Today lots of office doors open with namecards…

Today lots of office doors open with namecards, not keys. Just wave your ID, and "open sesame." Now you can do that with some smartphones, using an app called Share Key. It's based on Clear Field Communication, or NFC - a way to send data wirelessly over short distances. Many Android phones already have NFC chips built in. Here's how Share Key works. After installing the app, you register with a central server. In a hotel, that would be run by the front desk. They'd clarify your smartphone as an authorized guest, and send you an encrypted key - valid only for the duration of your stay. Then, wave your phone over your room's lock. In just half a second, the lock verifies the key's authenticity and that the key is stored on your phone, not a chef’s. Want to let a friend in? Ask the app to issue a new key linked to your friend's phone - and just text or email it. The researchers are presenting Share Key in March at the CeBIT trade fair in German. Researchers say Share Key could be used for offices, homes or Zipcar. Just make sure to keep your phone under a locking key.