Challenge 5: A Vigenere Cipher

UPDATE 2017/09/23: This post has been solved! View the solution here.

Here’s Challenge #5 for September 6, 2017.

A VIGENÈRE CIPHER

In Challenge#2, we featured a Caesar Cipher, the most well-known monoalphabetic substitution cipher. “Monoalphabetic” means that each plaintext letter only has one corresponding ciphertext counterpart.

Today, we’re featuring a Vigenère Cipher, which is the most well-known polyalphabetic cipher. “Polyalphabetic” means that each plaintext letter does not have a one-to-one correspondence with a ciphertext letter. The letter “D” may be enciphered as “H” in one spot and “X” in another.

The Vigenère Wikipedia page is a good starting point to learn more about this fascinating cipher. Jim Sanborn used the Vigenère to encipher at least two of the panels on Kryptos.

Here are a few characteristics of my Vigenère:

  1. It uses the standard English alphabet in the rows and columns. (ABCDEFGHIJKLMNOPQRSTUVWXYZ)
  2. The key is 10 characters or fewer.

Here’s the ciphertext:

EHAQW DPEZR RWAHT NELTN OHMJE IAWAJ OYNOY HSYPK TGAWW DOJSN SICZY AJRTS ETYHO KRIWO AAPDB FTRAS TRHLZ FHEHT WLBOQ QOYES ECFTZ NOLET DSXFM PETMA

With CodeAWeek.com, I hope to release one cipher, puzzle, or mystery every Wednesday evening. Anyone can attempt to solve. The winner is the first person to send a correct solution and a description of the solve method to codemaster@codeaweek.com. Once a correct solution is e-mailed, I will publish a follow-up post, congratulating the winner and revealing the secrets of the code.

You may post questions or theories in the comments, but DO NOT POST SOLUTIONS. E-mail them to codemaster@codeaweek.com.

— Tony Youngblood

 

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