text: fs = require('fs');
  const Auth = require('./auth.js');
  const auth = new Auth();
  
  function Utilize () {
  
      this.get_key = function (username, pvk=true) {
          var fname_kv = null;
          if (pvk) {
              fname_kv = username + '.key.pem';
          } else {
              fname_kv = './cards/' + username + '.pem';
          }
          // if (fs.readdirSync('./').indexOf(fname_kv) == -1) {
          //     console.log('Invalid username!');
          //     return -1;
          // }
          try {
              kv = auth.import_key(fname_kv);
          } catch (error) {
              console.log('! Cannot import key file ' + fname_kv);
              return -1;
          }
          return kv;
      }
  }
  
  module.exports = Utilize;