DaVigil Code — January 2007

This clue appeared in the January 2007 issue of Today's Parish Minister.

The Vigenere cipher (“erenegiv” spelled backwards) is named after a 16th century French diplomat, Blaise de Vigenere, who created a very simple cipher. If you Google “Vigenere cipher,” you’ll learn that the cipher uses an alphabet square as the basis for the code. In addition, the cipher relies on a repeating keyword to encode the letter based on the alphabet square.

So, in this case, the keyword is “Asterius.” The letters in “Asterius” are repeated as many times as necessary over the text to be encoded. For example:

Keyword: Asteriusa ste

Text: Christmas Day

Ciphertext: Czkmjbgss Vtc

The first letter of the text, C, is coded using the alphabet in row A, which is the first letter of the key. This is done by looking at the letter in row A and column C of the alphabet square, namely C. Similarly, for the second letter of the text, the second letter of the key is used; the letter at row s and column h is z. The rest of the plaintext is coded in a similar fashion. Decoding is done by reversing the process.

Using this process, the decode text from clue 4 reads:

O night more light than day
More bright than the sun
O night, night more white than snow
More brilliant than many torches
O night of more delight than is paradise.

So what night was Asterius, Bishop of Amasia in the fourth century referring to? More clues to follow!