C++ openssl ES256

ES256是一种基于椭圆曲线的数字签名算法，它使用256位的密钥长度，提供了比RSA更高的安全性和更短的密钥长度。下面是一个使用C++和OpenSSL库实现ES256签名和验证的例子：

#include <openssl/ec.h>
#include <openssl/ecdsa.h>
#include <openssl/obj_mac.h>
#include <openssl/evp.h>
#include <openssl/bio.h>
#include <openssl/pem.h>
#include <iostream>
#include <string>

// 生成EC_KEY对象
EC_KEY* generateECKey()
{
    EC_KEY* ec_key = EC_KEY_new_by_curve_name(NID_X9_62_prime256v1);
    if (ec_key == nullptr)
    {
        std::cerr << "Failed to generate EC key" << std::endl;
        return nullptr;
    }
    if (EC_KEY_generate_key(ec_key) != 1)
    {
        std::cerr << "Failed to generate EC key" << std::endl;
        EC_KEY_free(ec_key);
        return nullptr;
    }
    return ec_key;
}

// 对数据进行ES256签名
std::string signData(const std::string& data, EC_KEY* ec_key)
{
    EVP_MD_CTX* md_ctx = EVP_MD_CTX_new();
    if (md_ctx == nullptr)
    {
        std::cerr << "Failed to create EVP_MD_CTX" << std::endl;
        return "";
    }
    if (EVP_DigestSignInit(md_ctx, nullptr, EVP_sha256(), nullptr, ec_key) != 1)
    {
        std::cerr << "Failed to initialize digest sign context" << std::endl;
        EVP_MD_CTX_free(md_ctx);
        return "";
    }
    if (EVP_DigestSignUpdate(md_ctx, data.c_str(), data.length()) != 1)
    {
        std::cerr << "Failed to update digest sign context" << std::endl;
        EVP_MD_CTX_free(md_ctx);
        return "";
    }
    size_t sig_len = EVP_PKEY_size(EC_KEY_get0_private_key(ec_key));
    std::string signature(sig_len, 0);
    if (EVP_DigestSignFinal(md_ctx, reinterpret_cast<unsigned char*>(signature.data()), &sig_len) != 1)
    {
        std::cerr << "Failed to finalize digest sign context" << std::endl;
        EVP_MD_CTX_free(md_ctx);
        return "";
    }
    signature.resize(sig_len);
    EVP_MD_CTX_free(md_ctx);
    return signature;
}

// 验证ES256签名
bool verifySignature(const std::string& data, const std::string& signature, EC_KEY* ec_key)
{
    EVP_MD_CTX* md_ctx = EVP_MD_CTX_new();
    if (md_ctx == nullptr)
    {
        std::cerr << "Failed to create EVP_MD_CTX" << std::endl;
        return false;
    }
    if (EVP_DigestVerifyInit(md_ctx, nullptr, EVP_sha256(), nullptr, ec_key) != 1)
    {
        std::cerr << "Failed to initialize digest verify context" << std::endl;
        EVP_MD_CTX_free(md_ctx);
        return false;
    }
    if (EVP_DigestVerifyUpdate(md_ctx, data.c_str(), data.length()) != 1)
    {
        std::cerr << "Failed to update digest verify context" << std::endl;
        EVP_MD_CTX_free(md_ctx);
        return false;
    }
    int result = EVP_DigestVerifyFinal(md_ctx, reinterpret_cast<const unsigned char*>(signature.c_str()), signature.length());
    EVP_MD_CTX_free(md_ctx);
    return result == 1;
}

// 测试ES256签名和验证
void testES256()
{
    std::string data = "Hello, world!";
    EC_KEY* ec_key = generateECKey();
    if (ec_key == nullptr)
    {
        return;
    }
    std::string signature = signData(data, ec_key);
    if (signature.empty())
    {
        EC_KEY_free(ec_key);
        return;
    }
    bool verified = verifySignature(data, signature, ec_key);
    std::cout << "Verified: " << std::boolalpha << verified << std::endl;
    EC_KEY_free(ec_key);
}

int main()
{
    testES256();
    return 0;
}