I think I've found the solution to Kryptos K4. I believe that Jim Sanborn and Ed Scheidt used the last rows of K3, after a simple transformation, as a One Time Pad. Then they used "Letter" masks (a mask in the shape of a letter) to determine which characters of K3 would be used with the K4 ciphertext. They placed steganography around the edges to give a clue as to the letter mask used. The amazing thing is that they did it 6 times (reused the pad 6 times). So K4 is much longer than just 97 characters.
In order to do this they used "condensed - text message like" English, and there is in each a significant amount of misspellings ~ 16% (but they use the misspellings to form other messages).
The plaintext indicates, to me (this is my interpretation) that Kryptos is a memorial to one of the CIA's best spies, Oleg V. Penkovsky. In addition Jim Sanborn, Ed Scheidt and those at the CIA who helped them are calling out to save Penkovsky from a dishonor that has been placed upon him.
Oleg V. Penkovsky spied from the heart of the Soviet Union for us. The information he gave to the USA was of the most critical importance. Information which included reports on Soviet ICBM technology. This helped JFK during the Cuban Missile Crisis. Had he not done what he did, we quite possibly would have found ourselves in a nuclear war.
When he was captured by the KGB, during his interrogation he signaled the CIA and SIS that the Soviets were about to launch a surprise attack upon the west. The cover story has been that he told the KGB of this signal, but not what it meant, so that when the KGB sent it as a trap for our case officers working over there, the US might believe it and launch a nuclear counter attack.
This is the story the CIA has maintained - it is a false cover story, as I believe the Kryptos plaintext reveals. The true reason is that the KGB gave Penkovsky, since he was proving hard to get information out of, LSD, and probably tricked him into actually thinking that the Soviets were about to attack so that he would relieve his secrets.
The CIA formed a plan to save Penkovsky from execution, involving Kim Philby. But it failed, and they had to cover this up. The main, true, reason as Kryptos suggests, is that they could not reveal the use of LSD since that revelation would expose their Project MK Ultra, the CIA's secret mind control project of which the administering of LSD was a big part of (which was quite illegal). Thus they placed or allowed to be suggested a great lie upon Penkovsky, one of our greatest spies; that he wished to bring the whole world down with him. The reason that it would have lead to exposure was that the Soviets had learned about Mk Ultra from George Blake, who had also informed them, indirectly, about Penkovsky. Thus a deal was made between the KGB, the CIA, and the SIS not to expose each other. Penkovsky was lost in this deal. I realize that this sounds a bit amazing - and it's hard to see all of this interpretation, but it is there. This is what Kryptos is about, I believe.
I have it posted on DropBox at:
https://www.dropbox.com/s/ej67g58cg3iuty2/Kryptos%20K4%20Solution%20V5_1.pdf
Just download the file "Kryptos K4 Solution V5_1.pdf" (version 5.1). I hope the members of the group can reach it. If not then I'll figure out a better way of posting it somewhere where they can.
Please read it - I know it's very long - but it is amazing. Any questions you have please feel welcome to email me at ibnsifre at yahoo dot com. Please help me and Jim and Ed and all those that helped them reveal this so that honor is restored to Penkovsky.
Sincerely,
Ibn Sifre