I've spent a fair amount of time on K4, and my conclusion is that it's simply a poor puzzle. At this point 24 of 97 characters have been revealed, and yet there's seemingly still not enough information pointing to how the known plaintext corresponds to the ciphertext. Over the decades everything reasonable has been tried and eliminated, which means the solution is likely to be unreasonable.
elahieh · 1h ago
I'm inclining to this too. I heard about it first on Usenet in the 90s, and started looking at it again seriously in June 2017 when I came across the Bauer paper.
But after the 2020 clues (another 13 letters), it became clear that it wasn't any single ACA cipher type, and it was probably something very difficult (because of K4's very low index of coincidence, i.e. 0.036 just below "random" 26-letter text at 1/26, plus the huge number of revealed plaintext letters "in place" i.e. letter-for-lettter correspondence).
That plausibly left a combination of two or more well-known cipher types, but if they were somewhat complex ciphers, the chance of solution would be rather remote.
Hence I always thought a "good" end to the puzzle would be like the book "Masquerade" by Kit Williams where the only guy in cahoots with the creator (Bamber Gascoigne) thought the initial puzzle was an unrealistic challenge, but Williams released clues which enabled two schoolteachers to solve it. So that part was satisfactory, even if hardly anybody remembers the solvers' names!
In contrast, the cribs for K4 haven't helped at all.
Waterluvian · 25m ago
What makes a puzzle like this “unreasonable?” Like would it be a sort of “you had to know that you needed a bit of graffiti on a truck stop stall outside Anchorage” unfair scope issue or is there a different kind of unreasonable I cannot currently imagine?
derekp7 · 24m ago
A one time pad would be unreasonable.
Edit: Unless the one time pad is a well known relative document, such as the Declaration of Independence.
Waterluvian · 21m ago
Would that be akin to me offering a hash string as a puzzle and asking for the 10GB video file as the solution?
kop316 · 8m ago
Sort of. A one time pad does not destroy data, but a hash will.
In their example, "HELLO" is the plain text, "XMCKL" is the key, and the ciphertext is "EQNVZ". However, with a one time pad, an equally plausible plain text is "later" with the key "TQURI". Thus, without anymore data, it is simply impossible to know what the original message is.
pjbk · 1h ago
Probably correct. Different from the other cyphers, the number of symbols is short, and correlating part of the plaintext that has been revealed gives poor measures for the full string length. It has been said that the other solutions are required to solve K4, so if the solution relies on something like character alignment, matrix coding or an even more convoluted permutation arrangement, this can look (or directly be) a one-time pad cypher which are arguably the most difficult to solve.
cantrevealname · 57m ago
> These cryptographic systems were not designed by the sculptor himself but by Edward Scheidt, who retired as chairman of the CIA’s Cryptographic Center in 1989.
The article left me with a nagging question: Doesn’t the designer of the codes deserve a share of the proceeds of the auction? He’s still alive according to Wikipedia. It sounds like the unsolved code is what makes the art especially valuable. Was the cryptographer’s effort a “work for hire”, so he doesn’t get anything from the sale?
elahieh · 38m ago
Good point, and it's also entirely possible the code designer just did a terrible job. e.g. around 57:00 of https://youtu.be/JOXPYkjvDaA
As Kryptos gots a huge amount of media attention in 1999, references to him changed from "chairman of A cryptographic center" to "chairman of [THE] CIA's cryptographic center" when it doesn't even seem that it has such a center.
And the featured story (around 52:00 of the video) has him apparently claiming credit for helping solve a Caesar cipher!
But after the 2020 clues (another 13 letters), it became clear that it wasn't any single ACA cipher type, and it was probably something very difficult (because of K4's very low index of coincidence, i.e. 0.036 just below "random" 26-letter text at 1/26, plus the huge number of revealed plaintext letters "in place" i.e. letter-for-lettter correspondence).
That plausibly left a combination of two or more well-known cipher types, but if they were somewhat complex ciphers, the chance of solution would be rather remote.
Hence I always thought a "good" end to the puzzle would be like the book "Masquerade" by Kit Williams where the only guy in cahoots with the creator (Bamber Gascoigne) thought the initial puzzle was an unrealistic challenge, but Williams released clues which enabled two schoolteachers to solve it. So that part was satisfactory, even if hardly anybody remembers the solvers' names!
In contrast, the cribs for K4 haven't helped at all.
Edit: Unless the one time pad is a well known relative document, such as the Declaration of Independence.
Wikipedia has a good example: https://en.wikipedia.org/wiki/One-time_pad
In their example, "HELLO" is the plain text, "XMCKL" is the key, and the ciphertext is "EQNVZ". However, with a one time pad, an equally plausible plain text is "later" with the key "TQURI". Thus, without anymore data, it is simply impossible to know what the original message is.
The article left me with a nagging question: Doesn’t the designer of the codes deserve a share of the proceeds of the auction? He’s still alive according to Wikipedia. It sounds like the unsolved code is what makes the art especially valuable. Was the cryptographer’s effort a “work for hire”, so he doesn’t get anything from the sale?
As Kryptos gots a huge amount of media attention in 1999, references to him changed from "chairman of A cryptographic center" to "chairman of [THE] CIA's cryptographic center" when it doesn't even seem that it has such a center.
And the featured story (around 52:00 of the video) has him apparently claiming credit for helping solve a Caesar cipher!
https://web.archive.org/web/19990501000000*/http://www.tecse...