The 35-year saga of Kryptos, a mysterious sculpture containing four encrypted messages outside CIA headquarters, has just taken a bizarre turn. Although the first three passes were cracked by cryptographers in the 1990s, just a few years after artist Jim Sanborn erected the copper monolith, the fourth, known as K4, remained a 97-character fortress—that is, until September 2, when journalists Jarrett Kobeck and Richard Byrne found the answer in the archives of the Smithsonian Institution.
How to crack the world's most famous code? Breakthroughs on Kryptos are a tour of the cat-and-mouse game between code creators and code breakers it has defined information security for thousands of years.
Main task cryptography consists of sending a secret message safely in the presence of eavesdroppers. Strategy always includes the same ingredients: a message called plaintextdistorted ( encryption), so that anyone who intercepts it will only see garbled gibberish ( ciphertext). Ideally only those who have a secret key Maybe decipher This. If you share your private key with the intended recipient and no one else, then in theory you can communicate with them in code. Cryptography underpins everyday financial transactions and online communications, not just spy messages.
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To understand Kryptos, we need to delve into early cryptosystems and understand why they failed. One of the simplest and oldest encryption methods dates back to the historical secret keeper Julius Caesar. The Caesar cipher hides messages by shifting each letter of the alphabet by some fixed amount. Here the key is a number between 1 and 25. Let's say we choose 5. The encryption for “hello” would be “mjqqt” because M is the five letters after H, J is the five letters after E, and so on. (If you get to the end of the alphabet, go back to the beginning.) More interesting example: discerning fans 2001: A Space Odyssey noticed that the name of the rogue AI named HAL is spelled “IBM” with the Caesar cipher shifted back one letter. (Director Stanley Kubrick insisted it was a coincidence.) Although Caesar trusted this method in his confidential correspondence, it is a lousy way to protect state secrets. If an attacker finds out that you are encrypting messages using a Caesar cipher, he only needs to try 25 different keys to recover the original text.
A general replacement cipher offers the most natural renewal. Instead of just changing the alphabet, you encrypt it. The letter A can become Q, B can become X, C can become D, and so on, in no particular order. This Seems much safer. The Caesar cipher has only 25 possible keys, while the full substitution cipher has 403,291,461,126,605,635,584,000,000. (There are 26 factorial ways to mix up the alphabet, or 26 × 25 × 24 × 23… 3 × 2 × 1.) Brute-force with a target checking every key is not possible, but replacement ciphers are still extremely insecure today's standards. If you don't already know why, ask yourself what you would do with decrypting a page of text encrypted with a substitution cipher.
The disadvantage of the substitution cipher is that it leaves language samples untouched. The English language has a distinct fingerprint. The letter E accounts for more than 12 percent of all letters in English text, while the letter Z appears less than 0.1 percent of the time. If you intercept a page of gibberish encrypted using a substitution cipher, and the letter J appears more often than any other letter, you can bet that J stands for E. The second most common letter is probably T. Additionally, one-letter words almost certainly stand for A or I (the only commonly used one-letter English words), and common two- and three-letter words can also produce Codebreakers have their foot in the door. Called frequency analysisthis method is the subject of popular newspaper puzzles called cryptograms; he also played a crucial role in deciphering the first three passages of Kryptos.
Sanborn encrypted the first two Kryptos messages, named K1 and K2 and containing 63 and 372 characters respectively, using the next level: the Vigenère cipher. Invented in the 16th century and named after the cryptographer Blaise de Vigenère, it stood unbroken for 300 years, earning it the nickname “le chiffre indéchiffrable” (the undecipherable cipher). It works using several different Caesar's ciphers to one plaintext. For example, perhaps we move the first letter of the message forward by 19, the second letter forward by 16, the third letter forward by 25, and then repeat. (The fourth letter is shifted by 19, the fifth by 16, the sixth by 25, etc.) These shift values make up the key, which is usually represented by the word corresponding to those places in the alphabet. In this case, the key is SPY because S, P and Y are the 19th, 16th and 25th letters.
The Vigenère cipher is ingeniously superior to simple frequency analysis because, for example, not all E's will be mapped to the same letter. Imagine that the first two letters of the message are both E. The first is shifted by 19, becoming an X, and the second is shifted by 16, becoming a U. But smart cryptanalysts can still break through. If you can guess length keys (for example, three for SPY), you will be able to disassemble the problem into parts. You take the first, fourth, seventh, 10th, and so on letters of the ciphertext and put them in a stack. All this was shifted according to same key letter:S. Now you can carry out frequency analysis on this heap. You do the same with the second, fifth and eighth letters, shifted by the letter P, and so on. The “unbreakable” cipher becomes three simple Caesar ciphers. Not sure about the key length? Carefully examining the ciphertext can sometimes provide a clue, but if all else fails, try all possible lengths. Too much time? A computer program can help with the search.
Sanborn encrypted K1 and K2 with the keys “PALIMPSEST” and “ABSCISSA” respectively. The first, poetic choice, refers to a piece of text that has been erased and rewritten several times. Abcissa is X coordinate (X, th) coordinate pair. As is common with Vigenère ciphers, Sanborn also used a modified alphabet for the shift: in this case KRYPTOSABCDEFGHIJLMNQUVWXZ, which he engraved on the sculpture.
Sanborn switched methods for K3, a 337-character ciphertext. Here he chose transposition cipher in which he simply mixed up all the letters in the message as if it were a huge anagram. The disorder in this type of cipher usually follows certain rules, so that the intended recipient with the key can easily restore the letters to their rightful order. Cryptographers readily suspected that K3 used this cipher. How? You guessed it – frequency analysis. The distribution of letters in the ciphertext matched what would be expected in a typical English text, suggesting that the letters were not replaced, but simply shuffled.
At least three independent efforts have decrypted the first three Kryptos messages. Computer scientist Jim Gillogly claimed to have hacked them using a computer in 1999. Only then did the CIA reveal that its analyst David Stein had solved all three problems by hand. 1998. It was only then that the National Security Agency announced that a small internal team had defeated them in the distant past. 1992.
K4 resisted all attempts for 35 years. It is possible that Sanborn intentionally increased the difficulty to reflect the advances made in cryptographic science since the time of Vigenère. Breaking full-fledged modern cryptography would mean not just smarter applications of frequency analysis, but also a revolution in our understanding of mathematics itself. This is because modern encryption hides information behind mathematical problems (such as factoring huge numbers) that are supposedly intractable in any practical amount of time. Breaking the encryption would mean finding a quick solution to these seemingly impossible problems, an action that would overturn the fundamental tenets of modern mathematics.
This fall, Sanborn planned to auction off the K4 solution—an encrypted message beginning with “OBKR”—to relieve himself of being the sole custodian of its secrets. The auction announcement mentioned the Smithsonian's original “coding tables.” Instead of deciphering K4, journalists Kobek and Byrne requested access to the documents and found scraps of paper containing the plaintext of K4. On September 3, the duo emailed Sanborn with the decision.
The journalists who discovered the answer to K4 in the Smithsonian Institution archives are a perfect example of how hackers are breaking into 21st century cryptography: through side doors. As far as we know, modern encryption that protects your email and credit card purchases works when implemented correctly. Data breaches are rarely the result of hackers breaking encryption, but rather of discovering some other weak link in the security chain. They use phishing schemes to trick people into revealing their credentials. They exploit a bug in the website code. That is, they are aimed at flawed, forgetful and disorganized people who use encryption. Finding K4's plaintext was like finding someone's password written on a sticky note in their office. This climax is disappointing to some, but we can also see it as a fitting metaphor for a piece of art meant to celebrate cryptography through the ages.
This does not appear to be the artist's point of view: Sanborn asked journalists to sign non-disclosure agreements. (They refused.) Those still eager to solve the mystery are in luck, because the public doesn't know what K4 says or how it was encrypted. No one fully understands the mysterious messages that K1-K3 reveal. Sanborn also confirmed the existence of K5 in open letter published in August of this year. Codebreakers have a lot to look forward to in the next era of Kryptos.
