Security Weakness of Flexible Group Key Exchange with On-Demand Computation of Subgroup Keys

TL;DR

This paper analyzes the security flaws in the mBD+P and mBD+S group key exchange protocols, revealing insider attack vulnerabilities and proposing a countermeasure to enhance security.

Contribution

The paper identifies security weaknesses in existing protocols and introduces a simple countermeasure to mitigate insider attacks.

Findings

Both mBD+P and mBD+S are vulnerable to malicious insider attacks

A simple countermeasure effectively prevents insider attacks

The protocols' security assumptions are challenged by the identified vulnerabilities

Abstract

In AFRICACRYPT 2010, Abdalla et al. first proposed a slight modification to the computations steps of the BD protocol, called mBD+P. Then they extended mBD+P protocol into mBD+S protocol. In this paper, we show that both of mBD+P and mBD+S protocols are vulnerable to malicious insiders attack. Further, we propose a simple countermeasure against this attack.