Ryan Lackey Dynamic Locations: Secure Mobile Services Discovery and Dynamic Group Membership Ryan Lackey

Ryan Lackey Who? Interest in “cypherpunk” technologies from 1992 to present, particularly anonymized communications, agents, and electronic cash Ultimate goal: anonymous secure infrastructure from end to end: clients, servers, networks, pro Founded HavenCo/ran metacolo: offshore colo in 9 markets, related projects, including secure mobile systems

Ryan Lackey Introduction Lots of work has been done to network fixed equipment, and to secure fixed network connections, but most mobile apps are just slightly modified versions of fixed applications Most mobile networked systems have simplified security models; some link security but little application specific security end to end Fundamentally new kinds of applications are possible with secure mobile systems

Ryan Lackey Fundamental Constraints Power and bandwidth limited Many nodes in continual motion and appear/disappear rapidly Much infrastructure is closed and long cycles to upgrade and deploy UI complicated by devices and use cases (user attention not dedicated)

Ryan Lackey Platform HP/Compaq iPaq running Linux Laptops running Linux and FreeBSD b and 1xRTT IP-based communications Open systems for easy development, python for rapid development

Ryan Lackey Applications of Interest “Matchmaking” – letting parties meet with similar interests meet up Secure messaging (communications and message-based low-overhead protocols, including payment systems) Secure streams (VoIP, VPN)

Ryan Lackey “Matchmaking” Demo app is letting people define a set of interests, then announce to the world, without risk of being “interrogated” by third parties Useful for service discovery too – announce that you’re running certain services to others in the set, but not to the public (RIAA, MPAA, Government, etc) Attestations, with optional protection from traffic analysis as well

Ryan Lackey Secure short messages Text messaging Much easier technically than streams Store/forward possibility Also useful for many protocols, either in two way or polled mode

Ryan Lackey Streams Voice over IP is key market – encrypted cellphone using low-bandwidth channel (1xRTT or HSCSD GSM) and anonymization of calls

Ryan Lackey Interaction models True peer to peer “Security proxy” or user selected/operated operational server Centralized client-server operated by application developers Centralized client-server operated by communications providers

Ryan Lackey Existing p2p systems Generally designed for high bandwidth media sharing with minimal anonymity layered over existing IP networks Not really designed for interactive communication

Ryan Lackey Existing mobile client-server systems Designed with link encryption to the wireless hub, or to the server Closed development environment controlled by mobile companies Hard for users and application developers to really trust the security model

Ryan Lackey Early mobile p2p systems “lovegety” – a system to use RF to share information about membership in certain groups Subject to “trawling”, direction finding attacks, and “corraling” small numbers of users to identify

Ryan Lackey Security Implications Confidentiality, Integrity, Authentication solvable through traditional systems Traffic analysis is the hard problem Complete undetectability of special traffic Of course, reliability, availability, etc. are still major concerns, and special mobile constraints

Ryan Lackey Policy Implications Centralized systems vulnerable to technical or legal attack Who to trust – communications provider, applications provider? Trust is essential to enabling certain applications

Ryan Lackey Central Mediation Servers trusted by some party to take all communications and retransmit Defeats firewalls/proxies/NAT as well as provides protection from traffic analysis Persistence; can buffer communications for users with intermittent connectivity

Ryan Lackey True Peer to Peer Cryptographic Systems Computationally intensive on client Bandwidth intensive; may only be able to send single bits! Generally can put user into a “collusion set” but unless set is large, elimination can identify user

Ryan Lackey Covert channels for mobile use Masking using pre-recorded traffic Sniffing and simulating MITM “Design for MITM” – Dining Cryptographer’s Networks, etc.

Ryan Lackey Dining Cryptographer’s Network Due to David Chaum, described at Multiple parties can communicate without revealing to one another which is initiating the communications

Ryan Lackey Anonymizing r ers as model Store and forward messaging with latency added Complicated due to node unreliability Send out multiple messages; tradeoff of bandwidth waste vs. latency vs. reliability

Ryan Lackey Current solution Communications with a trusted server using fixed-rate messaging (tuned for bandwidth) Inter-server communications, allowing users to select “security proxy servers” to act on their behalf, optionally running servers themselves

Ryan Lackey Conclusions Mobile-specific (more properly, dynamic) security is a very hard problem Key is finding applications which fit currently available technology – message based, with secure service discovery

Ryan Lackey Future work Develop an application developer’s toolkit with service discovery on top of secure message-passing and streams systems “Killer apps” of VoIP and mobile payment – good stream based systems