c++ openssl ecc算法大文件加密解密示例代码

下面是一个使用C++和OpenSSL库进行ECC算法大文件加密解密的示例代码：

#include <openssl/ec.h>
#include <openssl/ecdh.h>
#include <openssl/evp.h>
#include <openssl/pem.h>
#include <openssl/err.h>
#include <iostream>
#include <fstream>
#include <string>

using namespace std;

int main()
{
    // 1. 生成ECC密钥对
    EC_KEY *key = EC_KEY_new_by_curve_name(NID_X9_62_prime256v1);
    if (key == NULL)
    {
        cout << "Error: Failed to create ECC key." << endl;
        return 1;
    }
    if (!EC_KEY_generate_key(key))
    {
        cout << "Error: Failed to generate ECC key." << endl;
        EC_KEY_free(key);
        return 1;
    }

    // 2. 保存私钥
    string privkey_filename = "ecc_private.pem";
    FILE *privkey_file = fopen(privkey_filename.c_str(), "w");
    if (privkey_file == NULL)
    {
        cout << "Error: Failed to create private key file." << endl;
        EC_KEY_free(key);
        return 1;
    }
    if (!PEM_write_ECPrivateKey(privkey_file, key, NULL, NULL, 0, NULL, NULL))
    {
        cout << "Error: Failed to write private key." << endl;
        fclose(privkey_file);
        EC_KEY_free(key);
        return 1;
    }
    fclose(privkey_file);

    // 3. 保存公钥
    string pubkey_filename = "ecc_public.pem";
    FILE *pubkey_file = fopen(pubkey_filename.c_str(), "w");
    if (pubkey_file == NULL)
    {
        cout << "Error: Failed to create public key file." << endl;
        EC_KEY_free(key);
        return 1;
    }
    if (!PEM_write_EC_PUBKEY(pubkey_file, key))
    {
        cout << "Error: Failed to write public key." << endl;
        fclose(pubkey_file);
        EC_KEY_free(key);
        return 1;
    }
    fclose(pubkey_file);

    // 4. 加密文件
    string plaintext_filename = "largefile.txt";
    string ciphertext_filename = "largefile.enc";
    ifstream plaintext_file(plaintext_filename, ios::in | ios::binary);
    if (!plaintext_file.is_open())
    {
        cout << "Error: Failed to open plaintext file." << endl;
        EC_KEY_free(key);
        return 1;
    }
    ofstream ciphertext_file(ciphertext_filename, ios::out | ios::binary);
    if (!ciphertext_file.is_open())
    {
        cout << "Error: Failed to create ciphertext file." << endl;
        plaintext_file.close();
        EC_KEY_free(key);
        return 1;
    }

    EVP_PKEY *evp_pubkey = EVP_PKEY_new();
    if (evp_pubkey == NULL)
    {
        cout << "Error: Failed to create EVP public key." << endl;
        plaintext_file.close();
        ciphertext_file.close();
        EC_KEY_free(key);
        return 1;
    }
    if (!EVP_PKEY_set1_EC_KEY(evp_pubkey, key))
    {
        cout << "Error: Failed to set EVP public key." << endl;
        plaintext_file.close();
        ciphertext_file.close();
        EVP_PKEY_free(evp_pubkey);
        EC_KEY_free(key);
        return 1;
    }

    EVP_CIPHER_CTX *ctx = EVP_CIPHER_CTX_new();
    if (ctx == NULL)
    {
        cout << "Error: Failed to create cipher context." << endl;
        plaintext_file.close();
        ciphertext_file.close();
        EVP_PKEY_free(evp_pubkey);
        EC_KEY_free(key);
        return 1;
    }
    if (!EVP_EncryptInit_ex(ctx, EVP_aes_256_cbc(), NULL, NULL, NULL))
    {
        cout << "Error: Failed to initialize encryption context." << endl;
        plaintext_file.close();
        ciphertext_file.close();
        EVP_PKEY_free(evp_pubkey);
        EC_KEY_free(key);
        EVP_CIPHER_CTX_free(ctx);
        return 1;
    }

    unsigned char plaintext_buffer[4096];
    unsigned char ciphertext_buffer[4096 + EVP_CIPHER_block_size(EVP_aes_256_cbc())];
    int num_bytes_read = 0;
    int ciphertext_len = 0;
    while ((num_bytes_read = plaintext_file.read((char *)plaintext_buffer, sizeof(plaintext_buffer)).gcount()) > 0)
    {
        if (!EVP_EncryptInit_ex(ctx, NULL, NULL, NULL, NULL))
        {
            cout << "Error: Failed to reset encryption context." << endl;
            plaintext_file.close();
            ciphertext_file.close();
            EVP_PKEY_free(evp_pubkey);
            EC_KEY_free(key);
            EVP_CIPHER_CTX_free(ctx);
            return 1;
        }
        if (!EVP_EncryptInit_ex(ctx, NULL, NULL, EVP_PKEY_get0(evp_pubkey), NULL))
        {
            cout << "Error: Failed to set public key for encryption context." << endl;
            plaintext_file.close();
            ciphertext_file.close();
            EVP_PKEY_free(evp_pubkey);
            EC_KEY_free(key);
            EVP_CIPHER_CTX_free(ctx);
            return 1;
        }
        if (!EVP_EncryptUpdate(ctx, ciphertext_buffer, &ciphertext_len, plaintext_buffer, num_bytes_read))
        {
            cout << "Error: Failed to encrypt plaintext." << endl;
            plaintext_file.close();
            ciphertext_file.close();
            EVP_PKEY_free(evp_pubkey);
            EC_KEY_free(key);
            EVP_CIPHER_CTX_free(ctx);
            return 1;
        }
        ciphertext_file.write((char *)ciphertext_buffer, ciphertext_len);
    }
    if (!EVP_EncryptFinal_ex(ctx, ciphertext_buffer, &ciphertext_len))
    {
        cout << "Error: Failed to finalize encryption." << endl;
        plaintext_file.close();
        ciphertext_file.close();
        EVP_PKEY_free(evp_pubkey);
        EC_KEY_free(key);
        EVP_CIPHER_CTX_free(ctx);
        return 1;
    }
    ciphertext_file.write((char *)ciphertext_buffer, ciphertext_len);

    plaintext_file.close();
    ciphertext_file.close();
    EVP_PKEY_free(evp_pubkey);
    EC_KEY_free(key);
    EVP_CIPHER_CTX_free(ctx);

    // 5. 解密文件
    ifstream ciphertext_file2(ciphertext_filename, ios::in | ios::binary);
    if (!ciphertext_file2.is_open())
    {
        cout << "Error: Failed to open ciphertext file." << endl;
        return 1;
    }
    ofstream plaintext_file2("largefile.dec", ios::out | ios::binary);
    if (!plaintext_file2.is_open())
    {
        cout << "Error: Failed to create plaintext file." << endl;
        ciphertext_file2.close();
        return 1;
    }

    EVP_PKEY *evp_privkey = EVP_PKEY_new();
    if (evp_privkey == NULL)
    {
        cout << "Error: Failed to create EVP private key." << endl;
        ciphertext_file2.close();
        plaintext_file2.close();
        return 1;
    }
    if (!EVP_PKEY_set1_EC_KEY(evp_privkey, key))
    {
        cout << "Error: Failed to set EVP private key." << endl;
        ciphertext_file2.close();
        plaintext_file2.close();
        EVP_PKEY_free(evp_privkey);
        return 1;
    }

    ctx = EVP_CIPHER_CTX_new();
    if (ctx == NULL)
    {
        cout << "Error: Failed to create cipher context." << endl;
        ciphertext_file2.close();
        plaintext_file2.close();
        EVP_PKEY_free(evp_privkey);
        return 1;
    }
    if (!EVP_DecryptInit_ex(ctx, EVP_aes_256_cbc(), NULL, NULL, NULL))
    {
        cout << "Error: Failed to initialize decryption context." << endl;
        ciphertext_file2.close();
        plaintext_file2.close();
        EVP_PKEY_free(evp_privkey);
        EVP_CIPHER_CTX_free(ctx);
        return 1;
    }

    ciphertext_len = 0;
    int plaintext_len = 0;
    while ((ciphertext_file2.read((char *)ciphertext_buffer, sizeof(ciphertext_buffer)).gcount()) > 0)
    {
        if (!EVP_DecryptInit_ex(ctx, NULL, NULL, EVP_PKEY_get0(evp_privkey), NULL))
        {
            cout << "Error: Failed to set private key for decryption context." << endl;
            ciphertext_file2.close();
            plaintext_file2.close();
            EVP_PKEY_free(evp_privkey);
            EVP_CIPHER_CTX_free(ctx);
            return 1;
        }
        if (!EVP_DecryptUpdate(ctx, plaintext_buffer, &plaintext_len, ciphertext_buffer, ciphertext_file2.gcount()))
        {
            cout << "Error: Failed to decrypt ciphertext." << endl;
            ciphertext_file2.close();
            plaintext_file2.close();
            EVP_PKEY_free(evp_privkey);
            EVP_CIPHER_CTX_free(ctx);
            return 1;
        }
        plaintext_file2.write((char *)plaintext_buffer, plaintext_len);
    }
    if (!EVP_DecryptFinal_ex(ctx, plaintext_buffer, &plaintext_len))
    {
        cout << "Error: Failed to finalize decryption." << endl;
        ciphertext_file2.close();
        plaintext_file2.close();
        EVP_PKEY_free(evp_privkey);
        EVP_CIPHER_CTX_free(ctx);
        return 1;
    }
    plaintext_file2.write((char *)plaintext_buffer, plaintext_len);

    ciphertext_file2.close();
    plaintext_file2.close();
    EVP_PKEY_free(evp_privkey);
    EVP_CIPHER_CTX_free(ctx);

    cout << "ECC encryption and decryption completed successfully." << endl;

    return 0;
}

注意：为了简化代码，这里没有进行错误处理和参数检查，实际应用中需要根据需要进行适当的错误处理和参数检查。