A method for handling performance monitoring data in a communication network comprising a plurality of network nodes; the performance monitoring data being generated by a network node; the performance monitoring data being a stream of data characterizing the performance of the network node; the method comprising: • determining, by the network node, whether an encryption condition for encrypting the performance monitoring data is fulfilled; • determining, by the network node, whether the network node has a valid and not expired encryption key available, and if not, authenticating, by the network node, a security network operation center and performing (456, 502) an agreement negotiation with the security network operation center on an encryption key and a corresponding decryption key; • retrieving and storing, by the network node, the agreed encryption key in an encryption key storage; • based on the result of determining whether an encryption condition for encrypting the performance monitoring data is fulfilled, encrypting with the encryption key, by the network node, the performance monitoring data; • subsequent to the encrypting, sending, by the network node, the encrypted performance monitoring data to a performance monitoring data collector; • receiving and storing, by the performance monitoring data collector, the encrypted performance monitoring data; • determining, by the performance monitoring data collector, whether a decryption condition for decrypting performance monitoring data is fulfilled, the decryption condition comprising authorizing, by the security network operation center, the performance monitoring data collector to decrypt the encrypted performance monitoring data; • based on a result of determining whether a decryption condition is fulfilled, the security network operation center delivering the corresponding decryption key to the performance monitoring data collector; and • after receiving the corresponding decryption key, decrypting, by the performance monitoring data collector, the stored encrypted performance monitoring data. • determining, by the network node, whether an encryption condition for encrypting the performance monitoring data is fulfilled; • determining, by the network node, whether the network node has a valid and not expired encryption key available, and if not, authenticating, by the network node, a security network operation center and performing (456, 502) an agreement negotiation with the security network operation center on an encryption key and a corresponding decryption key; • retrieving and storing, by the network node, the agreed encryption key in an encryption key storage; • based on the result of determining whether an encryption condition for encrypting the performance monitoring data is fulfilled, encrypting with the encryption key, by the network node, the performance monitoring data; • subsequent to the encrypting, sending, by the network node, the encrypted performance monitoring data to a performance monitoring data collector; • receiving and storing, by the performance monitoring data collector, the encrypted performance monitoring data; • determining, by the performance monitoring data collector, whether a decryption condition for decrypting performance monitoring data is fulfilled, the decryption condition comprising authorizing, by the security network operation center, the performance monitoring data collector to decrypt the encrypted performance monitoring data; • based on a result of determining whether a decryption condition is fulfilled, the security network operation center delivering the corresponding decryption key to the performance monitoring data collector; and • after receiving the corresponding decryption key, decrypting, by the performance monitoring data collector, the stored encrypted performance monitoring data.