PeerShare : A System for Secure Distribution of Sensitive Data among Social Contacts

1. PeerShare: A System for Secure Distribution of Sensitive Data among Social Contacts Marcin Nagy, N. Asokan, JörgOtt

2. Motivation • Key management is difficult • Online social networks popular (provide SSO) Observation: Social networks can be used for authentic public keys distribution (SocialKeys project) Concept: Securely distribute application-specific data to a specific set of social contacts

3. Example applications • Exchanging public keys • Sharing access point keys • Detecting nearby friends (<user name, device address>) • Finding common friends (<friendship proof>) • Authenticity-only vs. authenticity+confidentiality • User-specific vs. device-specific data

4. Requirements Threat model • Channel compromise • Unauthorized usage • Impersonation • Accessing restricted data

5. System design PeerShare Server PeerSharemaster bindings database Social Network (SN) SN access protocol (eg. Facebook Graph API) Social Network App PeerShareprotocol (server) • SN authentication protocol(e.g. OAuth) • PeerShareprotocol SN authentication protocol Applications PeerShare API PeerSharecommunicationmodule Bindings database PeerShare Service Device

6. Security considerations • Channel compromise • TLS • Impersonation • User: SN user authentication (e.g. OAuth + SSO) • Server: TLS + certificate “pinning” • Application: e.g. Facebook user access token validation • User access control • User specifies authorized recipients • Enforced by server and service-on-device • Application access control • Only an application that has created data can access it

7. Minimizing trust on the PeerShare server • Trusted-hardware (HSM) • On-board Credentials • Application-specific server

8. Sample applications Tethering App nearbyPeople Technical Report ACNS 2013 paper Technical Report ACSAC 2013 paper

9. Questions?Thank you!