Most smart meters in Europe use the DLMS communication protocol. They rely on this protocol to secure their communications to the head-end or data concentrator, or on the optical port.
DLMS, for many years now, offers good security features. But the DLMS security features are complex. In version 8 of the Green Book, the information security section takes 61 pages. There are several options to choose from for each feature. It is not always clear which combination of options leads to secure meters.
Moreover, the features are part of the DLMS application layer protocol. They need to be implemented by the meter manufacturers themselves. Manufacturers cannot use standard cryptographic libraries but must write their own code. As cryptographic algorithms and protocols are notoriously hard to implement, this is bound to lead to vulnerabilities. In the tests we have done since, we see that this is indeed the case.
In this document we describe what DLMS security features a DSO should select when procuring new meters, and how they should check if these are implemented well.