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Technologies
We use any communication protocol provided by a mobile phone to exchange data. Currently, four different technologies are supported (and used): Mail, Wifi-Direct, Bluetooth and NFC.
Wifi-Direct, Bluetooth and NFC are technologies to create spontaneous lokal networks. Those networks have a radius of under a centimeter (NFC) up to a hundred meters (WLAN). Sending data in lokal networks requires no IT communication infrastructure (no Internet provider). That means, it is free of charge and no digital traces are produced but on the mobiles phones.
Whenever possible, SharkNet uses lokal networks.
Larger distances are bridged by e-mail or by a SharkNet hop protocol which isn't yet implemented. Have a look for details on communication protocols on that page.
We are using Mail to send or retrieve Message if the users are not in the range to create an ad-Hoc network. But why are we using the Mail Technology and not a normal Server to exchange the data? The answer is that by forcing the user to enter the complete Mail Settings and even different Mail provider we can achieve that the messages will be send and retrieved by multiple servers an not just a single one. So it will be not that easy to restore a chat protocol if the messages are lying on different servers. That a decentralized Approach. During the Alpha phase we are allowing even the biggest Mail provider, but withing the next Releases we want to disallow the usage of theses providers. E.g. if all the users end up using their Google Mail to send their messages in SharkNet, all the chat conversations will be stored or leastwise send and retrieved on Google Servers. This is not the Approach we are aiming for.
Wifi-Direct gave us the opportunity to find users that are nearby using the same Service. By Service I mean a DNS Discovery Service. Android allows us to create a DNS Service and also listening to Services published by other Devices nearby. This way we accomplished a Chat with users nearby. Within this published DNS we are storing information about the sending user and his MAC Address. This allows us to use Bluetooth to send the Data. But why are we not using Wifi-Direct to send the Data? During the review of the technologies we came to the conclusion that the usage of Wifi-Direct is too error prone and took too much time to establish a connection within the created network. SharkNet will be mainly being used by devices that weren't static objects. Users are moving and so it is important that connections to other users will be established as fast as possible.
So by publishing our MAC Address it will be possible for the other users to connect to us using an RFCOMM.
By the Usage of NFC we removed any possibilities for Man-in-the-middle attacks during our key exchange. So any keys we are retrieving or sending will be transmitted using NFC. This means that is only possible to exchange keys by seeing each other!