bool get_sn_from_coc(const std::string & file , std::vector<std::string> & key_id_storage)
{
    key_id_storage.clear();

    BIO *bio;
    const char * file_name = file.c_str();
    X509_REVOKED * r = NULL;
//--------------------------------------------------------------
//open file
    if (file_name == NULL)
    {
        std::string msg ="file name is empty";
        throw sos_exception(msg.c_str());
    }
    else
    {
        bio = BIO_new_file(file_name, "r");
    }

    if (bio == NULL)
    {
        std::string msg ="Error open file ";
        msg.append(file); 
        throw sos_exception(msg.c_str());
    }
//--------------------------------------------------------------
    STACK_OF(X509_INFO) *xis = PEM_X509_INFO_read_bio(bio, NULL,NULL, NULL);
//--------------------------------------------------------------
    if (xis ==NULL )
    {
        std::string msg ="Error read bio file ";
        msg.append(file); 
        throw sos_exception(msg.c_str());
    }
    BIO_free(bio);
//--------------------------------------------------------------
    X509_INFO *xi =NULL;

    for(int i = 0; i < sk_X509_INFO_num(xis); i++)
    {

        xi = sk_X509_INFO_value (xis, i);
        //do paranoi check :)
        if (xi ==NULL )
        {
            std::string msg ="Error read X509_INFO_value from file ";
            msg.append(file); 
            throw sos_exception(msg.c_str());
        }
        if (xi->crl ==NULL )
        {
            std::string msg ="Error read X509_INFO_value (xi->crl) from file ";
            msg.append(file); 
            throw sos_exception(msg.c_str());
        }
        if (xi->crl->crl ==NULL )
        {
            std::string msg ="Error read X509_INFO_value (xi->crl->crl) from file ";
            msg.append(file); 
            throw sos_exception(msg.c_str());
        }
//--------------------------------------------------------------
        if (xi->crl->crl->revoked !=NULL)
        {
            while (sk_X509_REVOKED_num(xi->crl->crl->revoked))
            {
                r=sk_X509_REVOKED_shift(xi->crl->crl->revoked);
                ASN1_INTEGER * serialNumber = r->serialNumber;

                if (serialNumber!=NULL)
                {
                    std::ostringstream out;
                    for (int i = 0 ; i <serialNumber->length ; ++i)
                        out << std::hex<< (serialNumber->data[i]&255);
                    std::string str_key_id = out.str(); 
                    key_id_storage.push_back(str_key_id);
                    X509_REVOKED_free(r);
                }
            }
        }
    }
//--------------------------------------------------------------
    return true;
}