Abstract
Single Sign-On (SSO) is becoming an increasingly popular authentication method for users that leverages a trusted Identity Provider (IdP) to bootstrap secure authentication tokens from a single user password. It alleviates some of the worst security issues of passwords, as users no longer need to memorize individual passwords for all service providers, and it removes the burden of these service to properly protect huge password databases. However, SSO also introduces a single point of failure. If compromised, the IdP can impersonate all users and learn their master passwords. To remedy this risk while preserving the advantages of SSO, Agrawal et al. (CCS'18) recently proposed a distributed realization termed PASTA (password-Authenticated threshold authentication) which splits the role of the IdP across n servers. While PASTA is a great step forward and guarantees security as long as not all servers are corrupted, it uses a rather inflexible corruption model: servers cannot be corrupted adaptively and-even worse-cannot recover from corruption. The latter is known as proactive security and allows servers to re-share their keys, thereby rendering all previously compromised information useless. In this work, we improve upon the work of PASTA and propose a distributed SSO protocol with proactive and adaptive security (PESTO), guaranteeing security as long as not all servers are compromised at the same time. We prove our scheme secure in the UC framework which is known to provide the best security guarantees for password-based primitives. The core of our protocol are two new primitives we introduce: partially-oblivious distributed PRFs and a class of distributed signature schemes. Both allow for non-interactive refreshing of the secret key material and tolerate adaptive corruptions. We give secure instantiations based on the gap one-more BDH and RSA assumption respectively, leading to a highly efficient 2-round PESTO protocol. We also present an implementation and benchmark of our scheme in Java, realizing OAuth-compatible bearer tokens for SSO, demonstrating the viability of our approach.
| Original language | English |
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| Title of host publication | Proceedings - 5th IEEE European Symposium on Security and Privacy, Euro S and P 2020 |
| Publisher | Institute of Electrical and Electronics Engineers Inc. |
| Pages | 587-606 |
| Number of pages | 20 |
| ISBN (Electronic) | 9781728150871 |
| DOIs | |
| State | Published - Sep 2020 |
| Externally published | Yes |
| Event | 5th IEEE European Symposium on Security and Privacy, Euro S and P 2020 - Virtual, Genoa, Italy Duration: 7 Sep 2020 → 11 Sep 2020 |
Publication series
| Name | Proceedings - 5th IEEE European Symposium on Security and Privacy, Euro S and P 2020 |
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Conference
| Conference | 5th IEEE European Symposium on Security and Privacy, Euro S and P 2020 |
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| Country/Territory | Italy |
| City | Virtual, Genoa |
| Period | 7/09/20 → 11/09/20 |
Bibliographical note
Publisher Copyright:© 2020 IEEE.
Funding
Acknowledgment. This work received funding from the EU Horizon 2020 research and innovation programme under grant agreement No 786725 OLYMPUS and the BIU Center for Research in Applied Cryptography and Cyber Security in conjunction with the Israel National Cyber Bureau in the Prime Minister’s Office. We thank Michael Bladt Stausholm for his prototype implementation and performance testing. Most of Anja’s work was done while she was at IBM Research – Zurich. Part of the work of Carsten, Avishay and Tore was done while the authors were at Bar-Ilan University.
| Funders | Funder number |
|---|---|
| Horizon 2020 Framework Programme | 786725 |
Keywords
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