Universit`adegli Studi di Roma “Tor Vergata” Facolt`adi Ingegneria Dottorato di Ricerca in Informatica ed Ingegneria dell’Automazione Ciclo XXIII Open BAR A New Approach to Mobile Backup And Restore Vittorio Ottaviani A.A. 2010/2011 Docente Guida/Tutor: Prof. Giuseppe F. Italiano Coordinatore: Prof. Daniel P. Bovet to my parents because an example is worth a thousand words Abstract Smartphone owners use to save always more information, and more impor- tant data into the internal memory of their devices. Mobile devices are prone to be lost, stolen or broken; this causes the loss of all the information contained in it if these data are not backed up. While many solutions for making back- ups and restoring data are known for servers and desktops, mobile devices pose several challenges, mainly due to the plethora of devices, vendors, oper- ating systems and versions available in the mobile market. In this thesis, we propose a new backup and restores approach for mobile devices, which helps to reduce the effort in saving and restoring personal data and migrate from a device to another. Our approach is platform independent: in particular, we present some prototypes based on different mobile operating systems: Google Android, Windows Mobile 5 and 6 and Symbian S60. The approach grants the security of the information backed up and restored using novel cryptographic techniques optimized for mobile. Another feature of our approach lies in the capability of offering additional services to the final user or to administrator of the system. As an example, for users, we provide a service enabling the shar- ing of information in mobile devices among a group of selected persons. This can be useful in many situations e.g., in creating a mobile business network among a group of people. For administrators we offer a social network extrac- tor which, starting from information contained into the smartphone and data publicly available on the web generates a social graph of the backup network. This can be useful in situations like creating teams into an enterprise. i Acknowledgements During the years of my PhD several persons have passed into my life, some of these persons have leaved a sign that will never be deleted. First of all I want to thank Pino: your way to approach things, always search- ing for the best, inspires me everyday; I learned some of the most important sessions of my life thanks to you. I want to thank all the colleagues and friends who believed in me during hard times and who enjoyed with me successes; Emanuele, Cristina, Danilo and Paolo thank you guys for the support and for sharing with me your experience. Special thanks go to Fabio and to Ermanno. I will not write another thesis to explain this thanks: each one of you knows. Thanks to my family for your unconditioned love and trust in me. Words can- not fully express how important you are to me. Finally thank you Ramona, you are my love, my best friend and the reason why every morning I wake up and do my best to be a better person. iii Table of Contents 1 Introduction 1 1.1 Motivation . .1 1.1.1 How much does data loss cost? . .2 1.1.2 Focusing on mobile . .5 1.2 Our solution . .9 1.3 Contributions . 10 1.4 Thesis Outline . 11 2 Backup & restore in the third millennium 13 2.1 Backup features . 14 2.1.1 Full backup . 15 2.1.2 Incremental backup . 15 2.1.3 Differential backup . 16 2.1.4 File-based vs. device-based . 17 2.1.5 Scheduled backup vs continuous data protection . 18 2.1.6 Local backup vs. remote backup . 19 2.2 Mobile . 21 2.3 Local backup for mobile device . 21 2.4 Remote backup for mobile device . 22 3 Our approach to backup 25 3.1 A new approach to backup & restore . 26 3.1.1 Server . 28 3.1.2 Client . 29 v TABLE OF CONTENTS 3.2 Sharing backup data . 31 3.3 Social network analysis . 32 3.4 Security . 33 4 Data extraction 35 4.1 Forensic Style Approach . 37 4.1.1 Our methodology . 38 4.1.2 Symbian implementation . 39 4.1.3 Windows Mobile implementation . 41 4.1.4 Some remarks on this approach . 47 4.2 Selection of interesting data . 49 4.2.1 Symbian . 51 4.2.2 Android . 52 4.3 Performances . 53 4.4 Concluding remarks . 53 5 Data elaboration 55 5.1 Remote elaboration . 57 5.2 Our step-by-step Methodology . 59 5.2.1 Stage 0: Choice of the objective . 62 5.2.2 Stage 1: Files of interest identification . 62 5.2.3 Stage 2: Data hypotheses and entities injection . 64 5.2.4 Stage 3: Sequences similarity discovery . 67 5.2.5 Stage 4: Data interpretation . 68 5.2.6 Stage 5: Meta-format building . 70 5.2.7 Stage 6: Error correction . 72 5.2.8 Stage 7: Parser building . 74 vi TABLE OF CONTENTS 5.2.9 Stage 8: Testing and debugging . 74 5.3 Remote elaboration results . 75 5.4 Local elaboration . 77 6 Protecting saved data 81 6.1 Key agreement algorithm . 82 6.1.1 Mathematical setting: key agreement protocol . 83 6.1.2 J2ME implementation . 85 6.1.3 Performance testing methodology . 87 6.1.4 Performance evaluation . 89 6.1.5 Experimental results . 91 6.1.6 Concluding remarks . 93 6.2 Encryption algorithm . 93 6.2.1 Performances . 94 6.2.2 Statistically testing QP-DYN and RC4 . 98 6.3 Protecting inter process communication . 100 6.3.1 State of the art . 101 6.3.2 The framework . 103 6.3.3 The framework implementation . 108 6.3.4 On a real device . 112 7 Value added services on backup data 115 7.1 Sharing backup data with closed groups . 116 7.1.1 Social backup in business environment . 116 7.1.2 Sharing conference data . 117 7.1.3 Shared backup for smartphone . 118 7.1.4 Running the application . 119 vii TABLE OF CONTENTS 7.2 Extracting social network . 120 7.2.1 Introduction . 121 7.2.2 Related work . 122 7.2.3 Smartphone Data Analysis (SDA) . 124 7.2.4 Web Data Analysis (WDA) . 126 7.2.5 Clustering Analysis (CA) . 129 7.2.6 The Final Result: The Social Network . 132 7.3 Conclusions . 133 8 Conclusions and Future Work 135 A The Symbian S60 format 139 A.1 Address book . 139 A.2 Calendar . 141 A.3 Events log . 147 A.4 SMS . 150 B The Backup communication protocol 157 B.1 Backup item . 157 B.2 Contact item . 158 B.3 Calendar item . 159 B.4 Message item . 160 B.5 Generic file item . 161 B.6 Setting item . 162 B.7 List methods . 162 B.8 Restore . 164 B.8.1 Listing items on the server . 164 viii TABLE OF CONTENTS B.8.2 Choosing data to be restored . 164 C The Sharing communication protocol 167 C.1 Sharing methods . 167 C.1.1 Item listing . 167 C.1.2 Share a item . 168 C.1.3 Location based sharing . 169 C.1.4 Listing shared data . 170 C.2 Groups methods . 172 C.2.1 Creating group . 172 C.2.2 Listing groups . 172 C.2.3 Handling invitations . 173 Bibliography 189 ix List of Figures 1.1 Costs of data loss per industry sector (values are in million $ per year) . .3 1.2 Smartphone and PC sales prevision in Million of units . .5 1.3 2007 - 2010 trend mobile operating systems market share. .6 1.4 Mobile cellular, subscriptions per 100 people, 2009. .7 3.1 Backup and Restore system architecture. 27 3.2 Example of data model for a contact. 28 3.3 Example of a request of a contact. 29 3.4 Example of client server interactions. 30 4.1 Data collection workflow . 39 4.2 Windows Mobile 5.0 memory architecture. 42 4.3 (a) Symbian S60 tool’s screenshot, (b) Windows Mobile tool’s screenshot. 48 5.1 The methodology flow . 59 5.2 The format of the Ω operations sequence. In this figure is shown an example with contacts discovery as objective . 64 5.3 These figures show an example of a DBMS binary file before and after the Stage 3. In (a) the sample file after making pairs of calls of the same duration (Stage 2). In (b) equal sequences highlighted. In (c) the formatted file Φ^0 ............... 68 5.4 This three figures depict an example of the application of Stage 5 on a file containing the phone’s address book. 71 xi LIST OF FIGURES 5.5.