Manual authentication techniques have been designed to enable wireless devices to authenticate one another via an insecure wireless channel with the aid of a manual transfer of data between the devices. Manual transfer refers to the human operator of the devices performing one of the following procedures; copying data output from one device into the other device, comparing the output of the two devices, or entering the same data into both devices. Techniques currently being standardised are described which achieve this, and which require only small amounts of data to be transferred between the two devices. This makes the mechanisms particularly attractive for non-expert use, as required for ubiquitous mobile wireless devices.