This is another in a series of posts about Protective Technologies. Encryption in any of its forms is, arguably, the most important of the Protective Technologies that help keep us safe while using the Internet. Today’s encryption methods are quite sophisticated compared to those of the past, and here we are going to discuss the concept of using a Key.

Encryption with a Key:

Encryption depends on creating a rule to translate our messages to unreadable text. The inverse of the rule is applied by the person receiving the message in order to make it intelligible. The next level is to use a rule to generate a key that we need to take with us, rather than a simple rule. 

Suppose we want to send the message “porties are distinct”. (Portie, by the way, is short for Portuguese Water Dog.)

Fig. 1: Encrypting Portie messages

Here is the regular lower-case English alphabet followed by the alphabet randomized to be a key:

  • abcdefghijklmnopqrstuvwxyz
  • ifmhbcpnezlogtaqrxvkwjsduy

These characters are turned into an encryption guide in Fig. 2 below, so it’s easier to see which characters correspond.

Fig. 2: Encryption Guide

To encrypt the message, find the letter in the top row and use the corresponding letter directly under it in the second row. In our example the “p” becomes an “q”, the “o” becomes an “a”, and so on. The full message “porties are distinct” becomes “qaxkebv ixb hevketmk”.

Note that the method of encryption, the steps we go through, are the same as in the previous article. The added complexity comes from the random string of characters. If we lose this “key” we can’t just recreate it and go back to encrypting messages. We need to keep the key safe and available. 


If we receive the message “qaxkebv ixb hevketmk” how are we going to read it? First, we must already know the means to go back, that is, we need to already know the key that was used to encrypt the message. 

If we have the key then we can create the following to help us:

  • ifmhbcpnezlogtaqrxvkwjsduy
  • abcdefghijklmnopqrstuvwxyz

These characters are turned into an decryption guide in Fig. 3 below, so it’s easier to see which characters correspond. In our example the “q” becomes an “p”, the “a” becomes a “o”, and so on. The message “qaxkebv ixb hevketmk” is decrypted to “porties are distinct

Fig. 3: Decryption Guide

We are only using lower-case letters in this example. If we wish to include capital letters, the simplest way to do this is to agree that a capital letter in the original message will be translated to a capital letter in the encrypted message. We don’t have to make any other changes to our key.

A nice web page for creating randomized strings such as the one we have above can be found at: Just put in the characters you want to randomize and click the “Randomize Characters!” button.

Before we start exchanging secure messages, the sender and receiver have to agree on the method that will be used for the encryption/decryption. We can exchange the method we are going to use in a number of ways. We could do this in person, for example, that way there is less chance of the rules for our encryption/decryption being discovered. We can then separate and exchange secure messages.

Note that we aren’t encrypting spaces between words so the number of letters in a word is always fixed. If the text is long, this can be used to help decipher the message. We will discuss adding complexity and security to the encryption methods in later posts.

In the next post we will look at an example that uses a more complicated Encryption key with blanks, capital letters and special characters.