UNIVERSITY OF THE PHILIPPINES MANILA COLLEGE OF ARTS AND SCIENCES DEPARTMENT OF PHYSICAL SCIENCES AND MATHEMATICS RELIABLE AND ROBUST FILE TRANSFER SYSTEM OVER SHORT MESSAGING SERVICE A special problem in partial fulfllment of the requirements for the degree of Bachelor of Science in Computer Science Submitted by: Axel Philip Advento May 2018 Permission is given for the following people to have access to this SP: Available to the general public Yes Available only after consultation with author/SP adviser No Available only to those bound by confdentiality agreement No ACCEPTANCE SHEET The Special Problem entitled “Reliable and Robust File Transfer System over Short Messaging Service” prepared and submitted by Axel Philip Advento in partial fulfllment of the requirements for the degree of Bachelor of Science in Computer Science has been examined and is recommended for acceptance. _________________________________ Gregorio B. Baes, Ph.D. (candidate) Adviser EXAMINERS: Approved Disapproved 1. Avegail D. Carpio, M.S. __________ __________ 2. Richard Bryann L. Chua, Ph.D. (candidate) __________ __________ 3. Perlita E. Gasmen, M.S. (candidate) __________ __________ 4. Marvin John C. Ignacio, M.S. (candidate) __________ __________ 5. Ma. Shiela A. Magboo, M.S. __________ __________ 6. Vincent Peter C. Magboo, M.D., M.S. __________ __________ 7. Geoffrey A. Solano, Ph.D. (candidate) __________ __________ Accepted and approved as partial fulfllment of the requirements for the degree of Bachelor of Science in Computer Science. __________________________ __________________________ Ma. Shiela A. Magboo, M.S. Marcelina B. Lirazan, Ph.D. Unit Head Chair Mathematical and Computing Sciences Unit Department of Physical Sciences Department of Physical Sciences and Mathematics and Mathematics __________________________ Leonardo R. Estacio, Jr., Ph.D. Dean College of Arts and Sciences Abstract This study presents a reliable and robust method for transferring files over Short Messaging Service. By testing the system against a set of repeated rigid test cases and fault injection methods, it has proven itself reliable and robust enough to survive problems found on an unreliable SMS service. Protection against adversaries are also implemented as a feature using security measures such as encryption and authentication. Results show an effective alternative for sending and receiving files but show noticeable drawbacks in terms of speed. The work presented here has profound implications for future studies of utilizing low bandwidth but widely accessible means of communications such as Short Messaging Service and may help solve the problem of data transmission in places where Internet connectivity is unavailable or where other means of transmission of data is hazardous or impossible. Keywords: File transfer, Short Messaging Service, Reliability, Robustness ii Contents Abstract ii I. Introduction 1 A. Background of the Study . 1 B. Statement of the Problem . 4 C. Objectives of the Study . 6 D. Significance of the Study . 7 E. Scope, Limitations, and Assumptions . 8 II. Review of Related Literature 10 III. Theoretical Framework 13 A. Reliability . 13 B. Robustness . 13 C. Data Compression . 14 D. Binary-to-Text Encoding . 15 IV. Design and Implementation 17 A. Protocol . 17 iii B. Hardware Setup . 22 C. Software and Libraries Used . 22 D. Hardware and Software Requirements . 24 V. Results 26 VI. Discussions 37 VII. Summary and Conclusions 40 VIII. Recommendations 41 Bibliography 43 Appendix 47 A. Source Code . 47 Acknowledgements 157 iv I. Introduction A. Background of the Study File Sharing Methods and Technologies File sharing can be defined as "a method of distributing computer files, … among a large number of users".[24] Such practice enabled users to share various digital data such as documents, multimedia, and computer programs across the world. Files can be shared in a number of ways. They can be distributed using removable storage media, over wired connections, or wirelessly such as wireless Ethernet and mobile data. Files were first exchanged using non-volatile physical media. In 1725, Basil Bouchon used punched paper rolls to store instructions for machines. In 1846, punch tapes became viable for use in recording telegrams. Data stored on these storage devices were more of instructions for machines rather than actual recorded data, however. In 1880, Hermal Hollerith invented recording data on punch cards which ultimately became a format that IBM used in the following decades. Afterwards, various magnetic media such as magnetic tapes (used in 1951 as data storage medium), drum memory (1946), hard disk drives (1956), and floppy disks (1971) were used as storage media. Magnetic tapes and floppy disks saw widespread use as removable media. Around mid-1980s, specifications for storing digital signals on optical discs are completed which led to the development of Compact Discs (CDs), Digital Video Discs (DVDs), and Blu-ray Discs (BD). 1 Electronic flash memory were introduced for storing digital data later on. Examples include CompactFlash cards, Secure Digital (SD) cards, Memory Sticks, and USB Flash Drives. Concurrently, file sharing has also been a practice through wired connections. During 1970s up to late 1980s, file sharing was mostly done over landline telephones and modems using systems such as Usenet, BBS, and XModem. Internet Service Providers (ISPs) emerged on 1990s and the Internet became fully commercialized by 1995. This gave way to modern methods of distributing files such as the File Transfer Protocol (FTP), the World Wide Web, Internet Relay Chat (IRC) programs, Instant Messaging, and later on, the BitTorrent protocol.[13] Wireless connectivity made the Internet accessible to people who don't have access to wired connections and people living on locations where setting up infrastructure for wired services would be difficult or impossible. In 1996, access to mobile web was made possible with the introduction of the Nokia 9000 Communicator phone. It was done over 2G cellular networks, which initially do not offer data services. During the early 2000s, Wireless Access Protocol (WAP) and i-mode achieved popularity as means of accessing the mobile web and Internet services. In 2000, General Packet Radio Service (GPRS) was introduced as a packet-switched data service, which extends Global System for Mobile (GSM) Packet circuit-switched data capabilities. While in 2003, Enhanced Data rates for GSM Evolution (EDGE) was deployed on GSM networks which allows improved data transmission rates over GPRS. 2 The first Internet-ready satellite was made available for consumers in 2003. Satellite Internet was targeted mainly to rural areas as an alternative to traditional Internet connections such as dial-up and ADSL. The first commercial Third Generation (3G) network was also finally launched in the same year. With the advent of 3G cellular networks and its extensions, higher data speeds and better security compared to 2G networks are observed on 3G-capable devices. However, adoption in some countries are slowed down due to the large cost of upgrades and spectrum licensing fees. In 2013, Fourth Generation technologies (4G) started to roll out. Technologies can only be considered 4G if "a substantial level of improvement in performance and capabilities with respect to the initial third generation systems now deployed".[8] Short Messaging Service (SMS) and Its State in the Philippines Short Messaging Service is a component of web, telephone, and mobile device networks that enables users to send and receive text messages. SMS is part of standardized communication protocols that were defined in 1985 as part of the GSM standards. [25] SMS messages are sent to Short Message Service Centers (SMSC), which then attempts to forward the message to the recipient. This delivery however is "best-effort". In case the SMSC cannot reach the intended recipient, it keeps the message for a duration set by the mobile operator and retries until the recipient becomes available again, the message expires, or the retry limit set by the operator has been reached. This also means that there are no guarantees that the message will 3 be delivered on time or be delivered to the recipient at all. Despite being best-effort, SMS is an almost reliable service with an observed failure rate as high as 5.1% during normal operation conditions.[12] The Philippine Statistics Authority reported in 2017 that an estimated 8,957,952 people are subscribed on an Internet Service Provider which includes wired DSL, cable Internet, and wireless Internet. The reported number of active mobile telephone service subscriptions, on the other hand, is 130,319,459, which is more than the country's total population.[15] Various studies and news sources also consistently place the Philippines as the "text messaging capital of the world".[5] B. Statement of the Problem With the current technologies available to consumers today, ideally anyone should be able to send and receive digital data conveniently anytime and anywhere. Unfortunately, these methods and technologies are not as accessible or widely available in the real world. First, transferring files over wired connections is limited only to areas where wired telephone networks and ISPs had laid out infrastructure for their services. These areas exclude remote rural communities and areas where building infrastructure would be challenging or just impossible. Wireless Internet, on the other hand, has its own challenges as well. Satellite Internet typically