Secure Internet Exams Despite Coercion

We study coercion-resistance for online exams. We propose
two properties, Anonymous Submission and Single-Blindness which, if
hold, preserve the anonymity of the links between tests, test takers, and
examiners even when the parties coerce one another into revealing secrets. The properties are relevant: not even Remark!, a secure exam
protocol that satisfied anonymous marking and anonymous examiners
results to be coercion resistant. Then, we propose a coercion-resistance
protocol which satisfies, in addition to known anonymity properties, the
two novel properties we have introduced. We prove our claims formally
in ProVerif. The paper has also another contribution: it describes an
attack (and a fix) to an exponentiation mixnet that Remark! uses to
ensure unlinkability. We use the secure version of the mixnet in our new
protocol.