GEM is free and friendly android application.

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Bluetooth communication (no Internet required)

GEM requires smartphone users to enable the bluetooth communication to exchange their e-card information. Two users do not need to put smartphones back-to-back (like NFC), but their distance has to be less than 10 meters. Each exchange will do a pair operation with a default password.

Selective sending based gesture recognition

Traditionally, users will not arbitrarily choose neighbors to give out the name cards. They usually chat with others for a while and get to know others' background. If they need to further know the details or keep in touch with others in the future, they will exchange name cards for more effective communications. Therefore, selective sending is unique feature of name card exchange application.

The bluetooth communication of smartphones does not provide enough security protection. For example, a malicious attacker can change its own name and MAC address of smartphone to pretend someone else. The default password does not provide any help.

The solution of GEM is inspired from the traditional handshake gesture. GEM requires each SU to perform a gesture at the beginning. The gestures are as simple as shaking the smartphone towards an up, down, left, and right direction, or a composition of these simple gestures. One user need to repeat the gesture of the other and send the gesture information back to the original user. After confirming the right gesture, the original user then sends the e-card. Gestures can be regarded as temporary passwords only visible to close-enough users. Without seeing and repeating the gestures, the original user never proceed on sending the e-card.

Information protection of e-card

Although the gestures are used to confirm the involvement of right users, man-in-the-middle (MITM) attackers are able to successfully attack the GEM applications. As shown in the following figure, the MITM attackers A can obtain the namecards by intercepting the communications between U1 and U2.

To prevent the man-in-the-middle attacks, GEM further adopts identity-based crypto (IBC) systems. The MITM attackers can only obtain the encrypted e-card by delibrately hacking the communications (more details). However, without the the correct private key, the attackers cannot decrypt the ciphertext and obtain the e-card. The motivation of attackers is largely reduced, and the GEM can well protect the e-card information.

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