A device is arranged to carry out security-related tasks using one-time pad data. The device has a memory for holding multiple one-time pads, each pad having a different security rating and being intended for use by the device in executing a task to that security rating. Provisioning of the pads with one-time pad data involves carrying out a process for obtaining new secret random data. This process has a security rating with the value of this rating varying according to the nature and parameters of the process concerned. The security rating of the process used to obtain the new secret random data is matched to that of the pad to be provisioned with one-time data, or the other way around, such that the security rating of the process is as least as good as that of the pad to be provisioned.