Introduction - KNX

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Data Encryption Authentication / Device Signatures Signatures, or authentication in any way, are not included in the Dutch smart meter specifications. This is referred to in the OMS documents (OMS-Spec- Vol1_General_v100.pdf section 3.6.2) as work in progress. Encryption The Dutch smart meter specifications require two-way data encryption. The MUC to Meter data may contain control data (time synch, valve control, etc) so should be encrypted. The Meter to MUC data should be encrypted for privacy reasons (to mask zero or low consumption of temporarily uninhabited quarters). The MUC documents require only encryption for MUC to Meter data (MUC_080128_inkl_Anlagen.pdf SRR section 5.3.9). Note that the EN13757 only specifies encryption for Meter to MUC data. Encryption Algorithm The encryption algorithm is in both the Dutch smart meter specification and the OMS documents AES-128. The block chaining mode is in both specification documents CBC (Cipher Block Chaining). In the Dutch specification, the initialisation vector is binary zero, in the OMS specification the initialisation vector (IV) is built from data that is sent (in the same transaction as are the encrypted data) as unencrypted byte stream. Encryption key exchange In the Dutch smart meter specifications, a new encryption key is encrypted with a meter-specific default encryption key to prevent exchange of an unencrypted plaintext encryption key. This allows a relatively secure modification of encryption keys. In the OMS documents there is no exchange of encryption keys; hence changing encryption keys in an operational meter is not possible. The encryption keys in the OMS specification are configured in the production facility. The encryption key is then sent unencrypted from the meter to the MUC, and from there to the Head End, during installation. (MUC_080128_inkl_Anlagen.pdf SRR section 5.3.9). Comments: Review M-bus.doc 2 04/12/2008
• Does this mean that a “rogue” MUC can inquire with a meter and receive its encryption key? • How is the installation process initiated? M-Bus signature field. The M-Bus signature field (EN 13757-3 section 5.10) is modified to support the AES 128 encryption algorithm. The OMS documents (OMS-Spec_Vol2_Primary_v102.pdf section 4.2.2.2) however include the Hop Counter in the LSB of the signature field, to support repeater functionality in wireless networks. We are not sure if this implementation is according to the (preliminary) EN-13757-5 standard (ref also OMS-Spec_Vol2_Primary_v102.pdf section 2.2.1). The Dutch Smart meter documents do not support repeater or relaying functionality in wireless networks, and strictly follow the signature definitions in EN 13757-3 section 5.10. Infrastructure In the Dutch Smart Meter documents, the Electricity meter is built into the MUC gateway. This means the option to exchange electricity data over the M-Bus connection is not specified. In the MUC specification, the MUC and the Electricity meter are separate objects, and the exchange of E-data is described. This allows for a more flexible approach. System Installation And Initialisation The Dutch smart meter documents include detailed specifications of initialising connections. Specifically the binding of newly installed wireless meters to a MUC is described in detail. This is not included in the OMS specifications. Operational Data Transfer Tariffing The Dutch smart meter specification does not include exchange of tariff data. The OMS documents do (OMS-Spec-Vol1_General_v100.pdf section 3.7 and MUC_080128_inkl_Anlagen.pdf section 3). This means the Dutch meters can not display tariff or cost indications, just consumption data consisting of measured or calculated data. Valve commands Valve commands and Valve status reporting are handled differently in the Dutch and MUC documents (MUC_080128_inkl_Anlagen.pdf section 5.2.3) : Dutch definition German definition DIF 01H 89H VIF FDH FDH VIFE 1FH 1AH Review M-bus.doc 3 04/12/2008
Page 1: Review M-Bus documentation as inclu
Page 5 and 6: Other issues Frame Format The MUC_0

Introduction - KNX

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