Cloudless Wide Area Friend-to-Friend Networking Middleware for Smartphones Jo Inge Arnes and Randi Karlsen Department of Computer Science, UiT The Arctic University of Norway, Tromsø, Norway Keywords: Cloudless Peer-to-peer Mobile Communication, Friend-to-friend Networking, Unreachable IP Address. Abstract: Swirlwave is a middleware that enables peer-to-peer and distributed computing for Internet-connected de- vices that lack publicly reachable Internet Protocol (IP) addresses, that can be expected to disconnect from the network for periods of time, and that frequently change network locations. This is the typical case for smartphones. The middleware fits into the friend-to-friend subcategory of peer-to-peer systems, meaning that the overlay network is built on top of already existing trust relationships among its users. It is independent of clouds and application servers, it supports encryption for confidentiality and authentication, and it aims to be easily extensible for new applications. The solution described in this paper is implemented for smartphones running the Android operating system, but its principles are not limited to this. 1 INTRODUCTION cerning the app are managed there. The provider of the app usually gathers metadata about user activities, Smartphones and their Internet features are used in a such as whom they communicate with, when, where, wide range of areas in people’s lives. Examples are how often and about what. online banking, keeping up with news, education, ca- The extensive use of cloud services also raises reer, looking up health information, sharing pictures concerns with respect to waste of computing re- and videos, social networking, navigating in traffic, sources. Smartphones today have as much process- just to mention a few. In the U.S. 77 % use their phone ing power, memory, and storage capacity as a typical to share pictures, videos, or comments about events desktop PC a decade ago. With the increasing popu- happening in their community, and nearly one-in- larity of smartphones (Myers, 2016), it seems sensible three smartphone owners frequently use their phone to explore ways to harness more of these hardware re- for navigation (Smith, 2015). sources. The way a user accesses such services is generally An alternative to the cloud-based solutions is to through apps supported by an online service, where enable smartphones to communicate directly in a data is stored in the service provider’s data centers peer-to-peer fashion over the Internet. However, this or cloud services. This makes it possible to access is not a trivial solution, since smartphones usually data from multiple devices, and share with others, lack publicly reachable IP addresses and often change for example by sending a picture to friends through networks, which makes it difficult to keep track of the Snapchat1. In this case, the picture is uploaded to devices’ addresses. Most smartphone apps of today, Snapchat’s servers, the recipient friends are notified therefore, depend on clouds or application servers and can see the picture in their Snapchat app, which as middlemen to enable communication between de- downloads the picture from the Snapchat data center. vices. Smartphone apps that let users share and commu- In this work, we describe a novel approach to nicate with others over the Internet are commonly mobile peer-to-peer communication in wide area net- supported by cloud services, where communication works, which allows direct communication between passes through the cloud data centers. This can be a devices that frequently change networks and lack source of privacy concerns. In addition to storing data public IP addresses. We introduce Swirlware, a mid- that the user uploads, many other types of data con- dleware that enables wide area peer-to-peer commu- nication for smartphones, without the need for clouds 1https://www.snapchat.com or application servers for storing, processing, or shar- 255 Arnes, J. and Karlsen, R. Cloudless Wide Area Friend-to-Friend Networking Middleware for Smartphones. DOI: 10.5220/0006830102550264 In Proceedings of the 15th International Joint Conference on e-Business and Telecommunications (ICETE 2018) - Volume 1: DCNET, ICE-B, OPTICS, SIGMAP and WINSYS, pages 255-264 ISBN: 978-989-758-319-3 Copyright © 2018 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved WINSYS 2018 - International Conference on Wireless Networks and Mobile Systems ing data. Our approach also supports incorporating form for building peer web. It is described as an open- smartphones as nodes in a peer-to-peer or distributed source software platform for creating apps that exploit system, so that storage and processing capacities of the power of personal devices and put people in con- the smartphones can be utilized as part of a bigger trol of their data. Thali planned to use the Tor Onion whole. Service protocol4 (called hidden services at the time), Experiments show that Swirlwave handles cloud- the same protocol as Swirlwave builds on, but aban- less, mobile peer-to-peer communication well. It en- doned the idea, since onion services were designed for ables smartphones to be directly reached and sup- stationary services, not mobile ones.5 It is clear from ports continued communication when devices move the project’s homepage that Thali instead communi- between networks. cates over Bluetooth Low Energy (BLE), Bluetooth, In the following, we first compare Swirlwave to and Wi-Fi direct, none of which are wide area com- related work. We then give an overview of the pro- munications. In contrast to Thali, Swirlwave provides posed system, describing the architecture and under- functionality that enables the use of the Tor Onion lying communication. Section 4 describes the Swirl- Service protocol on mobile devices, can thus support wave middleware. Experiments and results are pre- wide area mobile communication. sented in Section 5, while the last sections present discussions and conclusion. 3 MOBILE PEER-TO-PEER COMMUNICATION WITHOUT 2 RELATED WORK PUBLIC IP ADDRESS The Swirlwave middleware provides a novel solution to peer-to-peer mobile communication, where obsta- This section describes the architecture for Swirlwave cles, such as unreachable IP addresses, disconnec- and how it builds on Tor and the Tor Onion Service tions and frequently changing network locations, are protocol6. We also describe the problem of unreach- handled. We here describe how Swirlwave relates to able IP addresses. previous work on mobile communication. Popescu et al. (Popescu et al., 2006) describe a 3.1 Unreachable Addresses friend-to-friend (F2F) architecture, called Turtle, for safe sharing of sensitive data. As Swirlwave, it builds Usually, when a personal computer is connected to the an overlay network from pre-existing trust relation- Internet, other computers cannot directly contact it. ships. Turtle differs from Swirlwave by being a the- This is because of network address translation (NAT). oretical description of a file sharing network archi- The computer can initiate contact with a server, but tecture, where search queries are flooded through the it cannot act as a server itself. The same is true for network. Swirlwave, on the other hand, is a mid- smartphones. The reason is that computers are not dleware enabling friend-to-friend networking without directly connected to the Internet, but are part of a being tied to specific applications. local area network (LAN) that communicates with the A variety of apps for using smartphones as servers outside world through a router. exist, for example, web servers for Android, but they Devices on a LAN are assigned IP addresses that only work as part of a local area network. To connect, are only valid inside the LAN. In the most common clients must be on the same local area network as the configuration, IPs are assigned by a DHCP-server. A server. This is a serious restriction when using mo- device is given an address when it connects to a LAN, bile devices. Swirlwave enables smartphone server but this address can be different the next time the de- apps to be available outside local area networks and vice connects to the same network. continue communicating with clients despite network When a computer connects to a server on the Inter- changes. net, the server will see the IP of the router. The server Orbot2 allows smartphones to be reached outside sends its replies to the router, which performs network local area networks, but it has no mechanism for address translation and routes the traffic to the correct changing addresses when the smartphone changes lo- computer (Comer, 2014). IPs of computers inside the cation. This problem is solved in Swirlwave, which LAN are not reachable from the Internet. This is also handles address changes. 4 Thali3 is a Microsoft sponsored experimental plat- https://www.torproject.org/docs/onion- services.html.en 2https://guardianproject.info/apps/orbot 5http://thaliproject.org/ThaliAndTorHiddenServices 3http://thaliproject.org 6https://www.torproject.org 256 Cloudless Wide Area Friend-to-Friend Networking Middleware for Smartphones the case for smartphones connected to the Internet via by other peers. To contact a server, the client appli- local Wi-Fi or cellular data such as 4G. cation need not know the address of the server peer. Neither does it need to know how to connect to the 3.2 Architecture underlying communication service Tor. A system based on Swirlwave has a shared-nothing architecture with independent and self-sufficient nodes that do not