Bifid

Breaks information for each letter up and spreads it out in the encoded message. An easy and fairly secure pencil & paper cipher.

The Bifid cipher is considered a more secure cipher because it breaks the message apart into two separate streams and then recombines them. This spreads each letter’s information out over multiple letters, increasing security. It uses a table with one letter of the alphabet omitted. Often the J is removed and people just use an I instead. Below is an unkeyed grid.

A B C D E
F G H I K
L M N O P
Q R S T U
V W X Y Z

To encode a message, you write out your message, “ABCD”, then figure out the row and column for each letter and write them below the letters, as the example shows. Then you read the numbers off, all of the rows first and then all of the columns. Taking this string of numbers in pairs, you look up the letters on the table again and get the encoded message.

letter: A B C D
   row: 1 1 1 1
column: 1 2 3 4

The numbers: 1 1 1 1 1 2 3 4
    Encoded:  A   A   B   O

All non-letters are skipped and not encoded. The one omitted letter will be automatically translated if you type it in the box. Numbers, spaces, and punctuation will remain in place and will not be encoded.

Examples: