A first network node (client-device-1) that is configured to be coupled in communication via a cloud service with other network nodes (client-device-j) , wherein the cloud service includes a plurality of server nodes (20A-N), wherein the plurality of server nodes (20A-N) are configured to communicate sensitive information (m), wherein the first network node is configured: (a) to register itself to the cloud service and thereafter to synchronize itself to other network nodes (client-device-j) in communication with the cloud service ; (b) to generate a string (si) that the first network node transmits to each of the plurality of server nodes (20A-N), wherein the first network node is configured to receive a response from each of the plurality of server nodes (20A-N), wherein the response is a function of the string (si) and a sub-key (Ki) allocated to each of the plurality of server nodes (20A-N); (c) to generate a password (PW) for the other network nodes (client-device-j) to use to access the sensitive information (m), wherein the password (PW) is configured to synchronize the sensitive information (m) to the other network nodes (client-device-j); (d) to instruct the plurality of server nodes (20A-N) to send the string (si) to the other network nodes (client-device-j), for the other network nodes (client-device-j) to use the password (PW) and the string (si) as confirmation responses back to the plurality of server nodes (20A-N); and (e) to instruct the plurality of server nodes (20A-N) to process the confirmation responses to generate a corresponding response from which the other network nodes (client-device-j) are configured to derive a root key (RK) for decrypting the sensitive information (m) at the other network nodes (client-device-j), wherein the root key (RK) is configured to perform an authentication of the other network nodes (client-device-j) with at least one of the plurality of server nodes (20A-N), whereafter the sensitive information (m) is transmitted from the at least one of the plurality of server nodes (20A-N) to the other network nodes (client-device-j) to be decrypted to provide the sensitive information (m). (a) to register itself to the cloud service and thereafter to synchronize itself to other network nodes (client-device-j) in communication with the cloud service ; (b) to generate a string (si) that the first network node transmits to each of the plurality of server nodes (20A-N), wherein the first network node is configured to receive a response from each of the plurality of server nodes (20A-N), wherein the response is a function of the string (si) and a sub-key (Ki) allocated to each of the plurality of server nodes (20A-N); (c) to generate a password (PW) for the other network nodes (client-device-j) to use to access the sensitive information (m), wherein the password (PW) is configured to synchronize the sensitive information (m) to the other network nodes (client-device-j); (d) to instruct the plurality of server nodes (20A-N) to send the string (si) to the other network nodes (client-device-j), for the other network nodes (client-device-j) to use the password (PW) and the string (si) as confirmation responses back to the plurality of server nodes (20A-N); and (e) to instruct the plurality of server nodes (20A-N) to process the confirmation responses to generate a corresponding response from which the other network nodes (client-device-j) are configured to derive a root key (RK) for decrypting the sensitive information (m) at the other network nodes (client-device-j), wherein the root key (RK) is configured to perform an authentication of the other network nodes (client-device-j) with at least one of the plurality of server nodes (20A-N), whereafter the sensitive information (m) is transmitted from the at least one of the plurality of server nodes (20A-N) to the other network nodes (client-device-j) to be decrypted to provide the sensitive information (m). <EOS>