Unpicking PLAID

Abstract

The Protocol for Lightweight Authentication of Identity (PLAID) aims at secure and private authentication between a smart card and a terminal. Originally developed by a unit of the Australian Department of Human Services for physical and logical access control, PLAID has now been standardized as an Australian standard AS-5185-2010 and is currently in the fast-track standardization process for ISO/IEC 25185-1. We present a cryptographic evaluation of PLAID. As well as reporting a number of undesirable cryptographic features of the protocol, we show that the privacy properties of PLAID are significantly weaker than claimed: using a variety of techniques we can fingerprint and then later identify cards. These techniques involve a novel application of standard statistical and data analysis techniques in cryptography. We discuss potential countermeasures to our attacks and comment on our experiences with the standardization process of PLAID.

Contactless Access Control Based on Distance Bounding

“…Informally, if an AC protocol is private then it is hard for an outside observer to identify or recognize a party who wants to access a system. Some previous works [14,8,7] touched on privacy. PLAID [14] claims to be private (with an informal definition) but Degabriele et al [8] show that it is weaker than what it claims.…”

“…Some previous works [14,8,7] touched on privacy. PLAID [14] claims to be private (with an informal definition) but Degabriele et al [8] show that it is weaker than what it claims. Dagdelen et al [7] give two privacy related definitions: identity hiding and untraceability.…”