Is anyone aware of legally (US and/or British law, specifically) "strong" stenographic techniques? Meaning a court would allow that this object is assigned to this person because of a stenographic key embedded in the object?
I suspect that the common law legal systems would approach this via case law. Unless case law exists already I think that if you wanted to claim ownership of a file you'd need to present your case including expert witnesses and persuade a judge/jury of its validity.