Since ZSE and DLMS have differing data types to represent the same attribute of SMETS information, there are some differences in the format of the data that is encrypted. These differences are laid out in this Section 8. However, Encryption and Decryption use the same cryptographic AES GCM primitives in the same way in all cases, regardless of protocol. The usage is the same as that to generate MACs for Remote Party Message protection, and therefore as per the AES GCM approach laid out in the Green Book.
Encryption of SMETS attributes is required when:
the Supplier reads the amounts held in Time Debt Register [1..2] and Payment Debt Register. Each of these is a single integer value;
the Supplier reads the values held in the Active Import Register or Secondary Active Import Register. Each of these is a single integer value;
a Known Party or an Unknown Party reads one or more entries from a Log (with each entry in the specific log having a Log specific structure), specifically:
the current or previous Supplier reads the Billing Data Log (excluding the export related parts), the Daily Read Log or the Prepayment Daily Read Log. Note that a previous Supplier is an Unknown Remote Party as far as the meter is concerned;
the Supplier, Network Operator, or an Unknown Remote Party reads the Daily Consumption Log or the Profile Data Log (Consumption parts);
a Device sends an Alert containing a single entry from the Billing Data Log (excluding the export related parts).