Method for replacing an existing key derivation key (KDK1) in a utility meter arranged in a meter communication infrastructure (MCI) for communication with a server side (SS) comprising a head-end system (HES), the method comprising the steps of: - deriving at the server side (SS) a new key derivation key (KDK2) based on a disaster recovery key (DRK), stored at the server side, and a key-generation information (KGI); - deriving at the server side an activation key (AK) from the new key derivation key (KDK2) ; - transmitting from the head-end system (HES) to the utility meter a command data message (CDM) comprising: - a request for replacing the existing key derivation key (KDK1) with the new key derivation key (KDK2); - the key-generation information (KGI); and - the activation key (AK) or an authentication code (CDM-AC) calculated based on the activation key (AK); - receiving in the utility meter the command data message (CDM); - deriving in the utility meter the new key derivation key (KDK2) based on a copy of the disaster recovery key (DRK) stored in the utility meter and on the key-generation information comprised in the received command data message (CDM); - deriving in the utility meter the activation key (AK) from the new key derivation key (KDK2); - verifying in the utility meter the activation key (AK) or the authentication code (CDM-AC) received in the command data message (CDM), based on the derived activation key (AK); and - replacing in the utility meter the existing key derivation key (KDK1) with the new key derivation key (KDK2) when the activation key (AK) or authentication code (CDM-AC) comprised in the received command data message (CDM) is verified. - deriving at the server side (SS) a new key derivation key (KDK2) based on a disaster recovery key (DRK), stored at the server side, and a key-generation information (KGI); - deriving at the server side an activation key (AK) from the new key derivation key (KDK2) ; - transmitting from the head-end system (HES) to the utility meter a command data message (CDM) comprising: - a request for replacing the existing key derivation key (KDK1) with the new key derivation key (KDK2); - the key-generation information (KGI); and - the activation key (AK) or an authentication code (CDM-AC) calculated based on the activation key (AK); - a request for replacing the existing key derivation key (KDK1) with the new key derivation key (KDK2); - the key-generation information (KGI); and - the activation key (AK) or an authentication code (CDM-AC) calculated based on the activation key (AK); - receiving in the utility meter the command data message (CDM); - deriving in the utility meter the new key derivation key (KDK2) based on a copy of the disaster recovery key (DRK) stored in the utility meter and on the key-generation information comprised in the received command data message (CDM); - deriving in the utility meter the activation key (AK) from the new key derivation key (KDK2); - verifying in the utility meter the activation key (AK) or the authentication code (CDM-AC) received in the command data message (CDM), based on the derived activation key (AK); and - replacing in the utility meter the existing key derivation key (KDK1) with the new key derivation key (KDK2) when the activation key (AK) or authentication code (CDM-AC) comprised in the received command data message (CDM) is verified. <EOS>