Authentication in Ubiquitous Computing Laurent BUSSARD and Yves ROUDIER Institut Eurecom Workshop on Security in Ubiquitous Computing UBICOMP 2002, Goteborg Sweden, 29 Sept 2002

Security in Ubicomp User-centric interactions in Ubicomp User-centric interactions in Ubicomp Intuitive interaction Intuitive interaction Physical entities (artifacts) Physical entities (artifacts) Security Security Rights, Delegation Rights, Delegation Trust, Ownership Trust, Ownership Non-repudiation of interactions Non-repudiation of interactions  Requires authentication of artifacts (personal digital assistants, electronic rings, doors or even clothes, offer embedded chips with computation power and communication facilities and are generally called artifacts)

Service Authentication in Ubicomp Classical network security Classical network security Authentication of a virtual service Authentication of a virtual service Verify knowledge of a private key Verify knowledge of a private key Ubiquitous computing Ubiquitous computing Authenticate an artifact offering a service Authenticate an artifact offering a service Provide rights to a given artifact Provide rights to a given artifact Verifying that a user is present Verifying that a user is present

The Gap

Attack 1: Device Impersonation

Attack 2: Device Impersonation

Attack 3: P2P Discounts Sharing

Filling the Gap

Local Proof of Knowledge Time-based approach Time-based approach Dedicated hardware Dedicated hardware − No application-level approach Simple distance evaluation Simple distance evaluation − Contact based approach No cryptography during exchange No cryptography during exchange − Responses pre-computed Simple exchanges Simple exchanges − One-bit challenge − One-bit response

Local Proof of Knowledge

No more Man-in-the-middle attacks No more Man-in-the-middle attacks No proxying in between (distance + logic) No proxying in between (distance + logic) Cannot get both responses Cannot get both responses One bit challenge-response One bit challenge-response Precise location Precise location High probability of successful attack p = 3/4 High probability of successful attack p = 3/4 Multiple rounds (n) Multiple rounds (n) Precise location Precise location Low probability of successful attack = (3/4)n Low probability of successful attack = (3/4)n

Conclusion: Impact on Usability Tamper resistance + cryptography not sufficient Changes in previous examples Changes in previous examples Point of Sale Terminal: LED on smart card Point of Sale Terminal: LED on smart card Shop offering discounts: board Shop offering discounts: board New user-centric interactions New user-centric interactions Touch to authenticate Touch to authenticate Drag-and-drop Drag-and-drop Touch to transfer ownership, delegate rights Touch to transfer ownership, delegate rights Authentication: a building block for developing Authentication: a building block for developing Access control Access control Ownership Ownership