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一、準備工作

1. 安裝依賴

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

2. 確認 OpenSSL 版本

openssl version

如果是 1.1.1 或 3.0+，就支持 SM2/SM3/SM4。

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二、C 語言示例代碼

這個程序會：

1. 生成 SM2 密鑰對
2. 使用公鑰加密一段明文
3. 使用私鑰解密恢復明文

#include <stdio.h>
#include <string.h>
#include <openssl/evp.h>
#include <openssl/ec.h>
#include <openssl/sm2.h>
#include <openssl/pem.h>int main() {EVP_PKEY_CTX *pctx = NULL;EVP_PKEY *pkey = NULL;// ========== 1. 生成 SM2 密鑰對 ==========pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_SM2, NULL);if (!pctx) {printf("EVP_PKEY_CTX_new_id failed\n");return -1;}if (EVP_PKEY_keygen_init(pctx) <= 0) {printf("EVP_PKEY_keygen_init failed\n");return -1;}if (EVP_PKEY_keygen(pctx, &pkey) <= 0) {printf("EVP_PKEY_keygen failed\n");return -1;}EVP_PKEY_CTX_free(pctx);printf("SM2 KeyPair generated successfully!\n");// ========== 2. 加密 ==========const char *plaintext = "Hello, SM2 Encryption!";size_t plaintext_len = strlen(plaintext);size_t ciphertext_len = 0;unsigned char *ciphertext = NULL;if (!SM2_encrypt(EVP_sm3(), (const unsigned char*)plaintext, plaintext_len,NULL, &ciphertext_len, pkey)) {printf("SM2_encrypt (get length) failed\n");return -1;}ciphertext = OPENSSL_malloc(ciphertext_len);if (!ciphertext) {printf("malloc failed\n");return -1;}if (!SM2_encrypt(EVP_sm3(), (const unsigned char*)plaintext, plaintext_len,ciphertext, &ciphertext_len, pkey)) {printf("SM2_encrypt failed\n");return -1;}printf("Ciphertext length = %zu\n", ciphertext_len);// ========== 3. 解密 ==========unsigned char *decrypted = OPENSSL_malloc(ciphertext_len);size_t decrypted_len = 0;if (!SM2_decrypt(EVP_sm3(), ciphertext, ciphertext_len,decrypted, &decrypted_len, pkey)) {printf("SM2_decrypt failed\n");return -1;}decrypted[decrypted_len] = '\0'; // 末尾加字符串結束符printf("Decrypted text: %s\n", decrypted);// ========== 4. 釋放資源 ==========OPENSSL_free(ciphertext);OPENSSL_free(decrypted);EVP_PKEY_free(pkey);return 0;
}

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三、編譯與運行

1. 編譯

gcc sm2_enc_dec.c -o sm2_enc_dec -lcrypto

2. 運行

./sm2_enc_dec

3. 可能的輸出

SM2 KeyPair generated successfully!
Ciphertext length = 115
Decrypted text: Hello, SM2 Encryption!

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四、總結

• EVP_PKEY_keygen() 生成 SM2 密鑰對
• SM2_encrypt() 使用公鑰加密
• SM2_decrypt() 使用私鑰解密
• 這里默認使用 SM3 作為哈希函數（推薦國密組合：SM2+SM3+SM4）

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