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 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 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. <EOS>