To play these puzzles requires Shockwave and either Netscape 3.0, 4.0 or Internet Explorer 3.0, 4.0. For Internet Explorer, you will need the ActiveX control for Shockwave rather than the Netscape plug-in.

What's Going On Here?

This interactive demonstration is designed to explain a little bit about DES (Data Encryption Standard), an algorithm for encrypting data. We're using colors instead of data bits since colors are easier to comprehend. On the top of our diagram, we have two colored balls. This is the data to be encrypted broken into two halves. On the side of our diagram, we have two additional colored balls. These are two portions of the DES key(s) we will use to encrypt our data. Take a few moments and click on the various color balls (inside the squares) and see how changing the data and the keys effects the encrypted data below. You'll notice that the two balls at the bottom are never the same color as the two balls at the top - that's because they have been encrypted using the two balls on the side as keys. What patterns do you notice? See if you can form any opinions as to how DES works.

EXPERIMENT: Try this

1. Set your unencrypted data to Black on the left and Green on the right
2. Set your encryption key to Red on the top and Green on the bottom
3. Notice the colors of the encrypted data at the bottom (both purple)
4. What happens if you change your unencrypted data to purple using the same key?
5. Why isn't it black and green?
6. Switch the encryption key order to green on the top and red on the bottom

What does that tell you about DES?

DES is considered a "near symmetric" algorithm. that means that the same algorithm is used for both encryption and decryption, except, the key order must be reversed to decrypt the message. Basically, DES breaks up the data to be encrypted into discreet portions and sends those portions through a round of encryption actions wherein each round causes the following to occur:

• Half of the data is combined with one key
• That result is combined with the other half of the data and these two portions are passed down to the next phase of our process
• The second half of the original data, which has not yet been encrypted, becomes the first half of the next encryption round where it is combined with the second portion of the key.
• This keeps happening over and over again, more and more, based on the size of the encryption key. The larger the key, the more permutations occur and the more difficult it is to break this algorithm.