cout << std::hex << byte;
        }
        std::cout << std::endl;

        std::string decrypted_text;
        decrypt(ciphertext, decrypted_text);

        std::cout << "Decrypted text: " << decrypted_text << std::endl;
    } catch (const std::exception& e) {
        std::cerr << "Error: " << e.what() << std::endl;
    }

    return 0;
}

3. GnuPG

GnuPG是一個用于加密和解密的工具，也可以通過命令行或編程接口使用。

安裝GnuPG

sudo apt-get update
sudo apt-get install gnupg

使用GnuPG進行加密和解密

#include <iostream>
#include <string>
#include <cstdlib>

std::string exec(const char* cmd) {
    std::array<char, 128> buffer;
    std::string result;
    FILE* pipe = popen(cmd, "r");
    if (!pipe) throw std::runtime_error("popen() failed!");
    while (fgets(buffer.data(), buffer.size(), pipe) != nullptr) {
        result += buffer.data();
    }
    pclose(pipe);
    return result;
}

void encrypt(const std::string& plaintext, const std::string& recipient) {
    std::string cmd = "echo -n '" + plaintext + "' | gpg --encrypt --recipient " + recipient;
    std::string ciphertext = exec(cmd.c_str());
    std::cout << "Ciphertext: " << ciphertext << std::endl;
}

void decrypt(const std::string& ciphertext, const std::string& passphrase) {
    std::string cmd = "echo -n '" + ciphertext + "' | gpg --decrypt --passphrase-fd 0";
    setenv("GNUPG_PASSPHRASE", passphrase, 1);
    std::string decrypted_text = exec(cmd.c_str());
    std::cout << "Decrypted text: " << decrypted_text << std::endl;
}

int main() {
    std::string plaintext = "Hello, World!";
    std::string recipient = "your-recipient@example.com";
    std::string passphrase = "your-passphrase";

    try {
        encrypt(plaintext, recipient);

        std::string ciphertext = "your-ciphertext-here"; // Replace with actual ciphertext
        decrypt(ciphertext, passphrase);
    } catch (const std::exception& e) {
        std::cerr << "Error: " << e.what() << std::endl;
    }

    return 0;
}

以上是幾種在Linux系統中使用C++進行加密的方法。選擇哪種方法取決于你的具體需求和環境。