RC4 Encryption Algorithm

Instructor: David Gloag

David has over 40 years of industry experience in software development and information technology and a bachelor of computer science

Encryption plays a major role in many things these days. In this lesson, we'll take a look at one of the basic algorithms, RC4. At the end of this lesson, you should have a good understanding of how it works, and when it might be used.

Protecting the Movement of Information

Computers have been around for years, sending information here and there. As a result, there is an inherent need to protect that information while in transit. And this trend will only increase. Global communications, and Internet commerce, are capturing the hearts and minds of businesses and individuals alike. Fortunately, there are companies like IBM, Hewlett Packard, and RSA Security, working hard to create new, and hopefully effective methods of protection. One such method is the RSA encryption algorithm.

What is Encryption?

Encryption is the process of taking information in one form (usually human-readable), and converting it to another form (not usually human-readable). It is mathematically based, often involving a series of complex calculations. There are several different types of encryption, and they are used for various things. Common examples include hiding sensitive information for your bank account, protecting the connections between your web browser and e-commerce websites like Amazon, and securing the password for your cell phone. It is like a silent partner, working behind the scenes, protecting the information that matters.

What is the RC4 Encryption Algorithm?

RC4 is an encryption algorithm created in 1987 by Ronald Rivest of RSA Security. It is a stream cipher, which means that each digit or character is encrypted one at a time. A cipher is a message that has been encoded. The process uses the same key for encrypting and decrypting the information, another way of saying it is symmetric. This type of algorithm is often referred to as a shared key algorithm. The key length varies from 40 to 2048 bits. The algorithm is computationally simple, and as such, lends itself to fast computer implementations.

How Does the RC4 Encryption Algorithm Work?

The algorithm is broken down into two parts. The first part creates a list of 256 random bytes that form the basis for the encryption. This is done by first generating a list of values, from 0 to 255, in order. Next, two indexes are used to swap, add, and modulus the values in the list. These operations mix the values up until their sequence becomes random. It is important to note that these operations were chosen because they can be performed quickly on a computer.

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