Despite many believing this, I consider it indecently unlikely. The only “training exercise” that could be obtained from such a cipher is that sometimes there are codes/ciphers that you will just never crack. If a person believes a one-time pad was used then they have effectively given up on Kryptos. The only suggestions we would have for the pad-text would be:
- The Morse Code text with the e’s (without them we only have 81 letters which is not enough)
- K1 is not an option as it only has 63 letters.
- K2 is an option but conceivably presents too many options as any sequential 97 letters is viable for the pad.
- K3 is an option with the same issues as K2.
- Howard Carter’s original journal entry.
For pencil and paper work, that’s prohibitively time consuming. Give a guy a computer and yeah, he could churn his way through the options but consider the possibility that the one-time pad used was not anything related to Kryptos.
You could use a phonebook, a dictionary, a cookbook, the Declaration of Independence.
The random options are finite as there is not an infinite amount of writing that was available to Sanborn and Scheidt at the time of encryption but it is beyond anyone’s ability to check K4 against everything that was available to them so it is practically an infinitely random barrier that is insurmountable.
I’m sure some folks didn’t give up and have tried different scenarios.
Personally, I consider it giving up. You basically say, “Hey, I can’t get it. What’s an impossible cipher to solve on which I can blame my failure. One-time pads, yeah, that could work.”
Here’s some background on the ole OTP.
In cryptography, the one-time pad (OTP) is an encryption algorithm in which the plaintext is combined with a secret random key or pad, which is used only once. A modular addition is typically used to combine plaintext elements with pad elements. (For binary data, the operation XOR amounts to the same thing.) It was invented in 1917 and patented a couple of years later. If the key is truly random, never reused in whole or part, and kept secret, the one-time pad provides perfect secrecy. It has also been proven that any cipher with the perfect secrecy property must use keys with effectively the same requirements as OTP keys. The key normally consists of a random stream of numbers, each of which indicates the number of places in the alphabet (or number stream, if the plaintext message is in numerical form) which the corresponding letter or number in the plaintext message should be shifted. For messages in the Latin alphabet, for example, the key will consist of a random string of numbers between 0 and 25; for binary messages the key will consist of a random string of 0s and 1s; and so on.
The “pad” part of the name comes from early implementations where the key material was distributed as a pad of paper, so the top sheet could be easily torn off and destroyed after use. For easy concealment, the pad was sometimes reduced to such a small size that a powerful magnifying glass was required to use it. Photos accessible on the Internet show captured KGB pads that fit in the palm of one’s hand, or in a walnut shell. To increase security, one-time-pads were sometimes printed onto sheets of highly flammable nitrocellulose.
The one-time pad is derived from the Vernam cipher, named after Gilbert Vernam, one of its inventors. Vernam’s system was a cipher that combined a message with a key read from a paper tape loop. In its original form, Vernam’s system was not unbreakable because the key could be reused. One-time use came a little later when Joseph Mauborgne recognized that if the key tape was totally random, cryptanalytic difficulty would be increased.
There is some ambiguity to the term due to the fact that some authors use the term “Vernam cipher” synonymously for the “one-time-pad”, while others refer to any additive stream cipher as a “Vernam cipher”, including those based on a cryptographically secure pseudorandom number generator (CSPRNG).
Look for cryptosystems all you want but this ain’t it.