I wonder if this guy was a consumer of Ovaltine when he was a kid, Ovaltine used radio broadcasts with secret codes that could only decoded by kids with a decoder ring. Something in this guys past sparked him into using codes so he might be using a system prior to the electronic era. His key obviously something personal to him but easy to compute in some transposition or substitutional way by table or geometric shape or something based on a Vernam cipher.

Ref: [link to en.wikipedia.org]

Time to feed the savant, Rain man!