The Routing Protocol for Low-Power and Lossy Networks (RPL) is a proposed standard by the Internet Engineering Task Force (IETF). Although RPL defines basic security modes, it is still subject to topology attacks. VeRA is an authentication scheme which protects against attacks, based on the version number and rank. This work presents two rank attacks which are not mitigated by VeRA. In the first attack, the adversary can decrease its rank arbitrarily. Hence, it can impersonate even the root node. In the second attack, the adversary can decrease its rank to that of any node within its access range. We present an enhancement of VeRA to mitigate the first attack. Additionally, a basic approach for mitigating the second attack is introduced.

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