Device-independent Tokens with Password Protection Against Token Stealing

Single Sign-On (SSO) systems permit an identity provider (IdP) to issue a token to an authenticated user that can be presented to a third party, referred to as the relying party (RP), for authentication and access. The RP will verify the IdP’s signature on the token and if valid, accepts the user’s identity claim. SSO systems are widely used because they allow the user to authenticate themself to different service providers using a single password. Basic tokens are not bound to the user’s identity and if stolen, allow the adversary to impersonate the user. Token stealing can be prevented by embedding the user’s public key in the token. This, however, requires using the corresponding private key, in a challenge-response protocol, that must be stored in the device’s secure element, effectively binding the token to the device(s) that store the private key.In this paper we propose a novel approach to token protection that removes both above shortcomings by using a password pwd<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</inf> that can be different from the authentication password. The user embeds a function of pwd<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</inf> in the token during the token issuing, and token presentation requires the proof of knowledge of pwd<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</inf>. The tokens, called Proof-of-Password (PoPwd) possession, can be used with any RP without prior password registration. We give a construction and prove its security against a powerful adversary that fully controls the network and has access to token generation and verification oracles. We also provide a proofof-concept implementation of PoPwd, and compare it with two other commonly used token systems, one with and one without protection against token stealing, that we implement, showing feasibility and advantages of our system in practice.