Apparently, Chapter 41 of “The Lost Symbol” namechecks a handful of cipher mysteries, which probably explains the Dorabella Cipher search query spike I noticed over the last few days. So, a minor mystery solved (for a change), I’d guess:-
“…after [Langdon’s] experiences in Rome and Paris, he’d received a steady flow of requests asking for his help deciphering some of history’s great unsolved codes—the Phaistos Disk, the Dorabella Cipher, the mysterious Voynich Manuscript.”
Of course, only a cryptological schmuck taking Elonka’s famous list of unsolved codes & ciphers at face value would put Dorabella right up there with the VMs – so that must have been added by the copy-editors, right?
PS: here’s a recent blog entry on a proposed solution to the Dorabella Cipher.