openssl下SM4算法OFB模式加解密运算实例

SM4算法ofb接口

加密

int openssl_sm4_encrypt_ofb(unsigned char *key,unsigned char *iv, unsigned char *in_buf, int in_len, unsigned char *out_buf,int* out_len)
{
    EVP_CIPHER_CTX* ctx = NULL;
    ctx = EVP_CIPHER_CTX_new();
    printf("%s %d\n", __func__, __LINE__);
    EVP_EncryptInit_ex(ctx, EVP_sms4_ofb(), NULL, key, iv);
    EVP_CIPHER_CTX_set_padding(ctx, 0);

    if (!EVP_EncryptUpdate(ctx, out_buf, out_len, in_buf, in_len))
    {
        EVP_CIPHER_CTX_free(ctx);
        return -1;
    }

    int tmplen = 0;
    if (!EVP_EncryptFinal_ex(ctx, out_buf + *out_len, &tmplen))
    {
        EVP_CIPHER_CTX_free(ctx);
        return -2;
    }
 
    *out_len += tmplen;

    EVP_CIPHER_CTX_free(ctx);
    return 0;
}

解密

int openssl_sm4_decrypt_ofb(unsigned char *key,unsigned char *iv, unsigned char *in_buf, int in_len, unsigned char *out_buf,int* out_len)
{
    EVP_CIPHER_CTX* ctx = NULL;
    ctx = EVP_CIPHER_CTX_new();
    int ret = 0;
    printf("%s %d\n", __func__, __LINE__);

    EVP_DecryptInit_ex(ctx, EVP_sms4_ofb(), NULL, key, iv);

    if (!EVP_DecryptUpdate(ctx, out_buf, out_len, in_buf, in_len))
    {
        EVP_CIPHER_CTX_free(ctx);
        return -1;
    }

    int tmplen = 0;
    ret = EVP_DecryptFinal_ex(ctx, out_buf + *out_len, &tmplen);
    if (ret)
    {
    //        RSP_TRACE("%s EVP_DecryptFinal_ex error ret=%d\n", __func__, ret);
        EVP_CIPHER_CTX_free(ctx);
        return -2;
    }

    *out_len += tmplen;

    EVP_CIPHER_CTX_free(ctx);
    return 0;
}