椭圆曲线加密算法c语言实现

以下是一个基本的椭圆曲线加密算法的C语言实现：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/ec.h>
#include <openssl/rand.h>
#include <openssl/err.h>
#include <openssl/evp.h>

#define BUF_SIZE 1024

int main(int argc, char **argv) {
int ret = 0;
int i = 0;
char msg[BUF_SIZE] = "Hello World!";
size_t msg_len = strlen(msg);

EC_KEY *key = NULL;
const EC_GROUP *group = NULL;
const EC_POINT *pub_key = NULL;
const BIGNUM *priv_key = NULL;

unsigned char *enc_msg = NULL;
size_t enc_msg_len = 0;
unsigned char *dec_msg = NULL;
size_t dec_msg_len = 0;

OpenSSL_add_all_algorithms();
ERR_load_crypto_strings();

// 创建椭圆曲线密钥对
key = EC_KEY_new_by_curve_name(NID_X9_62_prime256v1);
if (!key) {
fprintf(stderr, "Failed to create EC key\n");
return -1;
}

// 生成公私钥对
ret = EC_KEY_generate_key(key);
if (!ret) {
fprintf(stderr, "Failed to generate EC key pair\n");
EC_KEY_free(key);
return -1;
}

// 获取椭圆曲线参数
group = EC_KEY_get0_group(key);
if (!group) {
fprintf(stderr, "Failed to get EC group\n");
EC_KEY_free(key);
return -1;
}

// 获取公私钥
pub_key = EC_KEY_get0_public_key(key);
if (!pub_key) {
fprintf(stderr, "Failed to get EC public key\n");
EC_KEY_free(key);
return -1;
}
priv_key = EC_KEY_get0_private_key(key);
if (!priv_key) {
fprintf(stderr, "Failed to get EC private key\n");
EC_KEY_free(key);
return -1;
}

// 加密消息
enc_msg = (unsigned char*) malloc(msg_len + 1);
if (!enc_msg) {
fprintf(stderr, "Failed to allocate memory for encrypted message\n");
EC_KEY_free(key);
return -1;
}
memset(enc_msg, 0, msg_len + 1);

EVP_PKEY *evp_key = EVP_PKEY_new();
EVP_PKEY_set1_EC_KEY(evp_key, key);
EVP_CIPHER_CTX *ctx = EVP_CIPHER_CTX_new();

ret = EVP_EncryptInit_ex(ctx, EVP_aes_256_cbc(), NULL, NULL, NULL);
if (!ret) {
fprintf(stderr, "Failed to initialize encryption context\n");
goto cleanup;
}
ret = EVP_EncryptInit_ex(ctx, NULL, NULL, EC_POINT_point2oct(group, pub_key, POINT_CONVERSION_UNCOMPRESSED, NULL, 0, NULL), NULL);
if (!ret) {
fprintf(stderr, "Failed to set encryption key\n");
goto cleanup;
}
ret = EVP_EncryptUpdate(ctx, enc_msg, (int*) &enc_msg_len, (unsigned char*) msg, (int) msg_len);
if (!ret) {
fprintf(stderr, "Failed to encrypt message\n");
goto cleanup;
}
ret = EVP_EncryptFinal_ex(ctx, enc_msg + enc_msg_len, (int*) &i);
if (!ret) {
fprintf(stderr, "Failed to finalize encryption\n");
goto cleanup;
}
enc_msg_len += i;

// 解密消息
dec_msg = (unsigned char*) malloc(enc_msg_len + 1);
if (!dec_msg) {
fprintf(stderr, "Failed to allocate memory for decrypted message\n");
goto cleanup;
}
memset(dec_msg, 0, enc_msg_len + 1);

ret = EVP_DecryptInit_ex(ctx, EVP_aes_256_cbc(), NULL, NULL, NULL);
if (!ret) {
fprintf(stderr, "Failed to initialize decryption context\n");
goto cleanup;
}
ret = EVP_DecryptInit_ex(ctx, NULL, NULL, EC_KEY_get0_private_key(key), NULL);
if (!ret) {
fprintf(stderr, "Failed to set decryption key\n");
goto cleanup;
}
ret = EVP_DecryptUpdate(ctx, dec_msg, (int*) &dec_msg_len, enc_msg, (int) enc_msg_len);
if (!ret) {
fprintf(stderr, "Failed to decrypt message\n");
goto cleanup;
}
ret = EVP_DecryptFinal_ex(ctx, dec_msg + dec_msg_len, (int*) &i);
if (!ret) {
fprintf(stderr, "Failed to finalize decryption\n");
goto cleanup;
}
dec_msg_len += i;

printf("Original message: %s\n", msg);
printf("Encrypted message: ");
for (i = 0; i < enc_msg_len; i++) {
printf("%02x", enc_msg[i]);
}
printf("\n");
printf("Decrypted message: %s\n", dec_msg);

cleanup:
if (enc_msg) {
free(enc_msg);
}
if (dec_msg) {
free(dec_msg);
}
if (ctx) {
EVP_CIPHER_CTX_free(ctx);
}
if (evp_key) {
EVP_PKEY_free(evp_key);
}
if (key) {
EC_KEY_free(key);
}

ERR_free_strings();
EVP_cleanup();

return ret;
}