10214

# Effect of Keyword Length on the Letter Frequency in Encrypted Messages

This Demonstration shows the effect of keyword length on the letter frequency of an encrypted message.
Letter frequency analysis is a common tool used for decryption. Ordered by their frequency, the letters in English text are: e, t, a, o, i, n, s, r, h, l, d, c, u, m, f, p, g, w, y, b, v, k, x, j, q, z. The efficiency of a cipher can be rated by its ability to change this "normal" order.
Monoalphabetic ciphers (like the Caesar cipher) merely shift the order of the letters but do not change the frequency distribution.
Polyalphabetic ciphers (like the De Vigenere cipher or the Autokey cipher) use a keyword. The longer the keyword, the flatter the frequency distribution and the harder the decryption.

### DETAILS

Snapshot 1: change the offset for the Caesar cipher and see how the letters shift but the distribution remains unaffected
Snapshot 2: a short keyword with De Vigenere encryption slightly flattens the frequency distribution
Snapshot 3: a 26-letter keyword and Autokey encryption gives a flat frequency distribution

### PERMANENT CITATION

 Share: Embed Interactive Demonstration New! Just copy and paste this snippet of JavaScript code into your website or blog to put the live Demonstration on your site. More details » Download Demonstration as CDF » Download Author Code »(preview ») Files require Wolfram CDF Player or Mathematica.

#### Related Topics

 RELATED RESOURCES
 The #1 tool for creating Demonstrations and anything technical. Explore anything with the first computational knowledge engine. The web's most extensive mathematics resource. An app for every course—right in the palm of your hand. Read our views on math,science, and technology. The format that makes Demonstrations (and any information) easy to share and interact with. Programs & resources for educators, schools & students. Join the initiative for modernizing math education. Walk through homework problems one step at a time, with hints to help along the way. Unlimited random practice problems and answers with built-in Step-by-step solutions. Practice online or make a printable study sheet. Knowledge-based programming for everyone.