I hope not.
I kind of doubt it anyways. A Gronsfield cipher is just a type of Vigenere cipher that uses numbers instead of letters for the keyword.
“Well, if we’re considering everything, shouldn’t we at least try it?”
If the man used the same bloody ciphering on 3 out of the 4 parts of his monument to the CIA’s public image then I will have no part in it. I’d rather be wrong than believe that this thing is that lame. If you can believe them when interviewed, the gruesome twosome have stated that K1 and 2 are similar, K3 is different and K4 is different. So unless they’re complete liars then a Gronsfield was not used on K4.
I don’t feel compelled to exhaustively pursue either a Vigenere or a Gronsfield solution effort on Kryptos’ K4 anyways. I happily make the perhaps foolhardy assumption that cryptanalysis would have revealed their use in the previous 20 years of independent research, if it was there. I also assume that there are plenty of people who’ve tried enough mindless repetitions of Vigenere-style decryptions on K4 that someone would have stumbled across it by now.
If I’m wrong then I will be the first to petition the CIA to remove Kryptos and melt it down for recycling.