C中的OpenSSL:在应用程序运行中进行第二次解密后,结果的前16个字节是垃圾

here . 我不需要这是真正的安全

decryptFileAsBytes 函数返回正确的解密文件作为字节向量。在第二次调用中(在同一个应用程序运行中),结果的前16个字节是垃圾,其余的是正确的。这与我使用的密钥(128位)的大小有关吗?

static bool decryptFileAsBytes(std::string filename, unsigned char *ckey, unsigned char *ivec, std::vector<unsigned char> &fileBytes)
{
    std::ifstream ifs(filename, std::ios::binary | std::ios::ate);
    if (ifs.fail())
        return false;

    std::ifstream::pos_type pos = ifs.tellg();
    fileBytes.resize(pos);
    ifs.close();

    FILE *ifp;
    if (fopen_s(&ifp, filename.c_str(), "rb") != NULL)
        return false;

    int bytesRead;
    unsigned char indata[AES_BLOCK_SIZE];
    unsigned char *writePtr = fileBytes.data();

    /* data structure that contains the key itself */
    AES_KEY key;

    /* set the encryption key */
    AES_set_encrypt_key(ckey, 128, &key);

    /* set where on the 128 bit encrypted block to begin encryption*/
    int num = 0;

    while (1)
    {
        bytesRead = fread(indata, 1, AES_BLOCK_SIZE, ifp);

        AES_cfb128_encrypt(indata, writePtr, bytesRead, &key, ivec, &num, AES_DECRYPT);
        writePtr += bytesRead;

        if (bytesRead < AES_BLOCK_SIZE)
            break;
    }
    if (fclose(ifp) != NULL)
        return false;

    return true;
}