PPREM: Privacy Preserving REvocation Mechanism for Vehicular Ad Hoc Networks

• We design a mechanism to convey revocation data that preserves the user’s privacy.
• Certificate status checking can be performed within few milliseconds.
• Fresh revocation data is available even when disconnected from the infrastructure.
• Even if RSUs are compromised, attackers cannot infer personal information.
• Even if RSUs are compromised, attackers cannot infer personal information.
• Message loss ratio due to authentication delay is reduced to less than 5%.

One of the critical security issues of Vehicular Ad Hoc Networks (VANETs) is the revocation of misbehaving vehicles. While essential, revocation checking can leak potentially sensitive information. Road Side Units (RSUs) receiving the certificate status queries could infer the identity of the vehicles posing the query. An important loss of privacy results from the RSUs ability to tie the checking vehicle with the query's target. We propose a Privacy Preserving Revocation mechanism (PPREM) based on a universal one-way accumulator. PPREM provides explicit, concise, authenticated and unforgeable information about the revocation status of each certificate while preserving the users' privacy.