Understanding encryption

If you were trying to read an encrypted message such as a line

.won tnuomgolb no gnidaer ma I

You would not understand what it says unless you also knew how to decipher it. This is the whole idea behind encryption: prevent others from reading or viewing your encrypted files and messages if they don’t have the means of decoding it. With encryption, in theory only those to whom you provide means of decoding the files can read the content of the files.

Because you don’t have the means of decoding the top example line, you won’t understand what it is. If, however, you know that the line is simply a sentence that is reversed. With this information, you will be able to construct the sentence to an understandable format. Note spaces were removed from the top example line to make deciphering difficult. So our sentence is:

I am reading on blogmount now.

This is a very basic example of encryption. In practice, computers use complex algorithms to construct and deconstruct content. The following figure shows the whole process of encryption and decryption:

Figure 1 encrypting and decrypting a message
Figure 1 encrypting and decrypting a message


  • Creates the message,
  • Encrypts it with a key, and
  • Sends it


  • Receives the message,
  • Decrypts it using the key, and
  • Reads it

The figure shows, suppose you have a simple encrypted message that you want to share with someone. Because you consider the message sensitive, you have decided to use encryption. By applying encryption to your message, you and the receiver agreed on the method of how you want to encrypt the message.

Important note

If you want to share sensitive data and are concerned with how to send the encryption key, use a safe method of delivering. For example, if you are emailing a sensitive message and also want to send the encryption key by email, consider an alternative way of sending the encryption key. Perhaps, consider sharing the encryption key by phone or even better in person.

The key you use to encrypt will determine how the message is encrypted. For simplicity, assume these choices of encryption keys:

  • replace each and every character in your message (as we have done in the example above),
  • replace the entire word with one character, for example, for love you may use L
  • use symbols, for instance, you may indicate love with a heart!
  • use numbers, for instance letters of the alphabet are replaced by numbers. "Love" can be represented as 1215225, where "L" is represented by the number 12 because it is the twelfth letter of the alphabet, "o" is represented by the number 15 because it is fifteenth letter of alphabet, and so on.

What is a common approach used for encrypting? The answer is that each technique involves some kind of substitution, whether it is at character-level, word-for-word, or some other sophisticated method of substitutions. In essence, elements of the original message are replaced by the alternative values of the substitution used.

Encryption is an excellent choice for protecting information that is stored or transmitted. Text files, program files, and binary data can be encrypted. If you are concerned that others may access your files, it is a probably good idea to encrypt the files. This should not be however done with the simple method described here because the message can be easily decrypted instead use a software specifically designed for handling encryption and decryption tasks.

Posted on 11/6/2007
by Raj Singh