Distributed, Consistent and Secure USB Storage

1. Distributed, Consistent and Secure USB Storage Final Project Review Eddie Lai Matt Dube Sean Busch Zhou Zheng

2. Backing Up Data • Everyone needs to save their work and data • This data needs to be available in multiple locations • Data needs to be readily available • Today’s most popular storage device is the thumb drive • Backups have problems: reliability • Can be physically broken • Need to be carried around • Can wear out after a number of reads/writes • Reliability problem often solved by multiple backups • Multiple backups: consistency problems • Data changes create inconsistencies between backups • When many backups are created, data becomes vulnerable

3. Distributed Consistent Secure USB Hub • Our project: Distributed Consistent Secure USB Hub • Uses off-the-shelf USB drives for storage • Looks like a mass storage device to user’s PC • Distributed • Can be accessed anywhere without any software installation • Consistent • Storage Devices at different locations get updated • Synchronization as easy as a push of a button • Secure • Secret sharing prevents users’ data from being compromised

4. Outline • Introduction • System Operation • PC Interface • File Consistency Software • Hub Communication • User Interface • Secret Sharing Software • Prototype • Budget & Team Roles • Demonstration

5. Project Summary • Special hubs • Hubs are interfaced with PCs, networked with each other • Groups of USB drives • User updates file on USB drive from PC • Updates sent to other USB drives in the group

6. Current Solutions • There are currently several different services that allow users to back up data and access it anywhere • Dropbox, Google Docs • Functionality based on users releasing their data to the cloud • Some information may be too sensitive to store there • Project gives user added control over their data • Users possess the physical media their data is stored on

7. Hub Design • Built on embedded PC • Memory • To boot OS • A Network Interface • USB On the Go Port • USB Ports • User interface • Consistency Software

8. PC Interface • Hub connects to PC without any software installation • Not all users will be allowed to install software on their PC • Hub appears as a USB mass storage device • Use USB OTG port • By interfacing with the PC via this port, board appears as USB device • Shows contents of attached USB drives

9. File Consistency Software • Custom software to recognize when updates are made • Will only run on “trusted” USBs based on UUID • Changes recognized using conventional UNIX tools • Timestamps and checksums recorded, then “diff”ed with previous record

10. Hub Communication • Upon synchronization, the hubs will distribute updates across the network • When a hub is distributing updates, it will act as a client • The receiving hub will act as the server • TCP Client/Server Model • Secure using SSL • Each client will connect to a server, distribute its updates, then disconnect

11. User Interface • Hub is manually operated by user • Simple user interface consists of two buttons • One button initiates synchronization • One button ejects USB sticks • Buttons are mounted on Hub via embedded PC’s GPIO ports • Two LEDs provide feedback for users • One alerts user when a sync is in progress • The other shows when it is safe to remove USBs from hub

12. Secret Sharing • User has option to share information secretly with other hubs • If a USB drive is lost or compromised, no useful information about its contents can be recovered • (k,n) Threshold scheme: need k of n USBs to recover data • Implements Shamir's[1] secret sharing in the Galois Field • Functionality partially provided by libgfshare UNIX library [1] Shamir, Adi (1979), "How to share a secret", Communications of the ACM22 (11): 612–613, doi:10.1145/359168.359176.

13. Prototype • Our Hub is currently being prototyped on the BeagleBoard-xM • Board offers a slimmer form factor • Allows for portability while still containing all of the necessary peripherals • 4 USB ports, Ethernet port • Solid state memory (using microSD card) • Primary motivation for using BeagleBoard is its USB OTG port • Allows the board to be mounted on User’s PC as USB mass storage device

14. Budget and Team Roles • Hub Costs: • BeagleBoard-xM: $150 • Enclosure: $40 • 2 LEDs with mounts:$4 • 2 Buttons:$10 • USB 2.0 A Male to Micro-USB B: $8 • Estimated cost of production: $150-$175 per hub • Eddie: Consistency Software, Hub Communication • Matt: Prototype setup, USB Interface • Zhou: Website, User Interface • Sean: USB Interface

15. Project Summary • Distributed Consistent Secure USB Hub allows user to keep backups on multiple USB sticks consistent • Hub simplifies process for user • Hub appears as USB mass storage device • Doesn’t require software installation on user’s PC • Simple user interface allows hub to be operated with only two buttons • Hub distributes updates to backups securely across network • User has optional secret sharing functionality • Prototype built using BeagleBoard-xM

16. Demonstration • Non Secret Sharing • Scenario 1: Hub1 adds multiple files • Scenario 2: Hub2 removes file • Secret Sharing • Scenario 1: Hub1 adds multiple files • Scenario 2: Hub1 recreates a secret with all n shares present • Scenario 3: Hub2 recreates a secret with n-1 shares present