“The science of secrecy from ancient Egypt to Quantum Cryptography” The Code Book, a national bestseller brings you through the epic story of the evolution of cryptology. Throughout this book in which great minds tackle great problems, there is a common theme. No matter what you do, Never. Give. Up.
One of the great achievements in cryptology was the cracking of the Vigenère Cipher, this one cipher took humans 3 centuries to finally crack. This cipher was nothing like the monoalphabetic substitution ciphers that had previously been cracked because this was not vulnerable to frequency analysis. Mr. Babbage, the first person to crack it, almost took an entire year to do so. There were many steps that Mr. Babbage had to take to finally decipher the Vigenère Cipher. “While most cryptanalysts had given up all hope of ever breaking the Vigenère cipher, Babbage was inspired to attempt a decipherment by an exchange of letter with John Hall Brock Thwaites, a dentist from Bristol with a rather innocent view of ciphers.” (Singh, 67) With his different approach to this 300-year-old cipher, he had managed to crack it. But this wasn’t done without strong perseverance and all the failures that came with it. Although his work was not published and he didn’t gain the recognition he deserved, his contributions in cracking the Vigenère Cipher has made him one of the all-time great cryptanalysts.
World War II could’ve tilted the other way if it weren’t for this.
With tensions rising, Europe was on the brink of war, Germany seemed to have the ultimate cipher which would secure transmitted information, but there was 1 country who had already got a head start at tackling this machine. Poland. Polish cryptanalysts were determined exploit every weakness of the Enigma to gain access to German communications. First, a bit of background knowledge, the Nazis had a day key that consisted of 3 letters, and with every message that was sent with the Enigma the operators had picked a message key, also consisting of 3 letters. All day keys were predetermined and every month the lists for every day key would be distributed. But here was the weakness in the Enigma that Rejewski, the cryptanalyst leading the way for cracking the Enigma, had exploited. Every single day key had been typed twice into the Enigma machine before operators would switch to the message key. Repetition is every cipher’s weakness and Rejewski had started on this lead.
Rejewski had noticed the 1st and 4th letters of every message are encryptions of the same letter, the 2nd and 5th letters also share this relationship, as well as the 3rd and 6th. Knowing that all 1st and 4th letters were related by the initial setting of the Enigma machine had allowed him to find relationships between them. If he had intercepted enough messages, he would complete the alphabet in which he would know what the 4th letter would be encrypted as by looking at the 1st encrypted letter.
1st letter: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
4th letter: F Q H P L W O G B M V R X U Y C Z I T N J E A S D K
Rejewski knew that the table of relationships would be completely different every time the day key changed. From there, he had created chains of letters. For example, he would see that A on the top row was linked to F on the bottom row, F on the top row was linked to W on the bottom row, and W on the top row would link to A on the bottom row. That was a chain done. He would generate more chains with the rest of the alphabet. Once he was done, he would record the number of links. In our example:
A-F-W-A 3 links
B-Q-Z-K-V-E-L-R-I-B 9 links
C-H-G-O-Y-D-P-C 7 links
J-M-X-S-T-N-U-J 7 links
This was only for the 1st and 4th letters, he would do the same thing for the 2nd and 5th letter as well as the 3rd and 6th letters. Rejewski noticed that both the length of the chains and the letters in the chains changed every day. So what he did was figure out all 105,456 combinations of chains (3 rotors, 6 combinations, each rotor has 26 options) To this day, that library of chains can still be accessed. Now with only a few minutes of searching, the day key could be obtained and German communications could now be heard by the polish.
This little story is the start of an epic fight for the right of secret communications. But this was the story that allowed the enormous task of finding the 1 out of 158,962,555,217,826,360,000 possible combinations every day. This only talks about the successes of Rejewski, so just imagine how many times he had ideas that led to nowhere. If it weren’t for Rejewski’s determination to crack the Enigma, the world might now have been what it is today.
The science of secrecy is one that takes great determination and skill to succeed in. From Caesar preventing others reading his messages to hashing algorithms that keep everybody’s passwords safe, cryptology is subject that not many people pursue, but everybody relies on. If it weren’t for the perseverance of many cryptanalysts, cryptology would not be as advanced as it is today.