Strong Authentication without Temper-Resistant Hardware and Application to Federated Identities

Shared credential is currently the most widespread form of end user authentication with its convenience, but it is also criticized for being vulnerable to credential database theft and phishing attacks. While several alternative mechanisms are proposed to offer strong authentication with cryptographic challenge-response protocols, they are cumbersome to use due to the need of tamper-resistant hardware modules at user end. In this paper, we propose the first strong authentication mechanism without the reliance on tamper-resistant hardware at user end. A user authenticates with a password-based credential via generating designated-verifiable authentication tokens. Our scheme is resistant to offline dictionary attacks in spite that the attacker can steal the password-protected credentials, and thus can be implemented on general-purpose devices. More specifically, we first introduce and formalize the notion of Password-Based Credential (PBC), which models the resistance of offline attacks and the unforageability of authentication tokens even if attackers can see authentication tokens and capture password-wrapped credentials of honest users. We then present a highly-efficient construction of PBC using a "randomize-thenprove" approach, and prove its security. The construction does not involve bilinear-pairings, and can be implemented with common cryptographic libraries for many platforms. We also present a technique to transform the PBC scheme to be publiclyverifiable, and present an application of PBC in federated identity systems to provide holder-of-key assertion mechanisms. Compared with current certificate-based approaches, it is more convenient and user-friendly, and can be used with the federation systems that employ privacy-preserving measures (e.g., Sign-in with Apple). We also implement the PBC scheme and evaluate its performance for different applications over various network environment. When PBC is used as a strong authentication mechanism for end users, it saves 26%-36% of time than the approach based on ECDSA with a tamper-resistant hardware module. As for its application in federation, it could even save more time when the user proves its possession of key to a Relying Party.