Welcome to the resource topic for 2025/1371
Title:
Securing Credential Sequence Verification
Authors: Mamunur Rashid Akand, Reihaneh Safavi-Naini
Abstract:Credentials are used to verify a user’s identity and attributes
and form the basis of securing user access to the system resources. Users
obtain credentials and store them on their (mobile) devices, and present
them when needed. Anonymous credentials protect the user’s identity,
and ensure unlinkability of multiple showing of the credential. In this
paper, we consider a setting where a user is issued multiple credentials
in sequence (e.g., for completing courses), and credential subsequences
must be presented in order of issuance. We focus on the anonymous credential
system where information such as the time of issuing is hidden
for anonymity, or settings where there is no global clock and issuing
time information is not recorded. We propose a novel order-preserving
Proof-of-Credential-Subsequence (PoCS) system called KROM that allows
a user that is potentially untrusted, to present a subsequence of
their locally stored credentials to a verifier, while the relative chronological
order of issuance is preserved. We formalize the security and privacy
of KROM and present two constructions: a basic one that is based on
Merkle trees and one with batched verification that significantly improves
the efficiency of the system. We use KROM to construct an anonymous
order-preserving proof-of-location-subsequence system and prove its security.
The system enables users to selectively present a subsequence of
their visited locations to a verifier or an auditor. The main challenge that
is addressed is to ensure that the location information that must be in
plaintext, does not breach privacy when used in sequence.
ePrint: https://eprint.iacr.org/2025/1371
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