Update-tolerant and Revocable Password Backup (Extended Version)

TL;DR

PASCO is a novel password backup system that remains up-to-date despite password changes, can be revoked remotely to prevent leakage, and includes emergency access features, addressing critical practical challenges.

Contribution

This paper introduces PASCO, a new password backup scheme that is update-tolerant, revocable without physical access, and supports controlled emergency access.

Findings

PASCO effectively maintains password backups without updates despite portfolio changes.

Revocation of backups is possible remotely, enhancing security.

The system includes a secure emergency access mechanism.

Abstract

It is practically impossible for users to memorize a large portfolio of strong and individual passwords for their online accounts. A solution is to generate passwords randomly and store them. Yet, storing passwords instead of memorizing them bears the risk of loss, e.g., in situations where the device on which the passwords are stored is damaged, lost, or stolen. This makes the creation of backups of the passwords indispensable. However, placing such backups at secure locations to protect them as well from loss and unauthorized access and keeping them up-to-date at the same time is an unsolved problem in practice. We present PASCO, a backup solution for passwords that solves this challenge. PASCO backups need not to be updated, even when the user's password portfolio is changed. PASCO backups can be revoked without having physical access to them. This prevents password leakage, even when a user loses control over a backup. Additionally, we show how to extend PASCO to enable a fully controllable emergency access. It allows a user to give someone else access to his passwords in urgent situations. We also present a security evaluation and an implementation of PASCO.