So Ed Scheidt helped Jim Sanborn with the encryption. Although I believe the two of them discussed roughly what some of the message would entail, I can almost guarantee Jim made some adjustments. This falls into an interesting realm of discussion because in a television interview with Nova, James Gillogly stated that it wasn’t so much what the message was in Kryptos as how it was enciphered. I think this is a telling weakness in any intelligence agency attempts to decipher the piece. With Sanborn, it was very much about telling a story and imparting a message or philosophical ideal. Ed Scheidt likely gave him an overview of how to set up encryption techniques, they practised a few and Jim did the rest on his own.
That is why I find it interesting that the first two (K1 and K2) sections use the Quagmire III variation of a Vigenere cipher. As the methods become complex the further you go from morse code to the copper monolith; you wouldn’t expect two of them to be enciphered using the same method. Personally, I think Jim Sanborn did this because he wanted to use Palimpsest and Abscissa for some currently undiscovered reason. You can make an argument that they were hinted at in the morse code translation but it may be a little deeper. Perhaps palimpsest is in reference to the wax tablets used in early cryptology and abscissa is a dual reference to the geographic coordinates as well as the increasing dependence of cryptology on mathematical/computer advances. K3 is simply a tricky combination of two well known methods. Considering the fact that he painstakingly carved a vigenere table on panels 3 and 4 indicates to me that there is something of importance hiding in plain sight within the table and/or he was giving us all a gigantic hint. All K1 and K2 needed were the 2nd keywords in order to solve them. The recent revelation about the K3 solution involving the word Kryptos in numeric form is a further indication that these were not meant to be impossible puzzles, merely difficult.
What then is K4?
We know from interviews with Ed Scheidt that he used some kind of masking technique or steganography to further obfuscate the enciphered message. We do not know what the first layer is and until we do, we can never be sure we understand what the fourth piece actually consists of besides the orphaned 97 letters.
I think a reassignment of resources will be necessary to understand how the text/letters were modified or hidden or changed instead of fruitless attempts to decipher a small set of letters. Ed repeated again and again that frequency analysis and competence with the English language are aids to K1-3 but will not help a solver with K4. The reason no progress has been made so far is that we don’t fully understand all of the extraneous clues worked into the Kryptos artwork.
Because Jim Sanborn has stated that a solver has all he needs online to at least solve K1-4 (and with pencil and paper) we can assume that we do not need anything more than the morse code translation and the text of the copperplate letters. How to use them is how we will solve what we can outside of the CIA building.