A key distribution system can comprise a key packaging unit operable to package a key using a signature based upon an intrinsic property of a security token, a channel operable to have the packaged key transmitted therethrough; and a key unpacking unit operable to unpack the key using a signature based upon the intrinsic property of the security token. Thereby the key can be transmitted via a non-secure channel to a recipient for use thereby, without it being possible for a third party to obtain a copy of the key by monitoring the channel.