C++ 语言密码学在 C++ 中的应用

C++ 中密码学应用技术详解

密码学是研究信息加密、解密和认证的科学，它在保护信息安全、确保数据传输安全等方面发挥着至关重要的作用。C++ 作为一种高性能的编程语言，在密码学领域有着广泛的应用。本文将围绕 C++ 语言，探讨密码学在 C++ 中的应用技术，包括对称加密、非对称加密、哈希函数和数字签名等。

一、对称加密

对称加密是一种加密和解密使用相同密钥的加密方式。在 C++ 中，可以使用各种库来实现对称加密，如 OpenSSL。

1.1 OpenSSL 库

OpenSSL 是一个开源的加密库，支持多种加密算法。以下是一个使用 OpenSSL 实现AES对称加密的示例代码：

cpp include include include


int main() {

    const int keySize = 16; // AES-128

    unsigned char key[keySize];

    RAND_bytes(key, keySize);
    const int ivSize = 16; // AES-128

    unsigned char iv[ivSize];

    RAND_bytes(iv, ivSize);
    const int dataSize = 64;

    unsigned char data[dataSize] = "Hello, World!";

    unsigned char encrypted[dataSize];

    unsigned char decrypted[dataSize];
    AES_keysetup(key, keySize  8, AES_ENCRYPT, iv);

    AES_cbc_encrypt(data, encrypted, dataSize, key, iv, AES_ENCRYPT);
    AES_keysetup(key, keySize  8, AES_DECRYPT, iv);

    AES_cbc_encrypt(encrypted, decrypted, dataSize, key, iv, AES_DECRYPT);
    std::cout << "Original: " << std::string(data, dataSize) << std::endl;

    std::cout << "Encrypted: " << std::string(encrypted, dataSize) << std::endl;

    std::cout << "Decrypted: " << std::string(decrypted, dataSize) << std::endl;

return 0; }

1.2 Crypto++ 库

Crypto++ 是一个开源的加密库，提供了多种加密算法的实现。以下是一个使用 Crypto++ 实现AES对称加密的示例代码：

cpp include include include include include include


int main() {

    const std::string key = "1234567890123456"; // 16字节密钥

    const std::string iv = "1234567890123456"; // 16字节初始化向量

    std::string data = "Hello, World!";
    CryptoPP::AES::SetKey(key.data(), key.size()  8);

    CryptoPP::StringSource ss1(data, true, new CryptoPP::StreamTransformationFilter(

        new CryptoPP::AES::CBC::DecryptionFilter(

            new CryptoPP::StringSink(decrypted),

            new CryptoPP::PKCS7(CryptoPP::AES::blockSize())

        ), new CryptoPP::HexDecoder(new CryptoPP::StringSink(decrypted))));

    std::string decrypted;
    CryptoPP::AES::SetKey(key.data(), key.size()  8);

    CryptoPP::StringSource ss2(decrypted, true, new CryptoPP::StreamTransformationFilter(

        new CryptoPP::AES::CBC::EncryptionFilter(

            new CryptoPP::StringSink(encrypted),

            new CryptoPP::PKCS7(CryptoPP::AES::blockSize())

        ), new CryptoPP::HexEncoder(new CryptoPP::StringSink(encrypted))));

    std::string encrypted;
    std::cout << "Original: " << data << std::endl;

    std::cout << "Encrypted: " << encrypted << std::endl;

    std::cout << "Decrypted: " << decrypted << std::endl;

return 0; }

二、非对称加密

非对称加密使用一对密钥，即公钥和私钥。公钥用于加密，私钥用于解密。在 C++ 中，可以使用 OpenSSL 或 Crypto++ 库来实现非对称加密。

2.1 OpenSSL 库

以下是一个使用 OpenSSL 实现RSA非对称加密的示例代码：

cpp include include include include


int main() {

    // 生成RSA密钥对

    BIGNUM bn = BN_new();

    BN_set_word(bn, RSA_F4);

    RSA rsa = RSA_new();

    RSA_generate_key_ex(rsa, 2048, bn, NULL);
    // 将公钥和私钥写入文件

    FILE pubFile = fopen("public.pem", "wb");

    FILE privFile = fopen("private.pem", "wb");

    PEM_write_RSAPublicKey(pubFile, rsa);

    PEM_write_RSAPrivateKey(privFile, rsa, NULL, NULL, 0, NULL, NULL);

    fclose(pubFile);

    fclose(privFile);
    // 加载公钥和私钥

    FILE pubKeyFile = fopen("public.pem", "rb");

    FILE privKeyFile = fopen("private.pem", "rb");

    RSA pubKey = PEM_read_RSAPublicKey(pubKeyFile, NULL, NULL, NULL);

    RSA privKey = PEM_read_RSAPrivateKey(privKeyFile, NULL, NULL, NULL);

    fclose(pubKeyFile);

    fclose(privKeyFile);
    // 使用公钥加密

    unsigned char encrypted = new unsigned char[RSA_size(rsa)];

    int encryptedLen = RSA_public_encrypt(5, (unsigned char )"Hello, World!", encrypted, rsa, RSA_PKCS1_PADDING);

    std::cout << "Encrypted: " << std::string((char )encrypted, encryptedLen) << std::endl;
    // 使用私钥解密

    unsigned char decrypted = new unsigned char[RSA_size(rsa)];

    int decryptedLen = RSA_private_decrypt(encryptedLen, encrypted, decrypted, rsa, RSA_PKCS1_PADDING);

    std::cout << "Decrypted: " << std::string((char )decrypted, decryptedLen) << std::endl;
    // 清理资源

    RSA_free(rsa);

    RSA_free(pubKey);

    RSA_free(privKey);

    BN_free(bn);

    delete[] encrypted;

    delete[] decrypted;

return 0; }

2.2 Crypto++ 库

以下是一个使用 Crypto++ 实现RSA非对称加密的示例代码：

cpp include include include include


int main() {

    CryptoPP::RSA::PrivateKey privateKey;

    privateKey.GenerateRandomWithKeySize(2048);
    CryptoPP::RSA::PublicKey publicKey;

    publicKey = privateKey;
    std::string data = "Hello, World!";

    std::string encrypted, decrypted;
    CryptoPP::StringSource ss1(data, true, new CryptoPP::PKCS1OAEP::Encryption(

        publicKey,

        new CryptoPP::Base64Decoder(new CryptoPP::StringSink(encrypted))

    ));
    CryptoPP::StringSource ss2(encrypted, true, new CryptoPP::PKCS1OAEP::Decryption(

        privateKey,

        new CryptoPP::Base64Decoder(new CryptoPP::StringSink(decrypted))

    ));
    std::cout << "Original: " << data << std::endl;

    std::cout << "Encrypted: " << encrypted << std::endl;

    std::cout << "Decrypted: " << decrypted << std::endl;

return 0; }

三、哈希函数

哈希函数是一种将任意长度的输入（或“消息”）映射为固定长度的输出（或“哈希值”）的函数。在 C++ 中，可以使用 OpenSSL 或 Crypto++ 库来实现哈希函数。

3.1 OpenSSL 库

以下是一个使用 OpenSSL 实现SHA-256哈希的示例代码：

cpp include include


int main() {

    const char data = "Hello, World!";

    unsigned char hash[SHA256_DIGEST_LENGTH];
    SHA256_CTX sha256;

    SHA256_Init(&sha256);

    SHA256_Update(&sha256, data, strlen(data));

    SHA256_Final(hash, &sha256);
    std::cout << "SHA-256: ";

    for (int i = 0; i < SHA256_DIGEST_LENGTH; i++) {

        std::cout << std::hex << std::setw(2) << std::setfill('0') << (int)hash[i];

    }

    std::cout << std::endl;

return 0; }

3.2 Crypto++ 库

以下是一个使用 Crypto++ 实现SHA-256哈希的示例代码：

cpp include include include


int main() {

    const std::string data = "Hello, World!";

    CryptoPP::SHA256 hash;

    std::string digest;
    hash.Update((const byte)data.data(), data.size());

    hash.Final(digest);
    std::cout << "SHA-256: ";

    CryptoPP::StringSource ss(digest, true, new CryptoPP::HexDecoder(new CryptoPP::StringSink(std::cout)));

    std::cout << std::endl;

return 0; }

四、数字签名

数字签名是一种用于验证消息完整性和身份的技术。在 C++ 中，可以使用 OpenSSL 或 Crypto++ 库来实现数字签名。

4.1 OpenSSL 库

以下是一个使用 OpenSSL 实现RSA数字签名的示例代码：

cpp include include include include


int main() {

    // ...（省略生成密钥对和写入文件的代码）
    // 加载私钥

    FILE privKeyFile = fopen("private.pem", "rb");

    RSA privKey = PEM_read_RSAPrivateKey(privKeyFile, NULL, NULL, NULL);

    fclose(privKeyFile);
    // 加载公钥

    FILE pubKeyFile = fopen("public.pem", "rb");

    RSA pubKey = PEM_read_RSAPublicKey(pubKeyFile, NULL, NULL, NULL);

    fclose(pubKeyFile);
    // 生成签名

    unsigned char signature = new unsigned char[RSA_size(privKey)];

    int signatureLen = RSA_sign(NID_sha256, (unsigned char )"Hello, World!", strlen("Hello, World!"), signature, privKey);
    // 验证签名

    int verifyResult = RSA_verify(NID_sha256, (unsigned char )"Hello, World!", strlen("Hello, World!"), signature, signatureLen, pubKey);
    std::cout << "Signature: ";

    for (int i = 0; i < signatureLen; i++) {

        std::cout << std::hex << std::setw(2) << std::setfill('0') << (int)signature[i];

    }

    std::cout << std::endl;
    std::cout << "Verification: " << (verifyResult ? "Success" : "Failure") << std::endl;
    // 清理资源

    RSA_free(rsa);

    RSA_free(pubKey);

    RSA_free(privKey);

    BN_free(bn);

    delete[] signature;

return 0; }

4.2 Crypto++ 库

以下是一个使用 Crypto++ 实现RSA数字签名的示例代码：

cpp include include include include


int main() {

    // ...（省略生成密钥对和写入文件的代码）
    // 生成签名

    CryptoPP::StringSource ss1(data, true, new CryptoPP::PKCS1WithRSAEncryption(

        privateKey,

        new CryptoPP::Base64Decoder(new CryptoPP::StringSink(signature))

    ));
    // 验证签名

    CryptoPP::StringSource ss2(signature, true, new CryptoPP::PKCS1WithRSAEncryption(

        publicKey,

        new CryptoPP::Base64Decoder(new CryptoPP::StringSink(decrypted))

    ));
    std::cout << "Original: " << data << std::endl;

    std::cout << "Signature: " << signature << std::endl;

    std::cout << "Verification: " << (decrypted == data ? "Success" : "Failure") << std::endl;

return 0; }

结论

本文介绍了 C++ 中密码学应用技术，包括对称加密、非对称加密、哈希函数和数字签名。通过使用 OpenSSL 和 Crypto++ 库，我们可以轻松地在 C++ 程序中实现这些密码学功能。在实际应用中，选择合适的加密算法和库对于确保信息安全至关重要。

C++ 语言密码学在 C++ 中的应用

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