Abstract: A method for protecting sensitive data in an entry of a log file for later audit, which includes encrypting the sensitive data in the log entry by using a random cryptographic key for each auditor authorized to access the log entry, encrypting the random cryptographic key by using an auditor's personal cryptographic key, and for each auditor not authorized to access the log entry, encrypting a fake cryptographic key having the same properties as the random cryptographic key by using an auditor's personal cryptographic key.

Abstract: Communication between an administrator device and an administered device in a network is arranged in the form of a chain of digitally signed communication items including messages sent from an originator device to a recipient device. Each message has an associated respective digitally signed receipt, and the originator device is configured not to send a new item toward the recipient device in the absence of a respective digitally signed receipt for a previously sent item. With at least one, and preferably by both of the administrator device and the administered device, there is stored a history record of communication items exchanged therebetween. The history record is agreed upon and signed by both the administrator device and the administered device.