This disclosure relates to message encoding. Once claim recites an apparatus comprising: electronic memory for buffering identifying data associated with an entity or client; and a multi-purpose electronic processor programmed for: modifying the identifying data with a random or pseudo-random signal; error correction encoding the modified identifying data; and transforming a plural-bit message with the error correction encoded, modified identifying data to produce a key for use with message encoding. Of course, other claims and combinations are provided as well.