Homomorphic Encryption: Example & Definition

Instructor: David Gloag

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

We hear news about information leaks and compromises constantly. In this lesson, we'll take a look at an important method used to combat this, homomorphic encryption. We'll also look at what it is and how it works.

The Topic of Information

Compromised information is an important topic these days. We see it on the evening news or read about it in the newspapers. As an example, just think about the recent US Democratic National Committee email leak and the fallout from it. With these types of occurrences, is it any wonder that protection methods are getting more and more sophisticated? Absolutely not! But are current methods enough? Will technologies like encryption prove equal to the task?

What is Encryption?

Encryption is the process of taking information represented in one fashion (usually human-readable), and representing it in another fashion (not usually human-readable). It is mathematically based, often using complex calculations. It uses an external piece of information, known as a key, to perform this re-representation. There are several different types of encryption, and they are used for various things. Common examples include connections to Internet merchants like Amazon, protected military communications, and hiding the password to your cell phone. You likely won't even know it's there. But it is, quietly doing its thing.

The Problem

In regular encryption, the process follows a specific workflow. In particular, it looks as follows:

  • You encrypt your important information.
  • The encrypted information is stored for future use.
  • You retrieve the encrypted information for use.
  • You decrypt the information to perform any operation on it.
  • Once finished, you delete, or re-encrypt the information.

So, from the time from when you decrypt, to the time you delete or re-encrypt, the information is exposed. As you might imagine, this can be problematic.

What is Homomorphic Encryption?

Homomorphic encryption works differently. Instead of decrypting before use, this process uses the information in its encrypted form. In other words, once encrypted, the information is never decrypted and exposed until the very end. Think of it like putting a unique, protective case on your cell phone. If you put the phone down and want to find it later, you would search for the protective case rather than the phone. The end result is still the same, in other words, finding the phone. You just look for a different representation.

How is Homomorphic Encryption Used?

Let's look at an example. Say you want to do a search through IRS, or Revenue Canada, income tax records for John Doe. Further, let's say that the search is done remotely, meaning that you are not in a secure income tax office. Using regular encryption, the process would look as follows:

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